Remediation Of Chlorobenzene-contaminated Groundwater By Thermally Activated Persulfate

The current situation of groundwater pollution is increasingly serious. Chlorobenzene(CB), one of persistent organic pollutants, commonly exists in groundwater. This study applies the technology of thermally activated persulfate(PS) to remediate the chlorobenzene-contaminated groundwater, in order to discover an effective and economic technology for the treatment of chlorobenzene-contaminated groundwater.The following aspects were investigated in this dissertation:(1) the efficiency of chlorobenzene-contaminated groundwater remediation using thermally activated PS;(2)the effects of groundwater matrix on the degradation efficiency of CB;(3)the action-oriented research of chlorobenzene-contaminated groundwater remediation by thermally activated PS.The results of the efficiency of chlorobenzene-contaminated groundwater remediation using thermally activated PS demonstrated that the chlorobenzene oxidation by PS follows pseudo-first-order reaction kinetics. The degradation efficiency enhances with the increase of temperature. Since the activation energy of CB is88.376KJ/mol, higher temperature will be beneficial to the CB degradation. Therefore, the activation temperature of following experiments is set at50℃to ensure the full reaction. On the premise that the molar ratio of PS and CB is60, the degradation rate reached99.75%and the CB concentration was blew the groundwater chlorobenzene pollution standards. Thus, the optimum condition for the degradation is the initial CB concentration of100mg/L, the activation temperature of50℃and the molar ratio of PS and CB of60:1. Owing to the annihilation reactions among the radicals caused by high concentration of PS, the rate of degradation declined during the increase of initial concentration of CB.Alkaline or weak alkaline condition accelerates CB degradation reaction. Strong acidic condition, however, suppresses the degradation. Along with the degradation of CB, the amount of TOC in the solution drops. Furthermore, the pH of reaction system decreased to2.57after5hr.The study of the effects of groundwater matrix on the degradation efficiency of CB demonstrated that Cl-、HCO3-and CO32-are radical inhibitors of. These ions have an effect of restraining the progression of the degradation. The hierarchy of their influence on the reaction is as follows:CO32->Cl->HCO3-. The existence of Mg2+、Ca2+does not affect the reaction which means the hardness of water exerts no impacts on groundwater remediation. The action-oriented research of chlorobenzene-contaminated groundwater remediation by thermally activated PS illustrated that the degradation of CB in site cannot achieve the rate as in the laboratory due to the influence of numerous factors. To resolve the problem, three optimization ways have been tried and concluded that rising activation temperature enables to promote the degradation and shorten the reaction time. There is no obvious enhancement of CB degradation using the method of adding the agent many times. The combination of thermally activation and alkalinity activation could facilitate the degradation and after5hr degradation rate reaches99.99%. In addition, previously adding NaOH not only can ordinate pH and render the solution neutral after the reaction, but also reduce the negative impacts on groundwater environment.