Flotation separation of hemimorphite and quartz using potassium dodecyl hydrogen phosphate as a high efficiency collector: experimental and DFT simulation

Abstract

The flotation separation of hemimorphite and quartz presents challenges due to their analogous surface characteristics when conventional collectors are used. In this study, potassium dodecyl hydrogen phosphate (PDHP) was systematically evaluated as a highly efficient collector for the selective flotation of hemimorphite and quartz. Micro-flotation experiments demonstrated that PDHP displayed remarkably enhanced selectivity for hemimorphite compared to the conventional collector dodecylamine (DDA). Under neutral pH and in the absence of depressants, effective separation of artificially mixed minerals was achieved at a PDHP concentration of 4 × 10⁻⁴ mol/L. The concentrate exhibited a zinc grade and recovery of 48.26 % and 86.38 %, respectively, while the SiO₂ grade was merely 27.29 %. A battery of characterization techniques elucidated the selective adsorption behavior of PDHP on hemimorphite, revealing robust chemisorption between the phosphonic acid groups of PDHP and the Zn active sites of hemimorphite. Density functional theory (DFT) simulation calculations further elucidated that stable six-membered rings were formed through bidentate bonding structures, where the O and H atoms of the phosphonic acid groups were bonded to the Zn and O atoms of hemimorphite by chemical bonds and hydrogen bonds, respectively, with a calculated adsorption energy of −343.55 kJ/mol, ultimately achieving efficient flotation of hemimorphite.