Simultaneous Removal Of Chlorinated Methane And Cr(?) In Water By Nano Fe/Ni Bimetallic Catalyst

Chloromethane material is a kind of organic pollutants widely exists in the environment,easily in water detected,especially the use of chlorination process,resulting in a large number of chlorinated methane disinfection by-products produced.The chromium wastewater treatment is mainly from the tanning,fuel,electroplating and other industrial waste water and mineral mining and processing industry,the same is common environmental pollutants.However,these two substances belong to three substances,there is a potential threat to human health.Because of the increasingly serious water pollution,the compound pollution of heavy metals and organic pollutants in the water is generally in the water.In this study,Cr(?)is a common research object in the environment,and it is intended to seek an efficient way to remove the pollutants in order to achieve the effective removal of these two types of substances and reduce environmental risks.Nano scale zero valence iron reduction technology has broad application prospects in the field of pollutant removal,which has attracted wide attention of the international community in recent years.Due to the strong reduction of nanoscale zero valent iron,can make water oxidation state of matter happened electron reduction reaction,in theory,the nano zero valent iron reduction technology with the feasibility of simultaneous removal of chlorinated methanes compounds and Cr(?).Therefore,this study intends to carry out the simultaneous reduction of Cr(?)and compound pollution in water by using nano Fe/Ni bimetallic catalyst.In this study,nano-and-ferrous iron and nano-Fe/Ni double metal particles were prepared by liquid phase reduction method.After the characterization of the materials,the nanoparticles were found to have spherical shape,and the particle size distribution was found in nm 40?100.Ni after reduction of uniform deposition on the surface of nano zero iron,the EDS element analysis showed that the Fe/Ni dual metal particles prepared by step by step can make the solution of Ni ions completely reduced to the surface of Fe particles.After the reaction of Fe/Ni Bimetallic Particles appeared on the surface of dendritic shape,part appeared on the surface of platelet shaped structure,the XRD analysis showed that on the surface of the particles appeared iron oxide(Fe3O4,FeOOH)and FeCr2O4 and other compounds,suggesting iron surface occurred partial oxidation,Cr(?)in the solution in the form of sediment can be removed.This study examines the different influence factors(pH,Fe/Ni Bimetallic Catalyst investment quantity,Ni loading amount,initial chloroform concentration,temperature,etc.)of Fe/Ni bimetallic catalyst removal effect of chloroform and Cr(?)process.The results showed that the acidic condition was more conducive to the reduction of chloroform.When pH=3.0 was,the 100%h could be removed completely.Fe/Ni Bimetallic Catalyst cast dosage has obvious effect on the dechlorination process:low due to nano granular activated area to reduce and limit off the reactions of chlorine were.However,too high will be due to a large number of H2 generation attachment in particle surface also is not conducive to the occurrence of the reaction of chlorine removal,research is now the best Fe/Ni dosage was 1.0 g/L.The Ni loading also affects the bimetallic catalyst dechlorination activity:Ni and low load rate due to the catalytic active sites on the less and not conducive to removing the reactions of chlorine and high Ni load rate due to catalyst in iron particles over the surface coverage,which limits the electron transfer from the iron surface,also reduced the chloroform reductive dechlorination rate.Results show that optimal Ni load rate of 1.0 wt%.With the increase of the initial concentration of chloroform in the solution,the removal rate of chloroform was obviously improved,and the kinetics of the reduction of the reaction system was mainly due to the limitation of mass diffusion.Further study showed that chloroform in the surface of the Fe/Ni Bimetallic Catalyst Reduction de chlorine reaction rate and temperature according to the Arrhenius equation,with the rise of reaction temperature,dechlorination rate increased significantly;calculation results show,chloroform in the surface of the Fe/Ni Bimetallic Catalyst dechlorination reaction activation for 35.785 kJ/mol.It should be pointed out that,Cr(?)and total chromium are affected by different factors in the reaction is relatively small,in the experimental conditions can achieve Cr(?)100%and total chromium removal efficiency of more than 90%.In this study,the effects of different molecular structures of chlorinated methane on the reductive activity of Fe/Ni bimetallic catalysts were investigated.The study showed that the rate of reductive desorption of chlorine was increased significantly with the increase of the number of chlorine atoms.Under the same reaction conditions,the chloroform can be completely removed at 3 h,and the carbon tetrachloride is completely converted within 1.5 h,while the two carbon tetrachloride is still remaining in solution after 24 h reaction.Chlorinated methanes compounds,reductive dechlorination activity follow:carbon tetrachloride>chloroform>dichloromethane,and the three substances C-Cl bond cleavage can order is just the opposite.Based on of chlorinated methanes compounds reductive dehalogenation of chlorine in the process of analysis,this paper puts forward a new chlorinated methanes compounds of reductive dechlorination of chlorine mechanism for sequential dechlorination hydrogenation mechanism,namely every step of removing a chloride ion until completely remove chlorine products of methane generation:carbon tetrachloride,chloroform,dichloro methane,methane,methane;Cr(?)first in Fe/Ni bimetallic catalyst surface to accept electrons reduction of Cr(?)generation,and generated by the oxidation of Fe(?)binding,in the form of iron chromium oxide or hydroxide precipitation from solution removal.The development of this study will provide guidance and reference for the application of nano-zero-valence iron technology in the treatment of complex pollutants in the environment.