Study On Catalytic Degradation Of Phenols Wasterwater By Hydro-Plasma Combined With TiO₂

The technology of high-voltage discharge plasma degradation relates to a wide range of disciplines such as plasma physics, plasma chemistry, hydromechanics, thermodynamics, kinetics, high-voltage technology, and environmental engineering. The plasma degradation processes the synergistic effects of many water treatment technologies such as high temperature pyrolysis, photochemical oxidation, liquid electric cavitation degradation, superciritical water oxidation, and ozonization. It does not cause secondary pollution in treatment. It is one of the potentially applicable wastewater treatment technologies for treating refractory organic pollutants wastewaters such as papermaking wastewater, pharmaceutical wastewater and dyeing wastewater, the pollute water resource severely. Synergied hydro-plasma and catalyst would ultilize the high-voltage discharge energy greatly, and enhance the hydro-plasma discharge process.The hydro-plasma degraded high concentration 2,4-dinitrohpenol wastewater was preliminary discussed, and the process conditions of which influenced the degradation of 2,4-DNP wastewater by hydro-plasma was researched.With 2,4-dinitrophenol degradation in wastewater as a probe reaction, the process of hydro-plasma degraded and hydro-plasma combined with TiO₂ catalytic degraded phenols wastewater were studied. Used hydro-plasma degraded 2,4-DNP solely, under a voltage of 16kV, and a treated time of 30min, the 2,4-DNP was degraded completely, at 10min, the degradation rate was 70ï¼…, and with the increasing of reaction time, there was some opacity residues. Some kind of plasma acid was formed in wastewater after degraed by hydro-plasma, pH dropped to 3.30, and conductivity increased to 300μS.cm^-1. The hyro-plasma discharge process would be restrained by the high initial conductivity. And the lower initial 2,4-DNP concentration, the higher degradation rate, the greater the degradation rate. When the pH was 4.00, the degradation rate was highest. The influence of air velocity on 2,4-DNP degradation was not so big, blew in lots of air can raise gas-liquid mass transfer, helped phenols degradation.TiO₂,WO₃,SnO₂,CdS,LaCoO₃,Fe₂O₃,MnO₂ and Bi₂WO₆ were semiconductor, they degraded 2,4-DNP in hydro-plasma did not follow the general principles of photocatalytic, among them, TiO₂ got a better catalysis effect. TiO₂ coated with WO₃ could not increase the catalytic degradation efficiency of 2,4-DNP in hydro-plasma. The catalysis activity of TiO₂ Preparaed by ammonia precipitation was better than NaOH precipitation. The existence of chloride ions can greatly affect the catalytic activity in the process of TiO₂ preparation. And the catalysis activity of TiO₂ at calcination Temperatureof 673K was significantly higher than at the other.The process of hydro-plasma degraded and hydro-plasma combined with TiO₂ catalytic degraded 2,4-DNP wastewater were first order reaction, -ln(c/co)=kt+k₀. Reduced the 2,4-DNP concentration or rasied the discharge voltage could increase the degradation rate. the added of TiO₂ would enhance the degradation rate of 2,4-DNP, the degradation rate was highest at a initial concentration of 50mg·L^-1 and a TiO₂ dosage of 0.15ï¼…, and the catalytic effect enhance factor was 1.546. The discharge voltage was very great impact to 2,4-DNP degradation, and at the hydro-plasma degraded and hydro-plasma combined with TiO₂ catalytic degraded 2,4-DNP wastewater, the relation between discharge voltage and reaction rate constant was k=9.11×10^-3e^0.15791Uand k=21.38×10^-3e^0.13073U respectively.The calcination temperature of TiO₂ was great effect on the catalyticactivity of it combined with hydro-plasma, the optimum calcination temperaturewas 673K. The calcination temperature directly affected the crystalline structureof catalyst from the XRD patten and thermal analysis. A series ofcharacterization data shows that using TiO₂ as catalyst in hydro-plasma couldnot follow the general principle of photocatalytic. The suface hydroxyl groups ofTiO₂ decreased with the calcination temperature increase, and the amount ofsuface hydroxyl groups could impact on the catalytic activity. The crystal ofTiO₂ was not anatase in low calcination temperature, and could not form enoughlattice defects.