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  • 51. Jonoobi, Mehdi
    et al.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Natural Resources and Residues for Production of Bionanomaterials2014In: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Chapter in book (Refereed)
  • 52.
    Jonoobi, Mehdi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Producing low-cost cellulose nanofiber from sludge as new source of raw materials2012In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 40, no 1, p. 232-238Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to isolate cellulose nanofibers by ultrafine grinding, from sludge (residue from dissolving cellulose production) and cellulose (dissolving cellulose) and to characterize their properties. The mechanical fibrillation was found to be more energy efficient at low rotor speed (1440) and was estimated to be 1.7 and 1.3 kWh/kg for cellulose (CF) and sludge fibers (SF), respectively. Sludge (SNF) and cellulose (CNF) nanofibers had diameter less than 100 nm, as measured from transmission electron microscopy images. The specific surface area ranged from approximately 84 to 112 m2/g for CNF and SNF respectively. The apparent networks density increased with fibrillation, being approximately 330 and 370 for CF and SF while 907 and 986 kg/m3 for the corresponding nanosized ones. The scanning electron microscopy (SEM) study exhibited considerably smoother surfaces for the nanofiber networks compared to microsized. Fibrillation to nanosized fibers had positive impact on modulus and strength of both raw materials and the improvement was more significant for sludge, indicating more efficient fibrillation. The study showed that the isolation of nanofibers from sludge could be considered an economic, energy efficient and viable alternative to generate value-added product from cellulose sludge while minimizing the sludge disposal issues.

  • 53.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Claudpierre, Simon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanocellulose based functional membranes for water cleaning: Tailoring of mechanical properties, porosity and metal ion capture2016In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 514, p. 418-428Article in journal (Refereed)
    Abstract [en]

    Multi-layered nanocellulose membranes were prepared using vacuum-filtration of cellulose nanofibers (CNF) suspensions followed by dip coating with cellulose nanocrystals having sulphate (CNCSL) or carboxyl surface groups (CNCBE). It was possible to tailor the specific surface area, pore structure, water flux and wet strength of the membranes based on drying conditions and acetone treatment. CNF coated with CNCBE showed the highest a tensile strength (95 MPa), which decreased in wet conditions (≈3.7 MPa) and with acetone (2.7 MPa) treatment. The water dried membranes showed pore sizes in nanofiltration range (74 Å) from liquid nitrogen adsorption/desorption data and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194Å) with a concomitant increase (7000%) of the BET surface area. The water flux, also increased from zero to 25 Lm-2h-1 at a pressure differential of 0.45 MPa, for acetone treated ones. The membranes irrespective of the surface functionality showed exceptional capability (≈100%) to remove Ag+, Cu2+ and Fe3+ ions from mirror industry effluents. Surface adsorption followed by microprecipitation was considered as the possible mechanism of ion removal, which opens up a new generation of ultrafiltration membranes with high selectivity towards ions and low-pressure demands.

  • 54.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chitosan based nanocomposite membranes with cellulose nanowhisker as nanoadditive2013Conference paper (Refereed)
    Abstract [en]

    Biobased nanocomposite membranes were prepared using chitosan as te matrix and cellulose nano whisker as the reinforcing phase. Cellulosee production. Atomic force microscopy of the nanowhiskers showed diameters of 10 -20nm and lengths of 250 - 350nm. Nanocomposites were prepared in 1:1, 1:2 and 1:3 ratios to investigate the effect of nanoadditive concentration on the membrane properties. The nanocomposites were prepared by solution mixing followed by freeze-drying, to obtain porous structures with high degree of internal surface area. These nanocomposites were further treated with ammonia vapours to prepare the crosslinked nanocomposites and thereby stabilize it towards moisture and pH variations. The morphology, surface area, crystallinity, porosity, and mechanical properties of prepared membranes were studied. The effect of the nanocomposite composition, crosslinking and the pore size distribution on the water transport through the membranes was also evaluated.

  • 55.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hakalahti, Minna
    VTT Technical Research Centre of Finland.
    Tammelin, Tekla
    VTT Technical Research Centre of Finland.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Materials and Environmental Chemistry, Stockholm University.
    In situ TEMPO surface functionalization of nanocellulose membranes for enhanced adsorption of metal ions from aqueous medium2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 9, p. 5232-5241Article in journal (Refereed)
    Abstract [en]

    The current work demonstrates an innovative approach to develop nanocellulose based membranes with high water permeability, mechanical stability and high functionality via (1) tailoring the composition of the support layer of sludge microfibers/cellulose nanofibers (CNFSL) and (2) in situ TEMPO functionalization of the thin functional layer of cellulose nanocrystals (CNCBE) to enhance the metal ion adsorption capacity. SEM studies showed a porous network structure of the cellulose support layer and a denser functional layer with CNCBE embedded within gelatin matrix. AFM studies indicated the presence of a nanoscaled coating and increased roughness of membranes surface after TEMPO modification whereas FT-IR and conductometric titration confirmed the introduction of carboxyl groups upon TEMPO oxidation. The contact angle measurement results showed improved hydrophilic nature of membranes after in situ TEMPO functionalization. High networking potential of CNFSL made the membrane support layer tighter with a concomitant decrease in the average pore size from 6.5 to 2.0 μm. The coating with CNCBE further decreased the average pore size to 0.78 and 0.58 μm for S/CNCBE and S–CNFSL/CNCBE, respectively. In parallel, a drastic decrease in water flux (8000 to 90 L MPa−1 h−1 m−2) after coating with CNCBE was recorded but interestingly in situ functionalization of top CNCBE layer did not affect water flux significantly. The increase in adsorption capacity of ≈1.3 and ≈1.2 fold was achieved for Cu(II) and Fe(II)/Fe(III), respectively after in situ TEMPO functionalization of membranes. Biodegradation study confirmed the stability of layered membranes in model wastewater and a complete degradation of membranes was recorded after 15 days in soil.

