Changes in barite surface free energy due to its surface precoverage with tetradecyalmine chloride (TDACl) or sodium dodecylsulphate (DDSO₄Na)

Abstract

Surface free energy components, apolar γ ^LW_s , polar: electron donor γ ⁻_s , and electron acceptor γ _s/+ have been determined for the bare barite surface, as well as for those precovered with cationic collector: tetradecylamine chloride (TDACl) or anionic collector (DDSO₄Na). The surface coverages for TDACl were 0.25 and 1 statistical monolayers, and those for DDSO₄Na — 0.4 and 1 statistical monolayers. The γ ⁺_s component was found to be meaningless. Therefore, polarity of the surface is due to the γ ⁻_s component. The adsorbed collector decreases the γ ⁻_s component resulting from hydrogen bonding. The decrease is larger in the case when DDSO₄Na was used as the collector. Simultaneously, the apolar component γ ^LW_s increases for the surface precovered with TDCAl. It may be concluded that the adsorbing collector (or neutral TDA molecuels) by partially remove water molecules from the barite surface. In the case of DDSO₄Na γ ^LW_s increased at 0.4 monolayer precoverage (probably as a result of the surface dehydration), and then at 1 monolayer precoverage it decreased to the value characteristic for long-chain hydrocarbon. These results are consistent with the flotation results. Straightline dependence for DDSO₄Na was found between free energy changes ΔG accompanying the flotation process and flotability changes.