Removal of chloroquine from the aqueous solution by adsorption onto acai-based biochars: Kinetics, thermodynamics, and phytotoxicity

This study aimed at emerging contaminant chloroquine (CQN) removal, widely used in the COVID-19 pandemic through adsorption and employing a low-cost activated biochar from acai fruit endocarp. Two different adsorbents from the same precursor were applied. The first (CAA) was activated at a high temperature using ZnCl2, and the second (CA) was obtained by physical activation. The adsorbents were characterized through BET, FTIR, DRX, TG/DTG, and SEM. The results showed that zinc chloride activation furnished a material with a high specific surface area (SBET) and pore volume of 762 m2 g-1 and 0.098 cm3 g-1, respectively. Adsorption kinetics and isotherm were best adjusted through the pseudo-second-order (PSO) and Freundlich for both biochars. The process was thermodynamically favorable, occurring spontaneously without energy request. Additionally, the maximum adsorption capacity for CQN was 15.56 and 40.31 mg g-1 for CA and CAA, respectively, in pH 6.84, at a temperature of 25 degrees C, 50 mL solution and with 0.05 and 0.02 g of adsorbent. Those results are congruent with the literature showing the versatility of the material and the efficiency of the applied adsorption process.