  • 56.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanoporous membranes with cellulose nanocrystals as functional entity in chitosan: removal of dyes from water2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 112, p. 668-676Article in journal (Refereed)
    Abstract [en]

    Fully biobased composite membranes for water purification were fabricated with cellulose nanocrystals (CNCs) as functional entities in chitosan matrix via freeze-drying process followed by compacting. The chitosan (10 wt%) bound the CNCs in a stable and nanoporous membrane structure with thickness of 250-270 μm, which was further stabilized by cross-linking with gluteraldehyde vapors. Scanning electron microscopy (SEM) studies revealed well-individualized CNCs embedded in a matrix of chitosan. Brunauer, Emmett and Teller (BET) measurements showed that the membranes were nanoporous with pores in the range of 13-10 nm. In spite of the low water flux (64 L m-2 h-1), the membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, after a contact time of 24 h. The removal of dyes was expected to be driven by the electrostatic attraction between negatively charged CNCs and the positively charged dyes.

  • 57.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kokol, Vanja
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Wei, Jiang
    Alfa Laval Nakskov A/S, Business Center Membranes, Stavangervej 10, DK-4900, Nakskov, Denmark.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    High-flux affinity membranes based on cellulose nanocomposites for removal of heavy metal ions from industrial effluents2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 25, p. 20644-20653Article in journal (Refereed)
    Abstract [en]

    Fully biobased affinity membrane processing and its application in the removal of heavy metal ions from mirror industry effluents were successfully demonstrated; indicating the potential use of these membranes in point-of-use or point-of-entry water cleaning products that are cheap, environmentally friendly and efficient. Layered cellulose nanocomposite membranes were fabricated using cellulose microfiber sludge as a support layer and cellulose nanocrystals (CNCSL, CNCBE or PCNCSL) in a gelatin matrix as the functional layer. Scanning electron microscopy (SEM) studies revealed the bi-layered morphology of the membrane and well-individualized nanocelluloses in the functional layer. Bubble point measurements confirmed the membrane pore structure in the microfiltration range (5.0-6.1 μm), which provided very high water permeability (900-4000 L h-1 m-2) at <1.5 bars. A tensile strength of 16 MPa in dry conditions and a wet strength of 0.2 MPa, was considered sufficient for use of these membranes in spiral wound modules. Mirror industry effluent laden with metal ions (Ag+ and Cu2+/Fe3+/Fe2+) when treated with cellulose nanocomposite membranes, showed high ion removal capacity, being 100% for PCNCSL followed by CNCBE than CNCSL. The removal of metal ions was expected to be driven by interactions between negatively charged nanocellulose and the positively charged metal ions.

  • 58.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Cellulose nanocrystals based nanocompositemembranes for water purification: Process-Property correlation2015Conference paper (Other academic)
  • 59.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Fully biobased nanocomposite membranes: removal of heavy metals from polluted water2014Conference paper (Refereed)
    Abstract [en]

    Biobased nanoparticles viz cellulose nanocrystals (CNCs) and cellulose nanofiber (CNFs) isolated by mechanical process (grinding) were used to fabricate of fully biobased nanocomposite membranes. Biobased nanofibers were used as support layer via a very simple process of vacuum filtration was used for the fabrication of CNF support layer. In order to coat CNCs or CNCbio on the two sides to CNF layer, the membrane was dipped in a solution of cellulose nanocrystals. Scanning electron microscopy (SEM) confirmed the infusion of functional layer within supportive layer. Tensile strength was measured in dry as well as in wet conditions, illustrated mechanical performances compareble to commercially available membranes. To increase the flux, membranes were treated with acetone for 24 and 72 h. The drastic increase in the flux for acetone treated membranes confirmed the discontinuities of hydrogen . The membranes succefully removed two metal ions Ag+ and As3- from real wastewater, from mirror making and mining industries respectively, within Europe. Complete removal of Ag+ was reported after 24 h of incubation. The study concludes that, the developed membranes having good mechanical stability in wet conditions, high water flux and adsorption efficiency are potential candidates for heavy metal ion remediation of industrial effluents.

  • 60.
    Kekäläinen, Kaarina
    et al.
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Suopajärvi, Terhi
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Mathew, Aji P.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Laitinen, Ossi
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Niinimäki, Jouko
    Fibre and Particle Engineering Laboratory, University of Oulu.
    Effect of peroxide treatment on energy consumption of refining and quality2010In: International Paperworld, ISSN 1615-1720, Vol. 9, p. 12-17Article in journal (Refereed)
    Abstract [en]

    The effect of alkaline hydrogen peroxide treatment on microfibrillar cellulose (MFC) production in an inline homogenizer (ZRI) was reported. Never-dried bleached softwood Kraft pulp (BSK) from the Stora Enso Oulu mill in Finland and never-dried dissolving cellulose (DC) from the Domsjö Fabriker AB Örnsköldsvik mill in Sweden were used. The analyses of the celluloses were carried out in three phases that included for the early refining stage, the later stage of refining and for the final product. The final refining products and the commercial MFC were visualized by FESEM (Zeiss Ultra Plus) and by AFM (VEECO multimode scanning probe microscope with a Nanoscope V controller). The results showed that the particle size of the dissolving cellulose decreased more in the early refining stage, whereas the bleached Kraft pulp was refined more in the later stage of refining. Alkaline peroxide treatment had a significant effect on the fiber width development compared to the development of alkali-treated celluloses

  • 61.
    Kokol, Vanja
    et al.
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Bozic, Mojca
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Vogrinčič, Robert
    Faculty of Mechanical Engineering, Institute for Engineering Materials and Design, University of Maribor.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Characterization and properties of homo- and heterogenously phosphorylated nanocellulose2015In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 125, p. 301-313Article in journal (Refereed)
    Abstract [en]

