Study On Degradation Of Simulated Bisphenol A Wastewater By Strong Ionization Discharge/activated Persulfate Method

With the expansion of human social activities and the development of production industries,Bisphenol A?BPA?,as an important product and raw material in food packaging,electronics and medical manufacturing and chemical production,is gradually invading various water bodies,and it has brought aquatic ecological risks in various forms,threatening the health of mammals for a long time with various effects.Whether it is based on bisphenol A source control or total elimination,there is an urgent need for bisphenol A targeted,effective and environmental-friendly water treatment technology to overcome the low tolerance to phenolic pollutants and unsatisfactory result during traditional water treatment technology.In this study,a strong ionization discharge?SID?method was used in the pilot-scale water treatment system,which was further combined with a Fe???-activated persulfate system.The BPA degradation process in the SID system and the SID-Fe???/persulfate combined system were studied respectively.The influencing rules of variables and mechanisms during aqueous BPA removal using two various systems were investigated.The LC-MS and GC-MS analysis were combined to detect intermediates,and the oxidation pathways of BPA in two systems were discussed.To elaborate:?1?The experiment firstly applied a strong ionization discharge water treatment system of 80 L/time scale.The O₂?flow rate:5 ml/min?was used as the air medium.When the input voltage reached 3.2 kV,the O₃ concentration of plasma reactor was detected as 76.2 mg/L after 10 min ionization.The effect of BPA removal can be inhibited by 14.71%after the addition of free radical scavengers TBA?tert-butanol,Tert-Butanol?,proving the anticipation of hydroxyl radical?·OH?in the SID system.?2?The experiment investigated the degradation rules of BPA in the SID system under different variables?voltage,initial concentration,pH,inorganic ions and organic interferences?.The first-order kinetic model fitting shows that increasing the input voltage can significantly increase the degradation rate of BPA in SID system.When the input voltage was 3.2 kV,the pH value is 8.06,with no additive,the removal rate of 15mg/L BPA in the SID system was the highest:99.36%after 60min,and the accumulated power?R?injected per unit volume of the solution within 60min was 115.2 kJ/L.The increase of the initial concentration of BPA weakened the degradation effect of BPA within limited time.The acidic to weakly alkaline conditions were conducive to BPA degradation in SID system,while the strongly alkaline conditions show an inhibitory effect.After 10 min oxidation in SID system,the representative natural organic matter HA?Humic acid?weakened the BPA removal rate by 6.53%,while Cl^-had barely no effect on SID system.The inhibition order of different free radical scavengers was:TBA?IPA?isopropanol,isopropanol?>CO₃^2->HCO₃^-.?3?Ultraviolet scanning?UV-vis?,high-performance liquid?HPLC?,LC-MS and GC-MS chromatograms reflect the continuous shrinking of the peak of BPA material during the degradation process,and the abundance of degradation products rises and then decreases at different time periods.According to the detected substances by LC-MS and GC-MS,the possible oxidation route of BPA in the SID system was deduced:benzene rings were added by·OH,producing intermediates as dihydroxybisphenol A.·OH and O₃ opened the one-sided benzene ring or attacked the C-C bond between isopropyl and the benzene ring,producing relatively simple monobenzene-based substances as p-hydroxyacetophenone,1,2-phthalic acid Methyl ester,dihydroxybenzoic acid and cumene.The oxidation process was companied with the formation of functional groups as hydroxyl,carbonyl,and carboxyl groups,and the formation and free radicals such as methyl,alkoxy,and tert-butyl groups.Eventually,the benzene ring was opened by the active particles into linear molecules such as glycerol,methyl heptanoate and 3-ene-2,5-hexanedione,which will even be mineralized after continuous oxidation?chemical oxygen demand?42.85%;Total organic carbon?49.34%?.?4?The BPA degradation efficiency of different systems were compared:Fe²⁺/SPS/SID system>SPS/SID system>SID system>Fe²⁺/SPS system.The first-order kinetic fitting results show that the SID/SPS+Fe²⁺composite system exhibited the highest BPA degradation rate.When the voltage was 3.2 kV and the dosage of Fe²⁺/SPS was 0.2 mmol/L:0.6 mmol/L,the removal rate of 30 mg/L BPA after 30 min reached85.88%.When treated for 30 minutes,the SID-Fe²⁺/SPS combined system injected 57.6kJ of electrical energy per liter of solution within 30 minutes,and the SED?Specific energy density?value required to degrade BPA per unit concentration for 5 min was38.22 kJ/(mg·L^-1),dropping by nearly 89%compared with the bare SID system.The high initial BPA concentration clearly show the advantages of SID-Fe²⁺/persulfate combined system for BPA degradation.The degradation rate of BPA can exceed 85.88%at near-neutral pH,while strong alkaline conditions will quench free radicals and precipitate Fe²⁺.Cl^-exhibited stronger inhibitory effect than HCO₃^-and CO₃^2-.It is speculated that the anticipation ratio of SO₄·^-in SID-Fe²⁺/persulfate combined system was higher.The organic radical inhibitor methanol?MeOH?exhibited a stronger trapping ability for·OH and SO₄·^-composite radicals than TBA.The addition of HA reduced the BPA degradation rate by 4.23%.Referred to the BPA degradation pathway of in SID system,the possible oxidation pathway of BPA in strong ionization discharge combined with Fe???/persulfate system can be deduced:The electrophilic addition of·OH can produce hydroxylated bisphenol A derivatives,and SO₄·^-tends to attack the electron donating group of a BPA molecule,generating 4-isopropenylphenol or 4-isopropylphenol through electron transfer and hydrogen abstraction reaction.Under the combined oxidation of·OH,SO4·^-,and O₃,the intermediate can form monobenzenes containing functional groups such as carboxylic acid,ketone and aldehyde.Finally,the composite active particles open the benzene ring to form linear molecules such as oxalic acid and 3-ene-2,5-hexanedione until partially fully mineralization.