| Pharmaceuticals and personal care products?PPCPs? have been increasingly detected in environmental waters as emerging contaminants in recent years. As PPCPs are continuously emitted into environmental water via municipal sewage and surface runoff, traditional water treatment processes cannot fulfil the removal requirement of PPCPs. As a green oxidation technique with high reaction efficiency, advanced oxidation technologies?AOT? have been considered to be a promising method to treat PPCPs. Sulfate radicals for in situ removal of PPCPs have recently received great attention due to their strong oxidability and wide scope of application. Reaction rate constant is an important physical quantity and index in determining reaction mechanism and designing reactors in engineering fields. Although reaction rate constant can be determined by experiments, predictive methods based on empiral data should be developed to avoid high cost and long cycle of experiments. Quantitative structure-activity relationship?QSAR? models are a popular predicitve technique which can calculate reaction rate constants of sulfate radicals with pollutants based on empirical data and molecular structures.This study employed both experiment determination and model prediction to obtain reaction rate constants of sulfate radicals at a range of p H based on competitive kinetics experiments of typical PCPPs and sulfate radicals. QSAR models for reaction rate constants of PCPPs and sulfate radicals were developed by using softwares Chem Bio3 D MOPAC, Dragon6.0 and Matlab based OECD's guidances on QSAR. Main results were listed below:?1? Reaction rate constants of sulfate radicals with nine sulfonamide antibiotics were determined in the Co/PMS system at pH = 7 by using competitive kinetics mechanism and catalysis of homogeneous peroxysulphate by transition metal. The rate constants?M-1·s-1? were 1.06×1010 for sulfamethoxazole, 4.19×1010 for sulfamethoxypyridazine, 2.17×1010 for sulfadimidine, 1.43×1010 for sulfadiazine, 2.75×1010 for sulfathiazole, 2.65×109 for trimethoprim, 2.08×1010 for sulfadoxine, 4.33×109 for arsanilic acid and 2.39×109 for roxarsone.?2? Reaction rate constants of sulfate radical with five sulfonamide antibiotics were determined in the Co/PMS system under acidic conditions?p H = 4?. The results rate constants?M-1·s-1? were 1.80×109 for sulfamethoxazole, 9.8×108 for Sulfamethoxypyridazine, 1.09×109 for sulfadimidine, 1.69×109 for trimethoprim, and 3.80×109 for sulfadoxine.?3? Reaction rate constants of sulfate radical with five sulfonamide antibiotics were determined in the Co/PMS system under alkaline conditions?p H = 10?. The rate constants were 3.65×109 for sulfamethoxazole, 1.49×109 for sulfamethoxypyridazine, 2.68×109 for sulfadimidine, 1.68×1010 for sulfadiazine, and 2.47×1010 for sulfathiazole.?4? A QSAR model was developed based on rate constants of 87 organic pollutants obtained from this study and literatures. The model was established as Logk = 4.295 Spmax1Bh?p? + 0.253 [C-005] – 0.446 CATS2D04DA – 0.154 CATS2D06DL – 1.222 Sp MADEA?ri? – 5.728. The adjusted correlation coefficient square(R2adj) was 0.862, the root mean squared error?RMSEtrain? was 0.373 log units, and the leave-one-out cross-validated?Q2LOO? was 0.825, indicating good robustness and productivity. Empirical reaction rate constants were employed as validation set to confirm the kinetic model results. It showed that the model had good prediction ability and can be applied to predict the organic pollutants within the application domain. |
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