Abstract: The flotation separation of columbite from hematite is notoriously challenging due to their similar surface prop erties.To achieve efficient separation,this study systematically investigated the depression behavior and mechanism of ethylene diamine tetraacetic acid (EDTA) as a selective depressant in a benzohydroxamic acid (BHA) flotation system.Micro-flotation tests on pure and artificially mixed minerals were conducted,complemented by contact angle measurements,Zeta potential anal ysis,Fourier transform infrared spectroscopy (FTIR),and X-ray photoelectron spectroscopy (XPS).The results demonstrated that EDTA selectively and strongly depressed columbite while exerting a negligible effect on hematite.Under the optimized con ditions (pH=8.0,EDTA dosage of 75 mg/L,BHA concentration of 1.0×10-2 mol/L),the flotation recovery of columbite in pure mineral tests was drastically reduced to 13.04%,whereas that of hematite remained high at 91.52%.Consequently,a high-quality niobium concentrate with a Nb2 O5 grade of 63.66% and a recovery of 83.33% was obtained from the artificial mixed ore flotation.Mechanistic studies revealed that EDTA preferentially chelates and adsorbs onto the Nb active sites on the columbite surface,thereby preventing the subsequent adsorption of the collector BHA.In contrast,its adsorption on the hematite surface was too weak to interfere with BHA collection.This work confirms EDTA as an effective depressant for the flotation sep aration of columbite from hematite,offering a novel strategy for beneficiating such complex associated ores.

Key words: EDTA,columbite,hematite,reverseflotation,adsorptionmechanism