    Nano-sized cellulose ester derivatives having phosphoryl side groups were synthesised by phosphorylation of nanofibrilated cellulose (NFC) and nanocrystaline cellulose (NCC), using different heterogeneous (in water) and homogeneous (in molten urea) processes with phosphoric acid as phosphoryl donor. The phosphorylation mechanism, efficacy, stability, as well as its influence on the NC crystallinity and thermal properties, were evaluated using ATR-FTIR and 13C-NMR spectroscopies, potentiometric titration, capillary electrophoresis, X-ray diffraction, colorimetry, thermogravimmetry and SEM. Phosphorylation under both processes created dibasic phosphate and monobasic tautomeric phosphite groups at C6 and C3 positioned hydroxyls of cellulose, yielded 60-fold (∼1173 mmol/kg) and 2-fold (∼1038 mmol/kg) higher surface charge density for p-NFC and p-NCC, respectively, under homogenous conditions. None of the phosphorylations affected neither the NC crystallinity degree nor the structure, and noticeably preventing the derivatives from weight loss during the pyrolysis process. The p-NC showed high hydrolytic stability to water at all pH mediums. Reusing of the treatment bath was examined after the heterogeneous process.

  • 62.
    Leijonmarck, S.
    et al.
    Swerea SICOMP AB.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Division of Materials Science, Composite Centre Sweden, Luleå University of Technology.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Division of Materials Science, Composite Centre Sweden, Luleå University of Technology.
    Lindbergh, G.
    Division of Applied Electrochemistry, Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics. Swerea SICOMP AB.
    Direct electropolymerization of polymer electrolytes onto carbon fibers - A route to structural batteries?2014In: 16th European Conference on Composite Materials, ECCM 2014: Seville, Spain, 22 June- 26 June 2014, European Conference on Composite Materials, ECCM , 2014Conference paper (Refereed)
    Abstract [en]

    In an effort to further reduce weight of carbon fibre reinforced composites, the concept of structural batteries has arisen. A structural battery is a multifunctional material managing both energy storage and enabling of structural integrity. More specific, the carbon fibres in the composites are used as negative electrode in a Li-ion battery. A crucial part of such a battery is the preparation of a thin, ionically conductive and stiff polymer matrix. One route to realize this is the use of electropolymerization, which can cover each individual fibre with polymer. In this study, the surface morphology of coated carbon fibres is investigated with electron microscopy and atomic force microscopy. Additionally, the curing degree as a function of process temperature during polymerization is tested.

  • 63.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Borrell, Pere Ferrer
    Luleå tekniska universitet.
    Božič, Mojca
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Kokol, Vanja
    University of Maribor, Institute for Engineering Materials and Design, Smetanova ul. 17, SI-2000 Maribor, Slovenia.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanocelluloses and their phosphorylated derivatives for selective adsorption of Ag+, Cu2+ and Fe3+ from industrial effluents2015In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 294, p. 177-185Article in journal (Refereed)
    Abstract [en]

    The potential of nanoscaled cellulose and enzymatically phosphorylated derivatives as bio-adsorbents to remove metal ions (Ag+, Cu2+ and Fe3+) from model water and industrial effluents is demonstrated. Introduction of phosphate groups onto nanocelluloses significantly improved the metal sorption velocity and sorption capacity. The removal efficiency was considered to be driven by the high surface area of these nanomaterials as well as the nature and density of functional groups on the nanocellulose surface. Generally, in the solutions containing only single types of metal ions, the metal ion selectivity was in the order Ag+ > Cu2+ > Fe3+, while in the case of mixtures of ions, the order changed to Ag+ > Fe3+ > Cu2+, irrespective of the surface functionality of the nanocellulose. In the case of industrial effluent from the mirror making industry, 99% removal of Cu2+ and Fe3+ by phosphorylated nanocellulose was observed. The study showed that phosphorylated nanocelluloses are highly efficient biomaterials for scavenging multiple metal ions, simultaneously, from industrial effluents.

  • 64.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Goetz, Lee
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Biobased nanoparticles and membranes for water purification via selective adsorption: Possibilities and challenges2014Conference paper (Refereed)
    Abstract [en]

    With population expansion and industrialization, water pollutions have become one of the biggest threat to human society today. The combination of biotechnology and nanotechnology offers a new and green way to the problems. Cellulose nanofibers cellulose nanocrystals and chitin nanocrystals have nanoscaled diameters and have high specific surface areas, an advantage in membrane technology and the efficiency can be further enhanced using specific functionalization, enabling highly specific interactions with targeted contaminant entities in water. Moreover, the nano-dimensions of the used active species allow the fabrication of compact and ultra-thin multifunctional membranes by introducing an orientation and/or concentration gradient. This novel water purification approach combines the physical filtration process and the adsorption process exploring the capability of the nanocellulose and/or nanochitin (with or without functionalization) to selectively adsorb, store and desorb contaminants from industrial water and drinking water while passing through a highly permeable membranes/ filters. The aim is to tailor membarnes and filters with high flux which reduces pressure and thereby energy consumption while keeping the high selectivity efficiency due to surface adsorption. The results showed highly efficient removal of metal ions (Ag+, Cu2+ and Fe3)+ from mirror making industry using nanocellulose based membranes. High removal efficiency of dyes, nitrates and organic foulants using bio- based membranes/ filters was also confirmed. The nanocellulose and nanochitin based membranes also showed significant resistance to bio-fouling. The scaled up membranes is expected to be used in the form of spiral wound modules, cartridge modules and MBR modules for water treatment in mirror industries, printing industries, mining industries as well as municipal water and storm water in Europe.

