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Yang, Xiaofang
Publications (10 of 15) Show all publications
Dobryden, I., Yang, X., Almqvist, N., Holmgren, A. & Weber, H. (2013). An atomic force microscopy study of the interaction between magnetite particles: the effect of Ca2 + ions and pH (ed.). Paper presented at . Powder Technology, 233, 116-122
Open this publication in new window or tab >>An atomic force microscopy study of the interaction between magnetite particles: the effect of Ca2 + ions and pH
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2013 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, p. 116-122Article in journal (Refereed) Published
Abstract [en]

Force interactions between a microsize (m-s) magnetite probe and thin layers of synthesized magnetite particles as well as microsize (m-s) magnetite particles from magnetite concentrate were investigated using atomic force microscopy (AFM). Of special interest was the influence of Ca2 + ions and pH on the interaction between the probe and the two different magnetite particle surfaces. The probe and the magnetite surfaces were immersed in aqueous Ca2 + solutions (100, 10, and 1 mM) at various pH values (4, 6, and 10). The colloidal probe technique and a self-made computer program for automatic evaluation of adhesion forces were used. The analysis revealed an increase in adhesion force with increased calcium concentration at pH 6 for both the systems investigated. However, the adhesion behavior between the probe and the m-s and n-s magnetite particle surfaces is different at pH 10. The possible appearance of calcium carbonate precipitated onto the magnetite surfaces as well as the possible influence of already adsorbed silicate on magnetite particles from the concentrate is discussed. In addition to Ca, Cl and Na atoms, added to the working solutions, and the Fe and O detected signals, the SEM-EDS analysis also detected Si atoms on the surface of the m-s particles.

National Category
Other Physics Topics Physical Chemistry
Research subject
Experimental physics; Chemistry of Interfaces; Tillämpad fysik
Identifiers
urn:nbn:se:ltu:diva-13181 (URN)10.1016/j.powtec.2012.09.003 (DOI)000311134200014 ()2-s2.0-84867798457 (Scopus ID)c5e89ce0-75e4-467d-9005-64a33b60e9a9 (Local ID)c5e89ce0-75e4-467d-9005-64a33b60e9a9 (Archive number)c5e89ce0-75e4-467d-9005-64a33b60e9a9 (OAI)
Note
Validerad; 2013; 20120914 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Potapova, E., Yang, X., Westerstrand, M., Grahn, M., Holmgren, A. & Hedlund, J. (2012). Interfacial properties of natural magnetite particles compared with their synthetic analogue (ed.). Paper presented at . Minerals Engineering, 36-38(S1), 187-194
Open this publication in new window or tab >>Interfacial properties of natural magnetite particles compared with their synthetic analogue
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2012 (English)In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 36-38, no S1, p. 187-194Article in journal (Refereed) Published
Abstract [en]

Understanding of the interactions between iron oxides and flotation reagents is important both for flotation and agglomeration of iron ore. Model systems comprising synthetic iron oxides and pure chemical reagents are commonly applied in experimental work in order to obtain high quality data and to ease the interpretation of the empirical data. Whether the results obtained using model systems are valid for iron ore minerals and commercial reagents is a question seldom addressed in the literature. It is shown in this work that previously reported results obtained from a model system, concerning adsorption of a carboxylate surfactant and sodium metasilicate onto synthetic magnetite nanoparticles, as obtained by in situ ATR-FTIR spectroscopy and contact angle measurements, are applicable to adsorption of flotation reagents on magnetite concentrate. Additionally, the problem of restoring magnetite wetting after flotation is addressed since good wetting of a magnetite concentrate is required to produce iron ore pellets by wet agglomeration. The results from the present work indicate that the wettability of both synthetic magnetite coated with surfactant and magnetite concentrate after flotation can be improved by adsorbing a hydrophilizing agent such as silicate or polyacrylate.

