Mechanism Study Of The Degradation Enhancement Of Organic Ligands For Orange ? In Homogeneous UV-Fenton System

Homogeneous photo-Fenton process is one of the most promising technologies for wastewater treatment, especially for persistent organic pollutants. It is rather meaningful to study on the mechanism of carboxylic ligands' synergistic effect on UV-Fenton degradation process. This dissertation found out that sodium acetate had synergistic effect on UV-Fenton degradation process, compared the catalytic activities of sodium acetic acid, oxalic acid, sodium citrate, ethylenediamine tetraacetic acid disodium and malonic acid sodium in homogeneous UV-Fenton process of degradation of dye. The study focused on analyzing the catalytic performance and optimum catalytic conditions of sodium acetate, came up with part of the preliminary catalytic mechanism of its synergistic effect on degradation. The optimum dosing ratio of ligands with ferrous ions was achieved by comparing the synergistic degradation effect of three carboxylic ligands at different concentrations. As a new synergistic reagent, sodium acetate has a bright application foreground and research meanings. Conclusions include:When Cligands:Ciron ions:Cdye=1:1:2,the degradation effect followed sodium acetate>sodium oxalate>sodium malonate>trisodium citrate>ethylenediamine tetraacetic acid disodium. The synergistic ratio of sodium actate, sodium oxalate were 32.3% and-13.2% relatively. Sdium actate's degradation efficiency was 52.4% higher than sodium oxalate. Sodium actate's synergistic ratio was 45.5% higher than that of sodium oxalate.Sodium acetate produced appropriate amount of ferrous ions to synergy UV-Fenton process by photo-reduction. When the ferrous ions concentration was at a low level, less hydroxyl radicals were produced, when the ferrous ions concentration was too high, it became the scavenge of hydroxyl radicals. The photo-reduction rate of ferrous ions can be adjusted by ligand molecules' number of carboxyl, ligand concentration and so on. Carboxylate ligands will act as the scanvenger of hydroxyl radical as well. The intermediates produced during the degradation and organic ligands themselves might also affect the degradation efficiency.(3) The optimum catalytic conditions of sodium acetate was at 254 nm ultraviolet wavelength, pH:3, hydrogen peroxide concentration: 10mmol/L, Orange ?concentration: 0.2mmol/L, sodium acetate concentration: 0.1mmol/L, iron ions concentration: 0.1mmol/L. Basically, at all concentration of ligands, the degradation efficiency followed, sodium acetate>sodium oxalate>ethylenediamine tetraacetic acid disodium. The degradation rate constant at almost all concentration followed, sodium acetate(0.5607)>sodium oxalate(0.5004)>ethylenediamine tetraacetic acid disodium(0.3916). Under the optimum condition relatively, degradation rate constants of sodium acetate and sodium oxalate were increased by 32.3% and 18.0% relatively. Degradation rate constant of sodium acetate was 52.4% bigger than that of sodium oxalate. When sodium acetate, sodium oxalate and ethylenediamine tetraacetic acid disodium achieved the maximum amount of degradation rate, the dosage of organic ligands followed, ethylenediamine tetraacetic acid disodium< odium oxalate<sodium acetate. By qualitative analysis, it is possible to get that trisodium citrate and ethylenediamine tetraacetic acid disodium were more suitable to treat relatively high-concentration wastewater while sodium acetate, sodium oxalate and sodium malonate were more suitable to treat relatively low-concentration wastewater.