Catalytic Reductive Dechlorination Of Carbon Tetrachloride By Supported Ni/Fe Bimetallic Nanoparticals In Aqueous Solution

In recent years,carbon tetrachloride has been frequently detected in surface water and groundwater around the world,and it is gradually attracted people's attention due to its potential risk to human body.Based on this,it is necessary to find an effective way to treat organic wastewater.In this study,two supported nanoscale Ni/Fe bimetallic catalysts were prepared,characterized and used to ruduce carbon tetrachloride in aqueous solution.Several operation parameters(catalyst dosage,initial concentration of carbon tetrachloride,reaction temperature and the initial pH of solution)had been considered which may affect the catalytic degradation of carbon tetrachloride,and the kinetics of each group of bath experiments were investigated.Furthermore,the mechanism of catalytic reduction dechlorination of carbon tetrachloride and the possible degradation path of carbon tetrachloride were discussed.The main conclusions of the research are as follows:(1)Ni/Fe bimetals were successfully loaded on multi-walled carbon nanotubes(MWCNTs)and reduced graphene oxide(rGO)respectively.It was found that the two carriers could disperse nanoparticles commendably and prevent the agglomeration of metallic particles.The optimum contents experiment of the two supported catalysts were showed that 4 wt.%Ni doping ratio of Ni/Fe bimetal,2:1 and 4:1 loading ratio of MWCNTs and rGO respectively were the wise choice for these two catalysts.(2)The experimental results show that both of the catalyst can achieve a faster reaction rate when the system solution is acidic or neutral,while the reaction is inhibited to a certain extent when the solution is alkaline.It can also promote the reaction in the presence of Cl~-in solution.The experimental results showed that both catalysts can degrade 15 mg/L of carbon tetrachloride and reached over 95%of degradation efficiency in 35 minutes.(3)Under all experimental conditions,the degradation of carbon tetrachloride by two supported bimetallic catalysts were followed pseudo-first-order kinetics,and the apparent reaction rate constant conformed to Arrhenius law.The calculated apparent activation energy Ea indicated that the two catalysts had high catalytic activity in the degradation process.Moreover,repeated experiments shown that these two catalysts still have relatively satisfactory treatment effects after repeated use.(4)Based on the above experimental results,the concentration changes of various degradation products in the reduction of carbon tetrachloride were studied.It was concluded that CT was first reduced to CF,and then CF was further dechlorinated to form DCM and complete dechlorination products.Based on the reaction kinetics equation and the degradation product experiment,the reaction rate constants of each product were obtained.The degradation mechanism of CT in the two catalytic systems was discussed.It was inferred that the reduction of chloromethane was dominated by a series of carbon-centered free radicals.It was inferred that the reason for the high catalytic activity of the catalyst was the strong reducibility of atomic hydrogen(·H)during the reaction.