National Category
Chemical Process Engineering Physical Chemistry
Research subject
Chemical Technology; Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-4833 (URN)10.1016/j.mineng.2012.03.030 (DOI)000311773100026 ()2-s2.0-84867745073 (Scopus ID)2d28d52d-6bfd-4b9f-bfe7-c7cf376dc86b (Local ID)2d28d52d-6bfd-4b9f-bfe7-c7cf376dc86b (Archive number)2d28d52d-6bfd-4b9f-bfe7-c7cf376dc86b (OAI)
Note
Validerad; 2012; 20111214 (elipot)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Zheng, T.-T., Sun, Z.-X., Yang, X. & Holmgren, A. (2012). Sorption of phosphate onto mesoporous gamma-alumina studied with in-situ ATR-FTIR spectroscopy (ed.). Paper presented at . Chemistry Central Journal, 6
Open this publication in new window or tab >>Sorption of phosphate onto mesoporous gamma-alumina studied with in-situ ATR-FTIR spectroscopy
2012 (English)In: Chemistry Central Journal, ISSN 1752-153X, E-ISSN 1752-153X, Vol. 6Article in journal (Refereed) Published
National Category
Physical Chemistry
Research subject
Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-7679 (URN)10.1186/1752-153X-6-26 (DOI)000308745300001 ()2-s2.0-84859196487 (Scopus ID)6152e3c8-6aa5-4480-9aab-b6e88727bcd8 (Local ID)6152e3c8-6aa5-4480-9aab-b6e88727bcd8 (Archive number)6152e3c8-6aa5-4480-9aab-b6e88727bcd8 (OAI)
Note
Validerad; 2012; Bibliografisk uppgift: Article Number: 26 ; 20120405 (alho)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Dobryden, I., Yang, X., Almqvist, N., Weber, H. & Holmgren, A. (2011). Interaction forces between surface modified magnetite particles in aqueous solution (ed.). Paper presented at International Symposium on Colloids and Materials : 08/05/2011 - 11/05/2011. Paper presented at International Symposium on Colloids and Materials : 08/05/2011 - 11/05/2011.
Open this publication in new window or tab >>Interaction forces between surface modified magnetite particles in aqueous solution
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2011 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Other Physics Topics Physical Chemistry Other Physics Topics Chemical Process Engineering
Research subject
Experimental physics; Physical Chemistry; Tillämpad fysik; Chemical Technology
Identifiers
urn:nbn:se:ltu:diva-38930 (URN)d7d2f537-50da-488e-afc5-d8607414a403 (Local ID)d7d2f537-50da-488e-afc5-d8607414a403 (Archive number)d7d2f537-50da-488e-afc5-d8607414a403 (OAI)
Conference
International Symposium on Colloids and Materials : 08/05/2011 - 11/05/2011
Note
Godkänd; 2011; 20130306 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2018-04-26Bibliographically approved
Yang, X. (2011). Interaction of magnetite with soluble silicates and bentonite: implications for wet agglomeration of magnetite concentrate (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Interaction of magnetite with soluble silicates and bentonite: implications for wet agglomeration of magnetite concentrate
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Iron ore green pellets are produced by agglomeration of moist magnetite concentrates. The quality of green pellets is essential for the transportability and metallurgical benefits of the final product. The agglomeration behavior of magnetite concentrate particles is strongly influenced by its surface properties which are affected by the interactions with flotation reagents (i.e. water glass and collector) and species in process water. However, the mechanisms of these interactions and the influence on the following agglomeration process are still not completely understood. The present work has been focused on the interaction of magnetite with water glass (sodium silicate) and bentonite clay (silicate mineral) aiming for better fundamental knowledge of the magnetite surface properties in order to improve the agglomeration behavior of the magnetite concentrate. Water glass is used as a dispersing or depressing agent in flotation of magnetite. The former function is to improve the separation of mineral particles in the pulp, while the latter function is to protect the magnetite surfaces from attachment of the collector which is known to cause problems in the subsequent agglomeration process. Sodium activated bentonite clay is commonly used as an external binder in iron ore agglomeration owing to its swelling properties. The particle interaction between magnetite and bentonite platelets, which is expected to be affected by the surface properties of magnetite, is of importance for the wet and dry strength of the pellets. Sorption mechanisms of sodium silicate onto the magnetite surface at the molecular scale were studied at various pH and silicate concentrations using in-situ ATR-FTIR spectroscopy. Silicate concentration, pH, and conditioning time are the most important factors for silicate sorption and speciation at the surface of magnetite. A maximum sorption was observed in the pH range 8.5 - 9.5. Oligomeric or polymeric silicate species are formed and dominate at high surface loading of silicate. These oligomeric or polymerized species have stronger affinity for the magnetite as compared to monomeric species, resulting in a slower and less extent of desorption and implying a higher depressing efficiency in flotation. Sodium silicate makes the magnetite surface more negatively charged, while adsorbed calcium ions on the surface compensate this negative surface charge. Calcium ions promote the oligomerization of silicate on the surface of magnetite at high pH (pH > 10) possibly due to the increased local silicate concentration by additional sorption of silicate on adsorbed calcium at the surface. The competitive sorption between sodium silicate and collector (sodium oleate) for the magnetite surface was studied using the in situ ATR-FTIR technique. It was confirmed that oleate could still be adsorbed onto a sodium silicate modified magnetite surface but the amount of adsorbed oleate decreased with increasing concentration of silicate (0.1 - 5 mmol•L-1). This depression effect became much more significant when the concentration of sodium silicate was higher than 0.4 mmol•L-1 above which more dimers or oligomeric silicate species were formed at the magnetite surface. However, when the magnetite surface was pre-treated firstly with sodium oleate, the addition of sodium silicate only slightly reduced the adsorption of oleate. Meanwhile, the sorption of silicate anions was depressed and resulted in a lower degree of oligomerization or polymerization at high silicate dosage. Sessile drop method and Wilhelmy method were used to measure the water contact angle of synthesized magnetite, and Washburn method was used for contact angle measurements of magnetite concentrate. The synthesized magnetite has lower contact angle compared to mineral particles. Nevertheless, similar tendency of changes in wettability upon interaction with calcium, sodium silicate and collector was observed for synthesized magnetite and magnetite concentrate. Sorption of calcium and silicate increased the wettability of the surface, while adsorption of collector made the surface more hydrophobic. Further exposure of the collector modified magnetite surface to sodium silicate could restore the surface wettability. Therefore, an interesting implication for magnetite flotation and agglomeration is that the decreased hydrophilicity of magnetite by attachment of collector could be improved by further chemical conditioning with sodium silicate (water glass). The interaction of bentonite with magnetite was investigated by means of settling of bentonite platelets onto a layer of magnetite nano-particles. The magnetite layer was deposited on a horizontal ZnSe crystal to be able to examine the orientation of the platelets by polarized ATR-FTIR. The measured dichroic ratio of the bentonite platelets decreased with time in wet film and approached a minimum value in the dry bentonite film regardless of the pH of the bentonite suspension. This tendency is in good agreement with the results observed for settling on bare crystal, indicating a more ordered structure of platelets upon evaporation of water. The bentonite platelets in dry film were evidently tending to orient with their basal plane surfaces to the magnetite layer, whilst wet films adopted a much more disordered structure. Similarly, a rather disordered wet bentonite film was formed on the calcium and sodium silicate modified magnetite layer. These bentonite platelets became more ordered when the wet film was dried.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2011. p. 88
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Physical Chemistry Physical Chemistry
Research subject
Physical Chemistry; Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-17217 (URN)238860e0-ca36-46ff-bbfc-042efccc444c (Local ID)978-91-7439-210-4 (ISBN)238860e0-ca36-46ff-bbfc-042efccc444c (Archive number)238860e0-ca36-46ff-bbfc-042efccc444c (OAI)
Note

