ANTIMONY REMOVAL FROM AQUEOUS SOLUTIONS: POTENTIAL FOR ALUMINUM-BASED DRINKING WATER TREATMENT RESIDUALS AS A "GREEN" SORBENT

Antimony (Sb) and its compounds are used extensively in manufacturing and processing industries all around the world, and substantial amount of Sb is released every year into the environment. Despite its potential hazards to humans and environment, scientific data on accumulation, fate, transformation, and remediation of Sb is not abundant. Here, we attempted to remove Sb from aqueous solutions using a drinking water treatment waste, namely aluminum-based drinking water treatment residual (Al-WTR). Batch sorption experiments were conducted to investigate the effects of solid/solution ratio (SSR), pH, initial Sb concentration, and reaction time on Sb sorption by Al-WTR at an ionic strength of 0.01 M KCl, and an equilibration time of 24 hours in the absence and presence of two competing anions, phosphate (PO₄^2-) and sulfate (SO₄^2-). Antimony sorption on Al-WTR significantly increased with an increase in solid/solution ratio (p <0.0001). The optimal SSR was 50 g/L, where ~ 90% sorption took place. No clear pattern on pH dependency of Sb sorption emerged. Sorption decreased with increasing initial Sb concentrations (p <0.001), as well as with increasing concentrations of competing ligands PO₄^2- and SO₄^2- (p < 0.05). Approximately 85% sorption took place within 5 hours and reached a plateau of 99% within a day. Sorption isotherm indicated an S type curve, which implied relatively low affinity of Al-WTR at lower Sb concentration in solution. Sorption kinetics best fit second order reaction (R² = 0.99) model. Equilibrium data was fit to various models, and the best fit was obtained using the Freundlich isotherm model (R² = 0.99). This study indicated the potential of Al-WTR as a cost effective and environmental friendly sorbent for removal of antimony in contaminated media.