Process Mechanism of Formaldehyde Degradation in Aqueous Solution Using the UV-Fenton Method

摘要

This study was performed to further reveal the reaction mechanism and kinetic characters of UV-Fenton process for the degradation of formaldehyde (HCHO) in a batch photochemical reactor. The concentration changes of hydrogen peroxide, ferrous ions, and the intermediate products were analyzed. Through comparing the rate constants (k) of H_2O_2 consumption and the variation of Fe~(2+) concentration in the UV-H_2O_2, Fenton and UV-Fenton processes, it indicates that the Fe~(2+) and the UV light has a synergistic effect for the degradation of HCHO in the UV-Fenton system. The introduction of UV accelerates the reduction of Fe~(3+), and makes the cycle of iron obtain more paths. The products in the UV-Fenton reaction were analyzed by a gas chromatography-mass spectrometry and a chemical oxygen demand analyzer. Based on the results, the reaction pathways of HCHO degradation in the UV-Fenton system were proposed. The rate constants of the two consecutive first-order reactions in the degradation of HCHO are respectively k_1=0.543 min~(-1)and k_2 =0.045 min~(-1). The mineralizing of formic acid is the rate-controlled step of the reaction.