Degradation Of Synthetical Anionic Surfacants In Aquatic And Soil Environment

Surfactants indwelling in the environment impose positive and negative effect on the environment. On the one hand, it is labeled as environmental due to their trait of hard decomposition, on the other hand, it is a remediation reagent for some pollutants such as some organic matter and heavy metals. Being remediation reagent, it may risk a secondary pollution. Thus, research on natural and man-made intensificed degradation of surfactant residues in aquatic and soil environment is needed. Synthesized anion surfactant (SAS) is used most widely among all the surfactants. Degradation of surfactant mainly depends on biodegradation in soil while it depends on biodegradation and photodegradation in aquatic settings. Simulation test were applied to study natural photodegradation and artificial photodegradation of SAS in aquatic environment. SAS content of soil from dryland and paddy field sampled from thirty-nine districts or counties all over Chongqing and biodegradation of SAS in soil was studied subsequently.Effect factors on photodegradation of Dodecyl benzene sulfonic acid sodiumsalt (DBS) in aquitic environment were discussed applying single factorial experiment. The results were shown as follows: photodegradation rate became lower accompanied by increase of initial concentration of DBS while it became higher with augment of illumination intensity; the highest rate appeared when H₂O₂ was added to 2 g L^-1 ZnO as a catalyzer. With pH of 9 high rate could be achieved which was in appearence with favorable economic benefit. To some extent, categories and concentrations of inorganic anion in water influenced photocatalytic degradation rate of anion surfactant and the influence was complicated. SO₄^2- and Cl^- exerted restraint effect on photocatalytic degradation of DBS. Influence of H₂PO₄^- and PO₄^3- depended on their concentrations. Advance effects were detected in the range of low concentration while restraint effect appeared when a certain high concentration achieved.Results from orthogonal experiment of photocatalytic degradation in aquatic environment showed an order of priority for each factor was established as follows initial concentration of DBS > initial pH value > illumination intensity > catagories of catalyzer. In this experiment, optimal combination for artificial photocatalytic degradation of anion surfactant could be obtainned when inicial concentration of DBS was 40 mg L^-1, inicial pH was 9, catalyzer was H₂O₂+ZnO, illumination intensity was 320001ux.