QSAR Study For Reaction Rates Of Organic Pollutants In Fenton Process

The Fenton reaction is the most commonly employed for the treatment of organic contaminants and is an effective method to degrade organic compounds.Study on the degradation rule of organic compounds using Fenton reagents is helpful to quickly and effectively predict the degradation efficiency of organic compounds that lack of experimental data and the emerging organic pollutants.Herein,in this work,quantitative structure-activity relationship?QSAR?models have been established to reveal the general rule for organic matter degradation by Fenton process.Adsorption-dominated and oxidation-dominated QSAR grouping models are also bulit.Fenton QSAR models were expected to rapidly and accurately predict the treatment of emerging pollutants by Fenton process and provides an effective and economic treatment method of complex organic wastewater.In this thesis,all kinds of organic compounds were degraded by Fenton process.such as aromatic hydrocarbon compounds,amino compounds,heterocyclic compounds,organic acid,halides and so on.The color/TOC removal reaction kinetics were studied and in situ formed ferric-oxyhydroxides was used for adsorption during the Fenton degradation process.Quantum chemistry calculation method was built by Hyperchem,Gaussian and Material Studio.The results gave the parameters of quantum chemical structure for studied organic matters based on the quantum chemistry calculation,and illustrated the relationship between the parameters and the color/TOC reaction kinetic constants.Furthermore,QSAR models were also built based on multi linear regression methods and the important factors influencing degradation of organic compounds using Fenton reagents were proposed.The main conclusion of this study including:1.The color removal ratios and rates of organic matter were higher than that of TOC removal during Fenton process.2.The Fenton QSAR models for color and TOC removals of organic pollutants were built by multi linear regression method.The established optimum QSAR models(M7_COLOR and M6_TOC)for color and TOC removals of organic pollutants performed well with the aspects of goodness-of-fit,robustness and prediction.The excellent performance for many kinds of organic matters makes it widely usage in the future.Four molecular descriptors which influenced the degradation of organic matters were E²_GAP,q?H⁺?_x,f?0?_x and SAG.Two molecular descriptors which influenced he mineralization of organic matters were f?+?_x and?.3.The basic mechanism of Fenton process consists of chemical oxidation and coagulation of organic compounds.Based on adsorption percentage?AP?values,all organic compounds were divided into two groups.The organic compounds having AP values less than 15%were placed in Group NA?namely,non-adsorbed compounds?while compounds having AP values higher than 15%were placed in Group AD?namely,adsorbed compounds?.Relationship between reaction rate constants of organic pollutants and their molecular descriptors during Fenton oxidation and in situ formed ferric-oxyhydroxides were studied.The optimum QSAR models were also built respectively for two groups and their predictive ability were compared to that of Fenton QSAR models.?1?Oxidation-dominated QSAR model NA-M_COLORIn terms of color removal,QSAR model(NA-M_COLOR)built for Group NA had better predictive ability than the Fenton QSAR model(M7_COLOR).For Group NA,removal of the compounds by oxidation was the dominant process.In terms of TOC removal,ideal QSAR was not found for Group NA.Relative to the color removal,TOC removal were more complicated.During the mineralization process,both the property of the parent compound and that of intermediate compound was considered.?2?Adsorption-dominated QSAR model AD-M_TOCIn terms of color removal,compared to the Fenton QSAR model(M7_COLOR),QSAR model(AD-M_COLOR)built for Group AD did not improve predictive ability.For Group AD,removal by both oxidation and coagulation took place.In terms of TOC removal,QSAR model(AD-M_TOC)built for Group AD had better predictive ability than the Fenton QSAR model(M6_TOC).It was indicated that coagulation and adsorption had an important influence on the TOC removal for Group AD.4.k_COLOR is the sum of k_oxixi and k_ads.The color removal rate constants dominated by oxidation process for Group AD(k_oxi)were predicted by QSAR oxidation model(NA-M_COLOR).Fenton color removal rate constants(k_COLOR)were predicted by QSAR model M7_COLOR.The color removal rate constants dominated by adsorption function(k_ads)were obtained by subtracting k_oxi from k_COLOR.The results indicated that k_adsds was positively correlated with AP values.5.Based upon the Fenton QSAR models M7_COLOROLOR and oxidation-dominated QSAR model NA-M_COLOR,"Three-factor theory"influencing degradation of organic compounds using Fenton reagents were proposed.The important three factors was touch chance,active sites and bond cleavage.SAG represents the Touch chance.The larger SAG is,the greater the chance of Fenton reagent touch organic compounds is,and the reaction is easier.q?H⁺?_x,f?0?_x and f?+?_x represent the reaction site activity.The larger q?H⁺?_x,f?0?_x and f?+?_x are,the larger the reactive activity of organic compounds is,and the organic compounds are easier to attack.E²_GAP and E_LUMOUMO represent the difficulty of chemical bonds cleavage.The smaller E²_GAP and E_LUMO are,the smaller the chemical stability of organic compounds is,and the chemical bonds of organic compounds are easier to rupture."Three-factor theory"will provide an important theoretical basis for the study of the mechanism of Fenton oxidation degradation of organic matter.6.Based upon the adsorption-dominated QSAR model AD-M_TOC,the main factor influencing mineralization of adsorbed organic compounds using Fenton reagents was active sites.f?0?_x and BO_x represent the reaction site activity.The smaller f?0?_x is and the larger BO_x is,the larger the reactive activity of organic compounds is and then they are more likely to be adsorbed.Therefore,TOC is easier to remove mainly by absorption.