Resource Utilization Of Urban Sewage Sludge And Zinc Electroplating Sludge And Their Adsorption And Catalytic Degradation For Methylene Blue

With the rapid development of dyeing industry, China faces environmental problem of dyeing wastewater to be solved. Urban sewage treatment results in sewage sludge(SS), which usually contains a large number of toxic or harmful substances, such as persistent organic pollutants and heavy metals. Traditional methods of SS treatment include concentration, stabilization, conditioning, dehydration, drying and incineration, and SS disposal include landfill, land utilization and comprehensive utilization of building materials. With the environmental standards becoming more stringent and the revealing of disadvantages of these methods, it is urgent to find a new way to treat SS. At present, zinc electroplating water is generally treated by precipitation cost-effectively. However, it can result in great amount of zinc electroplating sludge(ES), which is much more difficult to deal with. As a kind of hazardous waste, reduction, reuse and recycle of ES are always the hot topics to domestic and foreign researchers. From the viewpoints of recycling SS and ES into high added-value products and utilizing waste to treat pollution, this paper was carried out. Sludge activated carbon(SAC), ES catalyst and sludge activated carbon-supported calcined zinc electroplating sludge(SCES) were prepared to remove methylene blue(MB). The following conclusions have been obtained:(1) Adsorption of MB could be achieved by SAC. Adsorption thermodynamic, kinetic and recyclability of SAC were studied by experiments, and the optimal conditions of MB removal by SAC were discussed. When the concentration of MB was 100 mg/L, the optimal SAC dosage and adsorption temperature were 6.0 g/L and 35 oC, respectively. Low concentration p H was not conducive to the adsorption. There was some relationship among the adsorption equilibrium time, equilibrium adsorption quantity and solution initial concentration, with the increase of initial concentration, the equilibrium time needed and equilibrium adsorption quantity increased. The equilibrium adsorption quantity of MB by SAC was 26.15 mg/g at 20 oC, and MBadsorption accorded with Langmuir isotherm adsorption and the adsorption type mainly was monolayer adsorption. The adsorption of MB onto SAC followed the pseudo second-order kinetic mode model. The recyclability of SAC could be easily realized by heat treatment and the efficiency was kept on 86.0% after 3 times.(2) Zn electroplating sludge catalysts could be used to remove MB under ultraviolet light(UV). Zn electroplating sludge catalysts were prepared, including calcined Zn electroplating sludge(CES), Electroplating sludge catalyst by acid leaching(ACES) and calcined electroplating sludge catalyst by supporting extract(ECES), and their catalytic capabilities under UV were studied. The results showed: ACES and ECES were prepared by changing the form of Zn, both of which were efficient on the removal of MB, while ECES was more efficient, and decolorization rate of 11.3% and decoloring amount of 2.825 mg/g were realized under UV after 2 h, respectively.(3) Effective removal of MB was achieved with SCES by UV-Fenton. CES had effective catalytic activity under UV-Fenton. When CES dosage was 0.4 g, H2O2 concentration was 2 mmol/L with 11 W UV light, decolorization rate of 85.13% and COD removal of 70.33% were realized in degradation of 500 m L of 50 mg/L MB. The main component of Zn Fe2O4 was observed in CES by morphology study. The UV-Fenton for MB removal got the best decolorization by SCES when ratio of SS and CES was 1:1. Under the conditions of SCES dosage of 0.4 g, H2O2 concentration of 2 mmol/L and 11 W UV light, which used for degradation of 500 m L of 50 mg/L MB, decolorization rate of 86.26% and decoloring amount of 53.91 mg/g were realized, respectively. What’s more, COD removal of 80.54% was achieved, which was higher than removal effect of MB by CES under the same conditions. The combination of SS and ES for UV-Fenton catalyst preparation realized the reclamation for both of them, which combined their advantages and realized the efficient removal of MB.