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Carboxymethyl Chitosan as a Selective Depressant in Differential Flotation of Galena and Chalcopyrite Open Access


Other title
sulfide minerals
differential flotation
carboxymethyl chitosan
Type of item
Degree grantor
University of Alberta
Author or creator
Xiang, Yahui
Supervisor and department
Liu, Qi (Chemical and Materials Engineering)
Examining committee member and department
Afacan, Artin (Chemical and Materials Engineering)
Choi, Phillip YK (Chemical and Materials Engineering)
Liu, Qi (Chemical and Materials Engineering)
Etsell, Thomas H (Chemical and Materials Engineering)
Department of Chemical and Materials Engineering
Chemical Engineering
Date accepted
Graduation date
Master of Science
Degree level
Toxic inorganic depressants are routinely used in the differential flotation of polymetallic sulfide ores and it is desirable that they be replaced with environmentally benign chemicals. Chitosan, as a natural and non-toxic polymer, has been proven to be an efficient depressant for copper sulfide (e.g., chalcopyrite) while allowing lead sulfide (e.g., galena) to be floated by xanthate collectors. However, the poor solubility of chitosan limits its potential applications as the flotation could only be carried out at about pH 4 where chitosan is soluble. Three carboxymethyl derivatives of chitosan, named N-CMC, O-CMC and N-O-CMC, were synthesized by introducing carboxymethyl groups on the backbones of chitosan. The substitution on amino groups significantly improved the solubility of chitosan. The structures of CMC were studied and compared with chitosan via Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (NMR) spectrometry. Flotation tests were performed on single minerals and mineral mixtures (with weight ratio of 1:1) with the addition of appropriate amounts of potassium ethyl xanthate (KEX) and N-CMC. The solution pH was varied from neutral to alkaline. The flotation concentrates and tailings were collected and analysed for the contents of copper and lead. Single mineral flotation tests indicated that N-CMC could depress either chalcopyrite or galena depending on pH. The results were not affected by the sequence of KEX and N-CMC addition. Therefore, N-CMC is potentially useful in Cu-Pb sulfide separation following a bulk Cu-Pb flotation. The N-CMC was also found to have surface cleaning functions, and was able to remove contaminating copper ions from galena surfaces. The adsorption mechanisms of N-CMC on sulfide minerals were then delineated by several analysis techniques. Metal ions binding tests showed that N-CMC had a stronger interaction with Cu2+ than Pb2+. The distribution of N-CMC on mineral mixtures was mapped out by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results of ToF-SIMS analysis confirmed that N-CMC preferentially adsorbed on chalcopyrite at pH 7 but uniformly distributed on both minerals at pH 10. The high resolution N 1s X-ray photoelectron spectroscopic (XPS) spectra of N-CMC-treated chalcopyrite and galena showed that chemical bonds formed between the secondary amino groups of N-CMC and both mineral surfaces. At pH 7, the bond with Cu was stronger than with Pb, while at pH 10, one additional bond was formed between N-CMC and Pb. Zeta-potential measurements showed the presence of electrostatic interaction between N-CMC and both chalcopyrite and galena, but it was not the reason for N-CMC’s selective depression of chalcopyrite. Mineral surface cleaning tests explained the good flotation result in the absence of any chelating reagents, such as EDTA, since N-CMC also possesses the similar function of removing the Cu2+ adsorbed on the galena surface. Overall, the application of N-CMC in sulfide ore flotation is expected to be more robust than the original chitosan.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Xiang, Yahui., Wang, Kaipeng., Liu, Qi. (2014). N-carboxymethyl chitosan in differential flotation of galena and chalcopyrite. In proceedings of XXVII International Mineral Processing Conference, pp 57-67.

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