Preparation Of Slow Release Persulfate Gel For Remediation Of 2,4-DNT

As a strong oxidant,persulfate has been widely used in the past few years.As the stability of persulfate is higher than other strong oxidants,it can be activated to form sulfate radical(SO4^-·)under the conditions of light,heat and transition metal,so it has important application value in soil and groundwater remediation.In the actual repair process,the utilization rate of persulfate is low,and the improvement of the utilization rate of persulfate still needs to be studied in detail.In order to improve the utilization rate of persulfate,this paper prepared persulfate gel sustained release agent（PGSR）based on silica gel sol-gel principle,controlled the slow release effect of persulfate under the condition of gel’s physical and chemical properties,and analyzed the factors influencing its gelation and release properties through a series of experiments,combined with the sustained release in aqueous medium.The degradation of 2,4-dinitrotoluene（2,4-DNT）by slow release agent was studied.The influencing factors of the preparation of persulfate gel sustained release agent were studied.The results showed that the microstructure of the material was a compact network structure composed of many silica spheres.The p H value,silica mass fraction,persulfate mass fraction,conventional anion and cation and organic colloid all affected the gelation process.When the p H value tended to neutral,the gelation time was shortened,and the gelation time would follow with the increase of the mass fraction of persulfate and silica,the high concentration of silica with low moisture content will inhibit the gelation.The two valence alkali metal ions and organic colloids will promote their gelation.The organic colloid can enhance the stability of the material structure after the injection of persulfate gel in water,indicating that the structure is more compact and smooth,and the absorption peak of silicon oxygen bond is single.The results of column experiments showed that the sustained release time of persulfate gel sustained-release agent increased by 2 times compared to that of only persulfate solution.The release time of the persulfate gel sustained release agent increased by 3.5D when the organic colloid was reinforced,and the persulfate gel slow release agent had different migration characteristics in three kinds of quartz sand medium systems,such as silty,fine and medium sand.In the silty and fine sand with poor permeablility,the persulfate gel sustained-release agent moves relatively under pressure.The migration in the medium sand with greater permeability is influenced by the material itself,which is fronting,and the permeability of the medium decreases after the gel.There was no significant decline in order of magnitude.The degradation experiment results showed that the degradation efficiency of persulfate gel sustained-release agent increased with the increase of persulfate mass fraction,and the overall degradation efficiency of 2,4-DNT decreased with the increase of water flow rate.The degradation time of 2,4-DNT in sand column can reach 24h,and the degradation efficiency of 2,4-DNT in the initial stage of experiment can be maintained above 80%,the overall average degradation efficiency is 58.3%.In the presence of carbon containing medium activation,the highest degradation rate is close to 98%,and the overall average degradation efficiency can reach 66.7%,which greatly improves the utilization rate of persulfate.