The Biodegradability Of Aromatic Compounds And QSAR Models

Aromatic compounds are significant raw materials,intermediates and products in petrochemical industry and widely exist in the chemical sewage.It is necessary to evaluate their biodegradability for predicting the impact on biological treatment system,determination an appropriate response and providing a theoretical basis to ensure effective wastewater treatment.23 aromatic compounds,BTEX,chlorobenzene,phenol and nitrobenzene were chosen for biodegradable experiment in this dissertation.The removal and stripping rate of aromatic compounds in aerobic biochemical system were got to compare the influence of different substituted groups,the number and position of the substituent groups on the removal and stripping rate.Calculate the molecular structure parameters of aromatic compounds.Establish quantitative structure-activity relationship(QSAR)models with the removal rate from experiment and molecular structure parameters from calculation and successfully predicted other compounds with the same type.Substitutes of carbon chain can promote the removal and stripping rate of aromatic compounds in the aerobic biological system and the effects are related to the carbon number and connection.Substitutes of-Cl groups,hydroxyl groups and nitro groups can persist biodegradability and the more such groups substituted,the more they persist.The biodegradability sequence of dichlorobenzene and methyl phenol is ortho>meta>para.Linear regress ion-QSAR models are established with LnK and molecular structure parameters,which are Gibbs free energy GE,Henry coefficient Keq,energy of lowest unoccupied molecular orbital ELUMO,energy of highest occupied molecular orbital EHOMO,Δ E,the molecular weight Mol.Wt and dipole μ respectively.All these six models can meet 99%of the internal reliability,but with poorly fitting and forecasting ability.Multiple regressions are adapted to establish multivariate linear and multiple second-order QSAR models with LnK and molecular structure parameters and the average prediction error is 33%and 19%respectively.GE and Δ E are the main factors of aromatic compounds removal rate in the aerobic biochemical system with establishing models by stepwise regression.A linear QSAR model with GE and Δ E can predict aromatic compounds removal rate in the aerobic biological system accuracy with 10%average prediction error.