Structure-Activity Relationship Of Kinetic Rate Constants Of Degradation For Organic Pollutants

Recently,with the rapid development of industry and the general improvement of people's living standards,human beings have become increasingly dependent on chemicals,and the types and quantities of pollutants entering the water are also increasing.Many organics have little content in the environment,stable chemical properties,long retention time,difficult biodegradation,strong toxicity,and pose a serious threat to the ecosystem and human health.In recent years,the degradation of organic pollutants has become a research field with wide attention and great research potential.It has become a frontier field of interdisciplinary research in environmental chemistry,ecotoxicology,environmental engineering and environmental economics.The second order rate constant of degradation for organic pollutants is of great significance to evaluate its degradation efficiency and environmental fate in aqueous solution.Quantitative structure-activity relationship is a quantitative analysis method based on the molecular structure of organic compounds,combining with the properties/activities of compounds,and establishing a prediction model by mathematical methods to predict the target properties.This method has played an important role in drug molecular design and environmental ecological evaluation.Based on the concept of norm index proposed by the research group,this paper proposes a series of new norm descriptors,which are successfully applied to the prediction of three rate constants for pollutant degradation:(1)Second order rate constant of degradation of organic pollutants by sulfate anion radical:a new mathematical norm formula and four norm descriptors are defined for the first time,and they are successfully applied to the establishment of QSPR model.The results show that the model has good fitting effect and high correlation coefficient(R2=0.8862).Cross validation and external validation show that the QSPR model has good stability and prediction performance.The Application Domain Analysis also shows that the model has strong reliability and wide applicability.(2)Second order rate constants of ozone-degraded organic pollutants:93 degradation datapoints of organic pollutants are used to calculate norm descriptors and establish a QSPR model to predict the second order rate constants of ozone-degraded organic pollutants by combining with the newly proposed norm calculation formula.The statistical parameters R2,F and RMSE of the model are 0.9359,49.38 and 0.4455,respectively.The results of internal and external validation parameters show that the model has good stability,prediction ability and reliability.(3)Secondary rate constant of hydroxyl radical degradation of organic pollutants:the rate constant of hydroxyl radical degradation for organic compounds at different temperatures(206-1364K)is collected.The data set containes 871 organic compounds,totaling 1523 data points.The influence of temperature is introduced into the model of degradation rate constant of organic compounds by hydroxyl radical,and the results of the model are good(R2=0.8536).The result of leave-one-out cross validation shows that the model has good robustness.The results of external verification and MAE verification show that the model has good external prediction ability and could predict the secondary rate constant of hydroxyl radical degradation of organic pollutants accurately.All the three models have good fitting effect,which indicates that the new norm calculation formula and the new norm descriptors are effective in predicting the rate constant of organic compounds.Through literature comparison,it is found that the experimental value and predicted value of the models established in this study have a good correlation,which indicates that the norm descriptors have a good applicability in predicting the degradation rate constant of organic compounds,and the norm descriptor is generalized and universal.