Efficient adsorption of acetaminophen from the aqueous phase using low-cost and renewable adsorbent derived from orange peels

Pharmaceutically active compounds (PhACs) are frequently detected emerging pollutants in water resources worldwide that provoke pernicious influences on human health and the ecosystem. Developing effective carbonaceous adsorbents from biomass for the efficient removal of PhACs has lately drawn significant research attention. Herein, an efficient and cost-effective activated carbon was produced via ZnCl2-activation, employing orange peels as a precursor (named hereafter as OPAC). OPAC was well-characterized and applied in the sequestration of acetaminophen (N-acetyl-para-aminophenol, APAP), a broadly used non-steroidal anti-inflammatory drug, from water media using the batch technique. OPAC exhibited excellent performance, and more than 95.5% APAP was removed after 90 min, in the pH range of 2.0-8.0, using 1 g/l adsorbent at 25 degrees C. Additionally, the equilibrium and the kinetic studies outcomes unveiled the suitability of the Langmuir and the pseudo-second-order kinetic models, respectively, to describe the adsorption process. Based on the pH-adsorption dependence and OPAC properties, the presumable mechanism was mainly dominated by non-electrostatic interactions, including hydrogen bonding, pi-pi interactions, and pore diffusion. Thermodynamically, the process was found to be spontaneous and endothermic. Ultimately, OPAC manifested outstanding recyclability, with at least 95% of the initial efficiency being preserved after five cycles, making it more attractive from the environmental and economic perspectives.