Reduced Degradation Of Halogenated Organics And Its QSAR Study

Zero-valent iron is a strong reducing agent. Nano iron particles have high specific surface area and small size, especially nano bimetallic catalyst, which can improve and enhance the reactivities in degradating the organic pollutants.In this study, the methods of modified liquid phase reduction are employed to prepare the nanoscale zero valent iron, and the orthogonal experimental method is taken to study the impact of the reaction time, the ratio of reaction medium and water, and the amount of surfactant on synthesizing nanoscale zero valent iron. In addition, the nano-scale Pd/Fe bimetallic catalyst is synthesized. 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.Because of the presence of those substructures such as benzene ring and chlorine atoms, chlorophenols have powerful anti-degradation. In this study, the nano Pd/Fe bimetallic particles are applied to degradate 2,4-dichlorophenol. Futhermore, the study emphasizes on the mass fraction of Pd in the bimetal, Pd/Fe bimetallic catalyst dosage, initial pH value, reaction temperature, and other possible factors. The results show that the higher mass fraction of Pd in the bimetal, the larger amount of Pd/Fe particles, the higher reaction temperature, and the lower pH value are conducive to the reaction. The degradation of 2,4-dichlorophenol follows the pseudo-first-order reaction kinetics.In this paper, intermediate and final products of 2,4-dichlorophenol with nanoscale Pd/Fe are determined by high performance liquid chromatography (HPLC). It can be concluded that the H2 produced by iron corrosion makes 2,4-dichlorophenol reduction by the catalysis of the Pd.Molecular electronegativity distance vector (MEDV) and electrotopological state indices for atom types (ETSI) are employed to characterize the chemical structures of 31 chlorinated organics, and quantitative structure-activity relationship (QSAR) model is constructed to describe the relationships between the molecular structures and the constant of degradation rates of organic compounds. The four structural groups—C—,—C＜,—Cl,—OH of the compounds affect logk values.