Sorptive Removal of Perfluorooctane Sulfonate from Aqueous Solution by Layered Double Hydroxides

Perfluorooctane sulfonate (PFOS) is one of the most often detected perfluorinated compounds in both aqueous systems and biota. Because of its common occurrence in water resources as well as its toxicity and bioaccumulation, PFOS has become a compound of global concern and been recognized as an emerging contaminant. In this study, we seek for efficient, cost-effective and sustainable materials, which can be utilized to treat PFOS contaminated groundwater. Layered double hydroxides (LDHs), a class of anionic clays with layered structures, were investigated to evaluate their efficiency to remove PFOS from aqueous systems, hence, their potential to be used as an injection reagent to remediate PFOS contaminated groundwater. Here, we studied the sorptive removal of PFOS from aqueous solution by the nitrate, carbonate and chloride forms of intercalated LDHs. Batch experiments showed that the sorption process was very fast with an equilibrium time of less than 1h and the nitrate form of LDH showed the greatest ability to sorb PFOS with a removal rate of 95.7% at 1 mg/L of initial concentration. The sorption equilibrium data was well fitted with the Langmuir model, indicating a monolayer sorption of PFOS by LDHs. The maximum PFOS uptake capacity of LDHs differed with three forms of LDHs, with the maximum uptake capacity reached 865 mg/g by the nitrate form of LDH. The solution chemistry factors including pH, ionic strength and coexisting ions influenced PFOS sorption by LDHs. The sorption mechanism included surface adsorption as well as intercalation.