| Chlorophenols (CPs), a kind of environmental priority pollutants, are highly recalcitrant towards to both chemical and biological degradation and carcinogenicity, mutagenicity and teratogenicity in our environment. A series of related researches have been studied how to degradation chlorophenols in the water domestic and overseas. Up to now, large numbers of measures have been developed. By the end of 1980s, nano iron particles have high specific surface area and small size, especially nano bimetallic catalyst, which can improve and enhance the reactivity in degradating the organic pollutants.They have become an important field in the chemical reduction.In this paper, modified liquid phase reduction was employed to prepare the nano scale zero valent iron and nano Pd/Fe bimetallic particles. Through transmission electronic microscopy (TEM), X-ray diffraction (XRD) and other analytical methods, the shape, size and crystal structure of the nano iron and nano Pd/Fe bimetallic catalyst can be characterized. The results showed that particles with small size were dispersed rather evenly and the diameter was between 25nm and 40nm. In addition, the palladium particles were loaded the surface of the iron particles.In this study,2-CP,3-CP,4-CP,2,3-DCP,2,4-DCP,2,5-DCP,2,6-DCP,3,4-DCP, 3,5-DCP were selected as the target compounds, and the reductive action of three kinds of chlorinated phenols and six kinds of dichlorophenol by nano scale Pd/Fe under Pd weight ratio 0.045% and 0.13% was studied. At the same time, the nano scale Pd/Fe particles were synthesized using self-designed experimental devices. From the degradation experiments of CPs and DCPs, investigating the treatment effect of chlorophenols in the water pollutants and exploring the mechanism of the reductive dechlorination process. Meanwhile, theoretical study of B3LYP method in density functional theory on chlorophenol reductive dechlorination reaction mechanism was studied, and some following main conclusions were put forward. Intermediate and final products of the reaction of CPs and DCPs with nano scale Pd/Fe were determined by HPLC. It can be concluded that the dechlorination reaction of the chlorophenols over nano scale Pd/Fe particles progresses through the catalytic reductive dechlorination by Gaussian09. The model involved the hydrogen produced as a product of corrosion of iron with water and adsorbed on the surface of the palladium particles.In the presence of Pd, H2 was a facile reluctant, and the corrosion reaction would contributed directly to dechlorination. Fe was oxidized to Fe2+ and then finally formed Ferric hydroxide, which was covered the surface of nano Pd/Fe particles and further impede catalytic reductive dechlorination. The dechlorination degree of three kinds of CPs with nano scale Pd/Fe was 3-CP> 4-CP>2-CP and the order of six kinds of DCPs degradation followed:3,5-DCP>2,5-DCP> 2,3-DCP>3,4-DCP>2,4-DCP>2,6-DCP. Furthermore, the degradation of chlorophenols and dichlorophenols followed the pseudo-first-order reaction kinetics. At the some time,theoretical study of B3LYP method in density functional theory on chlorophenol reductive dechlorination reaction mechanism had the consistency of results with the experimental conclusions. And the results of the experiments indicated that chemical environment of the chlorine atoms had significant influence in the process of degradating CPs and DCPs. Specifically, the order of the shedding chlorine atoms was meta-substituted chlorine atoms> para-substituted chlorine atoms> ortho-substituted chlorine atom. |
