The Washing Remediation Of The Contaminated Soil By PAHs With Surfactants

With the release of the Chinese policies of “suppressing the second industry and developing the third industry” and “relocation from urban areas to outskirts”,local governments start taking measures to relocate the enterprises causing heavy pollution like coking plants and chemical plants to outskirts and otherwise develop the left sites for use,leaving the most common pollutant PAHs of universally accepted “carcinogenicity”,“teratogenicity” and “mutagenicity” in topsoil.Soil flushing,a widely applicable and highly-effective technology of recovering polluted soils with large handling capacity,is considered appropriate to recover the soils polluted by PAHs.With the ability to increase the solubility of PAHs in soils through solubilization,surfactants are considered an eluant most commonly used in the technology.Using the batching method,in combination with the liquid chromatography,the paper initially made a study on the rule of solubilizing PAHs by the single surfactants including TritonX-100,SDS and Tween-80 and the composite surfactant SDS/TritonX-100.In addition,the paper researched the impact of the parameters of TritonX-100 and SDS/TritonX-100 like the solid-to-liquid ratio,concentration and length of flushing time on the effect of recovering the soils in the area to which Shenyang coke-oven gas plant relocated.Finally,relying on the ectopic leaching remediation of compound equipment,a pilot test was made on the effect of recovering the soils polluted by PAHs in the available appropriate condition.Main achievements were obtained as follows:(1)Single surfactants including TritonX-100,SDS and Tween-80 may significantly solubilize PAHs,among which TritonX-100 is more advantageous over SDS which is advantageous over Tween-80 in the solubilization effect.Where the concentration is less than 10mmol/L,Tween-80 fails to solubilize PAHs,but SDS could do so to an extent inferior to TritonX-100.(2)Comparing with single surfactants,composite surfactants have a more significant effect in solubilizing PAHs.In the event of the SDS concentration of 10mmol/L,20mmol/L,40mmol/L,60mmol/L and 80mmol/L,with the increase in the concentration of TritonX-10,composite surfactants would be more effective to solubilize PAHs,especially when the concentration of TritonX-100 is 60mmol/L.In addition,where the concentration of SDS and TritonX-100 is 20mmol/L and 60mmol/L respectively,it would achieve the best solubilization effect.Therefore,the optimal concentration ratio of the composite surfactant SDS/TritonX-100 should be 1:3 required for solubilization.(3)Both single surfactants and composite surfactants may flush PAHs out of soils to a certain extent,but there are differences between the two in the best flushing condition.To achieve the best effect,the liquid-solid ratio and the concentration of the single surfactant TritonX-100 should be 20:1 and 60mmol/L respectively,with which the flushing should last 90 min;the liquid-solid ratio and the concentration of the composite surfactant SDS/TritonX-100 should be 10:1 and 40mmol/L,with which the flushing should last 90 min.(4)The pilot test shows that,the polluted soils could be restored to a certain extent under the same flushing condition,and over 80% of the polluted soils have been restored by the ectopic leaching remediation of compound equipment according to the measured content of PAHs before and after the flushing.