Study On Supercritical Water Oxidation Of Pentachloronitrobenzene Wastewater

In order to resolve problems of high cost, low destruction efficiency and difficulties in biochemical degradation faced to pentachloronitrobenzene(PCNB) wastewater, supercritical water oxidation (SCWO) was adopt to treat this kind of water in this paper. The supercritical water oxidation experiment and the catalytic supercritical water oxidation (CSCWO) experiment were performed in an HXDK-01-A intermittent reactor with PCNB industrial wastewater as research object and O2 as oxidant. The result showed that both SCWO and CSCWO had nice treating effects.The experiments studied the application of SCWO on PCNB deeply with orthogonal and single-factor experiments as scheme. They researched on the effects of temperature, pressure, and retention time on the PCNB oxidative degradation. A conclusion was drawn that the important orders of the factors which affect the conversion were temperature, pressure and retention time in turn. It was observed that the best reaction condition is 500℃of temperature, 28MPa of pressure, and 30s of retention time.Both homogeneous and heterogeneous catalytic supercritical water oxidation experiments were studied with nano-meter TiO2,ZnO,analytically pure Cu(NO3)2,Zn(NO3)2,Fe(NO3)3 and Na2CO3 as catalyst , results showed that the catalyst can improve the reaction rate, decrease the temperature and pressure, alleviate the harsh conditions for SCWO. It can significantly increase the removal of COD as well to achieve high efficiency and energy-saving. In heterogeneous, the TiO2/ZnO bimetallic particles had higher catalytic efficiency than each single component. Homogeneous catalyst Zn(NO3)2 and Fe(NO3)3 had almost the same catalytic efficiency, and both of them higher than Cu(NO3)2, but Na2CO3 had the highest efficiency. The mechanism of the CSCWO was discussed in the end of this part of the paper.The global kinetics for PCNB disappearance was described by regress the experimental data, and the traditional exponential equation was modified, taking into account the influence of induction time.