| As a typical hazardous waste with high concentration of organic pollutants and heavy metal pollutants,electroplating sludge cannot be properly and efficiently disposed,which has always been the limiting factor for the development of electroplating industry.As a clean and efficient pollutant disposal technology,supercritical water oxidation technology has incomparable advantages in the field of pollutant disposal profit to the characteristics of supercritical water.Studies have shown that supercritical water oxidation technology can remove both organic pollutants and heavy metal pollutants at the same time.Therefore,this study introduced this technology into the treatment of electroplating sludge and obtained the appropriate working parameters and technical feasibility through the study,which opened up new ideas for the disposal of electroplating sludge,and studied the stabilization process of heavy metals and the degradation law of organic pollutants in the process of supercritical water oxidation technology in the treatment of high-iron electroplating sludge.The main content of this paper is as follows:(1)The effects of reaction temperature 623-823 K,oxidation coefficient 0-2 and other reaction conditions on the experimental results were studied.The results showed that the degradation rate of chemical oxygen demand(COD)increased with the increase of temperature and oxidation coefficient,and the maximum value was 92%.The reaction kinetics of organics in sludge was studied and it was found that when the reaction temperature reached 823 K,the reaction rate constant K=0.01381.The reaction activation energy of COD degradation was 37.411 KJ/mol.When the temperature was greater than 723 K and the oxidation coefficient was between 0.5 and 1.5,the degradation effect of total organic carbon(TOC)was significantly improved.However,when the oxidation coefficient reached 1.5,the effect of increasing the oxidation coefficient on TOC degradation was not significant.(2)When the temperature is low(623?723 K),increasing the oxidation coefficient has little effect on the transfer of heavy metals from the liquid products to the solid products.When the temperature increases gradually,increasing the oxidation coefficient has a significant effect on the transformation of heavy metals.From the view of chemical speciation transformation results,supercritical water oxidation technology for zinc and chromium in the electroplating sludge stabilization has played a positive role,effectively promote the chromium and zinc from the form to the stable form transformation of unstable,reduced chromium and zinc ecological toxicity and biological availability,reducing the potential environmental risk of chromium and zinc.The leaching toxicity of raw sludge and solid products under different reaction conditions was tested by acetic acid buffer solution method based on the leaching toxicity of solid waste.The results showed that the leaching toxicity of Zn and Cr in solid products treated with supercritical water oxidation under different conditions decreased significantly,and the higher the reaction temperature,the lower the leaching toxicity of Zn and Cr in solid products.(3)XRD,SEM and EPMA analysis of solid products under different conditions showed that with the increase of temperature and oxidation coefficient,Zn,Cr and Fe in solid products were significantly transformed from amorphous forms to crystalline compounds,with significantly reduced bioavailability and ecological toxicity and enhanced stability.After adding a large amount of iron-containing flocculant to electroplating wastewater,it becomes more difficult to treat traditional treatment technologies such as biochemical treatment technology and cement curing technology.In contrast,supercritical water oxidation technology can deal with this problem well. |
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