Degradation Of Phenol And Aniline Contaminants In Groundwater By Combined KMnO₄ Slow-Release Materials With The Circulation Well

With the rapid development of modernization and the increasing intensity of human production and life in China,the arbitrary discharge of three wastes has led to severe soil and groundwater pollution problems,which posing a serious threat to national health and constraining the sustainable development of China’s economy and society.In-situ chemical oxidation is one of the effective ways to control the risk of groundwater pollution.The traditional in-situ chemical oxidation directly injecting oxidants into the contaminated groundwater,resulting in waste of oxidants,concentration rebound and secondary contamination.The slow-release technology has shown excellent remediation effects in in-situ chemical oxidation,achieving sustained and targeted degradation of pollutants.Circulation well technology can be applied to groundwater remediation in combination with various technologies such as air disturbance,chemical oxidation and microbial remediation and is considered one of the most promising technologies due to its low environmental disturbance,high efficiency and low energy consumption.In this study,potassium permanganate slow-release oxidation technology was combined with circulation well technology to enhance oxidant stability and achieving effective oxidant transport in groundwater remediation.A slow-release material was prepared with potassium permanganate as the oxidizing agent,with phenol and aniline as the target pollutants.The slow release effect and degradation performance of the potassium permanganate slow-release materials were investigated through static experiments and a two-dimensional dynamic simulation tank driven by the hydraulics of a circulation well.The main studies and results are as follows:（1）The potassium permanganate slow-release materials were prepared by melting and molding method,with varying conditions to compare release properties.The smaller slow-release materials size and the larger mass ratio of potassium permanganate to paraffin in slow-release materials,the better release effect.The optimal ratio of slow-release materials is ultimately determined as paraffin:potassium permanganate:activated carbon:silica sand=3:3:2:1.The release kinetic analysis showed that the static release of the slow release material can be divided into a rapid release period and a slow release period,and the materials have a long service life and excellent slow release properties.Through the characterization of the slow release material,the release mechanism is analyzed as dissolution-diffusion release,and its own tight and stable spatial structure is an important factor in controlling the slow release performance.（2）The static degradation of phenol and aniline by potassium permanganate slow-release materials demonstrated that the slow-release materials could achieve continuous degradation of pollutants compared with the direct application of oxidant.Batch experimental studies found that the degradation efficiency of slow-release materials for phenol within a p H range of 3-9 increased with increasing p H.A significant autocatalytic phenomenon was observed during the later stages of aniline oxidation,with the degradation rate first increasing and then decreasing;The presence of SO₄^2-,HCO₃^-and Cl^-and organic matter in the solution inhibited the degradation of pollutants by the slow-release material,and the inhibition of the pollution degradation became stronger with increasing initial concentration.The presence of NO₃^-had almost no effect on the degradation of pollutants.（3）A sand tank simulation device based on a circulation well was constructed,which demonstrated that potassium permanganate spreads uniformly in the sand tank in a fan shape pattern with the slow-release material at its center under the hydraulic drive of the circulation well.The diffusion of potassium permanganate slow-release material under different circulation well parameters was simulated and analyzed using COMSOL simulation software,and the simulation results verified the accuracy of the indoor experiments.The radius of hydraulic influence of the circulating well increased with increasing pumping flow rate and pumping section spacing,leading to a corresponding increase in the scope of oxidant diffusion.（4）The experimental results of coupling circulating well with potassium permanganate slow-release materials to remediate phenol-aniline contaminated groundwater demonstrated that the contaminant removal area was conical in shape,and the area significantly increased over time,allowing for comprehensive removal of contaminants.Thus,the combination of in-situ oxidation technology and groundwater circulation well technology can improve remediation efficiency and oxidants utilization,reduce remediation costs,and hold broad development prospect in groundwater pollution in-situ remediation projects.