  • 65.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adsorption Characteristics of Cu2+ from Aqueous Medium onto TEMPO oxidised cellulose nanofibers (TOCNF)2015Conference paper (Refereed)
  • 66.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adsorption study of Cu(II) ions onto TEMPO oxidised cellulose nanofibers (TOCNF)2015Conference paper (Refereed)
  • 67.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Multifunctional materials for environmental applications based on TEMPO-oxidized cellulose nanofibers (TOCNF)2015Conference paper (Refereed)
  • 68.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kokol, Vanja
    Bozic, Mojca
    Adsorption characteristics of heavy metal ions from aqueous medium onto polysaccharide nanocrystals2013Conference paper (Refereed)
  • 69.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Božič, Mojca
    Kokol, Vanja
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adsorption Characteristics of Heavy Metal Ions from Aqueous Medium onto Nano Polysaccharides2014Conference paper (Refereed)
    Abstract [en]

    Cellulose nanocrystals and fibers isolated form bioresources or residues are being used as functional additives in many applications during the past decades, recently these nanocrystals and fibers in its native form or modified form has been used as functional component in water purification processes.1,2 The current study explores the equlibrum adsorption time and adsorption capacitiy of three heavy metal ions: Ag+, Cu2+; Fe3+. Cellulose nanocrystals (CNCs) with different surface functionalities were used as adsorbant mateials. All the nano materials have nano-scale diameters from 10 – 20 nm (measured by AFM) and high specific surface area. Zeta sizer studies showed very negatively charged surface for all the nanocrystals at neutral pH conditions.The adsorptions of silver, copper and iron ions onto the differents CNCs were evaluated using ICP-OES (inductively coupled plasma- optical emission spectrometry) and EDS (energy dispersive spectroscopy). The nature and amount of surface groups are found to significantly impact the functionality of cellulose nanocrystals and the adsorption efficiency. It was hypothised that the electrostatic interactions between the negatively charged nanocrystals and positively charged metal ions drives the adsoprtion process. Theoretical modelling was used to gain insight into the mechanism of adsorption.Acknowledgment: Financial support from European Commission under EU FP7, NMP4-SL-2012-280519, NanoSelect is gratefully acknowledged. Johnny Grahn is acknowledged for the help with EDS measurements. University of Maribor is acknowledged for supplied functionalised cellulose nanocrystals.Reference:1. Ma, H.; Hsiao, K. B.; Chu, B. Nanofibrous Microfiltration Membrane Based on Cellulose Nanowhiskers. Biomacromolecules 2012, 13, 180−186.2. Lui P;Sehaqui H, Tingaut P, Wischer A, Oksman K, Mathew AP, Cellulose and chitin nanomaterials for capturing silver ions (Ag+) from water via surface adsorption. Cellulose, doi : 10.1007/s10570-013-0139-5.

  • 70.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adsorption characteristics of nanocrystals isoltaed from bioresidues: effect of pH and surface charge2013In: Book of Abstracts, 7th EEIGM International Conference on Advanced Materials Research: March 21 - 22, 2013, LTU, Luleå - SWEDEN, 2013, p. 4-Conference paper (Refereed)
    Abstract [en]

    Cellulose nanocrytals and chitin nanocrystals respectively were isolated from bioresidues viz, sludge from special cellulose production and crab shell waste using acid hydrolysis. The atomic force micrscopy images showed that the diameter of CNWs ranged from 10 - 20 nm and chitin whiskers ranged from 20 - 40 nm. Thermal degrdation temperatures of nanocellulose and nanochitin whiskers were found to be 186 °C and 234 °C respectively. The crystallinity index of CNWs was 72.3 % while that of chitin nanowhiskers was as high as 87.2 %. Conductivity titration and zeta sizer studies proved the high surface charge of both CNWs and chitin nanowhiskers. Besides, chitin nanowhiskers are positively surface charged at acidic pH and negatively surface charged at alkaline pH. ICP-MS (inductively coupled plasma mass spectrometry) and XPS (X-ray photoelectron spectroscopy) will be conducted to evaluate the adsorption potential of CNWs and chitin nanowhiskers to heavy metal ions as functions of pH and surface charge.

  • 71.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Surface adsorption and self assembly of Cu(II) ions on TEMPO-oxidised cellulose nanofibers in aqueous media2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 464, p. 175-182Article in journal (Refereed)
    Abstract [en]

    TEMPO-mediated oxidized cellulose nanofibers (TOCNFs) have shown potential in the bioremediation of metal ions from contaminated water due to their interaction with positively charged metal ions via electrostatic interactions involving surface carboxyl groups. Copper is one of the most common pollutants in industrial effluents and is thus the target metal in the current study. The specific surface adsorption of Cu(II) was similar for TOCNFs with different degrees of functionalization and directly impacted the zeta potential. SEM imaging of the TOCNF after Cu(II) adsorption revealed interesting nanostructured clusters that were attributable to Cu(II) ions first being adsorbed by carboxylate groups on the TOCNF and subsequently being reduced and self-assembled to Cu(0) nanoparticles (NPs) or copper oxide NPs by microprecipitation. TOCNF turned superhydrophilic and resulted in faster water filtration after copper adsorption due to the stronger polarity of the copper ions or the self-assembled Cu(0) NPs creating voids or highly water-permeable channels at the interface between the interconnected TEMPO-oxidized nanofibers. Thus, the adsorption of Cu(II) ions and self-assembly into the Cu NPs on TOCNF favors a faster water purification process and provides a viable route to reuse/recycle TOCNFs studded with Cu nanoparticles as biocidal materials

  • 72.
    Liu, Peng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sehaqui, Houssine
    Swiss Federal Laboratories for Materials Testing and Research (EMPA).
    Tingaut, Philippe
    Swiss Federal Laboratories for Materials Testing and Research (EMPA).
    Wichser, Adrian
    Swiss Federal Laboratories for Materials Testing and Research (EMPA).
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose and chitin nanomaterials for capturing silver ions (Ag+) from water via surface adsorption2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 1, p. 449-461Article in journal (Refereed)
    Abstract [en]

