Oxygen and phosphorus-enriched mesoporous biowaste-based carbonaceous material: A sustainable solution for efficient removal of diclofenac and chromium (VI) from polluted water

In response to the current environmental crisis, this study focuses on converting biowaste into phosphorus-oxygen-rich activated hydrochar (AH) for removing persistent pollutants such as Diclofenac (DCF) and chromium (VI) (Cr (VI)) from polluted water. The AH was prepared via hydrothermal carbonization of argan nut shells followed by H 3 PO 4 activation under an oxygen-rich atmosphere. The obtained AH was characterized by a high specific surface area of 1879 m 2 g −1, remarkable mesoporosity, and wide pore diameters. The AH was further analyzed revealing its highly aromatic nature, as well as the abundance of phosphorus and oxygen functional groups on its surface. These properties led to high adsorption capacities of diclofenac and chromium (VI) of 240 mgg −1 and 539 mgg −1, respectively. The investigations indicated that the AH applied physical and chemical forces for removing Cr (VI), while the uptake of DCF molecules was governed by physical forces. Indeed, the high aromaticity and oxygen functionality of AH facilitated the DCF adsorption through hydrogen bonding, π-π interactions, and pore-filling. Meanwhile, the oxygen functionality and the oxygen and phosphorus electron-providing sites on the AH’s surface favor the removal of Cr (VI) ions through physical and chemical interactions, including electrostatic attractions, ion exchange, complexation, and oxidation–reduction reactions. These findings highlight the effectiveness of AH in the elimination of DCF and Cr (VI) from polluted water.