Improving collecting selectivity of dithiophosphate collector towards the flotation separation of oxidized pentlandite from serpentine via designed hydrogen-bond interaction

Abstract

The effective recovery of oxidized pentlandite remains challenging in sulfide ore processing due to coexisting oxidized/sulfide surface regions and serpentine entrainment caused by conventional dithiophosphate (DTP) collectors. In this study, a novel low-foaming bifunctional collector was synthesized to address this issue. A range of dithiophosphate collectors featuring different alkoxy chain lengths were developed and utilized. Flotation tests revealed that the newly synthesized O, O-bis(4-butoxyphenyl) phosphorodithioate (BHP) delivered a commendable recovery rate in both the oxidized pentlandite/serpentine mixed flotation system (95.5%) and the actual mineral flotation system (74.5%), thereby clearly demonstrating the significant collecting selectivity of BHP. The foaming test and entrainment test demonstrated that BHP exhibits lower foaming performance and a reduced serpentine entrainment rate. Adsorption capacity and contact angle measurements further confirmed that BHP exhibited significantly stronger adsorption on oxidized pentlandite compared to conventional DTP collectors. FTIR and XPS investigations indicated that BHP undergoes chemical adsorption at Fe and Ni sites within the sulfide areas of oxidized pentlandite. Furthermore, quantum chemical calculations analysis demonstrated that the butoxy group and the extended hydrophobic carbon chain enhanced the reactivity of the dithiophosphate structure with sulfide regions. Meanwhile, the presence of the butoxy group facilitated hydrogen bonding interactions with oxidized regions, thereby improving the overall flotation performance of BHP for oxidized pentlandite. These results offer significant guidance for the design of innovative bifunctional collectors aimed at enhancing the flotation efficiency of challenging nickel sulfide ores.