Direct force measurement between hydrophobic glass sphere and covellite electrode in potassium ethyl xanthate solutions at pH 9.2

Abstract

An atomic force microscope (AFM) was used to conduct direct surface force measurements between covellite (CuS) and glass sphere. Molecularly smooth surfaces of covellite were obtained by cleaving the mineral along the {0001} direction. The glass sphere was hydrophobized by octadecyltrichlorosilane so that its water contact angle was 109°, while the hydropobicity of the covellite surface was controlled by adsorbing potassium ethyl xanthate (KEX) from solution. The results may provide information relevant to the bubble–particle interactions occurring during flotation, assuming that air bubbles are hydrophobic. The xanthate adsorption on covellite was controlled by control of the electrochemical potential of the mineral electrode. It has been found that the hydrophobic forces measured in KEX solutions at pH 9.2 are strongly dependent on the electrochemical potentials of the covellite electrode. The potential region at which strong hydrophobic forces are observed corresponds to that where the flotation of covellite reaches a maximum.