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[Display omitted] • DL adsorption on sphalerite surfaces with different Fe substitutions is analyzed. • Fe substitution enhances the overall acidity and improves the reactivity. • PDOS and charge transfer analyses confirm space matching and orbital matching. • The micro-flotation and contact angle show strong adsorption of DL on marmatite. • DL is a feasible green selective depressant. Conventional flotation processes often employ cyanide as a depressant for sphalerite, posing environmental concerns. This study investigates the adsorption of 2-Amino-3-mercaptopropionic acid (also known as DL-Cysteine) on sphalerite surfaces with varying degrees of Fe substitution using density functional theory calculations. The focus encompasses electronic properties, charge transfer, and orbital coordination. The potential of DL-cysteine as a sphalerite depressant was assessed and subsequently confirmed experimentally. Our findings indicate that Fe substitution increases the acidity of the mineral surface, thereby enhancing its reactivity to readily interact with the S, O, and N atoms abundant in lone-pair electrons. The Fe-substituted sphalerite surface primarily adsorbs DL-cysteine through interactions with -SH and –NH 2 groups on Fe ions, in contrast to those on Zn ions. Analyses of the partial density of states and charge transfer confirm the spatial and orbital compatibility in the system. Moreover, micro-flotation tests, contact angle measurements, and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy substantiate that DL-cysteine efficaciously adsorbs onto marmatite surfaces, thereby reducing their hydrophobicity. On the contrary, the adsorption strength of sodium diethyldithiocarbamate on the mineral surface is significantly weaker. Overall, the potent adsorption capability of DL-cysteine makes it a viable, eco-friendly depressant alternative for marmatite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Study on adsorption difference of sodium alginate on galena and marmatite. • Iron atom is the main active site on the surface of marmatite. • The existence of iron enhances the bonding strength between SA and marmatite. • Fe2+ can form π-backbonding with SA by providing a pair of π electrons. • vdW, steric effects and weak covalent interactions dominate the adsorption of SA. In this study, density functional theory (DFT) was used to simulate the adsorption of sodium alginate (SA) on the surface of sphalerite, marmatite (1 1 0), and galena (1 0 0). The results showed that SA was mainly adsorbed on the surface of sphalerite by van der Waals interaction and steric hindrance without iron substitution. However, the substitution of iron on the surface of sphalerite significantly increased the adsorption energy of SA. In particular, the substitution of a large amount of iron significantly changed the surface properties of sphalerite, and the adsorption of SA on the surface of sphalerite changed from physical to chemical adsorption. The results of a density of states comparative analysis, charge transfer, and coordination theory analysis also confirmed that the adsorption of SA on a marmatite surface was easier and more stable than that on galena or sphalerite. Overall, the high selectivity of SA is expected to make it a green depressant of marmatite. [ABSTRACT FROM AUTHOR]