Degradation of paraquat from contaminated water using green TiO2 nanoparticles synthesized from Coffea arabica L. in photocatalytic process

The TiO 2 nanoparticles synthesized from the extract of Coffea arabica L. (or TiO 2 /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 TiO 2 nano-catalyst. The value of pH pzc of TiO 2 /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 TiO 2 /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 TiO 2 /C, TiO 2 , and without TiO 2 , respectively, under the presence of ultraviolet (UV) and H 2 O 2 . The combined TiO 2 /C with UV and H 2 O 2 was the most efficient process, exhibiting a maximum 66.3% degradation of 50 mg/L over 90 min at pH 10.