    The study explores the potential of cellulose nanocrystals (CNC), cellulose nanofibers (CNF) and chitin nanocrystals (ChNC) isolated from bioresidues to remove silver ions from contaminated water. Zeta sizer studies showed negatively charged surfaces for CNC and CNF isolated from cellulose sludge in the acidic and alkaline pHs, whereas ChNC isolated from crab shell residue showed either positive or negative charges depending on pH conditions. Model water containing silver ions showed a decrease in Ag+ ion concentration (measured by inductively coupled plasma-optical emission spectrometer; inductively coupled plasma mass spectrometry), after treatment with CNC, CNF and ChNC suspensions. The highest Ag+ ion removal was measured near neutral pH for CNC, being 34.4 mg/g, corresponding to 64 % removal. ChNC showed 37 % and CNF showed 27 % removal of silver ions. The WDX (wavelength dispersive X-ray analysis) and XPS (X-ray photoelectron spectroscopy) analysis confirmed the presence of silver ions on the surface of the nanocellulose and nanochitin after adsorption. Surface adsorption on the nanoparticles via electrostatic interactions is considered to be the prominent mechanism of heavy metal ion capture from aqueous medium, with CNC with negative surface charge and negatively charged functional groups being most favourable for the adsorption of positively charged Ag+ ions compared to other native bionanomaterials

  • 73.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bio- based membranes for water purification: Possibilities and challenges2015Conference paper (Refereed)
  • 74.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanocomposite fibers:possibilities and challenges2015Conference paper (Refereed)
  • 75.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Interpenetrating polymer networks: Processing, properties and applications2013In: Advances in Elastomers I: Blends and interpenetrating networks, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2013, p. 283-301Chapter in book (Refereed)
    Abstract [en]

    Interpenetrating polymer networks (IPNs) are defined as combination of two or more polymers in network form with at least one of which is polymerised and/or crosslinked in the immediate presence of the others. IPNs are based on combinations of two or more polymers and are younger cousins to polymer blends, blocks and grafts. All these are members of a larger class of multicomponent polymeric systems, where as in IPNs, the polymers are crosslinked, thus providing a mechanism for controlling the domain sizes and reducing creep and flow. Though the idea behind IPN synthesis is to effect molecular level interpenetration of the polymer networks, most IPNs form immiscible systems with phase separation during some stage of synthesis. Aylsworth, in 1914 invented the first known IPN, but the term IPN was coined much later in 1960, by Millar who developed PS/PS IPNs to be used as ion exchange resin matrices (Aylsworth, US Patent 1, 111, 284, 1914), (Millar, J. Chem. Soc. 1311, 1960). The literature review shows that Sperling and coworkers at Lehigh university, USA followed by Frisch from University of Detroit and Frisch from Suny, Albany have made the most contributions to this research area. The current review on IPNs summarises the processing, properties and applications of IPNs, with special focus on some recent developments and trends

  • 76. Mathew, Aji P.
    Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers2002In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 3, no 3, p. 609-617Article in journal (Refereed)
    Abstract [en]

    Nanocomposites were prepared from waxy maize starch plasticized with sorbitol as the matrix and a stable aqueous suspension of tunicin whiskers-an animal cellulose-as the reinforcing phase. The composites were conditioned at different relative humidity levels. The conditioned films were characterized using scanning electron microscopy, differential scanning calorimetry, water uptake experiments, and wide-angle X-ray scattering studies. Contrarily to our previous report concerning tunicin whisker filled glycerol plasticized starch nanocomposites (Macromolecules 2000, 33, 8344), the present system exhibited a single glass-rubber transition, and no evidence of transcrystallization of amylopectin on cellulose whisker surfaces and resultant antiplasticizing effects were observed. It was found that the glass-rubber transition temperature of the plasticized amylopectin matrix first increases up a whiskers content around 10-15 wt % and then decreases. A significant increase in crystallinity was observed in the composites by increasing either moisture content or whiskers content

  • 77. Mathew, Aji P.
    et al.
    Chakraborty, A.
    Oksman, Kristiina
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Sain, Mohini
    Polylactic acid (PLA) cellulose nanocomposites processed by twin screw extrusion2005In: Abstracts of papers, 229th ACS national meeting: San Diego, CA, March 13 - 17, 2005, Washington, DC: American Chemical Society (ACS), 2005Conference paper (Refereed)
  • 78. Mathew, Aji P.
    et al.
    Chakraborty, Ayan
    University of Toronto.
    Oksman, Kristiina
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Sain, Mohini
    University of Toronto.
    The structure and mechanical properties of cellulose nanocomposites prepared by twin screw extrusion2006In: Cellulose Nanocomposites: Processing, Characterization and Properties, Washington DC USA: American Chemical Society (ACS), 2006, p. 114-131Chapter in book (Refereed)
  • 79. Mathew, Aji P.
    et al.
    Dufresne, Alain
    Université Joseph Fourier.
    Plasticized waxy maize starch: effect of polyols and relative humidity on material properties2002In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 3, no 5, p. 1101-1108Article in journal (Refereed)
    Abstract [en]

    The plasticizing effect of different polyols such as glycerol, xylitol, sorbitol, and maltitol on waxy maize starch was investigated. The concentration of plasticizer was fixed at 33 wt % (dry basis of starch). The structure and mechanical performance of resulting films conditioned at different relative humidity levels were studied in detail. The effect of the plasticizer on the glass-rubber transition temperature (Tg) and crystallinity was characterized using differential scanning calorimetry. It was found that Tg decreases with increasing moisture content and decreasing molecular weight of the plasticizer. The water resistance of starch increased steadily with the molecular weight of the plasticizer and was directly proportional to the ratio of the end to total hydroxyl groups. As the molecular weight of the plasticizer increased, the brittleness of the dry system increased. However, the use of high molecular plasticizer allowed good mechanical properties of the moist material to be obtained in terms of both stiffness and elongation at break.

