As-synthesized MCM-41 silica: new adsorbent for perchlorate

Abstract

Here we demonstrate that the as-prepared MCM-41 mesoporous silica material, which is synthesized using cetyltrimethylammonium bromide as a cationic surfactant exhibits very high capacity for perchlorate uptake from solutions. Thus we discover a new function for the as-synthesized mesoporous materials containing cationic surfactants. These materials are shown to have better capacity than the currently used activated carbon, which is preloaded with cationic surfactant. As-synthesized MCM-41 has a higher removal of perchlorate with 0.378 ± 0.038 meq/g than the surfactant modified activated carbon sample, which removed 0.304 ± 0.005 meq/g i.e., MCM-41 has a 24 % higher capacity than the surfactant modified activated carbon sample for perchlorate uptake because of higher surfactant content and higher positive charge in the former. The residual positive charge on the cationic surfactant micelles trapped in mesopores of silica is responsible for the high perchlorate uptake. The excess positive charge on the micelles in the as-synthesized MCM-41 silica is balanced by bromide ions and these ions are involved in exchange with perchlorate ions.