The Enhanced Mechanism Of Hydroxybenzoic Acid In Poly-Silicate-Ferric Heterogeneous Uv-Fenton System

The heterogeneous UV-Fenton technology with Poly-Silicate-Ferric（PSF）as a catalyst is used to treat dye wastewater.It has the advantages of high efficiency,thorough degradation,no secondary pollution,etc,and can achieve the effect of treating waste with waste.It is a very promising sewage One of the processing technologies.The key to the rapid and thorough degradation of organics in the system is how to get Fe³⁺into the system and how to accelerate the Fe³⁺/Fe²⁺redox cycle,so as to increase the production rate of·OH in the PSF heterogeneous UV-Fenton reaction,and ultimately degrade the organics.There are many kinds of hydroxybenzoic acids in nature,and they have different ways of affecting iron ions.The addition of different hydroxybenzoic acids is expected to accelerate the degradation of pollutants in the system.It is very important to prove the enhanced mechanism of hydroxybenzoic acid to the PSF heterogeneous UV-Fenton system.In this paper,based on the PSF heterogeneous UV-Fenton system,the effect of different hydroxybenzoic acid on the degradation of orangeⅡis compared,Then we established the UV-PSF-HBA system and explored the effect of hydroxybenzoic acid on Fe³⁺/Fe²⁺in the UV-PSF-HBA system.The enhanced mechanism of transformation,summarized the enhanced mechanism of various hydroxybenzoic acids to the system Fe²⁺,and finally used systems with different enhanced mechanisms to degrade Orange II and the refractory organic sucralose and compared them,the specific research content of this paper is as follows:1.The effects and comparison of protocatechuic acid and gentisic acid on the decolorization and mineralization of orange II in the PSF multiphase UV-Fenton system were explored,and it was found that gentisic acid has a stronger synergistic ability.The 0.2 mmol/L synergist can increase the orangeⅡ"first stage"decolorization rate constant by 14.27 times and 21.55 times respectively,and avoid the loss of iron in the catalyst and secondary pollution.2.Three enhanced mechanisms of hydroxybenzoic acid for Fe³⁺/Fe²⁺conversion in the UV-PSF-HBA system are revealed:chemical reduction mechanism;solubilization mechanism;photoreduction mechanism.The three mechanisms act individually or together to promote the conversion of Fe³⁺/Fe²⁺in the UV-PSF-HBA system,thereby accelerating the decomposition of H₂O₂ and the generation of·OH.3.It was found that three kinds of hydroxybenzoic acid played a enhanced effect on the degradation of orange II and sucralose:all of them could increase the decolorization rate of orange II,By comparison,it was found that 2,5-DHBA had the relatively best synergistic rate;The mineralization of Orange II found that 0.2mmol/L of hydroxybenzoic acid was the best enhanced concentration;as the concentration of the synergist increased,the mineralization rate of sucralose in the system could be gradually increased after 60 minutes.