Study On Removal Of Sodium 3-aminobenzenesulfonate In Groundwater By Controlled-release KMnO₄

China is a big country in the production of dye intermediates.The waste liquid and waste leaching filtrate in the process of dye intermediate production have the characteristics of high chroma,high salinity,complex organic components and difficult biodegradation.Once these pollutants enter the groundwater environment,they will pose a serious threat to groundwater safety.The permeable reactive barrier?PRB?is an in-situ groundwater control and remediation technology,which is an effective way to control the groundwater pollution risk.The remise of the PRB technology to effectively control the diffusion of groundwater pollution is to screen the reaction medium that meets the specific site conditions.This paper relies on the typical site where groundwater has been contaminated by sodium 3-aminobenzenesulfonate,through the analysis of site pollution hydrogeological characteristics and laboratory experiments,screening reaction materials of PRB,studying the controlled-release mode for long-term effects,analyzing the removal effect and degradation products,and exploring the effects of chemical characteristics of groundwater and filling medium conditions on the removal process.Based on the analysis of site pollution characteristics and the comparison of reaction materials,Fenton reagent,Fenton-like reagent,and activated Na₂S₂O₈ and KMnO₄ of oxide materials were initially screened.The results of batch experiments using four oxidants showed that KMnO₄ was the preferred oxidant.In order to further extend the action time of KMnO₄,paraffin-coated KMnO₄ was used as a controlled-release method.The results showed that the removal rate of candle-like controlled-release KMnO₄ to sodium 3-aminobenzenesulfonate was 50%in 10 days,while the removal rate of granular controlled-release KMnO₄ was about 100%in 6 hours.When the initial concentration of sodium 3-aminobenzenesulfonate was less than 100 mg/L,the removal rate of the granular controlled-release KMnO₄ to sodium 3-aminobenzenesulfonate was 100%in 1 hour.The removal rate of granular controlled-release KMnO₄ to sodium 3-aminobenzenesulfonate was 100%and the removal rate of granular controlled-release KMnO₄ to COD and TOC was less than 60%.It was speculated by GC-MS that one of the reaction pathways was that sodium 3-aminobenzenesulfonate was first oxidized to benzoquinones by controlled-released KMnO₄,and then the benzene ring of the benzoquinone was opened to form small-molecule aldehydes such as glutaraldehyde.The chemical characteristics of groundwater affect the removal of granular controlled-release KMnO₄ to sodium 3-aminobenzenesulfonate.The standard oxidation-reduction potential of KMnO₄ is high under acidic conditions where the removal of sodium 3-aminobenzenesulfonate by KMnO₄ is faster and more thorough,and the suitable pH is below 5.And the removal rate of controlled-release KMnO₄ to it was 100%in 12 hour at the pH condition of the site.The initial Cl^-concentration has almost no effect on the removal effect.However,the presence of SO₄^2-in the solution has an inhibitory effect on the removal effect and the degree of inhibition is low when the SO₄^2-concentration is lower than 140 mg/L.And the removal rate of controlled-release KMnO₄ to it was 100%in 24 hour at the SO₄^2-concentration of the site.In order to increase the groundwater flow of reaction materials,considering the effect of mixing the filling medium and the controlled-released KMnO₄ to remove pollutants,a batch experiment was carried out from the two aspects of the particle size and content of the filling medium.The results show that the removal effect by PRB with a particle size of0.38mm-0.83mm is better and the removal effect is good when the mass ratio of the filling medium to the controlled-release KMnO₄ is less than 2:1.The paper studied the types,effects and products of slow-release oxidants suitable for the site,and discussed the optimization parameters of chemical characteristics of groundwater and filling medium conditions,and provided key parameters for the construction of PRB in site.