Flotation separation of chalcopyrite from pyrite using levodopa as a novel depressant under low-alkalinity conditions

Conventional flotation separation methods for Cu–Fe sulfide minerals, such as highly alkaline processes and cyanidation processes, often lead to environmental pollution. As a result, the development of low-alkalinity processes and environmentally friendly reagents has become both critical and challenging. In this study, levodopa (L-dopa) was evaluated as a potential depressant for the flotation separation of Cu–Fe sulfide minerals, with a focus on its selective depressive effect under low-alkalinity conditions. Micro-flotation test showed that, under low-alkalinity conditions, L-dopa at a concentration of 4 × 10 –4 mol/L demonstrated a notable selective depression effect on pyrite. Specifically, the pyrite recovery was only 11.81 %, while chalcopyrite recovery reached 94.53 %. Zeta potential, total organic carbon (TOC), adsorption quantity, and atomic force microscopy (AFM) studies confirmed that L-dopa adsorbed differently on the surfaces of the two minerals. The adsorption of L-dopa on pyrite was substantially stronger than on chalcopyrite. Furthermore, pretreatment with L-dopa effectively hindered KBX adsorption on the pyrite surface, further diminishing its floatability. In contrast, L-dopa had a relatively minor effect on the adsorption of KBX on chalcopyrite. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) analyses indicated that L-dopa was likely chemisorbed onto the pyrite surface, with Fe sites acting as active binding sites. In contrast, the adsorption of L-dopa on chalcopyrite was relatively weak. Thus, L-dopa demonstrated a potent selective depressive effect on pyrite, showing promise for the effective separation of chalcopyrite from pyrite under low-alkalinity conditions.