Chitosan in differential flotation of base metal sulfides

Chitosan, a naturally occurring polymer, was studied as a potential selective depressant in the differential flotation of sulfide minerals. In single mineral flotation tests, chalcopyrite, galena, sphalerite and pyrite were depressed to different extents. However, in the differential flotation of the sulfide mineral mixtures (Cu-Pb, Zn-Pb and Fe-Pb), chitosan selectively depressed chalcopyrite, sphalerite or pyrite while galena was selectively floated using xanthate as a collector.;X-ray photoelectron spectroscopic (XPS) analyses were performed to study the adsorption mechanisms between chitosan and the sulphide minerals. High resolution binding energy spectra of N 1s and O 1s electrons were obtained for chitosan-treated chalcopyrite, sphalerite, pyrite, and galena. The spectra showed chemical shifts of the N 1s electrons of the protonated amine groups and the O 1s electrons of the hydroxyl groups from chitosan. Therefore it was concluded that the selective adsorption of chitosan on chalcopyrite, sphalerite and pyrite was due to a strong chemical interaction between the surface copper, zinc or iron atoms and the amine and the hydroxyl groups on chitosan. No such a strong interaction was observed between galena and chitosan. The competitive adsorption was attributed to the differences in the electron affinity of the lattice metal ions. Chitosan was found to bind strongly with metal ions with a high electron affinity.;To delineate the adsorption mechanisms of chitosan on the sulfide minerals, several surface analysis techniques were applied. Time-of-flight secondary ion mass spectrometric (ToF-SIMS) measurements were conducted to map chitosan distribution on the different mineral surfaces within a mineral mixture. The ToF-SIMS measurements showed that chitosan preferentially adsorbed on chalcopyrite, sphalerite or pyrite but not on galena in the chalcopyrite-galena, sphalerite-galena and pyrite-galena mixtures.