Design A Combined Reduction-oxidation Process For Efficient Degradation Of Aqueous Atrazine And Its Mechanism

The issue of pesticides chemical pollution has become one of the most serious environmental problems that are urgent to be solved.Atrazine is a triazine-ring herbicide,atrazine and its intermediates have resulted in wide soil and groundwater pollution.Because of the high toxicity,atrazine and its residues in soil and groundwater could affect the growth of plants and animals and cause the environmental and health problem.Although there are many methods to remove atrazine,most of these methods have shortcomings of time-consuming and inexhaustive atrazine degradation.Therefore,seeking efficient atrazine degradation method is still a hot spot in pollution control research field.In recent years,the advanced oxidation processes and chemical reduction methods have drawn more attention.Each method has advantage in removal of organic matters,but still was faced some shortages.The combined oxidation-reduction technology was developed to totally remove organic matters in order to overcome the shortcomings of each oxidative or reductive process.Recently,aerobic bimetallic systems have been widely studied because of their efficient dehalogenation of organic pollutants.Meanwhile,electrochemical method can implement the reduction and oxidation processed at the cathode and anode pool respectively.In this study,we attempted to construct combined reduction-oxidation systems on the base of aerobic iron-palladium bimetal process and the double-cell electrochemical process in order to realize the efficient atrazine degradation and mineralization.The detailed results are as following two parts:1 We prepared the nanoscale iron-palladium bimetal material,developed a combined reduction-oxidation iron-palladium bimetal/air process,and investigated the atrazine removal efficiency and mechanism with the aerobic iron-palladium bimetal/Air process.We found that iron-palladium bimetal/air system exihibed higher atrazine degradation performance than the zero-valent iron/air counterpart,the aerobic atrazine removal by iron-palladium bimetal is ascribed to a combined reduction-oxidation processes.In the reduction process,the 4-ethylamino-6-isopropylamino-1,3,5-triazine was the main intermediate generated by reaction between atrazine and hydrogen of free radicals,which was more easier to be triazine ring-opened.In the oxidation process,the additional palladium could promote the production of ferrous ions and accelerate the Fe(?)/Fe(?)cycles,thus enhance the production of reactive oxygen species to improve the atrazine degradation efficiency.Based on the determination of the amount/species of hydrogen and reactive oxygen species in the iron-palladium bimetal/air system,we proposed the enhanced atrazine degradation mechanism of the molecular oxygen activation by palladium and iron.Additionally,GC/MS and LC/MS were used to detect the intermediate products in the course of atrazine removal with the iron-palladium bimetal/air process,the possible atrazine degradation pathway was proposed.2 A combined reduction-oxidation double-cell electrochemical system was developed to degrade atrazine by using the RuO2/Ti electrode as anode and the Pt electrode as cathode.By comparing the atrazine degradation efficiency and pathway in the single-cell system and double-cell system,we found that the double-cell system showed a superior over the singer-cell process,a much higher atrazine degradation was observed in the double-cell system.The atrazine was firstly reductively to generate the main intermediate of 4-ethylamino-6-isopropylamino-1,3,5-triazine in the cathodic cell,then the EIST was oxidatively degraded and ring-opened in the anodic cell.The atrazine degradation mechanism in the double-cell electrochemical process was proposed on the base of determination of free radicals,pH,and intermediate products.