Plant extract-stabilized nanoiron for the treatment of aqueous paraquat in the presence of H₂O₂ and UV light

This work aimed to increase the working ability of iron nanoparticles in Fenton and photo-Fenton process by preventing the aggregation of the catalysts using the plant extract with a green chemistry approach. We used extracts from tea, coffee, and garlic as stabilizing agents to cap the iron nanoparticles. Various iron nanoparticles were used to remove paraquat, a known herbicide presented in agricultural wastewater, from aqueous solution. The organic molecules from the plant extract induced the decreasing of the pH_pzc toward a very low acidic pH. The values of pH_pzc of iron nanoparticles were lower from 4.1 (without plant extract) to 1.6 with tea extract resulting in the high adsorption ability of paraquat. Among three types of catalysts, the iron nanoparticles obtained from tea extract provided the highest degradation percentage of paraquat using Fenton and photo-Fenton processes. It was found that the maximum removal percentage of paraquat was obtained within 20 min. The kinetic data of all types of iron nanoparticles was well explained by pseudo-first-order pattern with the reaction constants in the range of 1.83–3.82 × 10^–2 min^–1 for Fenton process and 7.27–10.94 × 10^–2 min^–1 for photo-Fenton process.