Effect Mechanism Of Dissolved Organic Matter In Water On The Removal Of Emerging Pollutants By Electrochemical Technology

Electrochemical treatment technology has become the research emphasis of advanced treatment of emerging pollutants due to its advantages of strong reaction stability,no need to add auxiliary chemical agents,etc.However,the treatment performance of electrochemical technology for emerging pollutants in actual wastewater is much lower than that of simulated wastewater in the laboratory.Dissolved organic matter（DOM）refers to the organic matter that can pass the 0.45μm filter.As an important part of actual water,DOM must have a non-negligible influence on electrochemical treatment of organic matter.In this study,various spectral and mass spectrometry were used to explore the change mechanism of DOM in electrochemical oxidation at the molecular level,and then microplastics and antibiotics were used as representatives of soluble and insoluble emerging pollutants.The influence mechanism of electrochemical removal of emerging pollutants is studied.Based on the above research results,it provides a corresponding theoretical reference for the selection of water supply sources and the actual advanced treatment of emerging pollutants in factories.This study mainly includes three parts as follows:（1）The change mechanism of DOM in water during electrochemical oxidation was explored.Excitation emission matrix parallel factor analysis（EEM-PARAFAC）showed there contains two components of humus and protein in the natural source DOM,two-dimensional correlated infrared spectroscopy（2D-FTIR-COS）suggested that the free radicals generated in electrochemistry would preferentially oxidize saturated chemical bonds such as-CH₂.Fourier transform ion cyclotron resonance mass spectrometry（FTICR-MS）indicated that most DOM molecules unsaturation reduced after oxidation,and further analysis based on the above results showed that DOM molecules would be transferred to precursor of refractory organics or mineralized small molecules by electrochemical oxidation.These precursors of refractory organics may belong to humus.Therefore,factories should choose a water source with low humus content as industrial water supply,or use physical or chemical methods to degrade humus before industrial water supply.This study provides a theoretical reference for the selection of industrial water supply sources.（2）The influence mechanism of tailwater DOM on electrocoagulation to removal of microplastics was explored.The results of EEM-PARAFAC,scanning electron microscopy（SEM）,Zeta potential analyzer and other analysis results showed that tailwater DOM promotes the production of flocs and free radicals during electrocoagulation.Fe²⁺and Fe³⁺are adsorbed on the surface of DOM molecules and combine with·OH to form flocs.While DOM promotes the production of free radicals,which accelerate the aging of microplastics,flocs with DOM as nucleus can prevent toxic substances and smaller microplastic pieces from polluting water again.Therefore,electrocoagulation is the preferred method for removing microplastics of high-concentration DOM tailwater.This study provides an important reference for electrocoagulation to remove microplastics in actual water.（3）The influence mechanism of natural source DOM and tailwater DOM on electrochemical treatment of tetracycline（TC）was discussed.The analysis results of UV-Vis,EEM-PARAFAC,HPLC and other analysis results showed that the natural source DOM would restrain electrochemical oxidative degradation of TC,and the tailwater DOM also promoted its own degradation in the process of promoting electrochemical oxidation of TC.Some components in the DOM from both sources are stable during electrochemical oxidation.The ROS produced are produced by the spontaneous oxidation from DOM and electrochemical oxidative degradation pathways of TC.The path TC degradation by DOM spontaneous oxidation and electrochemical oxidation produces final intermediates are m/z=59 and m/z=74,respectively.Compared with tailwater DOM,natural source DOM has a stronger effect on promoting ROS under light conditions.The tailwater DOM can produce more substances that can produce free radicals continuously under dark conditions.Therefore,before the further advanced oxidation process of antibiotic-containing sewage,a regulating tank with light conditions should be set up,so that both the surface water source DOM and tailwater DOM can promote TC degradation effectively.This study provides a reference for wastewater treatment plants to antibiotic-containing sewage.In summary,this study mainly uses electrochemical experiments combined with a variety of spectroscopic,mass spectrometry,and other analysis to explore the influence mechanism of DOM as an important substrate in actual water bodies on electrochemical removal of emerging pollutants,which provides a corresponding theoretical reference for the selection of industrial water sources and the optimization of process selection and operation parameters of wastewater containing emerging pollutants in sewage treatment plants.