Adsorption of chitosan on chalcopyrite and galena from aqueous suspensions

Chitosan was recently found to be a potential replacement for toxic inorganic depressants commonly used in the flotation separation of Cu–Pb sulfide minerals. The current work focused on the interaction mechanisms and investigated the reasons for the preferential adsorption of chitosan on copper sulfide (chalcopyrite) over lead sulfide (galena). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) were employed in the study. ATR-FTIR spectra of chitosan showed that the absorption peaks due to amino groups shifted upon adsorption on chalcopyrite. High resolution XPS spectra detected binding energy shifts of N 1s and O 1s electrons on chitosan-treated chalcopyrite. ToF-SIMS ion mass spectra revealed CuNH3 as the dominant stable species as a result of chalcopyrite–chitosan interactions. It was therefore concluded that the adsorption of chitosan on chalcopyrite was due to a strong chemical interaction between the surface copper atoms and the protonated amine as well as the hydroxyl groups on chitosan. Such a strong chemical interaction was not observed on galena.

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► Chitosan chemisorbed on chalcopyrite through the deacetylated (amine) groups.
► Chitosan physically adsorbed on galena through the acetylated groups.
► Chitosan selectively adsorbed on chalcopyrite when both minerals are present.
► The selectivity was higher for chitosan with a higher degree of deacetylation.