| With the development of the dye industry, the dyes are of diversities., furthermore, they are more and more difficult to be photolysized, oxidized and biodegraded, which makes the water pollutants more complicated. Dye wastewater is hard to decolor and contains refractory organic chemicals. The most effective methods to remove dyes are the advanced oxidation processes (AOPs), which could produce the free radicals. The non-thermal plasma is a kind of new AOP, which could generate UV radiation. shock waves, radical species, ions, free electrons to oxidize the dyes and to remove the colour and CODcr.In this paper, the typical azo dyes-reactive black5(KN-B) removal from aqueous solution by dielectric barrier discharge was studied, the optimal condtion for the oxidative degradation was investigated.The degradation mechanism was revealed, the degradation kinetics and energy efficiency was analyzed, and the biodegradability and acute toxicity of degradation products was illustrated.The treatment of refractory the dye wastewater by the hybrid process of dielectric barrier discharge and SBR was studied. The main results are summarized as following:(1) Experimental results showed the degradation rate of KN-B increasesd with the increasesd of input voltage and the input power, or decreased with the higher initial pH and conductivity; The degradation efficiency declined along with the increasing of initial KN-B concentration, but the absolute removal amount increased with the higher initial concentration;(2) CO32-would significantly reduce the degradation rate of the KN-B, and the higher concentration, the greater inhibition. NO32-and SO42-does not affect the degradation of the KN-B obviously; Low concentrations of Cl1-, Fe2+,Fe3+,Mn2+could enhance the degradation, however, they hinder the degradation at higher concentrations. H2O2alone can not degraded the K.N-B dye, low concentrations of H2O2could promote the degradation of the KN-B,but high concentrations could lead to the inhibition. The removal efficiency of KN-B declined along with the addition of the surfactant DBS, but when the concentration of the DBS was more than1mmol/L, the degradation of KN-B could be enhanced with the higher concentration of DBS; the addition of other dyes will significantly reduce the removal of KN-B. The degradation rates of different dyes are not same, the removal rates of disperse blue2BLN> reactive brilliant red X-3B> reactive black KN-B> cationic red.(3) After10min of treatment, decolorization efficiency of100mg/L KN-B was98.76%, while the removal rates of CODcr and TOC was only52.51%and15.36%separately. Dielectric barrier discharge could not reduce CODcr and TOC observably, the decolorization rate of KN-B dye was higher than the mineralization rate. Hydroxyl radical played a major role in KN-B degradation process, ozone and hydrogen peroxide producing by discharge involved in the oxidation of organic matter in the liquid phase.(4) With the increasement of oxidation time, the BOD5/CODcr ratio of KN-B solution increased from0.079to0.495. The toxicity testing by DeltaTox showed that the toxic of degradation solution increased firstly and then decreased.(5) The kinetics of of KN-B degradation by dielectric barrier discharge technology follows the first-order reaction. The absolute removing amount of KN-B increased with the higher energy input, but there was no linear relationship.(6) After10min degradation by dielectric barrier discharge, the absorption spectrum of actual dye wastewater in the visible region disappearanced gradually and the colour disappeared. The removal rate of CODcr, BOD5, TOC could reached89.13%,58.50%,16.13%and25.26%respectively, the B/C value increased from0.0196to0.397. With the combined process of dielectric barrier discharge and SBR, the removal rate of color could be increased from89.13%to95.25%, the removal rate of CODcr and BOD5were89.29%and64.55%respectively. The treatment efficiency of combined process is better than the single dielectric barrier discharge plasma process. |
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