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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] • DFT calculations revealed the mechanism of flotation depressant by nitrobenzoates. • All positional isomers of nitrobenzoates had same reactive sites. • The unoccupied π orbitals in flotation depressant can form covalent bonds with π orbitals on the mineral surface. Nitrobenzoate can effectively depressor the flotation of arsenopyrite, making theoretical studies to elucidate the mechanism essential. This study investigates the structure-reactivity relationship of nitrobenzoate as a flotation depressant for arsenopyrite by density functional theory calculations. The results revealed that O/N heteroatoms participated in the formation of chemical bonds with the metal atoms on the mineral surface as o-nitrobenzoate, m-nitrobenzoate, and p-nitrobenzoate molecules and had significant chemical reactivities. The interaction of the flotation depressant with the mineral surface followed the order: m-nitrobenzoate > p-nitrobenzoate > o-nitrobenzoate, which was further confirmed by flotation experiments. Furthermore, the reactive sites of the three nitrobenzoate isomers were investigated, and the results revealed that all three isomers had the same reactive sites, but interacted differently with the metal atoms. [ABSTRACT FROM AUTHOR]

The selective interaction of reagents with mineral surfaces is the core basis for mineral flotation separation. Herein, the interaction mechanism of a novel depressant m-nitrobenzoate with arsenopyrite has been investigated with the help of density functional theory (DFT) simulations, supplemented by micro-flotation tests and X-ray photoelectron spectroscopy (XPS) analyses. It is found that the adsorption of m-nitrobenzoate on the surface of arsenopyrite was mainly due to the effect of –NOO– in m-nitrobenzoate. These findings provide a clear correlation between the experiments and DFT, indicating that the –NOO– in m-nitrobenzoate can adsorb on the surface of arsenopyrite via a covalent bond, thereby realizing the depress of arsenopyrite. [Display omitted] • The oxidative properties of the -NOO- exacerbate the oxidation of arsenopyrite. • The presence of π-back bonding favors the interaction between ligands and metal ions on the mineral surface. • The lone pair of electrons of the depressant gives the empty orbital of the surface metal ion to form a positive σ bond. [ABSTRACT FROM AUTHOR]