Mechanism For Coupling And Polymerization Of Emerging Organic Pollutants In Waters

With the continuous discharge of external low-concentration and great-risk emerging organic contaminants into waters,the related pollution problems have draw increasing attentions.However,harmless humic substances were also widely observed in waters with much higher concentration,traditional water treatment methods always show low efficiency in the removal of target emerging organic contaminants.Therefore,how to effectively control emerging organic contaminants with the presence of other organic matters has been an important issue in water deep-treatment field.In this study,we focus on the coupling transformation of target pollutants in enzymatic catalysis,manganese oxides oxidation,peracetic acid oxidation,and spontaneous coupling system.Quantum chemistry is further applied to predict the regioselectivity and toxicity variation,and explore the detailed coupling mechanism for traget pollutants removal.The main work and results are listed as follows:?1?Laccase-catalyzed coupling transformation kinectis and mechanism of CAP in the presence of phenolic humic substances was studied.Fukui function was further used to predict the reactive sites of substrates.We found that the humic substances may firstly transform to corresponding quinoid intermediates or carbon-centered radical cations during laccase-catalyzed one-electron oxidation,which greatly impacted the further coupling of CAP molecules and combination conjugates formation,CAP finally incorporate into humic substances with C-S-C combinations.Furthermore,detailed coupling mechanism of DCP was proposed based on DFT study,combined enzymatic-electronic technology was explored,in which CO₂ and current was adjusted to control the reaction pathways for detoxification of chlorophenols.?2?MnO₂ direct-oxdiation and composite MnO₂ material-based photocatalysis were employed to study the transformation kinetics and mechanism of E2.The result of reaction kinetics indicated that the prepared MnO₂-doped TNTs is more efficient in the oxidation of E2 than pure TNTs or MnO₂.On the basis of theoretical spin density and charge population analysis,corresponding explanations were proposed:MnO₂-induced pre-oxidation could facilitate the barrier-less coupling of E2 radical and ·OH,moreover,heterojunction structure of MnO₂ and titanate may also promote the visible-light-driven photocatalytic activity?3?Peracetic acid-based oxidant was studied to explore its direct and indirect oxidation behavior toward organic pollutants.The results showed that the direct oxidation of amino acids by peracetic acids is relatively weak,the oxidation products were mainly[O]addition conjugate and relative dimers.Moreover,we found that Co2+ may effectively activate peracetic acid to generate reactive radicals,such as CH3C?=O?O·,CH3C?=O?·,·OH and ·CH3,which may react with target pollutants through nucleophilic/electrophilic addition reactions.Color-shifting was observed during the oxidation of crystal violet in Co2+ catalyzed peracetic acid system,this may be caused by the radical addition on the chromophore groups of crystal violet.A QSAR model was established based on the structural physiochemical parameter of organic pollutants and reaction kinetics in Co2+ catalyzed peracetic acid oxidation system to predict the reactivity of other organic pollutants in this system,the equation is kPAA· =1.573-6.961×?ELUMO-EHOMO?-0.676×#Charge.?4?The spontaneous coupling reaction of toxic chlorobenzoquinones intermediates and electron-rich amino acids without additional oxidants was investigated.Based on products identification and bacteria toxicity assessment,the reaction mechanisms were proposed as follows:electron-rich amino acids could react with chlorobenzoquinones through nucleophilic addition,which is a detoxification step by occupying the reactive site of quinones through C-N-C combination.Theoretical calculations suggested that the structure and physicochemical property may decide the corresponding electron affinity,oxidative potential and toxicity of CBQs,and further impact the spontaneous coupling pathways and toxicity change with amino acids.