  • 80.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gong, Guan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Björngrim, Niclas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wixe, David
    Luleå University of Technology.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Moisture absorption behaviour and its impact on the mechanical properties of polyvinyl acetate (PVAc) based cellulose nanocomposites2011In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 51, no 11, p. 2136-2142Article in journal (Refereed)
    Abstract [en]

    Cellulose nanowhisker (CNW) reinforced polyvinyl acetate (PVAc) nanocomposites were prepared by melt-extrusion using a master batch process. Microscopy images showed no visible aggregation of whiskers in the matrix. The influence of CNWs and moisture absorption on the mechanical behavior of the nanocomposites was studied. The water sorption studies indicated low water uptake (<10 wt%) for all the materials. However, higher moisture uptake was obtained in the nanocomposites compared to the matrix though the diffusion co-efficient of the nanocomposites was lower. The tensile strength and modulus were decreased with the addition of CNWs to PVAc, but the reduction is lower at higher CNW concentration indicating that the plasticizing effect of the moisture was counteracted to some extent by the reinforcing effect of CNWs. Higher tensile ductility and toughness, which were dependent on moisture absorption, were achieved in the nanocomposites than pure PVAc.

  • 81. Mathew, Aji P.
    et al.
    Groeninckx, Gabriel
    Mahatma Gandhi University.
    Michler, G.H.
    Martin Luther Universität.
    Radusch, H.J.
    Martin Luther Universität.
    Thomas, Sabu
    Mahatma Gandhi University.
    Viscoelastic properties of nanostructured natural rubber/polystyrene interpenetrating polymer networks2003In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 41, no 14, p. 1680-1696Article in journal (Refereed)
    Abstract [en]

    The effects of the blend ratio and initiating system on the viscoelastic properties of nanostructured natural rubber/polystyrene-based interpenetrating polymer networks (IPNs) were investigated in the temperature range of -80 to 150 °C. The studies were carried out at different frequencies (100, 50, 10, 1, and 0.1 Hz), and their effects on the damping and storage and loss moduli were analyzed. In all cases, tan and the storage and loss moduli showed two distinct transitions corresponding to natural rubber and polystyrene phases, which indicated that the system was not miscible on the molecular level. However, a slight inward shift was observed in the IPNs, with respect to the glass-transition temperatures (Tg's) of the virgin polymers, showing a certain degree of miscibility or intermixing between the two phases. When the frequency increased from 0.1 to 100 Hz, the Tg values showed a positive shift in all cases. In a comparison of the three initiating systems (dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile), the dicumyl peroxide system showed the highest modulus. The morphology of the IPNs was analyzed with transmission electron microscopy. The micrographs indicated that the system was nanostructured. An attempt was made to relate the viscoelastic behavior to the morphology of the IPNs. Various models, such as the series, parallel, Halpin-Tsai, Kerner, Coran, Takayanagi, and Davies models, were used to model the viscoelastic data. The area under the linear loss modulus curve was larger than that obtained by group contribution analysis; this showed that the damping was influenced by the phase morphology, dual-phase continuity, and crosslinking of the phases. Finally, the homogeneity of the system was further evaluated with Cole-Cole analysis.

  • 82.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanocellulose as functional material for water cleaning2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247Article in journal (Refereed)
  • 83.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanocellulose for water purification membranes2013In: Production and Applications of Cellulose Nanomaterials, TAPPI Press, 2013, p. 155-156Chapter in book (Refereed)
    Abstract [en]

    Nanocelluloses have demonstrated good adsorption capacity towards dyes, heavy metal ions, pesticides etc. and combined with their good mechanical strength, high surface area, crystallinity and moisture stability are expected to be a promising functional entity in the next generation of nano-enabled membranes. Furthermore, the large number of functional groups present on the surface of these membranes gives a positive approach to modify the surface according to our needs, thus increasing the selectivity of pollutants. When used in combination with biopolymers/ biodegradable polymers can lead to fully biobased water purification membranes.

  • 84. Mathew, Aji P.
    et al.
    Laborie, Marie
    Washington State University.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cross-Linked Chitosan/Chitin crystal nanocomposites with improved permeation selectivity and pH stability2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 6, p. 1627-1632Article in journal (Refereed)
    Abstract [en]

    This study is aimed at developing and characterizing cross-linked bionanocomposites for membrane applications using chitosan as the matrix, chitin nanocrystals as the functional phase, and gluteraldehyde as the cross-linker. The nanocomposites' chemistry and morphology were examined by estimation of gel content, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and atomic force microscopy (AFM), whereby the occurrence of cross-linking and nanoscale dispersion of chitin in the matrix was confirmed. Besides, cross-linking and chitin whiskers content were both found to impact the water uptake mechanism. Cross-linking provided dimensional stability in acidic medium and significantly decreased the equilibrium water uptake. Incorporation of chitin nanocrystals provided increased permeation selectivity to chitosan in neutral and acidic medium.

