The Dft Study On The Reactive Sites And Quantitative Structure-partition Coefficient Relationship Of Selected Paes And Vocs

Industrial wastewater contains high concentrations of volatile organic compounds and a small amount of refractory pollutants such as phthalates.The advanced oxidation technology based on sulfate radical and two-phase distribution bioreactors?TPPBs?with silicone oil as the non-aqueous phase liquid can provide a highly efficient method for the treatment of such contaminants.The prediction of active site of free radical reaction has become a research hotspot;expression of interphase mass transfer requires knowledge of the partition coefficient of volatile compounds between silicone oil and air(K_SiO/A),a knowledge which is currently mostly lacking.Density functional theory calculations can be used to predict the reactive sites of organic pollutants,effectively explore and complement the experimentally measured reaction mechanism,and also provide the necessary quantum chemical parameters for quantitative structure-activity/property relationship studies.In this dissertation,the reactive sites of the typical refractory organic pollutants,dibutyl phthalate?DBP?by SO₄^-?was studied using DFT-B3LYP method.The QSPR study was performed on the octanol-water partition coefficient(K_OW)of phthalic acid esters and the silicone oil-air partition coefficient(K_SiO/A)of hydrophobic compounds.The specific research content and main conclusions are as follows:?1?The properties of the persulfate system were calculated at the 6-311+G?2d,p?basis level.The results show that the peroxide bond energy and bond length of S₂O₈^2-are 129kJ·mol^-1 and 1.475?,respectively.The SO₄^-?has a single electron whose electrophilicity is5-6 times that of persulfate and the oxidation-reduction potential is also increased to+2.40 V.The DBP molecular structure was optimized at the 6-31G?d,p?level,then was confirmed by the dipole moment and the characteristic peaks of IR and UV-Vis spectra.Theoretical calculations showed that the initial reaction of DBP with SO₄^-?is mainly by hydrogen abstraction.Then the reactivity site was determined from the theoretically analysis of frontier orbitals,local activity index,atomic charge,quantitative molecular surface analysis and the dissociation enthalpy of C—H bond,at last we proposed and verified its initial reaction path.?2?Quantum chemical parameters of PAEs were calculated using the 6-311G?d,p?basis set,which were used for the quantitative structure-property relationship?QSPR?study for lgK_OW.The correlation analysis shows that the correlation coefficients between average polarizability???,thermodynamic parameters(ZPE,E^?_th,H^?,S^?,G^?,C_v^?)and lgK_OW are all greater than 0.9.The optimal regression model developed is lgK_OW=-3.468+0.041?,and the validation parameters are R²=0.99,RMSE=0.33,Q²_LOO=0.97,Q²_BOOT=0.98,Q²_EXT=0.98,indicating that the model has satisfactory goodness-of-fit,robustness,and prediction ability.The lgK_OWW value of PAEs is positively related to?,and the strength of intermolecular dipolar interactions,especially the dispersion interaction,is the main intrinsic mechanism that affecting the n-octanol-water partitioning properties of PAEs.The comparative analysis results of the model show that the model established this time is simple and intuitive,the algorithm is more transparent,and the prediction performance is good.?3?The quantum chemical parameters of selected compounds,including alkanes,alcohols,aromatic hydrocarbons,chlorides,ketones,esters,and ethers,were obtained at the 6-311G?d,p?level,and molecular composition parameters were also taken into account.A linear regression model for predicting lgK_SiO/A was established using finite data.The optimal model is lgK_SiO/A=2.845+0.280×#nonHatoms–0.245×E_gap,with statistical validation parameters R²=0.922,F=67,VIF=1.31,RMSE=0.247,Q²_LOO=0.91,Q²_BOOT=0.92,Q²_EXT=0.89?after removing the outliers?,showing that the model has good fit,stability and predictability.The applicability domain of the developed models was characterized by Euclidean distance method and Williams plot.Dispersion interactions and electron-transfer interactions are the key factors affecting lgK_{Si O/A},#nonHatoms have a significant positive correlation with lg K_{Si O/A},while E_gap is negatively correlated.The physicochemical significance of the descriptors in the model is specific,and the mechanism is fully explained.There is no need to predict the lgK_SiO/AiO/A values for compounds according to their functional groups,and the model has clear applicability domain and better application performance compared with previous study.