The TiO2 nanoparticles synthesized from the extract of Coffea arabica L. (or TiO2/C) were used to remove paraquat from contaminated water in heterogeneous photocatalysis process. In this work, the sol-gel process using Coffea arabica L. as the solvent chemical were performed to obtain the TiO2 nano-catalyst. The value of pHpzc of TiO2/C was 2.9 which caused a highly acidic surface of catalyst. The paraquat is effectively removed in alkaline medium due to the adsorption ability of paraquat on the surface of TiO2/C. The paraquat degradation followed the pseudo-first-order model with the apparent rate constants of 5.84 × 10−2, 4.08 × 10−2, and 2.28 × 10−2 min−1 for TiO2/C, TiO2, and without TiO2, respectively, under the presence of ultraviolet (UV) and H2O2. The combined TiO2/C with UV and H2O2 was the most efficient process, exhibiting a maximum 66.3% degradation of 50 mg/L over 90 min at pH 10.

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