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Boosting Copper Sulfide Ore Flotation Efficiency through a Substantial Replacement of Xanthate Collectors with Organosolv Lignin Particles
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. (Biochemical Process Engineering)ORCID iD: 0000-0002-1132-8947
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. (Biochemical Process Engineering)
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. (Biochemical Process Engineering)ORCID iD: 0000-0002-3687-6173
Boliden Mineral AB, SE-936 81 Boliden, Sweden.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The green transition requires a lot of metals or minerals that must be mined and processed. One of the most widely used processes to recover sulfidic minerals is froth flotation. Flotation reagents are necessary for the selective recovery of target minerals. The main purpose of the study was to demonstrate a novel sustainable flotation process for selective extraction of chalcopyrite from sulfide ores, based on partial replacement of fossil-based xanthate flotation collectors with bio-based, biodegradable, and non-toxic organosolv lignin particles. The addition of organosolv lignin particles provided increased recovery of copper by almost 20 % with high selectivity in the rougher flotation. The amount of required xanthate was significantly lowered by 75% in the newly proposed process. In addition, the economical and environmental impact of the whole process could be improved by removal of lime, as pH adjustment through lime addition was not necessary to achieve good selectivity.

Keywords [en]
Organosolv Lignin, Nanoparticles, Froth Flotation, Sulfides, Chalcopyrite
National Category
Chemical Process Engineering
Research subject
Biochemical Process Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-105135OAI: oai:DiVA.org:ltu-105135DiVA, id: diva2:1852192
Available from: 2024-04-17 Created: 2024-04-17 Last updated: 2024-04-17
In thesis
1. Potential of Organosolv Lignin Nanoparticles as a Sustainable Flotation Reagent: Towards a Low-Carbon Footprint Mining Industry
Open this publication in new window or tab >>Potential of Organosolv Lignin Nanoparticles as a Sustainable Flotation Reagent: Towards a Low-Carbon Footprint Mining Industry
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Potential för organosolv lignin nanopartiklar som en hållbar flotations reagens : ett steg mot en gruvindustri med ett lågt koldioxidavtryck
Abstract [en]

The green transition is driving a steep increase in the demand for minerals, which has put the focus on more responsible and sustainable mining practices as there is a growing pressure on mining operations to minimise their environmental footprint, mitigate risks in neighbouring communities, and decrease the consumption of natural resources. In 2022, mineral froth flotation was used to recover 18 million tonnes of copper from copper ore, accounting for 80% of total copper mine output. The mineral froth flotation process can be made more sustainable through the use of bio-based and biodegradable flotation reagents. Currently, xanthates are used as collectors for the recovery of copper-bearing sulfide minerals from sulfide ores. However, xanthates are fossil-based and pose significant risks, particularly to aquatic life and ecosystems. Additionally, a significant part of xanthates is currently obtained from production sites in Asia, which can lead to supply dependency and delays, as evident during the global pandemic.

The aim of this thesis was to develop an efficient, sustainable, and environmentally friendly mineral froth flotation process based on total or partial replacement of xanthates with bio-based, biodegradable, and low-carbon footprint organosolv lignin particles (OLP). The lignin was obtained through organosolv fractionation of residual forest biomass, i.e. spruce and birch. The particles were produced via solvent exchange method from the homogenized lignin solution. As a result, 4 different particle types were produced: birch nanoparticles (BN), birch microparticles (BM), spruce nanoparticles (SN), and spruce microparticles (SM). At first, the characterization and surface chemistry study of the OLP was carried out to deepen the understanding of interaction mechanism between the OLP and mineral surfaces. The lignin was characterized by gel permeation chromatography and nuclear magnetic resonance for its molecular size and content of functional groups. While morphology, surface charge and stability in dispersion of the particles was determined using scanning electron microscopy, ζ-potential, and Turbiscan. All 4 particles were spherical with the diameter around 100 nm for nanoparticles and 1μm for microparticles. The ζ-potential measurement showed the surface variation caused by the difference in size and content of functional groups. Spruce particles, SN and SM, had higher negative charge due to higher content of carboxylic and total phenolic groups. Under alkali conditions, the ζ-potential below -20mV for all particles, with the lowest at −55.1 mV for SM. Finaly, the interaction of OLP with mineral surfaces was examined using quartz crystal microbalance. While the attachment of all OLP was very rigid for both, chalcopyrite and pyrite surfaces, the affinity for attachment was notably greater in the case of pyrite compared to chalcopyrite.

The OLP was tested in proof-of-concept study on three different ore samples, and improvements in the flotation performance was observed, including better selectivity and increased recovery. The further evaluation of the OLP as flotation reagent was conducted with copper ore samples. The flotation trials were carried out with 600 g of ore sample in laboratory flotation cell. Starting with the dosage study, the results were confirmed in rougher-cleaner flotation tests. However, the OLP could not be used as a sole collector, it was shown that significant part of xanthate in the flotation mix could be replaced by OLP resulting in improved copper recovery and selectivity. Additionally, a synergy was observed when the OLP and xanthate mixture was used as combined reagents performed better than each of them separately at the same dosage. The copper recovery was increased from 82.2% to 88.7% in a semi-pilot rougher flotation when 50% of xanthate was replaced by OLP compared to the xanthate alone. Significant depression of iron recovery was observed when the OLP was utilized, even in absence of lime. Thus, the OLP reagents eliminated the need for lime, which is required on an industrial scale. Further positive effect of OLP application was indicated recovery of other valuable elements in the concentrates, such as cobalt and molybdenum, while there was no increase in penalty elements. The amount of OLP needed was up to 10 g/ton of ore, which is very small amount, and it is roughly 10 times less compared to any other modifier used in such a process. Therefore, this thesis demonstrates the potential of OLP as flotation reagent. If implemented, the proposed flotation system would lead to better resource efficiency and lower environmental impact.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2024
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Organosolv lignin particles, Nanoparticles, Flotation reagent, Copper recovery
National Category
Chemical Process Engineering
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-105140 (URN)978-91-8048-542-5 (ISBN)978-91-8048-543-2 (ISBN)
Public defence
2024-09-26, C305, Luleå University of Technology, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2024-04-17 Created: 2024-04-17 Last updated: 2024-05-30Bibliographically approved

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