Quantitative Structure-Activity Relationships Study For Ozonation Of Refrectory Organic Componunds

The treatment of refrectory organics wastewater is difficult,ozonation as one kind of advanced oxidation technology has been increased concerned and been applied in the refrectory organic wastewater treatment.The oxidation-reduction potential of ozone is 2.07V,and the oxidation-reduction potential of the hydroxyl radical generated by ozone decomposition is 2.85V,therefore,ozonation has very strong oxidizing ability.In this paper,the degradation of 17 kinds of refractory organic pollutants such as Orange G,indigo and methyl blue were studied under 5different temperature conditions?T1=298K,T2=303K,T3=313K,T4=323 K and T4=333K?.The color removal rate constants of 16 organic compounds and TOC removal rate constants of 17 organic compounds were studied.Based on this,the color removal activation energy(Ea_COLOR)of 16organic compounds and the TOC removal activation energy(Ea _TOC)of17organic compounds were calculated by using the Arrhenius formula.And then the relationship between the Ea_COLOR and Ea_TOC with the quantum chemical structure parameters of the organic compounds were discussed.The conclusions are as follows:?1?Ozonation can achieve a very good effect on color removal of 16organic compounds during the first 2 minutes reaction.After 30min reaction,the color removal efficiency of almost all substances can be reached 100%.Besides,the color removal rates of organic compounds were accord with the pseduo first-order kinetics model during the initial reaction time,and with the increase of temperature,the kinetic constant of color removal of organic matters intend to be improved,which indicated that rise temperature could accelerate the color removal of organic matter during ozonation process;?2?At 298K,the TOC removal rates of the 17 organic compounds were ranged from 25.99%to 69.16%,and at 333K,were ranged from 56.46%to94.52%.Similar with color removal,the TOC removal rates of organic compounds were also accord with the pseduo first-order kinetics model during the initial reaction time,and with the increase of temperature,it was also found that,the kinetic constant of color removal of organics were much larger than the kinetic constant of TOC removal of organics,indicated that during the ozonation process,organic matters can't directly and completely been mineralized into CO₂ and H₂O,instead,they were oxidized into small molecules first,and then small molecules were completely mineralized;?3?17 molecular structural parameters were calculated by Gaussian 09.The correlations between Ea_COLOR and Ea _TOC with 17 quantum chemical structure parameters were analyzed.The results showed that Fukui?0?_min,Fukui?+?_min,Fukui?-?_min and Bond orders?C-C?_minin had a higher correlations with Ea_COLOR than other parameters;q?C-?_max,Bond orders?C-C?_max and Fukui?-?_min had a higher correlations with Ea_TOC than other parameters,and showed positive correlation.It can be seen that in the process of ozone oxidation,the Fukui index and bond order have a great correlation both with the Ea_COLOROLOR and Ea _TOC of organic matter;?4?The optimal QSAR models for Ea _COLOR and Ea_TOC were obtained by multiple linear regression?MLR?regression:M4_COLOR and M4_TOC,M4_COLOR:Ea_COLOR=11.545-126.236Fukui?0?_min-80.628E_HOMO-153.926 Fukui?-?_min-12.559Bond orders?C-C?_max,R²=0.952,SD=1.362.Ea_TOC=11.433+37.676Bond orders?C-C?_max-316.081q?C-H⁺?_max-42.914 q?C?_min-21.011E_HOMO,R²=0.948,SD=2.054,and the stability and prediction ability of model M4_COLOR and M4_TOC were tested by t-test,internal and external verification,Y random verification and multiple linear diagnosis,indicated that model M4_COLOR and M4_TOC had a good stability and prediction ability.So,model M4_COLOR and M4_TOC can be used for the prediction of Ea _COLOR and Ea_TOC of organic matters in ozonation process respectively.