Collector attachment to lead-activated sphalerite – Experiments and DFT study on pH and solvent effects

Graphical abstract: - Highlights: • DFT and experimental study of collector interactions with Pb-activated sphalerite. • Sphalerite activation in acidic media due to surface adsorption of Pb cations. • Substitution of surface zinc atoms by Pb not supported from experiments and DFT. • Collector adsorption on activated sphalerite hindered in solvated aqueous media. • Collector adsorption on surface deposited Pb(OH)₂ energetically favorable. - Abstract: The interactions of diisobutyl dithiophosphinate with bare (un-activated) and lead-activated sphalerite were studied both experimentally and through DFT simulations. Sphalerite activated by lead in acidic and alkaline conditions showed considerably greater affinity for diisobutyl dithiophosphinate adsorption than bare sphalerite. Experimental observations supported by DFT simulations concur in that attachment of the solvated collector to the activated sphalerite surface is through adsorbed lead cations or lead hydroxides where as for the bare sphalerite, the collector was most stable in its solvated state and not as an adsorbed specie. Accounting for solvation effects by including a swarm of water molecules in DFT simulations was necessary to infer plausible surface interactions between collector, solvent, and bare or lead-activated sphalerite. The experimental data and DFT simulations indicate, affinity of the collector toward surface-adsorbed lead species was predicted to form stable covalent bonds between collector sulfur atoms and lead.