Enhancing the sorption capacity of CTMA-bentonite by simultaneous intercalation of cationic polyacrylamide

Abstract

The saturated level of cationic exchange capacity (CEC) of bentonite by organic cations can significantly influence the sorption capacity of the resulting organobentonites. In this work cationic polyacrylamide (CPAM) was applied to saturate part of the CEC of the cetyltrimethylammonium (CTMA) modified bentonite, with the aim to enhance their sorption capacity. XRD was applied to investigate the basal spacings of the organobentonites with and without CPAM, and the sorption characteristics of the organobentonites towards phenol and nitrobenzene to CTMA-bentonite was also studied. The XRD characterization results showed that the resulting organobentonites (C/P-Bt) had larger basal spacings than the CTMA modified bentonite (C-Bt), which indicated that both CPAM and CTMA could intercalate into the interlayer spaces of C/P-Bt. The saturated CEC of C/P-Bt increased with the intercalated amounts of CPAM. The sorption coefficients (K(d)) of phenol and nitrobenzene on C/P-Bt were shown to first increase with the saturated CEC until the maximum, and then began to decrease as the saturated CEC further increased. The maximum increase of K(d) reached 41% and 23% for phenol and nitrobenzene, respectively, which could be ascribed to the enhanced affinity of the adsorbed CTMA aggregates towards the sorbates. Results of this work showed that the simultaneous intercalation of CPAM could be a novel method to enhance the sorption capacity of the traditional organobentonites.