Adsorption of Cr(VI) and Phosphate on Mg–Al Hydrotalcite Supported Kaolin Clay Prepared by Ultrasound-Assisted Coprecipitation Method Using Batch and Fixed-Bed Systems

Abstract

Modified kaolin clay (MKC) was synthesized through ultrasound-assisted coprecipitation method, and its adsorption behaviors to Cr(VI) and phosphate (P) from single and binary solutions were investigated by batch and column experiments. The adsorption capacities of Cr(VI) and P in single-ion solutions were found to be 309.60 and 605.75 mmol/kg, respectively. Because of competition adsorption, the adsorption capacities in binary solutions were reduced to 145.38 and 461.61 mmol/kg, respectively. The single and binary adsorption data fitted the pseudo-second-order kinetic model and the Langmuir isotherm well. The simultaneous addition of the two adsorbates led to a decrease and an increase in adsorption rate of Cr(VI) and P onto MKC, respectively. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were performed to confirm the adsorption phenomenon. FTIR spectroscopy demonstrated that hydroxyl groups, NH4+...