Enhanced sorption of perfluorooctane sulfonate and Cr(VI) on organo montmorillonite: influence of solution pH and uptake mechanism

An effective sorbent to remove the perfluorooctane sulfonate (PFOS) and hexavalent chromium (Cr(VI)) simultaneously from simulating plating wastewater was prepared in this study. The removal of Cr was pH-dependent. However, PFOS removal on organo-montmorillonites (Mts) was not sensitive to pH changes. The presence of micelles and hemi-micelles resulted in an enhanced PFOS sorption capacity which reached 1,000 mg/g on the hexadecyltrimethylammonium bromide (HDTMAB) modified montmorillonite. The cationic surfactants on organo-Mts were largely responsible to the hydrophobic partition. For Cr(VI), the stable coordination compounds between amido, sulfhydryl groups and HCrO₄ ^? were beneficial to its sorption on AET–Mt and AET–HDTMAB–Mt (AET, 2-aminoethanethiol hydrochloride). The result indicated that the AET–HDTMAB–Mt was highly effective for removing both PFOS and Cr(VI) simultaneously, and their sorption capacities reached 890 and 14 mg/g respectively.