Exploring the adsorption of sodium hexametaphosphate on lepidolite-albite-quartz in anionic-cationic collector systems from hydrophobic interaction

Background In mixed anionic-cationic collector systems, sodium hexametaphosphate (SHMP) is commonly required as a depressant to realize the flotation separation of lepidolite from albite and quartz. However, its effect mechanism to the flotation performance of anionic-cationic collector is unclear. Methods Micro-flotation, contact angle, Zeta potential, adsorption capacity, optical microscopy, FTIR, in-situ AFM imaging and AFM force measurements were employed to investigate the flotation performance and the adsorption mechanism of SHMP and dodecylamine (DDA) + sodium lauryl sulfate (SLS) on lepidolite, albite and quartz. Significant Findings With 5.0×10 −5 mol/L SHMP pre-addition, DDA+SLS achieved 90.01% Li 2 O recovery with 4.04% Li 2 O grade from an artificial ternary mixture of 1.83% Li 2 O at pH∼7.0, DDA: SLS molar ratio = 2: 1 and C DDA +C SLS =1.5×10 −4 mol/L. SHMP adsorbed on albite and quartz by the hydrogen bonds between P-OH/P-O − groups of SHMP and Si-O − /Si-OH and Al-O − /Al-OH sites on albite as well as Si-O − /Si-OH sites on quartz. With SHMP+DDA+SLS addition, SHMP-DDA and SLS-DDA complexes formed and adsorbed onto lepidolite basal planes through the hydrophobic interactions, whereas no adsorption occurred on albite and quartz due to the absent hydrophobic interactions. This differential adsorption generated the distinct surface wettability, enabling the selective lepidolite recovery.