Selective depression mechanism of ferric chromium lignin sulfonate for chalcopyrite–galena flotation separation

Selective recovery of chalcopyrite–galena ore by flotation remains a challenging issue. The development of highly efficient, low-cost, and environmentally friendly depressants for this flotation is necessary because most of available reagents (e.g., K₂Cr₂O₄) are expensive and adversely affect the environment. In this study, ferric chromium lignin sulfonate (FCLS), which is a waste-product from the paper and pulp industry, was introduced as a selective depressant for galena with butyl xanthate (BX) as a collector. Results show that the residue recovery of Pb in Cu concentrate was substantially reduced to 4.73% using FCLS compared with 10.71% using the common depressant K₂Cr₂O₄. The underlying mechanisms were revealed using zeta-potential measurements and X-ray photoelectron spectroscopy (XPS). Zeta-potential measurements revealed that FCLS was more efficiently absorbed onto galena than onto chalcopyrite. XPS measurements further suggested that FCLS enhanced the surface oxidation of galena but prevented that of chalcopyrite. Thus, FCLS could be a potential candidate as a depressant for chalcopyrite–galena flotation because of its low cost and its lack of detrimental effects on the environment.