Towards finding an efficient sorbent for antimony: comparative investigations on antimony removal properties of potential antimony sorbents

Removal of antimony, classified as a pollutant of priority importance, is a challenge due to its presence in various forms in solution and the low concentration in which it is to be removed. In this study, sorption profile and the sorption mechanisms associated with the removal of antimony in its two oxidation states (+3 and +5) have been investigated in detail through batch studies involving titania sorbents, strong base anion resin, a chelating resin, and a biosorbent. Significant sorption-associated change in solution pH was observed with all the sorbents, which revealed the nature of respective sorption equilibrium involved. The results have shown that Sb(V) is removed only as anionic species, while Sb(III) is removed either as an anionic species or as cationic species according to the functional groups present in the sorbent and the solution conditions. Titania-based sorbents were found to be effective sorbents for Sb(III) and Sb(V) within a narrow pH range, while anion resin was found to be superior for removing Sb(V) as Sb(OH)(6)(-) under a wide range of solution conditions. The suitability of the sorbents for column mode of operation has also been investigated. This report is a first attempt at a rational comparison of promising sorbents for antimony, and the results demonstrate the complexity involved in antimony sorption and give an understanding of the available options for handling the antimony removal problem in large-scale applications.