Selective depression of pyrite with a novel functionally modified biopolymer in a Cu-Fe flotation system

In the flotation of copper sulfides, pyrite is often activated by Cu2+ ions dissolved from copper-bearing minerals in alkaline media (pH 9), which results in pyrite entering the copper concentrate. To reduce the floatability of pyrite, we designed a novel functionally modified biopolymer, tricarboxylate sodium starch (TCSS), that showed superior depression selectivity towards pyrite in low pH solutions when employed in Cu-Fe flotation separation in the presence of sodium butyl xanthate (SBX) as a collector. TCSS depressed the floatability of pyrite more strongly than that of chalcopyrite in single mineral flotation in the pH range 4-6. The most selective separation was achieved at pH similar to 6; the recovery of Cu in the concentrate was over 77%, and the grade was improved to 24.50% compared to the initial feed grade of 12.50%. Surface characterization analyses, including zeta potential, X-ray photoelectron spectroscopy (XPS) analysis, and Fourier transform infrared (FTIR) spectroscopy, confirmed the different degrees of interaction of TCSS with the two minerals. TCSS was adsorbed on the pyrite surface, possibly via a chemisorption mechanism, as reflected in the FTIR and XPS analyses. The adsorption of TCSS passivated the pyrite surface, which inhibited the adsorption and oxidation of the collector. On the other hand, the adsorption and oxidation of the collector on chalcopyrite surface were effective even in the presence of TCSS, attesting to the weak interactions between chalcopyrite and TCSS.