Preparation Of Sulfo-gemini Surfactant And Study On Solubilization Of PCE In Aqueous Layer

Chlorinated hydrocarbons are among the most common organic pollutants in aquifers,widely distributed and highly toxic.They are heavy non-aqueous phase liquids(DNAPLs)with high density,low water solubility and high oil-water(O/W)interfacial tension,especially chlorinated hydrocarbons that exist in the underground environment as free and residual phases.Retained in the pores of the medium,it is difficult to be extracted and removed,and it will slowly dissolve into the water for a long time,resulting in secondary pollution and difficult repair and high cost and long time.Surfactant enhanced acquifer remediation(SEAR)is one of the most effective remediation technologies for remediation of chlorinated hydrocarbon-contaminated aquifers.The dissolved amount in water is increased,and it is effectively removed by pumping.The selection of suitable surfactant is the key to obtain good repair effect.At present,traditional commercial single-chain surfactants are mostly used in practical applications,but their solubilization of chlorinated hydrocarbons is generally within an order of magnitude of that of clean water,and they can’t have good environmental compatibility and biodegradability at the same time.Therefore,it is urgent to develop environmentally friendly surfactants with both efficient solubilization and environmental compatibility.In this study,a sulfonate gemini surfactant,ethylene glycol bismaleate dodecyl diester sulfonate sodium gemini surfactant(GS-12),was designed and synthesized,and its physicochemical properties and biodegradability were tested.The solubilization ability of GS-12 and its different compound systems to typical chlorinated hydrocarbon tetrachloroethylene(PCE)was studied,and the most suitable GS-12 compound for SEAR was screened by the system density,viscosity and low temperature resistance.The suitable conditions for in-situ solubilization of PCE in the GS-12 complex system(media particle size,residual saturation of pollutants,flow rate of flushing fluid)were explored through one-dimensional simulated column experiments.The main conclusions are as follows:(1)GS-12 has good surface activity and excellent resistance to medium adsorption,and its primary biodegradation degree is higher than 99%.It is an environmentfriendly surfactant and has good application potential.(2)The solubilizing ability of GS-12 to PCE is better than that of traditional surfactants,sodium dodecyl sulfate(SDS)and triton-100(TX-100).The combination of GS-12 and inorganic salts alone produced synergistic solubilization effect,and the combination of 30 g/L GS-12 and 3‰ Ca Cl2 produced the best solubilization effect of PCE,while the combination of GS-12 with short-chain alcohols and surfactants did not produce obvious synergistic solubilization effect.(3)The synergistic effect is obvious when GS-12 is compounded with inorganic salts and short-chain alcohols at the same time.Among them,the compound system of30 g/L GS-12+3‰ Ca Cl2+5‰ n-butanol has low density and low viscosity The system can be used as a formula for the remediation of chlorinated hydrocarboncontaminated groundwater.(4)The best compound system of GS-12 is suitable for the polluted aquifers with fine sand and high PCE saturation residual degree;the PCE concentration in the effluent of flushing the PCE polluted aquifer with the best compound system of GS-12 can reach 23301 mg/L,the repair effect is better than the traditional surfactants SDS and TX-100.(5)Compared with the same type of surfactant SDS,GS-12 has simpler and more efficient production process,more convenient operation and safer process.The production cost of GS-12 is lower than that of general commercial surfactants,and the application cost of GS-12 compound system is 53% and 76% lower than that of SDS and TX-100,respectively.