Effects And Mechanisms Of Organic Hydrotalcite On The Removal Of Polycyclic Aromatic Hydrocarbons From Soil Washing Effluents

Polycyclic aromatic hydrocarbons(PAHs)are a class of typical hydrophobic organic pollutants with harmful effects.The content of PAHs in contaminated soils in some areas of China exceeds the risk screening value,which seriously threatens human health and ecological safety.Surfactant-enhanced remediation(SER)is a commonly used remediation method for PAHs contaminated soil,which has the advantages of saving time,effectiveness and low cost.Although SER can quickly and efficiently remove PAHs in soil,it will produce a large amount of soil washing effluents,which must be properly disposed,otherwise it will lead to secondary pollution of the environment.Commonly used soil washing effluents treatment technologies include physical treatment,chemical oxidation,biological treatment,etc.,wherein the adsorption method has the characteristics of high efficiency and low cost.The method generally uses a porous solid adsorbent material,and the pollutants in the washing effluents are adsorbed on the surface of the solid material during the treatment.Common adsorbents include activated carbon,organic bentonite,molecular sieve and the like.In this thesis,LDHs are used as the main raw material,and organo-LDHs are prepared by organic modification to adsorb the typical PAHs phenanthrene and pyrene in soil washing effluents.The main conclusions are as follows:(1)Sodium dodecyl sulfate(SDS)modified organo-LDHs are successfully prepared.The characterization results show that SDS is successfully loaded into the LDHs layer to form an organic phase,which is beneficial to the adsorption of PAHs.The content of organic carbon in organo-LDHs increases with the increase of SDS dosage.The spacing of LDHs increases with the increase of SDS loading.(2)organo-LDHs can efficiently treat soil washing effluents containing PAHs.The adsorption kinetics experiments show that the adsorption equilibrium time of organoLDHs is 2h,which indicates that the adsorption rate of PAHs by organo-LDHs is faster;the isotherm adsorption line is linear,and its adsorption capacity increases with the increase of SDS loading.When the solubility of PAHs is high,the adsorption performance of organo-LDHs is much higher than that of activated carbon.(3)The mechanism by which organo-LDHs efficiently removes PAHs from the washing effluents is a partitioning effect.The isotherm adsorption line is linear,and the partition coefficient increases with the increase of organic carbon content.In addition,the low specific surface area of the organo-LDHs also indicates that the surface adsorption is basically negligible.