  • 85.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bionanocomposite mbranes for water purification: Tailoring the morohology and selectivity for pollutants2013Conference paper (Refereed)
  • 86.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanocellulose and functional material for water cleaning2014Conference paper (Refereed)
  • 87.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanocellulose and Nanochitin in Membrane Applications2014In: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Chapter in book (Refereed)
  • 88.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Kokol, Vanja
    Saarivouri, Elina
    VTT Technical Research Centre of Finland, Espoo.
    Pajula, Tiina
    VTT Technical Research Centre of Finland, Espoo.
    Bio- nanocomposite membranes and adsorbents for water purification: Performance and environmental impacts2014Conference paper (Refereed)
    Abstract [en]

    NanoSelect project deals with the development of fully biobased membranes and adsorbants containing nanocellulose and nanochtin as functional entities to selectively adsorb and remove contaminants from water. Nanocellulose isolated from bioresources or industrial residues showed potential for removal of contaminants from industrial water. Biobased membranes and adsorbents were prepared using native and surface modified nanocellulose as functional additive by different methods as freeze drying, vacuum filtration or coating on support layers. The prepared membranes/ adsorbents had pore structures in the range of ultra and nanofiltration membrane. The mechanical properties of prepared membranes were studied as a function of nanocomposite composition, processing methods, crosslinking and environmental factors. All membranes were stable in use conditions and showed a tensile strength as high as 10 MPa in wet conditions. The developed membranes showed high flux (16X106 L/h/m2/KPa) as well as high percentage removal of dyes (up to 99%) especially when functionalized nanoparticles were used. The results indicate that cheap and efficient biobased membranes prepared by simple processes as vacuum filtration and coating has great potential as water purification membranes in industrial waste water treatment. Furthermore, the environmental performance of the membranes is evaluated based on LCA methodology. This will contribute to the further product development. In the first phase the presumably most significant elements of the value chain in terms of environmental impacts have been identified.

  • 89.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bionanomaterials: Separation Processes, Characterization, and Properties2014In: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Chapter in book (Refereed)
  • 90.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanocomposites for ligament replacement2013In: Production and Applications of Cellulose Nanomaterials, TAPPI Press, 2013, p. 219-222Chapter in book (Refereed)
    Abstract [en]

    Cellulose nanofibers can be considered for biomedical application as cellulose presents low toxicity, biocompatibility and excellent mechanical properties, which make it an excellent candidate for load bearing components in biomedical applications. Two types of composites were developed using the cellulose nanofibers as the reinforcing phase i) All cellulose nanocomposites and ii) Fibrous nanocomposites based on collagen and cellulose nanofibers. The prepared materials showed tensile properties similar to that of natural ligament or tendon, in simulated body conditions. These materials were also found to be biocompatible confirming their potential application in ligament or tendon replacement

  • 91.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanofiber based composites for use as ligament or tendon substitute2010In: International Conference on Nanotechnology for the Forest Products Industry 2010: Otaniemi, Espoo, Finland, 27-29 September 2010, Norcross, GA: TAPPI Press, 2010, p. 980-982Conference paper (Refereed)
    Abstract [en]

    Cellulose nanofibers were isolated from softwood pulp by mechanical fibrillation process and were utilized to develop biobased nanocomposites for biomedical application. Different processing techniques were attempted to develop nanocomposites for use as artificial ligament or tendon and the composites mechanical properties at room conditions as well as at simulated body condition (37 °C and 98 % RH) were studied. These initial studies indicated that the inherent properties like low toxicity, biocompatibility and biodegradability together with excellent mechanical properties of nanocelluloses makes cellulose based nanocomposites an excellent candidate for load bearing components in biomedical applications

  • 92. Mathew, Aji P.
    et al.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chitin nanocomposites for medical applications2010In: Nanocomposites, Weinheim: Wiley-VCH Verlagsgesellschaft, 2010, p. 53-79Chapter in book (Other academic)
  • 93. Mathew, Aji P.
    et al.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mechanical isolation of cellulose nanofibers and their utilization in novel nanocomposites for medical applications2010In: 10th International Conference on Wood & Biofiber Composites & Cellulose Nanocomposites Symposium / [ed] Nicole Stark, Forest Products Society, 2010Conference paper (Other academic)
  • 94.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    ◦Processing of Bionanocomposites: Solution Casting2014In: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Chapter in book (Refereed)
  • 95.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Karim, Zoheb
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Khan, Saad Ahmad
    Naseri, Narges
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Process scale up and characterization of wood cellulose nanocrystals hydrolysed using bioethanol pilot plant2014In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 58, p. 212-219Article in journal (Refereed)
    Abstract [en]

    The paper discusses the isolation of cellulose nanocrystals (CNCBE) from wood resources by integrating the processing with pilot-scale bioethanol processing unit. The nanocrystals were isolated from cellulose obtained by acid pretreatment of wood chips in a bioethanol pilot-scale facility, followed by a series of chemical processes and subsequent homogenization using a lab-scale homogenizer. The isolated nanocrystals had diameters of 5-15 nm, cellulose I crystalline structure and formed a thick semi-transparent gel at low concentration (2 wt%). XPS data showed that these nanocrystals had predominantly O=C-O surface groups which also contributed to its high negative zeta potential. Casted CNCBE films showed excellent mechanical performance (200 MPa of strength, 16 GPa of modulus) and transparency and were also found to be cytocompatible. The developed process route resulted in high-quality nanocellulose crystals with a yield of 600 g/day.

  • 96.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pierron, Dorothée
    Laboratoire d‘Evaluation des Matériaux Implantables (LEMI), Technopole Bordeaux-Montesquieu, 2 allée François Magendie, Martillac.
    Harmad, Marie-Franciose
    Laboratoire d‘Evaluation des Matériaux Implantables (LEMI), Technopole Bordeaux-Montesquieu, 2 allée François Magendie, Martillac.
    Crosslinked fibrous composites based on cellulose nanofibers and collagen with in situ pH induced fibrillation2012In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 1, p. 139-150Article in journal (Refereed)
    Abstract [en]

    Collagen and cellulose nanofiber based composites were prepared by solution casting followed by pH induced in situ partial fibrillation of collagen phase and crosslinking of collagen phase using gluteraldehyde. Microscopy studies on the materials confirmed the presence of fibrous collagen and cellulose nanofibers embedded in the collagen matrix. The cellulose nanofiber addition as well as collagen crosslinking showed significant positive impact on the nanocomposite's mechanical behaviour. The synergistic performance of the nanocomposites indicated stabilization and reinforcement through strong physical entanglement between collagen and cellulose fibres as well as chemical interaction between collagen matrix and collagen fibrils. The mechanical performance and stability in moist conditions showed the potential of these materials as implantable scaffolds in biomedical applications. The collagen-cellulose ratio, crosslinking agent and crosslinking level of collagen may be further optimised to tailor the mechanical properties and cytocompatibility of these composites for specific applications such as artificial ligament or tendon

