Modification Palygorskite with Surfactants by the Aid of High-Shear Emulsifying Process for Chromium(VI) Absorption

Palygorskite (PAL) was modified with octadecyltrimethyl ammonium bromide (OTAB) and dimethyldioctadecyl ammonium bromide (DOTAB) with the aid of high-shear emulsifying process. Thermo gravimetric (TG) and Infrared spectroscopy (IR) analyses confirm that surfactants were attached onto PAL. The surface charges of PAL first decreased and then increased with increasing the dosage of OTAB and DOTAB. The adsorption properties of the surfactant-modified PAL for Chromium (Cr, VI) were investigated at 30 °C. Results show that the maximum adsorption capacity at pH 3 reaches 25.4 mg·g^–1 for OTABmodified PAL, which is much higher than 4.1 mg·g^–1 of unmodified PAL. The mechanism for the adsorption of Cr(VI) onto surfactant-modified PAL was discussed. It was revealed that the adsorption process follows pseudo-second-order kinetic models. The disaggregation of PAL crystal bundles and in situ organification were achieved by one-step process, which present a new approach to design highly efficient adsorbent for removal of toxic Cr(VI) anions from aqueous solution.