ZnFe_2O_4-chitosan magnetic beads for the removal of chlordimeform by photo-Fenton process under UVC irradiation

摘要

A simple protocol was proposed for the preparation of magnetic chitosan beads ZnFe_2O_4-CS via a co-precipitation method. The use of synthesized magnetic ZnFe_2O_4-CS beads as catalyst for the heterogeneous photo-Fenton treatment of chlordimeform insecticide (CDM) was evaluated. The photo-Fenton experiments were carried out with different synthesized catalysts by varying the molar ratio Zn/Fe in chitosan beads, the catalyst concentration and pH. Under optimal conditions using 1 g of ZnFe_2O_4-CS beads with a molar ratio Zn/Fe = 0.35 and at pH_(initial) = 3, a real wastewater doped with 20 mg L~(-1) of CDM was treated and complete removal of the insecticide was achieved after 7 min with a total TOC removal after 2 h of treatment. The generated carboxylic acids and ions during the photo-Fenton process were identified and quantified. The stability of the photocatalytic activity of the best catalyst in terms of pollutant removal, ZnFe_2O_4-CS(0.35) beads with a molar ratio Zn/Fe equal to 0.35, was satisfactory validated by four consecutive cycles. This optimal catalyst was characterized, before and after use, by Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy, X-Ray Powder Diffraction and Vibrating Sample Magnetometry analysis.