Study On Stability And Degradability Of Oxidative Repair Oxidants In Contaminated Site

In recent years,in-situ chemical oxidation technology has been widely used to repair contaminated soil and groundwater,and the types of treatment agents are increasing.The safety of oxidants in use and the decomposition of oxidants are becoming more and more prominent.There are few studies on the stability of oxidants in the stage,so this paper specifically studies the stability and degradability of oxidants in contaminated sites.This paper can be divided into two parts.The first part is to study the effects of Soil and water composition and use conditions on the stability of hydrogen peroxide and sodium percarbonate.The effects of experimental conditions such as temperature,oscillation,p H,humic acid,oxidant concentration,anions,cations and clay mineral on the stability of oxidant were studied.The results show that increasing the temperature of the system,adjusting the acidity or weak alkalinity of the solution,and increasing the concentration of hydrogen peroxide.The reaction decomposition rate of hydrogen peroxide for 7 days is less than 5%.The solution is adjusted to be very alkaline,or added to CO₃^2-,cations and clay minerals,and the decomposition of hydrogen peroxide is significantly accelerated.The reaction decomposition rate of hydrogen peroxide for one day may be more than 20%.For the sodium percarbonate system,increasing the reaction temperature and adding cations can significantly increase the decomposition reaction rate,12 hours decomposition rate is above 50%.However,oscillation,humic acid,clay minerals,anions,etc.do not affect the decomposition of sodium percarbonate,24 hour decomposition rate is only 78%.When the solution is acidic or weakly alkaline,the decomposition reaction of sodium percarbonate is inhibited.In the second part of this paper,the effects of different experimental conditions on the degradation of OG by hydrogen peroxide system and sodium percarbonate system were studied.The effects of temperature,p H,anion,cation and oxidant concentration on the degradation performance of oxidant were studied.The results show that the addition of CO₃^2-,cation and strong alkaline solution to the hydrogen peroxide system can significantly promote the degradation of OG by hydrogen peroxide,2 hours degradation rate above 65%.Elevated temperature and oxidant concentrations,or acidic or weakly alkaline solutions,as well as the addition of several other anions,4 hours degradation rate is less than 5%.In the sodium percarbonate system,increasing the temperature,the strong alkaline solution,and increasing the concentration of the oxidant can significantly increase the degradation reaction rate,4 hours degradation rate is higher than 85%.After adding Cl^-,Br^-,CO₃^2-,the degradation reaction of sodium percarbonate is also inhibited,2 hours degradation rate is less than 65%.In addition,when the percarbonate degradation OG well be inhibited.