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Abstract BACKGROUND This study aimed to produce activated carbon (AC) from spent coffee ( Coffea arabica ) grounds by chemical activation using zinc chloride (ZnCl 2 ) and nitric acid to remove bentazone from aqueous solutions. RESULTS The fresh spent coffee grounds were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and the AC by X‐ray diffraction (XRD), infrared spectroscopy (FTIR), Brunauer–Emmett– Teller (BET), point of zero charge, scanning electron microscopy (SEM) and the Boehman method. Adsorption experiments were carried out in a batch system. The results showed a 70% efficiency in bentazone removal using ZnCl 2 carbon. Kinetic studies indicate that the adsorption rate increased slowly up to 720 min; the first‐ and second‐order models fitted the experimental data at a concentration of 50 mg L −1 . The adsorption equilibrium is represented by the Langmuir model with a high adsorption capacity of 279.33 ± 6.29 mg mg −1 . The adsorption efficiency was also confirmed by toxicity analysis of the effluent with bentazone at 50 mg L −1 , using the Allium cepa bioassay, a high‐sensitivity test for pollutants in water. CONCLUSION Before adsorption, the effluent caused significant cytogenotoxicity to onion root meristems. After adsorption, the generated effluent no longer caused toxicity to the test system, and the results obtained were similar to the control with distilled water. © 2024 Society of Chemical Industry (SCI).
Rocha et al. (Fri,) studied this question.