To solve the problem of mechanical entrainment and slime coating of fine sericite and chlorite hindering the flotation separation of gold-bearing pyrite in low-grade gold ores, ethylenediamine-N,N’-disuccinic acid (EDDS) was innovatively used as a selective and eco-friendly depressant. A systematic set of tests, including micro-flotation, artificial mixed mineral flotation, zeta potential measurement, adsorption capacity test, solution chemistry analysis and X-ray photoelectron spectroscopy (XPS) characterization, was conducted to explore its flotation performance and action mechanism. The results showed that pH 8 and 200 mg/L EDDS were the optimal conditions under which EDDS reduced the recoveries of sericite and chlorite to ~20% and ~15%, respectively, while restoring pyrite recovery to ~80% with a notable upgrade in concentrate grade. EDDS exhibited strong chemical adsorption on sericite and chlorite via chelating their active Al/Mg sites, significantly enhancing their hydrophilicity. In contrast, it only undergoes weak physical adsorption on pyrite, with negligible observed influence on its hydrophobicity and the adsorption of (sodium butyl xanthate) SBX. At pH 8, EDDS mainly existed as HEDDS3− (~90%), whose triple negative charge strengthened electrostatic interaction with positively charged gangue surfaces, boosting selective adsorption. This study confirms EDDS as a highly efficient depressant for pyrite–sericite/chlorite flotation under pure mineral and artificial mixed mineral conditions. Since the present study is based on pure minerals and artificial mixtures, further validation using real ore samples is still required before practical industrial application. This research expands the application of EDDS in mineral processing and provides a novel eco-friendly technical approach for the laboratory-scale separation of fine gold-bearing pyrite from low-grade gold ores with high clay gangue content.
Qian et al. (2026) studied this question.