QSAR models for degradation of organic pollutants in ozonation process under acidic condition

• We model an ozonation treatment system of various organic compounds with complex structures.
• We study removal ratio and kinetics of each molecule to find universal ozonation degradation rules.
• Fukui indices are considered in QSAR analysis as research emphasis.
• Highest f(0) of main-chain carbons is more closely related to reaction rate than other quantum descriptors.
• Recommended model shown optimum stability and predictive potential by statistical methods.

Although some researches about the degradation of organic pollutants have been carried out during recent years, reaction rate constants are available only for homologue compounds with similar structures or components. Therefore, it is of great significance to find a universal relationship between reaction rate and certain parameters of several diverse organic pollutants. In this study, removal ratio and kinetics of 33 kinds of organic substances were investigated by ozonation process, including azo dyes, heterocyclic compounds, ionic compounds and so on. Most quantum chemical parameters were conducted by using Gaussian 09 at the DFT B3LYP/6-311G level, including μ, q H+, q(C)minq(C)max, ELUMO and EHOMO. Other descriptors, bond order (BO) as well as Fukui indices (f(+), f(−) and f(0)), were calculated by Material Studio 6.1 at Dmol3/GGA-BLYP/DNP(3.5) basis for each organic compound. The recommended model for predicting rate constants was ln k′ = 1.978 − 95.484f(0)x − 3.350q(C)min + 38.221f( + )x, which had the squared regression coefficient R2 = 0.763 and standard deviation SD = 0.716. The results of t test and the Fisher test suggested that the model exhibited optimum stability. Also, the model was validated by internal and external validations. Recommended QSAR model showed that the highest f(0) value of main-chain carbons (f(0)x) is more closely related to ln k′ than other quantum descriptors.