Degradation Of Trace BHC With Electrochemical Oxidation In The Water Environment

Being persistent, semivolatile, bioaccumulated and high toxic, Persistent Organic Pollutants(POPs) are becoming a research hotspot in the world. With the development of chiral environmental chemistry, scholars have come to realize that a considerable portion of POPs have enantiomers. BHCs have so excellent insecticidal effect that food production has been greatly improved, making organochlorine pesticides widely used in the agricultural sector. Because of high toxicity, persistence, bioaccumulation, they can exist in soil, air and water for long time. The BHCs adsorbed by crops, vegetables and and livestock can enter the body through the food chain, accumulate and do harm to human health. Therefore, the study of the distribution and accumulations of BHC in water, analysis of their possible sources, can enrich the basic theory of bioaccumulation, and provide a theoretical basis for environmental management and food security.Interest in the development of innovative treatments of wastewaters containing BHC that traditional processes cannot completely oxidize is growing. A relevant method is the electro-chemical technique, which is considered an environmentally friendly tool for pollution management, treatment, and control. According to previous reports, electrochemical techniques have numerous advantages, such as environmental compatibility, versatility, energy efficiency, safety, selectivity, amenability to automation, and cost effectiveness.Therefore, this paper based on the environmental protection industry research projects of Shandong province," Advanced treatment technology for POPs consist in small towns sewage treatment process". In the present study, an electro-oxidation process was investigated for its ability to oxidize BHC in aqueous solution using titanium (Ti) covered with lead oxide (PbO2) electrode prepared by electro-deposition. The main research contents are as follows:(1) Expanded titanium covered with PbO2electrode was produced by electrodeposition. The surface morphology and the structure of the prepared thin film were characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), respectively. The prepared Ti/PbO2electrode exhibited larger active surface area and higher oxygen vacancy deficiency, which resulted in its higher electrocatalytic activity. The electrochemical activity of the electrode for oxygen evolution reaction was examined by electrochemical test. Electrode potential oxygen evolution is1.83Vvs.SCE.(2) Electroxidation of methylene blue in aqueous solution was studied to evaluate the potential applications with PbO2thin film as positive electrode and stainless steel as negative electrode. The effects of initial pH, retention time, supporting electrolyte, current density on the process performance were examined. Experimental results revealed that current density of5×10-2A/cm2, initial pH of6, supporting electrolyte of5g/L were beneficial for Methylene blue oxidation. Methylene blue could be diminished up to99%under this condition. And at the current density of0.25×10-2A/cm2, oxidation has the lowest energy consumption.(3) Expanded titanium (Ti) covered with lead oxide (PbO2) electrode and prepared by electro-deposition was applied to anodically oxidize benzene hexachloride (BHC) in aqueous solution. The influences of major operating conditions including current density, treatment time, electrolyte concentration, initial pH, and temperature were examined. Experimental results show that a current density of9mAcm-2was the optimum condition for BHC oxidation. Under this current density imposed in the electrolysis cell for360min, the degradation rate of total BHC concentrations for4isomers could reach95.7%. No obvious effect of the electrolyte (Na2SO4) concentration on oxidation efficiency in the range of2.5-15gL-1was observed. Likewise, under optimal conditions,90%TOC was removed. Most BHCs were mineralized. These results suggest that electrochemical degradation is a promising treatment for effective and rapid removal of BHC.(4) Application research shows that, electrochemical oxidation technology is a promising treatment for effective and rapid removal of BHC and PAHs.