| In this paper, we studied the radiation degradation of wastewaters contaminated with organochlorine fungicides which were difficult to deal with such as HCB, PCP and PCNB by using ionizing radiation technology. Simulate wastewater containing each pesticide solution was prepared, and the before and after concentration of corresponding pesticide radiated by 60Co-γwas measured by GC/MS. And we studied the impact of a number of factors (radiation, pH, additives, etc.) on the degradation of corresponding pesticide. The results showed that: 1. Photocatalytic TiO2 particles mainly depended on the free radical ?OH to degrade phenol. The yield of ?OH radical was relevant with the structure of TiO2 particles. And its capacity of degradation was achieved through radical ? OH yielded by photocatalysis. The 60Co-γand the photocatalysis of TiO2 all could effectively degrade phenol. When radiation absorbed dose was 10 kGy, the rate of degradation of phenol could reach to 96%; In the process of radiation degradation of phenol solution, ?OH played a major role, and next was e–aq. The ?OH, the hydrated electron and hydrogen radicals produced in the process of radiation could react with phenol, so the phenol opened the loop and happened dechlorination oxidation reaction. The ultimate degradation products of phenol were small molecular substances, carbon dioxide, water and gas. The activity of radical was strong in neutral solution, so it was propitious to degrade phenol.2. 60Co-γcould effectively degrade HCB. When radiation absorbed dose was 10 kGy, the rate of degradation of HCB could reach to 90%; When radiation absorbed dose was 17 kGy, the rate of degradation of HCB could reach to 95%; in the process of radiation degradation of phenol solution, ?OH played a major role. The ?OH, could react with HCB, so the HCB opened the loop and happened dechlorination oxidation reaction. The ultimate degradation products of HCB were small molecular substances, carbon dioxide and gas; the pH of HCB aqueous solution had an important impact on the radiation degradation of HCB aqueous solution. In the alkaline solution, the activity of free radical was strong, so it was helpful to the degradation of HCB. Na2CO3, NaNO3, H2O2 and TiO2 added into HCB aqueous solution could affect free radicals involved in degradation reaction. Na2CO3 and TiO2 could improve the degradation efficiency of HCB, while NaNO3 and H2O2 could reduce the degradation efficiency of HCB; when TiO2 particles were added into, the degradation of synergies was better than the degradation of a single.3. 60Co-γcould effectively degrade PCP which was typical organic pesticide. When radiation absorbed dose was 10 kGy, the rate of degradation of PCP could reach to 90%; When radiation absorbed dose was 17 kGy, the rate of degradation of PCP could reach to 96%; in the process of radiation degradation of phenol solution, ?OH played a major role. The ?OH produced in the process of radiation could react with PCP, so the PCP opened the loop and happened dechlorination oxidation reaction. The ultimate degradation products of PCP were carbon dioxide and gas; the pH of PCP aqueous solution had an important impact on the radiation degradation of PCP aqueous solution. In the acid solution, the activity of free radical was strong, so it was helpful to the degradation of PCP. Na2CO3, NaNO3, H2O2 and TiO2 added into PCP aqueous solution could affect free radicals involved in degradation reaction. Na2CO3, H2O2 and TiO2 could improve the degradation efficiency of PCP, while NaNO3 could reduce the degradation efficiency of PCP; when TiO2 particles were added into, the degradation efficiency of PCP was improved. So the degradation of synergies was better than the degradation of a single.4. 60Co-γcould effectively degrade PCNB which was typical organic pesticide. When radiation absorbed dose was 8.5 kGy, the rate of degradation of PCNB could reach to 95%; When radiation absorbed dose was 17 kGy, the rate of degradation of PCNB could reach to 96%; in the process of radiation degradation of phenol solution, e–aq played a major role. The hydrated electron produced in the process of radiation could react with PCNB, so the PCNB opened the loop and happened dechlorination oxidation reaction. And nitro-group and chloric-group were removed owing to radiation. The ultimate degradation products of PCNB were carbon dioxide and gas; the pH of PCNB aqueous solution had an important impact on the radiation degradation of PCNB aqueous solution. In the alkaline solution, the activity of free radical was strong, so it was helpful to the degradation of PCNB. Na2CO3, NaNO3, H2O2 and TiO2 added into PCNB aqueous solution could affect free radicals involved in degradation reaction. Na2CO3 and TiO2 could improve the degradation efficiency of PCNB, while NaNO3 and H2O2 could reduce the degradation efficiency of PCNB; the reasons of their roles were all promoting or inhibiting the quantity or activity of e–aq, ?OH and ? H radicals, when TiO2 particles were added into, the degradation of synergies was better than the degradation of a single.This study also prepared 5 mg/L mixed solution containing pentachloronitrobenzene, cypermethrin, fenvalerate, and the mixed solution was degraded by 60Co-γradiation. The result showed that the radiation degradation method had obvious degradation effect for each pesticide under the condition of various pesticides existing, and the purpose of a variety of pesticide contamination degraded at the same time could be carried out.60Co-γirradiation had a better degradation effect on the HCB, PCP and PCNB. In response to the treatment of extremely difficult degradation persistent organic pollutants, the radiation was a more promising method.
|
PDF Full Text Request