  • 97.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pierron, Dorothée
    Laboratoire d‘Evaluation des Matériaux Implantables (LEMI), Technopole Bordeaux-Montesquieu, 2 allée François Magendie, Martillac.
    Harmand, Marie-Françoise
    Laboratoire d‘Evaluation des Matériaux Implantables (LEMI), Technopole Bordeaux-Montesquieu, 2 allée François Magendie, Martillac.
    Biocompatible fibrous networks of cellulose nanofibres and collagen crosslinked using genipin: potential as artificial ligament/tendons2013In: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195, Vol. 13, no 3, p. 289-298Article in journal (Refereed)
    Abstract [en]

    Bio-based fibrous nanocomposites of cellulose nanofibres and non-crosslinked/crosslinked collagen were prepared by in situ pH-induced fibrillation of collagen phase and sterilized using gamma rays at 25 KGy. Collagen phase is crosslinked using genipin, a bio-based crosslinker that introduces flexible crosslinks. Microscopy studies of the prepared materials showed nanostructured fibrous collagen and cellulose dispersed in collagen matrix. Mechanical performance of the sterilized nanocomposites was close to that of natural ligament and tendon, in simulated body conditions. Cytocompatibility studies indicated that these nanocomposites allowed human ligament cell and human endothelial cell adhesion, growth, and differentiation; which is eminently favourable to ligament tissue engineering.

  • 98.
    Mathew, Aji P.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pierron, Dorothée
    Laboratoire d‘Evaluation des Matériaux Implantables (LEMI), Technopole Bordeaux-Montesquieu, 2 allée François Magendie, Martillac.
    Harmand, Marie-Françoise
    Laboratoire d‘Evaluation des Matériaux Implantables (LEMI), Technopole Bordeaux-Montesquieu, 2 allée François Magendie, Martillac.
    Fibrous cellulose nanocomposite scaffolds prepared by partial dissolution for potential use as ligament or tendon substitutes2012In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 87, no 3, p. 2291-2298Article in journal (Refereed)
    Abstract [en]

    Fibrous cellulose nanocomposites scaffolds were developed and evaluated for their potential as ligament or tendon substitute. The nanocomposites were prepared by partial dissolution of cellulose nanofiber networks using ionic liquid at 80 °C for different time intervals. Scanning electron microscopy study indicated that partial dissolution resulted in fibrous cellulose nanocomposites where the dissolved cellulose nanofibers formed the matrix phase and the undissolved or partially dissolved nanofibers formed the reinforcing phase. Mechanical properties of the composites in simulated body conditions (37 °C and 95% RH) after sterilization using gamma rays was comparable to those of natural ligaments and tendons. Stress relaxation studies showed stable performance towards cyclic loading and unloading, further confirming the possibility for using these composites as ligament/tendon substitute. In-vitro biocompatibility showed a positive response concerning adhesion/proliferation and differentiation for both human ligament and endothelial cells. Prototypes based on the cellulose composite were developed in the form of tubules to be used for further studies.

  • 99. Mathew, Aji P.
    et al.
    Oksman, Kristiina
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Sain, Mohini
    University of Toronto.
    Mechanical properties of biodegradable composites from poly lactic acid (PLA) and microcrystalline cellulose (MCC)2005In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 97, no 5, p. 2014-2025Article in journal (Refereed)
    Abstract [en]

    Biodegradable composites were prepared using microcrystalline cellulose (MCC) as the reinforcement and polylactic acid (PLA) as a matrix. PLA is polyester of lactic acid and MCC is cellulose derived from high quality wood pulp by acid hydrolysis to remove the amorphous regions. The composites were prepared with different MCC contents, up to 25 wt %, and wood flour (WF) and wood pulp (WP) were used as reference materials. Generally, the MCC/PLA composites showed lower mechanical properties compared to the reference materials. The dynamic mechanical thermal analysis (DMTA) showed that the storage modulus was increased with the addition of MCC. The X-ray diffraction (XRD) studies on the materials showed that the composites were less crystalline than the pure components. However, the scanning electron microscopy (SEM) study of materials showed that the MCC was remaining as aggregates of crystalline cellulose fibrils, which explains the poor mechanical properties. Furthermore, the fracture surfaces of MCC composites were indicative of poor adhesion between MCC and the PLA matrix. Biodegradation studies in compost soil at 58°C showed that WF composites have better biodegradability compared to WP and MCC composites. The composite performances are expected to improve by separation of the cellulose aggregates to microfibrils and with improved adhesion

  • 100. Mathew, Aji P.
    et al.
    Packirisamy, S.
    Mahatma Gandhi University.
    Kumaran, M.G.
    Thomas, Sabu
    Transport of styrene monomer through natural rubber1995In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 36, no 26, p. 4935-4942Article in journal (Refereed)
    Abstract [en]

    The diffusion and transport of inhibitor-free styrene through crosslinked natural rubber (NR) have been studied at various temperatures. NR has been vulcanized by conventional, efficient, peroxide and mixed vulcanization techniques. The dependence of diffusion coefficient on the crosslinking system has been studied for all the systems. The influence of temperature on the sorption and the activation energies of sorption have been calculated. The interaction parameter, permeability, sorption coefficient and molecular weight between crosslinks have been evaluated using the diffusion data. The effect of degree of crosslinking on the sorption characteristics of styrene through NR has also been investigated for the different crosslinking systems. The peroxide system showed lowest uptake and the conventional system showed highest uptake.

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