Synthesis and application of an unprecedented bioadsorbent for removing arsenic from aqueous systems

Abstract

A quaternary ammonium anion exchanger (SBTEA) was prepared from sugarcane bagasse (SB) employing an improved two-step synthesis method by chemical modification with epichlorohydrin (EPI) and triethylamine (TEA) using N,N-dimethylformamide as a solvent without catalyst. Two multivariate optimizations were utilized to determine optimum conditions for SBTEA synthesis using Doehlert experimental designs. The optimum synthesis conditions were: VEPI = 12.8 mLgSB−1; VTEA = 22.0 mLgSB−1; and T1 (etherification step) = T2 (amination step) = 100 °C. The chlorine and nitrogen contents of the SBTEA produced under these conditions with a 21-fold increase in the synthesis scale (SBTEA-LS) were 4.2 ± 0.1% and 1.485 ± 0.007%, respectively. The 13C Multi-CP SS NMR revealed that 1.7 quaternary ammonium groups were introduced for 10 cellobiose units. SBTEA-LS was used to remove As(V) from contaminated groundwater samples with high removal efficiency (95 ± 4%), even with strong competitors such as SO42−. The interactions involved in the adsorption were investigated through macroscopic and microscopic measurements, which suggested that the adsorption of As(V) on SBTEA-LS occurred mainly by ion exchange. Desorption experiments proved that SBTEA-LS could be efficiently regenerated (Edes > 90%) using an HNO3 solution, reducing operating costs and favoring technology upscaling.