The Study Of Behaviour Trace Of Ozone And Transformation Rule Of Coagulant Hydrolysis In Hybrid Ozonation-Coagulation System

This study aims to clarify the two action pathways of ozone between organic matter and metal coagulant existing in the Hybrid Ozonation-Coagulation（HOC）system.By evaluating the removal effect of dissolved organic matter,kinetic analysis,instrument characterization and other means,the trajectory of ozone between organic matter and metal salt coagulant was explored,the removal path of organic matter under multiple actions was clarified,the conversion path of intermediate products in the degradation process of organic matter was revealed,and the formation and formation of coagulant hydrolysate were explored.The transformation law provides a certain theoretical support for mastering the coordinated control technology in the system,enhancing the removal efficiency of dissolved organic pollutants,and providing a certain amount of theoretical support for advanced sewage treatment.In order to clarify the action trajectory of ozone,high performance liquid chromatography was used to determine the removal effect of organic matter in ozone alone,HOC and HOC-phosphate systems（phosphate radicals can shield the reaction between ozone and coagulant）under different ozone dosage,the results show that Ozone preferentially oxidizes organic matter,and then interacts with the hydrolysate of the coagulant to produce synergistic effects between ozone and coagulants（SOC）to promote the generation of hydroxyl radicals（·OH）;To explore the hydroxyl production and the surface functional groups of the coagulant in the three systems,this study use the tert-butanol method（t-Bu OH）,Electron Paramagnetic Resonance（EPR）,Fourier Infrared Spectroscopy（FT-IR）and X-ray Photoelectron Spectroscopy（XPS）,the results further verify that ozone has competitive characteristics between the organic matter and the surface hydroxyl groups of the coagulant;To study the contribution of multiple reactions in the organic matter removal process in HOC system,the active oxygen components in the ozone alone and HOC system were quenched,and quantitatively evaluated were use through kinetic analysis,the results show that the oxidation of ozone molecules dominates under low ozone content,and the oxidation of hydroxyl groups increases with the increase of ozone content.Among them,the contribution rate of the ozone chain decomposition reaction is stable at about 20%,the contribution rate of the peroxone reaction increases first and then decreases,and the contribution rate of the SOC starts to increase significantly after the amount of ozone at 9.6 mg/L.Liquid-mass spectrometry（HPLC-MS）was used to identify and analyze the intermediate products in the organic degradation process in the ozone alone,HOC and HOC-phosphate systems,and the conversion path of the intermediate products was inferred based on the structural changes of their functional groups.The results show that the organic matter first undergoes hydroxylation reaction,followed by a series of decarboxylation,demethylation and dehydrogenation reactions,and finally ring-opening and cracking to form small molecular organic acids,and then complete mineralization.Ozone alone is the same as the intermediate product of the HOC-phosphate system.In addition,three unique intermediate products have been detected in the HOC system,indicating that the SOC reaction has occurred and the oxidative decomposition of organic matter has been strengthened.In order to explore the changes of coagulant hydrolysis forms under the action of ozone,the Al-Ferron time-lapse complex colorimetric method and electrospray mass spectrometry（ESI-MS）were used to determine the type and distribution of morphology of the coagulant hydrolysates in traditional coagulation and HOC systems,respectively.The results of the Al-Ferron method show that the introduction of ozone converts Al_a and Al_c into the dominant hydrolyzed form Al_b.Al_b can more effectively catalyze the ozone decomposition to produce more·OH and strengthen the oxidation capacity of the system.The results of ESI-MS show that ozone obviously affects the distribution of coagulant hydrolysis forms,the proportion of highly polymerized hydrolysates increases,and the polymerization reaction between coagulants accelerates.The essence of the SOC reaction mechanism between ozone and the coagulant is that under the action of ozone,the surface hydroxyl groups of the coagulant and the surface protonated hydroxyl groups combine to form-OH·OH₂ bridge bonds,and then form Al-OH-Al chemical bonds during the continuous polymerization process,and produced high polymerized hydrolysate finally.