Application Research Of Paper Mill Sludge-derived Activated Carbon In Catalvtic Ozonation Degradation Of Orange ?

Dye wastewater is typical refractory organic pollutant for its high chromaticity, complex components and poor biodegradability, and its treatment is a challenge in environmental protection. It is difficult for traditional treatment process of dye wastewater to meet the enhanced environmental standards. Thus, it is urgent to develope some cost-effective technologies. In recent years, activated carbon catalytic ozonation has developed rapidly and exhibits a promising application prospect in treatment of dye wastewater. It is pivotal to find extensive and low cost activated carbon catalyst. While, paper mill sludge, which is extensive, with high content of inorganic substance and is difficult to handle, can be used for the preparation of activated carbon.Furthermore, this has a realistic meaning for promoting resource utilization of paper mill sludge and developing efficient treatment technology for dye wastewater.This paper put forward a new thought about preparation of activated carbon derived from paper mill sludge and using it as catalyst in catalytic ozonation for treatment of dye wastewater. The paper mill sludge was used to produce activated carbon(SAC) by chemical activation (ZnCl2 used as activation reagent). Effect of preparation conditions on the characteristics of SAC was studied by some characterization methods, and the optimal preparation process was obtained. The prepared SAC was used as catalyst in ozonation to degrade Orange ?, and the removal efficiency of Orange ? and TOC under different reaction conditions was investigated. In addition, the mechanism of catalytic ozonation of Orange ? by SAC was investigated. The results were as follows:1. The best preparation condition was ascertained:the mass ratio of sludge to activation was 2:1, the activation reagent temperature was 600?, the roasting time was 60min and the stirring time was 12h. On this condition, surface area and pore structure analysis show that the BET surface area was up to 466.9m2/g, total pore volume was about 0.2491cm3/g, average pore size was 3.198nm and the SAC was with a more open pore structure and suitable for the adsorption of the dye molecular. The results of infrared spectroscopy and pHpzc are that the surface of SAC may contain abundant functional groups such as -OH, unsaturated-C=C-,-C=O, in paraffin and so on,and the major oxygen groups was acid group.TG showed that the role of activator ZnCl2 is condensation anddehydration, so that the O and H were separated in the form of water and keep more carbon in the SAC.2. Degradation of Orange ? by SAC catalytic ozonation was systematically studied. The effect of ozone gas flow, SAC dosage,initial concentration of Orange ? and pH value were discussed as well as the cooperation factor in adsorption-catalytic ozonation system.The results shows that when SAC dosage was 1g/L, ozone inlet flux was 0.1L/min, initial concentration of Orange ? was 300mg/L and aqueous pH value was 3, reaction time was 60min, the removal of Orange ? was 100% and the TOC removal was about 60%. It was obvious that the removal efficiency of Orange ? by SAC/O3 was much higher than single ozonation,especially in the early period of reaction, synergistic effect was very intensive. The increase of SAC dosage and ozone inlet fluxes will improve the removal effience of Orange ? and TOC,to the contrary, the low initial concentration of Orange ? and pH value will increase the ramoval effience. At the same time, we investigate how the pH value affect single ozonation and SAC adsorption alone, we found that high pH value was advantageous to single ozonation,while, low pH would enhance SAC adsorption. The most likely reason is that the aqueous pH value will affect the surface charge of SAC.3.The mechanism of SAC catalytic ozonation of Orange ? was preliminarily ascertained. The reaction was not inhibited by the presence of tert-buyl alcohol, indicating that OH was not the mojor active material in SAC catalytic ozonation process. The removal efficiency of Orange ? and TOC was better under acid condition than alkaline condition,this proved that adsorption was important to catalytic ozonation. We also studied the full spectrum scanning of Orange ? at different reaction time, Orange ? was damaged in the reaction process,without absorption peak at 485 nm at the end of the reaction, Orange ? decolorizing reaction basic completely. Orange ? is broken into CO2 and H2O or small molecule. At last, the stability and reusability of SAC were studied,when the SAC was used five times, it could also keep activated.