Activated carbon-clay composite as an effective adsorbent from the spent bleaching sorbent of olive pomace oil: Process optimization and adsorption of acid blue 29 and methylene blue

An activated carbon-clay (ACC) composite was prepared using spent bleaching sorbent generated from refined olive pomace oil through carbonization followed by K2CO3 activation. The adsorption-removal efficiencies for acid blue 29 (AB 29) and methylene blue (MB) of the developed ACC were examined. The K2CO3 activation process was optimized using Box-Behnken design. The optimum conditions were a K2CO3 impregnation ratio of 1:1, an activation temperature of 800 °C, and an activation time of 120 min, under which the optimized ACC achieved 83.81% AB 29 and 96.20% MB removal. The surface properties of the optimized ACC were characterized by different physicochemical measures and techniques, including surface area, point of zero charge, scanning electron microscopy, and Fourier transform infrared spectroscopy. Pseudo-second-order and Langmuir models best fitted the adsorption kinetics and isotherm experimental data. The maximum monolayer adsorption capacity of the ACC was 104.83 and 178.64 mg/g for AB 29 and MB, respectively, at 30 °C. All these results indicated the potential application of ACC in dye adsorption.