Enhancing the performance of alumina-pillared clay for phenol removal from water solutions and polyphenol removal from olive mill wastewater: Characterization, kinetics, adsorption performance, and mechanism

Abstract

An alumina-pillared clay (Al-PILC) has been synthesized and tested for its ability to adsorb phenol from aqueous solutions, and polyphenols from Olive Mill Wastewater (OMW). The synthesis processes were investigated by varying parameters like the Al/clay ratio, with a molar ratio of [OH−]/[Al3+] = 2.4. Various techniques, including XRD, BET, XRF, FTIR, and SEM were used to characterize the resulting solids. The effect of key factors as pH, initial pollutant concentration, and contact time, were examined in order to evaluate the phenol adsorption capacities of raw clay (RC) and optimized Al-PILC10 materials. The specific surface areas of RC and Al-PILC10 were 40 and 127 m2/g, respectively, resulting in increasing the phenol adsorbed quantity from 14.15 mg/g for RC to 30.61 mg/g for Al-PILC10 clays, at pH 2 and 45 °C. Pseudo-second-order kinetics and Freundlich adsorption isotherm were suitable for describing phenol adsorption on both clays. Furthermore, Al-PILC10 exhibits an impressive removal efficiency of 76 % for polyphenols from OMW, in contrast to the 50 % achieved by RC at acidic pH. Furthermore, Al-PILC10 showcased a superior desorption rate and a favorable regeneration capacity of 64 % compared to RC (45 %), even after multiple adsorption-desorption cycles. These findings emphasize the potential of pillared clay as a cost-effective adsorbent for the efficient removal of phenol and polyphenols from wastewater.