An Investigation Of Degradation Of Resin Effluent In The Catalytic Wet Air Oxidation System

Wet air oxidation (WAO) is an effective method to treat the hazardous, toxic and high concentrated organic wastewater. However, the severe operation conditions and high cost prevented WAO from being widely used. In order to shorten the reaction time and ameliorate operating conditions such as the reaction temperature and pressure, catalytic wet air oxidation (CWAO) has been developed to increase the oxidation efficiency. The development of heterogeneous catalysts with high activity and stability and an appropriate type of reactor have gained great attention and become one of the major techniques in the application of CWAO for different industrial wastewaters. As an innovative material, active carbon-ceramic complex combines the properties of ceramic materials (i.e., high mechanical strength, three-dimensionally enhanced structure, etc) with those of carbonaceous materials (i.e., adjustable surface properties).These materials are abrasion resistant and have a high crushing strength, a low pressure drop and a good textural development. Therefore, it increases reaction rate while reducing pressure losses and plugging of the catalyst.The aim of this work is to prepare active carbon-ceramic sphere and investigate the activity and stablity of the active carbon-ceramic sphere supported ruthenium catalysts for the CWAO of resin effluent. Moreover, the reaction process parameters of CWAO including reaction temperatures, reaction pressure, reaction time, pH value of the solution and the flow order of the packed-bed reactor, were studiedThe preparation procedure of active carbon-ceramic sphere were coating a porous ceramic sphere, as the framework, with a thermoset phenolic resin, curing, carbonization, activation with KOH etching, washing and drying. In optimal conditions, the material obtained exhibited a high carbon percentage (-4.73 wt.%) with a mean pore radius size of 13264 A and the apparent porosity (q) of carbon-ceramic sphere was 31.4%. The activated material shows a uniform carbon distribution, good adsorption properties and a high mechanical strength (24MPa). The total pore volume and the specific surface area of active carbon in the sample KC-120 was 0.69 cm3g1 and to 1100 m2g-1, respectively, and the adsorption isotherm of active carbon in the sample KC-120 is an isotherm of the Type IV.The preparation process, including the impregnation method, the concentration of RuCl3 solution, the reduction temperature and otherwise condition, which might affect on the activity of Ru/KC catalyst, was optimized, and results were as follows. The effect of impregnation solvent of RuCl3 on activity was explored and the results show that the catalyst has higher activity that prepared with H2O solvent than with acetone solvent, and over 24 h impregnation time should be conducted in the preparation. The reduction temperatures of Ru/KC catalyst in the range of 350-450℃for times should be above 6 h. The activity order of active carbon-ceramic sphere supported ruthenium catalysts:Ru/KC-120> Ru/KC-80> Ru/KC-60> KC-120> without catalysts, the Ru loading was fixed at 3 wt.%of active carbon in the active carbon-ceramic sphere. The activity of the Ru/KC-120 catalysts for wet air oxidation of resin effluent increased as the Ru loading increased up from zero to 3 wt.%, then seemed constant for the catalysts of which the Ru loading is higher than 3 wt.%. This was possible good advantageous for producing the oxygen reactive species, such as HO2·and increasing the Ru dispersion on the support, when Ru/KC catalysts doped with CeO2.The reactive parameters of CWAO including reaction temperatures, reaction pressure and pH value of the resin effluent, were studied, and results were as follows. The optimized conditions in this work was the reaction temperature of 200℃, the oxygen pressure of 1.5 MPa, the initial pH value of 9, the reaction time of 60min and the ratio of oxygen to wastewater 17.88. Under above optimized conditions, activity and stability of the Ru/ CeO2/KC-120 catalyst was performed in a packed-bed reactor for 30 days. From the experimental results, it indicated that the Ru/CeO2/KC-120 catalyst shows the excellent activity and stability in the CWAO of resin effluent, around 94% COD and 98% phenol removals was obtained. It's favorable to promote reaction effects of CWAO and protract catalyst life, when resin effluent and oxygen was mixed, heated and pre-degraded for WAO of resin effluent in the pre-mix reactor.The reaction kinetics for WAO and CWAO of resin effluent over the supports and catalysts was studied in the packed-bed reactor. The rate of COD reduction was described by two steps first-order kinetics. The rate coefficient and activation energies of catalysts were determined at a temperature range of 160 to 240℃and at oxygen pressure 1.5 MPa. The kinetic model was found to agree well with experimental results. It is helpful for the application of CWAO in industrial wastewater treatment.Resin effluent was degraded with multi-treat technics consists of polycondensation method, CWAO and biodegradation. The optimal operation conditions of multi-treat technics were ascertained and the equipment investment and run cost of multi-treat technics were evaluated according to the experimental results. Both treatment effect and economy cost of multi-treat technics meet the industrial application demand.