Surfactant Strengthened And Activated Sodium Persulfate To Remediation Phenanthrene Contaminated Soil

As a typical organic pollutant of PAHs,phenanthrene,has become a popular research topic in recent years.How to efficiently remediate soil contaminated by polycyclic aromatic hydrocarbons?PAHs?has become a technical challenge.Chemical oxidation technology is often used in the remediation of PAHs-contaminated soil,in which high-efficiency oxidant,sodium persulfate?Na₂S₂O₈?,has received more and more attention;In addition,the addition of the oxidation system can effectively improve the efficiency of oxidation degradation of pollutants.This paper selects sodium dodecyl diphenyl ether disulfonate(C₁₂-MADS)anionic surfactant to increase the solubility of phenanthrene in soil and transfer it to water phase.The efficiency of oxidation degradation of phenanthrene by was improved through Na₂S₂O₈heat-activation,which provides an economic,environmentally-friendly and efficient technology for the removal of target pollutants.The main results are as follows:?1?Effect of surfactant on phenanthrene dissolution in soil.Experimental results show that C₁₂-MADS has a good solubilization effect on phenanthrene in soil.The weight solubilization ratio values?WSR?were 11.29,30.67,66.24,39.94 under the concentration of C₁₂-MADS in1×10³,2×10³,5×10³and 1×10⁴mg/L,respectively,which indicated that the solubilization effect was no longer improved when the concentration of surfactant reached a certain value.Under the conditions of 25,40,60 and 80?,WSR values were 21.72,25.60,66.24 and 55.80,respectively.When the temperature increased from 25?to 60?,WSR values also increased with the temperature of the reaction system,while when the temperature increased to 80?,WSR values decreased.The results showed that 60?was the optimal solubilization temperature and 5×10³ mg/L was the optimal solubilization concentration of C₁₂-MADS.?2?Effect of surfactant on thermal activation of sodium persulfate.The interaction between four different surfactants and sodium persulfate was investigated.The most suitable surfactant was selected to strengthen the sodium persulfate oxidation system.The three kinds of surfactant SDS?SLS?SDBS will have a certain effect on the system when coexisting with the Na₂S₂O₈,and will produce a certain precipitation or turbidity as SDS?SLS?SDBS reaction proceeds.while the degree of turbidity the three monovalent anionic surfactants decreases with the increase of temperature of reaction,when the system temperature reaches 40?,there is still partial precipitation in the SDS?SDBS,and the C₁₂-MADS from the reaction.When the surfactant was used to study the stability of sodium persulfate,it was found that the decomposition efficiency of sodium persulfate in the three groups of SDS,SLS and SDBS increased significantly with the increase of the temperature of the reaction system.This indicated that C₁₂-MADS does not degrade Na₂S₂O₈ and has a better stability effect and can reduce the decomposition efficiency of persulfate.?3?Effect of surfactant on the degradation of phenanthrene in soil enhanced by sodium persulfate.The thermal activation of Na₂S₂O₈to degrade phenanthrene in soil conforms to the quasi-first-order reaction kinetics,and the degradation effect is affected by Na₂S₂O₈concentration,concentration of C₁₂-MADS,reaction temperature,ratio of water/soil,p H,and coexistence ions.With the increase of Na₂S₂O₈ concentration,the removal efficiency of phenanthrene increases,and there was a certain linear relationship between the Na₂S₂O₈concentration and the removal efficiency of phenanthrene.However,when the concentration of Na₂S₂O₈ increased from 2.5×10⁴ mg/L to 5×10⁴ mg/L,the degradation efficiency of phenanthrene did not increase significantly.As the concentration of C₁₂-MADS increases,the oxidative degradation efficiency of phenanthrene also increases.When the concentration of C₁₂-MADS rises to 1×10⁴ mg/L,the oxidative degradation efficiency of phenanthrene flattens out and does not significantly improve with the progress of the reaction.The removal efficiency of phenanthrene was positively correlated with temperature and ratio of water/soil.However,when the temperature reached 80?and the ratio of water/soil was 30:1,the removal efficiency of phenanthrene gradually leveled off.When the p H value is 6-8,the removal efficiency of phenanthrene decreases from 89.80%to 31.64%at 16 h with the increase of p H,indicating that the higher the p H value of the system,the more unconducive the degradation of phenanthrene.At the same time,the addition of HCO₃^-and OH^-would lead to the decrease of the oxidative degradation efficiency of phenanthrene.