Mercaptobenzothiazole collector adsorption on Cu sulfide ore minerals

Abstract

The species adsorbed on Cu sulfide ore minerals from near neutral or alkaline solutions of the flotation collector 2-mercaptobenzothiazole (MBT) have been established by X-ray photoelectron spectroscopy (XPS). Previous XPS studies of the species adsorbed on chalcocite from very dilute solutions were extended to adsorption on air-exposed Cu metal, cuprite, chalcocite, covellite, cubanite, chalcopyrite, bornite and pyrite from more concentrated solutions to simulate processing of variably oxidised ores and slug addition of collector under plant conditions. It was found that even in alkaline solutions, HMBT adsorbed in addition to molecular CuMBT, (MBT)2 and chemisorbed MBT on Cu metal, CuI oxide or Cu sulfide minerals. For all Cu-containing surfaces conditioned in a collector solution of concentration higher than 10−5M, adsorbed molecular (multilayer) CuMBT remained a minor species within the pH range investigated. For substantial collector coverage, when the concentration of adsorbed HMBT and (MBT)2 exceeded that of chemisorbed MBT and adsorbed CuMBT, the surface was not obviously hydrophobic. Neither a Cu nor Fe surface oxide layer was predominantly removed by the collector, but MBT chemisorption involved direct interaction with surface Cu atoms rather than via intermediate O atoms. There was strong evidence for a Cu—N interaction in bulk CuMBT, and hence in MBT chemisorbed on surface Cu atoms, in addition to the principal interaction through the MBT exocyclic S atom. It was concluded that adsorption of some multilayer MBT species on Cu sulfide ore minerals can be deleterious, and this should be taken into account when variably oxidised ores are being processed.