Removal of Cr(VI) in aqueous solution using cationic gemini surfactant-modified rectorite

The adsorption of hexavalent chromium (Cr(VI)) on rectorite (REC) modified by gemini surfactant (butane-1,4bis (dodecyl dimethyl ammonium bromide)) (gBDDA) was investigated in this research. The results of a series of characterization methods such as X-ray diffraction (XRD), infrared spectroscopy, and thermogravimetric analysis proved that gBDDA was successfully embedded into the interlayer of REC. The effect of the amount of gBDDA on the adsorption of Cr(VI) by gBDDA-modified REC was studied (gBDDA: cation exchange capacity = 1:2 or 1:4). The adsorption capacity of Cr(VI) by gemini surfactant-modified REC reached 38 mg/g, which was higher than that of tetradecyl trimethyl ammonium bromide-modified REC. In addition, ultrasound-assisted synthesis was found to have an effect on the adsorption capacity of REC modified with a high ratio of gemini surfactant. The structures of gBDDA before and after adsorption were analyzed to clarify the adsorption mechanism. The electrostatic interaction between Cr(VI) and two positively charged groups in the gBDDA was found to be crucial during the adsorption process. The foundings of this study demonstrate that REC modified by gBDDA can be used as an adsorbent for the removal of Cr(VI) in water.