| Contaminated Sites are the products of long-term industrialization, which are related to raw materials storage, process loss in industrial production and improper discharge of solid waste. These potential pollution sources will pollute the soil or groundwater, then endanger human health and environmental safety. Therefore, it is necessary to remediate the contaminated sites effectively.The low-temperature plasma is a rapid and effective remediation technique and gets more attention in contaminated sites remediation. The technology is one of the advanced oxidation technology combined with optical, electrical and chemical oxidation. The low-temperature plasma technology has shown great potential for contaminated industrial sites remediation due to its non-selective for the pollutants and high treating rates.In this paper, two different pollutants, dyes of textile industry and antibiotics of pharmaceutical industry, were selected as treatment targets by dielectric barrier discharge (DBD) technology. The operation conditions were optimized and the removal mechanisms were investigated. The following works were carried out and the main results are summarized as follows:(1) A panel DBD reactor for the pollutants treatment was designed. Through investigating the controlling factors (such as applied voltage, frequency, gas gap and soil filling) that effect discharge characteristics of reactor, better structure parameters of reactor are obtained.(2) The investigation of Acid red 73 (AR 73)-contaminated soil was conducted by DBD technology. Increasing applied voltage and frequency was beneficial for AR 73 decomposition, meanwhile decreasing gas gap and dielectric thickness achieved the same effects. When the air flow rate was 0.28 m·min-1, better results can be obtained. Extending treatment time influences little on AR 73 degradation. The degradation efficiency decreased with the increase of AR 73 initial concentration and soil thickness, while the corresponding energy efficiency performed contrary phenomenon. The removal of COD value achieved about 74% during the degradation, and the reaction was in line with the apparent first order kinetics. The degradation process was discussed through UV-Vis spectra of AR 73. After AR 73-contimanited soil was treated for 25 min under applied voltage 17.6 kV, frequency 300 Hz, air flow rate 0.28 m·min-1, degradation efficiency of AR 73 and maximum energy efficiency were 93% and 0.71 g kWh-1, respectively.(3) The remediation of antibiotics-contaminated soil using DBD plasma at atmospheric pressure was investigated. Increasing applied voltage was beneficial for CAP decomposition. Large oxygen flow rate favored the abatement of CAP in soil. When the soil moisture content was 10%, better results can be obtained. Extending treatment time influences little on CAP degradation. As iron element abounded in soil, the effect of Fe0 with different levels was examined and the improvement on CAP degradation was obtained. The energy efficiencies increased with the soil mass in the range from 1 g to 10 g. There exists an initial concentration range for high level CAP decomposition. CAP molecules experienced dechlorination reactions and phenyl-N bonds rupture through identifying intermediates of CAP degradation using HPLC/MS. Experiments conducted under different gas atmospheres (O2, air, N2, Ar) indicated that O3 made a major contribution to CAP degradation. Based on HPLC/MS analysis, a possible pathway of CAP degradation in soil in this system was also proposed. After CAP-contimanited soil was treated for 20 min under applied voltage 18.4 kV, frequency 500 Hz, air flow rate 0.14 m·min-1, soil moisture content 10%, Fe/soil 2%, degradation efficiency of CAP and maximum energy efficiency were 81% and 1.18 g kWh-1, respectively. |
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