Study On The Removal Of P-Nitrophenol In Soil By Pulsed Discharge Plasma

Based on the limitations of traditional methods for the remediation of the organic compounds polluted soil,and a variety of advantages of pulsed discharge plasma（PDP）,the technology of PDP was chosen to treat the organic compounds in soil.Firstly,the PDP system for the p-Nitrophenol（PNP）removal in soil was set up to study the effect of different parameters for PNP degradation;Secondly,due to the complexity of the real contaminated soil,the PNP-Cu²⁺ compound contaminated soil was simulated to explore the impact of their concentration change on the PNP degradation,at the same time,the effect of clay（kaoline）addition on the removal of PNP with or without Cu²⁺ was also investigated;Finally,the experimental system of spectral analysis was set up to illustrate the crucial effect of the ·OH and the ·O on the organic compounds degradation in the soil remediation system by investigating the relative amount and the changing rule of the ·OH and the ·O under different reaction conditions.（1）A soil remediation system by the PDP with a seven needle-net electrode was set up and the PNP was chosen as the target pollutant.The effectiveness of the PNP polluted soil remediation by the PDP was investigated from three aspects,including the electrical parameters,the soil properties,and the gas parameters.The obtained results indicated that the higher pulse peak voltage,the lower initial concentration of the PNP,the acidic soil and the oxygen（O₂）bubbling were all beneficial for the degradation of PNP.Quantitative analysis for the degradation intermediates was carried out and it was concluded that the phenol and the catechol was the two main intermediates of the PNP degradation in the PDP system when air was used as the bubbling gas.（2）Effect of the existence of Cu²⁺ in the PNP polluted soil and the addition of the clay（kaoline）on the PNP degradation was investigated.The obtained the results show that the degradation rate of the PNP increased with the addition of the Cu²⁺ in the PNP polluted soil and the enhancement was higher with the increase of the Cu²⁺addition.The degradation rate of PNP increased in the sole PNP polluted soil and the PNP-Cu²⁺ polluted soil when kaoline was added into the PNP system.The above results show that the presence of Cu²⁺ or clay were beneficial for the degradation of the organic compound in the PDP system for the soil remediation.（3）The relative emission spectra of the ·OH and the ·O in the PDP system by spectrum detecting technique was investigated.The change of the relative emissionspectra of the ·OH and the ·O under the conditions of without soil addition,with the original soil addition,with the organic compound polluted soil addition and with the organic compound-heavy metal polluted soil addition were firstly investigated.The effect of pulse peak voltage,electrode gap and O₂ flow rate on the relative emission spectra of the ·OH and the ·O were also studied to explain the changing rule of the active species in the PDP system.The obtained results show that the addition of soil is beneficial for the formation of the ·OH and the ·O in the PDP system.The relative emission spectra of the ·OH and the ·O in the PDP system with PNP polluted soil addition were lower than those in the PDP system with the original soil addition,which proved the oxidation of the ·OH and the ·O on the organic compounds degradation in the remediation system.The addition of Cu²⁺ were favorable to the degradation of PNP in the PDP system.Furthermore,the increase of the peak pulse voltage as well as the O₂ flow rate was in favor of the formation of the ·OH and the·O,while the relative emission spectra intensity of the ·OH and the ·O were lower under the condition of the higher electrode gap.The research illustrate the critical effect of ·OH and ·O on the organic compound degradation in the soil remediation system by the PDP.