Nano Zero Valent Iron Repair PBDES Contaminated Soil

PBDEs are a brominated flame retardant additive,and have wide range of applications, because of its low price and excellent flame retardant properties, they are applied in most industries, such as electronics, construction, home decoration materials. Application of the material to bring the convenience of human life, but also to bring more serious burden to environment. PBDEs in various environmental media can be detected, especially in soils and sediments, the levels of PBDEs is higher than others. With the social and economic development, the levels of PBDEs in the environment is growing, meanwhile, the people are also gradually realized that the brominated flame retardants to human health and the natural environment can cause serious harm. For example, PBDEs have toxicity, can interfere with the body’s thyroid hormone, with the liver and nervous system toxicity. However, because the stable chemical structure, the PBDEs existied in the environment is more difficult to degrade, in order to reduce or even eliminate the PBDEs content in the environment, related to the repair and remove technique has become necessary to research. This paper focuses on the use of nano zero valent iron repair system to remove PBDEs in contaminated soil, discusses to remove the effect of BDE-209 about the system, provide a scientific basis for practical applications.Zero-valent iron has a reactive chemical, with a big negative electricity, due to its electrode potential E⁰ (Fe²⁺/Fe⁰)=-0.44 V, its ability of restore is strong, and the surface area of nano zero valent iron is larger, and have multiple contact sites with pollutants. Therefore, based on the catalytic reduction of nanoscale zero valent iron, this study nanoscale zero valent iron repair system to remove PBDEs in contaminated soil. Decabromodiphenyl ether （BDE-209） as the target pollutants, and studied the system of results of processing BDE-209 contaminated soil. The experiments were conducted the effects of reaction time on the degradation of BDE-209 and the degradation kinetics.The experimental results of reaction time show that, attributed to a sharp increase after the removal of lead flat with time, when the reaction to the last, the number of bromine atoms on the benzene ring of PBDEs gradually reduced, the less the number of bromine atoms, and the remaining bromine atom also becoming more and more difficult to restore, the reaction to the last low bromine biphenyl essentially no reaction with nano zero valent iron or response has been very slow, late stage, removal was basically unchanged or changed very little.Experimental studies show that the dynamics of the system follows the quasi-second-order kinetics, and the correlation coefficient higher than the quasi-first-order kinetics. The quasi-second kinetic equation is Y= 0.0015X 0.0009. The coefficient of correlation is 0.9922, the constant of reaction is 0.0015.This paper investigate the mechanism of degradation of the system, there may be two situations:first, nano zero valent iron and produced Fe²⁺ and H₂ in the reaction reduce the bromine atoms on the benzene ring, which was replaced by a hydrogen atom, reach to the role of reductive debromination; second, the direct adsorption of nano zero valent iron. The main role is the degradation of nanoscale zero valent iron.Through the above experiment, we preliminary study the a nanoscale zero valent iron system repair the BDE-209 in contaminated soil, provide some technical theory, explore a new repair methods of the degradation of PBDEs.