The Synergistic Effect Of Cathode And Persulfate On Phenol Degradation

Advanced oxidation technology based on persulfate(S2O82-, PS) activation is a new one developed in recent years. This technology has great potential in water pollution control and prevention because of its unique features, such as economy, efficient and environment friendly. This thesis aimed to explore the potential use of cathode(Pt)/persulfate(PS)/Fe2+(Fe3+) system with low-concentration Fe2+(Fe3+) for degradation of phenol, a typical phenolic pollutant, which is wildly found in contaminated environment and of high toxicity. The mechanism of the system was also briefly analyzed.Several control experiments were conducted to investigate the feasibility, and the results showed that Cathode/PS/Fe2+(Fe3+) system with low-concentration of Fe2+(Fe3+) could effectively degrade phenol, and was more energy-saving and higher in PS utilization than traditional metal activation system and electrochemical strengthening system.The study on influential factors showed that phenol degradation rate increased first and then tended to be stable with increasing current density while an excessive current density would lead to system collapse due to soluble iron concentration decrease because of p H raise. Phenol degradation rate was positively related to initial Fe2+ concentration and negatively to supporting electrolyte(sodium sulfate) concentration. With increasing initial PS concentration, phenol degradation rate increased to maximum at an initial PS concentration of 14.17 mmol L-1 and then decreased slightly.According to chemical and mathematical analysis, ?[PS]/[e-] could be used to characterize the utilizations of current and persulfate. This index was always less than 1 due to inevitable reduction of PS on cathode, and its value, namely the utilizations of current and persulfate, was negatively related to current density and positively to initial Fe2+ and PS concentration, and it was first positively and then negatively related to supporting electrolyte concentration, reaching maximum when supporting electrolyte concentration was 50 mmol L-1.Mechanism analysis demonstrated that, Fe2+/Fe3+ cycle on cathode surface was the core of this system. Possible intermediates of phenol degradation might be hydroquinone, catechol, resorcinol, benzoquinone and maleic acid, etc. Radical quenching study showed that both sulfate radicals and hydroxyl radicals were responsible for phenol degradation. Phenol degradation fitted with zero-order kinetics within the main period of degradation time.