Synthesis of a crosslinked poly(ionic liquid) and evaluation of its antimony binding properties

First ever ionic liquid derived sorbent for antimony was synthesised. The charged functional groups of the polymer showed preferential binding and strong affinity for difficult to remove anionic species of antimony. The sorbent was synthesised by crosslinking co-polymerisation of 1-butyl-3-vinylimidazolium bromide with N,N-methylenebis(acrylamide). SEM-EDS analysis showed that the polymer retained the bromide counter ions. Antimony removal properties under wide solution conditions, including the presence of competitor ions, were investigated. Maximum antimony binding and selectivity was at pH 3.0. Variation in saturation capacity with respect to the crosslinker amount matched with the calculated capacity values. Maximum uptake obtained was 4.6 and 3.2 mmol/g for Sb(III) and Sb(V) respectively. Tartrate salt of Sb(III) showed better binding through the interaction of tartrate with the imidazole moieties of the polymer. In less than 15 min, saturation capacity was achieved for Sb(III), while over 90% of uptake was complete for Sb(V). Investigations on sorption mechanism, which included synthesis and comparative evaluation of the non-ionic counterpart polyvinylimidazole as sorbent, indicated the uptake to be through anion exchange. Sb(III) specific binding against Sb(V) was seen in the presence of nitrilotriacetic acid.