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

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.