Godkänd; 2011; 20110118 (xiayan); Opponent: Prof. James McQuillan, University of Otago, New Zealand Date and Time: 2011-02-23, 10.15 Place: C305, LTU campus

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-03-15Bibliographically approved
Potapova, E., Yang, X., Grahn, M., Holmgren, A., Forsmo, S., Fredriksson, A. & Hedlund, J. (2011). The effect of calcium ions, sodium silicate and surfactant on charge and wettability of magnetite (ed.). Paper presented at . Colloids and Surfaces A: Physicochemical and Engineering Aspects, 386(1-3), 79-86
Open this publication in new window or tab >>The effect of calcium ions, sodium silicate and surfactant on charge and wettability of magnetite
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2011 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 386, no 1-3, p. 79-86Article in journal (Refereed) Published
Abstract [en]

Anionic carboxylate surfactants and sodium silicate are used in the reverse flotation of iron ore to separate magnetite from apatite. In this work, consecutive adsorption of sodium silicate and an anionic surfactant on synthetic magnetite modified with calcium ions was studied in the pH range 7.5–9.5 using in situ ATR-FTIR spectroscopy. The effect of these chemicals on the zeta-potential and wetting properties of magnetite was also investigated. While adsorption of silicate increased with increasing pH, subsequent surfactant adsorption went through a maximum at pH 8.5. Surfactant adsorption in the presence of calcium ions was not affected by the amount of silicate adsorbed on magnetite. Calcium ions were found to render the magnetite surface positive in the pH range 3–10 and could reduce the dispersing effect of silicate in flotation of apatite from magnetite. While treatment with calcium chloride and sodium silicate made magnetite more hydrophilic, subsequent adsorption of the anionic surfactant increased the water contact angle on the magnetite surface from about 10° to 40–50°. Although the latter values are not high enough to make magnetite float, the hydrophobic areas on the magnetite surface could result in the incorporation of air bubbles inside the iron ore pellets produced by wet agglomeration, lowering the pellet strength.

