Reversible Solubilization Of Ferrocene-based Amphiphilic Molecules On Organic Pollutants In Soil

Polycyclic aromatic hydrocarbons（PAHs）are a common class of organic pollutants in the soil environment,which have become an important topic in soil pollution control be-cause of their strong toxicity,low water solubility and refractory degradation.Surfactant-enhanced remediation（SER）has attracted much attention as a fast and efficient remediation method for organic contaminated soil,and the selection of a surfactant that is environmen-tally friendly,economical and efficient is the focus of research.The ferrocene group con-tained in the ferrocene-based switching surfactant has excellent redox reversibility,and we can change the properties of the surfactant by applying external stimuli,so that it can be mutually converted between the oxidation state and the reduced state,so as to realize its solubilization effect on polycyclic aromatic hydrocarbons and realize the recovery and reuse of surfactants.In this study,through molecular design,we successfully synthesized six nov-el ferrocene-based switching surfactants,and systematically studied the redox properties,solubilization and remediation of typical PAHs in soil by the two-block copolymer PEGn-Fc（n=350,500,1000,2000）,the triblock copolymer Fc-PEG800-Fc and the star copolymer3PEG1000-3Fc,which provided a basis for future studies on the removal of PAHs in soil.The results of the study are as follows:1.Successfully synthesized a series of ferrocene-based surfactants PEG350-Fc,PEG500-Fc,PEG1000-Fc,PEG2000-Fc,Fc-PEG800-Fc,3PEG1000-3Fc,and confirmed these compounds by UV-Vis,FT-IR,¹H-NMR and ¹²C-NMR and other analytical methods.2.The possibility of reversibility of ferrocene-based switch surfactants was confirmed by chemical redox,and the electrochemical behavior of these ferrocene-based switch sur-factants in different solutions was studied by cyclic voltammetry,which proved that the electrochemical response of ferrocene-based switch surfactants was dependent on solvents,and also proved that these ferrocene-based switch surfactants had good electrochemical re-versibility.3.The size of the critical micelle concentration of ferrocene-based switching surfactant measured by surface tension method is:PEG2000-Fc<PEG1000-Fc<PEG500-Fc<3PEG1000-3Fc<PEG350-Fc<Fc-PEG800-Fc.And in the aqueous solution,these ferro-cene-based switch surfactants will spontaneously form micelles,and after oxidation of iron sulfate,they will dissociate into monomers,and then add ascorbic acid to restore their solu-bilization properties.4.Using the reversible solubilization characteristics of ferrocene-based switching sur-factants,it can be used to remediate PAHs-contaminated soil.When the concentration of eluent is 2.0 g/L and the rinsing time is 9 hours,the rinsing efficiency of the three-block fer-rocene-based switching surfactant Fc-PEG800-Fc on pyrene-contaminated soil is higher than that of other surfactants,the leaching efficiency reaches 97%,and it can still be main-tained at 80%after three recovery cycles,which can effectively remove organic pollutants in the soil.