Study On The Process And Mechanism Of Catalytic Ozonation Of Microbubbles In Degradation Of Pharmaceutical Wastewater

Pharmaceutical wastewater has the characteristics of high concentration of pollutants,strong biological toxicity,complex composition,etc.After biochemical treatment,the concentration of pollutants in the wastewater is still high.This research used traditional bubble ozonation（CB/O₃）,traditional bubble catalytic ozonation（CB/O₃/LDHs）,microbubble ozonation（MB/O₃）,microbubble catalytic ozonation（MB/O₃/LDHs）technology for the treatment of simulated pharmaceutical wastewater（p-chlorobenzoic acid（p CBA）and actual pharmaceutical wastewater.To evaluat the treatment performance of different reaction systems on p CBA and pharmaceutical wastewater,and analyzed the effects of different initial p H values and the addition of Na HSO₃on the performance of microbubble catalytic ozonation.The soluble organic matter（DOM）of the actual pharmaceutical wastewater before and after the treatment of the four systems were fractionated into six components containing hydrophobic base（HOB）,hydrophobic acid（HOA）,hydrophobic neutral（HON）,hydrophilic base（HIB）,Hydrophilic Acid（HIA）and Hydrophilic Neutral（HIN））.Analyzed and explored the reaction characteristics of DOM components in different ozone oxidation systems,and clarifiedthe process and mechanism of microbubble catalitc ozonation and degradation of pharmaceutical wastewater.Below were key research findings:1)The p CBA degradation efficiency of the MB/O₃/LDHs was the highest in the four systems,and the degradation efficiency of p CBA could reach 99.8%after 15 minutes treatment.The·OH accumulation rate was 7.88,4.88 and 1.18 times that of CB/O₃,MB/O₃ and MB/O₃ system respectively.In the MB/O₃/LDHs,the order of p CBA degradation rate and·OH production rate under different p H conditions was:p H=7﹥p H=9﹥p H=5﹥p H=3﹥p H=11.Under the neutral condition,the accumulation of·OH was the highest and the treatment effect was the best.After Na HSO₃was added as·OH trapping agent,the·OH accumulation rates of CB/O₃/Na HSO₃,CB/O₃/LDHs/Na HSO₃,MB/O₃/Na HSO₃,MB/O₃/LDHs/Na HSO₃were 40%,27%,11%and 10%respectively.Among them,MB/O₃/LDHs/Na HSO₃ had the most significant inhibitory effect.2)The MB/O₃/LDHs reaction system had the best degradation effect in treating actual pharmaceutical wastewater.It had a significant removal effect on COD,UV₂₅₄ and three-dimensional fluorescent substances.The biodegradability and biological toxicity of the wastewater had been significantly improved.Under different p H conditions,the order of removal rate of COD and UV₂₅₄ in the catalytic ozonation of pharmaceutical wastewater by microbubbles was:p H=9﹥p H=11﹥p H=7﹥p H=5﹥p H=3.The removal efficiency of pollutants and ozonation efficiency in alkaline conditions were significantly better than those under acidic conditions.The removal rate of COD,UV₂₅₄ and ozone oxidation efficiency was the highest when the p H was 9,and the improvement effects of biodegradability and biological toxicity were the best.The inhibitory effects of Na HSO₃on different treatment systems were 3.75%,6.92%,6.20%and 16.69%respectively.3)The DOM of actual pharmaceutical wastewaterwas divided into six components before and after treatment by CB/O₃,CB/O₃/LDHs,MB/O₃ and MB/O₃/LDHs system.Compared with hydrophilicity,the hydrophobic components were easier to be removed.Hydrophobic components could be directly oxidized and removed by ozonation.Since the hydrophilic components contained a large number of difficult-to-degrade aromatic ring structures and unsaturated structures,they mainly rely on·OH oxidation to remove.The MB/O₃/LDHs system had the highest overall removal efficiency of DOM,reaching52.51%,of which the overall removal rate of hydrophobic components was 56.67%,and the overall removal rate of hydrophilic components was 46.93%.DOM has a conversion relationship in the oxidation process,the conversion of functional groups to acidic groups,the conversion of humic substances to fulvic and humic acids,and the conversion of other components to HIA components.The MB/O₃/LDHs system has stronger oxidation ability,and it destroyed the unsaturated structure and fluorescent structure of the DOM component most significantly.