Studies On Degradation And Quantitative Structure Property Relationship Of Chloroaromatics In US/Fe～0

Generally speaking, we could study the mechanism of a complicated system by experiments or in theory. Because in US/ Fe~0 are there three phases including solid, liquid and gas phase and two reaction relating to oxidation and reduction, US/Fe~0 system was intricate, which made studies on mechanism of US/Fe~0 system difficult. Quantitative Structure-Property Relationships (QSPR), which correlates and predicts the transport and transformation process data of organic pollutants from their physicochemical and quantum-structure descriptors, was a popular method to study complicated systems or reactions. QSPR therefore would be a useful tool to describe and predict degradation of chloroaromatics in US/Fe~0 system.M-dichlorobenzene in presentative of chloroaromatics as pollution of water was degraded in US/Fe~0 system with different experimental conditions and the best experimental conditions were got. Additionally, water sollution of 18 chloroaromatics including 5 chlorobenzenes, 8 chlorophenols and 5 chlorotoluenes were set in US/Fe~0 system near the same best conditions that we got before and in the past. Experimental results show that: value of degradation rate followed the descending order of chlorophenols, chlorobenzenes and chlorotoluens; degradation of these three chloroaromatics in US/Fe~0 followed pseudo-first-order reaction kinetics. Based on the experiment results we got, relationship between the logarithm values of degradation rate constant and 26 physicochemistry and quantum-chemistry descriptors was studied. Partial Least Squares (PLS) with leave-one-out cross-validation were used to build the regression models with 16 logk values, for another 2 logk values to validate the model. Then the best model was obtained, which gave a predictive correlation coefficient (R) of 0.97 and Q2 (the fraction of the total variation of the dependent variables that can be predicted by the all components) of 0.9 respectively. Additionally, from the analytical results of PLS model, it was found that degradation rate was governed by descriptors such as Henry's law constant, octanol/water partition coefficients, the highest occupied molecular orbital and heat of formation. Based on the most important parameters of the best model, it may conclude that pyrolysis and oxidation was the main effect in US/Fe~0 system.As another main work of the article, the reaction path ways of pentachlorophenol (PCP) and hydroxyl radicals were studied in theory with a method of Density Functional Theory (DFT). (u)B3LYP/G-31g(d, p) were used to study the structure and electronic property of PCP, which suggested that ortho position was the most reactive. Structure, relative energy, frequency and activity energy of the some reactants, intergradations and mid-productions were found. Caculated results showed that activity energy of the reaction of pentachlorophenol (PCP) and hydroxyl radicals were low and dipolar value of the intergradations was a little high, which suggested that the raction would take place much easier in polarity solvent.