Structural and sorptive characteristics of the cetyltrimethylammonium and polyacrylamide modified bentonite

In this work cetyltrimethylammonium bromide (CTMA) and cationic polyacrylamide (CPAM) were used to simultaneously modify bentonite, with the aim to synthesize novel organobentonites possessing high sorption capacity towards phenol, nitrobenzene and aniline. The XRD characterization results showed that the resulting organobentonites (C/P-Bt) had larger basal spacing than the corresponding CTMA modified bentonite (C-Bt) and CPAM modified bentonite (P-Bt). This indicated that the two modifying agents were simultaneously intercalated into the interlayers of C/P-Bt. FTIR characterization results showed that the νas(CH2) and νs(CH2) modes of CTMA on C/P-Bt shifted to low wavenumbers comparing with those on the corresponding C-Bt, which indicated CTMA had higher trans/gauche conformation ratio and packing density within the interlayers of C/P-Bt. C/P-Bt showed a synergistic sorption effect towards the tested sorbates, with a sorption efficiency better than that of C-Bt + P-Bt. In addition, the sorption capacity of C/P-Bt was shown to increase with the saturated CEC until the maximum, and then began to decrease as the saturated CEC further rose. The optimal saturated CEC was in the range 114–127%. Results of this work provided additional evidence that the packing density of organic cations could significantly influence the sorption capacity of organobentonites, and also showed a method for synthesizing novel organobentonites with high sorption efficiency towards organic pollutants.