National Category
Chemical Process Engineering Physical Chemistry
Research subject
Chemical Technology; Physical Chemistry
Identifiers
urn:nbn:se:ltu:diva-12889 (URN)10.1016/j.colsurfa.2011.06.029 (DOI)000295150100010 ()2-s2.0-80051553435 (Scopus ID)c0b18926-68e7-421e-8e9c-bc8570a51435 (Local ID)c0b18926-68e7-421e-8e9c-bc8570a51435 (Archive number)c0b18926-68e7-421e-8e9c-bc8570a51435 (OAI)
Note
Validerad; 2011; 20110706 (elipot)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Yang, X., Dongsheng, W., Zhongxi, S., Huijuan, L. & Holmgren, A. (2010). Application of ATR-FTIR spectroscopy in the study of adsorption on environmental micro-interfaces (ed.). Paper presented at . Huaxue jinzhan, 22(6), 1185-1194
Open this publication in new window or tab >>Application of ATR-FTIR spectroscopy in the study of adsorption on environmental micro-interfaces
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2010 (English)In: Huaxue jinzhan, ISSN 1005-281X, Vol. 22, no 6, p. 1185-1194Article in journal (Refereed) Published
Abstract [en]

Interfacial adsorption process is the initial step or key step for most of environmental micro-interface reactions. The online study of environmental micro-interfacial adsorption by in situ research methods provides direct information about interface reactions and reliable evidence for the detection of reaction mechanisms which are of great importance to understand the rule of transformation and distribution of pollutants in the environment. Because of its unique sampling principle, convenient sample pre-treatment and wide applicability, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) is becoming a powerful tool for investigating the interface reactions. Based on a brief introduction of the working principle of ATR-FTIR, the application of this technique in the investigation of adsorption on environmental interfaces, especially mineral-water interfaces, is summarized. Furthermore, the perspective of this method is discussed as well.

National Category
Physical Chemistry
Research subject
Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-13863 (URN)d2a5ce90-980e-11df-8806-000ea68e967b (Local ID)d2a5ce90-980e-11df-8806-000ea68e967b (Archive number)d2a5ce90-980e-11df-8806-000ea68e967b (OAI)
Note
Validerad; 2010; 20100725 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-04-05Bibliographically approved
Roonasi, P., Yang, X. & Holmgren, A. (2010). Competition between sodium oleate and sodium silicate for a silicate/oleate modified magnetite surface studied by in-situ ATR-FTIR Spectroscopy (ed.). Paper presented at . Journal of Colloid and Interface Science, 343(2), 546-552
Open this publication in new window or tab >>Competition between sodium oleate and sodium silicate for a silicate/oleate modified magnetite surface studied by in-situ ATR-FTIR Spectroscopy
2010 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, no 2, p. 546-552Article in journal (Refereed) Published
Abstract [en]

Attenuated Total Reflection (ATR) IR spectroscopy was utilized to monitor adsorption of sodium oleate and sodium silicate onto synthetic magnetite at pH=8.5, both individually and in a competitive manner. Oleate was adsorbed within a concentration range of 0.01 mM-0.5 mM. It was observed that adsorption of oleate increased linearly with increasing concentration of oleate in solution up to a concentration of 0.1 mM. The infrared spectrum of oleate showed a broad single band at 1535 cm-1 assigned to the asymmetric stretching vibration of carboxylate, implying chemisorption of oleate to the magnetite surface. The kinetics of oleate adsorption followed a pseudo first-order reaction with an apparent rate constant of k1= 0.030 ± 0.002 min-1. Competitve adsorption of silicate and oleate was performed either by adding silicate solution to a magnetite film initially equilibrated with 0.1 mM oleate or adding oleate solution to magnetite treated with silicate solutions in the concentration range 0.1 mM - 5mM. It was shown that silicate, within reasonable time, had only minor effect on the amount of oleate already adsorbed on magnetite. On the other hand, oleate did not efficiently compete with silicate if the latter substance was already adsorbed on the iron oxide.

