| Tanning effluent is conventional high contamination and non-biodegradation waste water, Traditional treatment method cannot be in keeping with the improvement of emission standard. A great deal of tanning agents and auxiliary tanning agents are adopted in tannery production process. They are mainly the non-biodegradation materials with stable structure.In this paper, selecting tannin and Sodiumβ-naphthalenesulfonate as model (auxiliary) tanning agent, the efficiency and mechanism of Fenton degradation on tannin andβ-NaSS were studied. Effect and reasons of initial pH, hydrogen peroxide dose, ferrous salt dose, aeration rate, reaction temperature and reaction time on the Fenton Oxidation were analysed. Then studied on the effect of coagulation and sedimentation with residual ferric salt after Fenton OxidationThe interaction of initial pH, reaction time, hydrogen peroxide dose and concentration of the pollutant was research by response surface method in order to make a brief analysis of the reasons. After creating response surface models of the two kind pollutants, It showed that the models were fitting well with analysis of variance and hypothesis testing. Reaction conditions were optimized by the models and lab testing results were accordance to the optimization conditions. Experiment with actual waste water in optimization condition gained good effect. ESI-MS was used to analyse the products generated by Fenton Oxidation of tannin andβ-NaSS so as to study the mechanisms of Fenton Oxidation of tannin andβ-NaSS. Single factor experiment indicated that initial pH, H2O2 dose, ferrous salt dose and reaction time are more important to Fenton Oxidation than reaction temperature, aeration rate. The optimal conditions are pH about2.5 to 3, the mol ratio of H2O2 dose and COD≈1:1, the mol ratio of Fe2+ and H2O2 from 1/20 to 1/5, reaction time=60min.The pH changs during Fenton Oxidation was also researched by single factor test. It can reflect the exist form of tannin,β-NaSS, H2O2 and iron ion, and explain how these factors affect the Fenton oxidation. the greater affection is ferrous ion and ferric ion s exist form . Removal ratios of tannin andβ-NaSS by coagulation and sedimentation after Fenton were improved above 5% generally, some up to 13%.ESI-MS analysis showed that during Fenton oxidation of tannin andβ-NaSS process, the hydroxy free radicals priority attack benzene ring with functional group and form quinone. Quinone was easily lead benzene rings to breaking into carboxylic acid, ketone and other intermediate products .If free radicals are enough, these intermediate products can be oxidated to phenol. Phenol was mineralized totally by way of p-benzoquinone, maleate, CO2 and H2O.Response surface method verified that interaction of concentration of pollutant, H2O2 dose, and pH was outstanding. oefficients of correlation(R2)of fitting models were above 0.9, meanwhile the models'confidence level was 99% with high signal to noise ratio.It could be obtained optimal conditions using model optimize. Taking laboratory experiment in optimal conditions, tannin and NaSS error was only 0.84%and 1.38%. Experiment with actual waste water in optimization condition also gained good effect.After Fenton oxidation of biological treatment effluent of tanning waste water, COD could be blow 60mg/L and meet emission standard. |
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