Degradation Of Bisphenol A In Aqueous Solution With Sulfate Radicals Generated By Different Methods

In recent years, endocrine disrupting chemicals (EDCS) have already been the research hotspot. Bisphenol A (BPA:2,2-Bis(hydroxyphenyl)propane) is widely used as an intermediate in the manufacture of polycarbonate, epoxy and polysulfonate resins. It is-demonstrated to have hormone-mimetic properties, which can affect reproductive function. BPA originating from the production factories and various wastewaters have been found in rivers, lakes and ocean. As BPA is relatively stable in environment, hardly degraded and tending to bio-accumulate, which makes the study of BPA elimination urgent and meaningful.Degradation of bisphenol A (BPA) in aqueous solution was studied with high-efficiency sulfate radical (SO4-·), which was generated by the activation of persulfate (S2O82-) with UV254nm or ferrous ion. And the research focused on the mechanism of BPA degradation in the two activated system. At last, Co2+was utilized to catalyze PMS. At last, with the addition of benzene, which was the competitor of SO4-·, the second reaction rate constant of BPA and SO4-· were calculated. The detailed results are as follows:In UV254nm/S2O82-system, degradation of BPA was effected significantly by several factors, such as initial concentration of persulfate and the illumination intensity, as well as the initial BPA concentration and pH value of the mixture. In this system, BPA degradation was well formulated to the apparent first-order kinetics. BPA removal rate increased with the increasing concentration of persulfate. When the concentration of persulfate reached4mM, the degradation rate of BPA was the highest of89%in30min. Besides, the elimination of BPA increased when the irradiation distance decreased. As the initial concentration of BPA decreased, its removal rate will increased. And66.3percentage point of BPA was eliminated in5min when the initial BPA concentration was20μM. But the total amounts of BPA removal were effected reversely by its initial concentration. When the solution was neutral, the removal rate of BPA reached the highest of93%in30min.In Fe2+/S2O82-system, S2O82-was activated by Fe2+to produce SO4-·, iron powder (Fe0) was used as a slow-releasing source of dissolved Fe2+. The major oxidation products of BPA were determined by LC/MS. The mineralization efficiency of BPA was monitored by total organic carbon (TOC) analyzer. BPA removal efficiency was improved by the increase of initial S2O82-and Fe2+concentrations, and then decreased with excess Fe2+concentration. The adding mode of Fe2+had significant impact on BPA degradation and mineralization. BPA removal rates increased from49%to97%with sequential addition of Fe2+, while complete degradation was observed with continuous diffusion of Fe2+. Continuous diffusion of Fe2+achieved higher TOC removal rate of78%than sequential addition of Fe2+. When Fe0was employed as a slow-releasing source of dissolved Fe2+,100%of BPA degradation efficiency was achieved, and the highest removal rate of TOC (85%) was obtained within2h. In the Fe0-S2O82-system, Fe0as the activator of S2O82-could offer sustainable oxidation for BPA, and higher TOC removal rate was achieved. It was proved that Fe0-S2O82-system was probably a promising process to eliminate and mineralize BPA in real wastewater. Moreover,4-hydroxyacetophenone (or p-isopropylphenol) was detected by LC-MS as one probable ring-cleavage product of BPA.In the Co2+/PMS system, BPA degradation was also well matched to the apparent first-order kinetics. With the addition of benzene, the secondary kinetic constant of BPA and SO4"’were calculated through studying the competition between BPA and benzene. And the constant was about1.85×109M-1S-1. And the equilibrium concentration of SO4-· produced in the UV system was speculated to about1.32×10-13-7.97×10-13M.