| With the development of industrialization and urbanization, the Polycyclic Aromatic Hydrocarbons (PAHs) polluted sites problem of chemical industry relocation was increasingly serious, which would cause a great threat to the soil environmental safety and human health. However, traditional soil remediation technology couldn’t satisfy the remediation requirement of the fast and high-efficiency. Non-thermal plasma technology regard as a new soil remediation technology, which has the advantages of high-efficiency, short remediation period, no secondary pollution and so on, therefore, it has been paid attention of scholars at home and abroad. Based on this, remediation of contaminated soil by needle to plate corona discharge plasma technology that was supplied by pulse power and combined with metal oxides catalysts was proposed in this paper, which provided reference for the effective remediation of PAHs contaminated soil. The main results are as follows:(1) The optimization of high voltage supply system and needle-plate reactor was studied, which investigated the effect of forming capacitance, pulse frequency, the soil medium and soil thickness on energy to improve the state of discharge, energy input and decrease the energy consumption. Results showed that increasing the pulse forming capacitance and frequency benefited the injection of energy. As the forming capacitance and pulse frequency was100pF and70Hz, respectively, the pulsed discharge was at the optimum state. The existence of soil medium could improve injection energy. Increasing soil thickness could promote energy and specific energy efficiency. When the soil thickness was1mm, energy per unit soil mass was achieved the highest, which produced most active radicals during the gas ionization and benefited the Phe degradation.(2) Research on the feasibility of applying pulsed corona discharge plasma for remediating Phe contaminated soil, the effects of electric parameters, gas parameters, concentration of the pollutants and yield of ozone on Phe degradation efficiency were investigated. Results showed that great Phe degradation performance was presented by pulsed corona discharge plasma. Phe degradation efficiency was achieved70.5%after40min treatment. Increasing the pulse peak voltage and pulse frequency benefited the Phe degradation. Under different gas atmosphere, the Phe degradation efficiency from high to low was oxygen, air, nitrogen and argon atmosphere in order. The reactive oxygen species oxidation was the main cause of Phe degradation. With a certain range, increasing the gas flow rate could improve the diffusion of active species, contributing to Phe degradatio. And the optimum gas flow rate was0.8L/min. The Phe degradation and energy efficiency increased with the increase of initial Phe concentration. The increase of pulse peak voltage and pulse frequency contributed to the production and availability of ozone. Ozone reacted with Phe by direct or indirect oxidaitons.(3) The feasibility of combining pulsed corona discharge plasma with supported catalyst for remediating Phe contaminated soil was studied. The effect of the usage of the supported catalyst on Phe degradation was studied. The stability and energy efficiency of different catalysts, the physical properties of catalysts before and after discharge were investigated. Experiment results showed the collaborative technology could promote the degradation efficiency of Phe. When the0.2g of CuO/γ-Al2O3, MnO2/γ-Al2O3, Fe2O3/γ-Al2O3or TiO2/γ-Al2O3was added, the Phe degradation efficiency improved9.4%,14.3%,11.0%and6.1%, respectively. The highest energy efficiency of0.22mg/kJ was observed when using MnO2/γ-Al2O3catalyst, and then was Fe2O3/γ-Al2O3, CuO/γ-Al2O3and TiO2/γ-Al2O3in turn. After the catalysts was used five times in succession, degradation efficiency of Phe was still achieved approximately67%. The results of XRD, BET and total pore volume proved that physical property of catalyst had no obvious change by the discharge. |
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