National Category
Physical Chemistry
Research subject
Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-5691 (URN)10.1016/j.jcis.2009.12.002 (DOI)000274602200019 ()20060541 (PubMedID)2-s2.0-75349114732 (Scopus ID)3daf7090-e655-11de-bae5-000ea68e967b (Local ID)3daf7090-e655-11de-bae5-000ea68e967b (Archive number)3daf7090-e655-11de-bae5-000ea68e967b (OAI)
Note
Validerad; 2010; 20091211 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Potapova, E., Yang, X., Sammelin, D., Grahn, M., Holmgren, A. & Fredriksson, A. (2010). Surfactant adsorption at the iron oxide/water interface: the effect of pH, silicate and calcium ions (ed.). Paper presented at Conference of the European Colloid and Interface Society : 05/09/2010 - 10/09/2010. Paper presented at Conference of the European Colloid and Interface Society : 05/09/2010 - 10/09/2010.
Open this publication in new window or tab >>Surfactant adsorption at the iron oxide/water interface: the effect of pH, silicate and calcium ions
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2010 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Chemical Process Engineering Physical Chemistry
Research subject
Chemical Technology; Physical Chemistry
Identifiers
urn:nbn:se:ltu:diva-32473 (URN)6fab6d50-c616-11df-a707-000ea68e967b (Local ID)6fab6d50-c616-11df-a707-000ea68e967b (Archive number)6fab6d50-c616-11df-a707-000ea68e967b (OAI)
Conference
Conference of the European Colloid and Interface Society : 05/09/2010 - 10/09/2010
Note
Godkänd; 2010; 20100922 (linste)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-04-05Bibliographically approved
Yang, X., Roonasi, P., Jolsterå, R. & Holmgren, A. (2009). Kinetics of silicate sorption on magnetite and maghemite: an in-situ ATR-FTIR study (ed.). Paper presented at . Colloids and Surfaces A: Physicochemical and Engineering Aspects, 343(1-3), 24-29
Open this publication in new window or tab >>Kinetics of silicate sorption on magnetite and maghemite: an in-situ ATR-FTIR study
2009 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 343, no 1-3, p. 24-29Article in journal (Refereed) Published
Abstract [en]

Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to monitor the in situ sorption of sodium metasilicate from aqueous solution onto synthesized magnetite and maghemite particles in the pH range 10.8-7.0 using silicate concentrations between 0.1 mM and 5 mM. The spectral data showed that both pH and silicate concentration had great influence on the interfacial reaction between soluble silicate and the iron oxide surfaces, regarding the amount adsorbed per unit mass of iron oxide and the surface species formed. A pH dependent sorption of silicate on iron oxides was observed, implying that a maximum sorption took place in the pH range of 9.5 - 7.0. All experiments showed a fast initial increase in the absorption intensity followed by a slower sorption stage which was strongly dependent on the concentration of silicate in solution and the pH value. The amount of sorption onto magnetite was 3 to 5 times larger than onto maghemite, but there was no significant difference in the line shape of corresponding absorption bands. At pH 8.5 and low concentration (≤ 0.1 mM), the silicate monomers dominate in solution and on the iron oxide surface also monomeric species were dominating as evident from the infrared band at 950 cm-1. However, at higher concentration (0.4-5.0 mM), the dominating absorption band at about 1000 cm-1 shifted to higher frequency during the sorption indicating that oligomeric surface silicate species were formed on the iron oxide surface. Desorption of silicate from the surface of the iron oxides was easier to accomplish at low silicate concentration, whilst the highest concentration showed a comparatively low relative amount of desorbed silicate, suggesting that polymerized species had a stronger affinity for the iron oxide surface as compared to monomeric species.

National Category
Physical Chemistry
Research subject
Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-6519 (URN)10.1016/j.colsurfa.2009.01.041 (DOI)000267527600006 ()2-s2.0-67349175994 (Scopus ID)4befcbb0-3010-11de-bd0f-000ea68e967b (Local ID)4befcbb0-3010-11de-bd0f-000ea68e967b (Archive number)4befcbb0-3010-11de-bd0f-000ea68e967b (OAI)
Note
Validerad; 2009; 20090423 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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