NMR Study On The Co-solubilization Mechanism Of Polycyclic Aromatic Hydrocarbons In Single Or Mixed Surfactants

As a non-invasive method,nuclear magnetic resonance(NMR)method can individually detect each component in mixed systems at the molecular or atomic level,and obtain various microscopic information about the molecular structure,interaction and dynamics.Polycyclic aromatic hydrocarbons(PAHs)are a type of insoluable organic matter widely present in soil.The remediation method based on surfactant solubilization has attracted much attention because of its remarkable solubilization enhancement.In terms of the co-solubilization of PAHs,the solubility of one PAH in the presence of other PAHs and its synergy/inhibition mechanism have been mainly studied.However,the total solubility of PAHs and the relationship between the micellar environment and overall solubilization of PAHs have not been reported.In this paper,the co-solubilization mechanism of phenanthrene,anthracene and pyrene by single polysorbate 80(Tween 80)or sodium dodecyl sulfate(SDS)and their mixed systems are studied by NMR spectroscopy at the molecular level.First,the pollution status and main remediaion methods of PAHs from soil are briefly introduced.Then,the related research on the solubilization of PAHs by surfactants is reviewed.Finally,the application of NMR methods in the research of the solubilization of PAHs by surfactants is reviewed.Second,the co-solubilization mechanism of phenanthrene,anthracene and pyrene by single Tween 80 or SDS is investigated.The synergism/inhibition level,solubilization sites,the total solubility(St)and its relationship with the chemical environment of micelles are studied by 1H NMR,2D NOESY and ROESY.In Tween 80 solutions,inhibition for phenanthrene,anthracene and pyrene is observed in most binary and ternary systems.However,in SDS solutions,synergism is predominant.After analysis,we find that the different synergism or inhibition effect between Tween 80 and SDS is related to the different types of surfactants used and the resulting different co-solubilization mechanisms.We also find that three PAHs have similar solubilization sites in both Tween 80 and SDS.Due to the similar solubilization sites,the chemical shift changes of surfactant and PAH protons follow the same pattern in all solubilization systems,and the order of chemical shift changes is consistent with the order of changes in the St of PAHs.In this case,it is feasible to evaluate St of PAHs by chemical shift.In both Tween 80 and SDS solutions,the ternary solubilization system have relatively high St rankings.Therefore,in practical applications,a good overall solubilization effect can be expected.Third,the co-solubilization mechanism of phenanthrene,anthracene and pyrene in the mixed Tween 80/SDS solution is futher investigated.The solubilization sites of phenanthrene,anthracene and pyrene and the St of the co-solubilization system are studied by NMR.The results show that in the mixed Tween 80/SDS solution,similar to the single Tween 80 and SDS solution,the three PAHs still have similar solubilization sites.Due to the similar solubilization sites,the chemical shift changes of surfactant and PAH protons also follow the same pattern in all solubilization systems,and the order of chemical shift changes is also consistent with the order of changes in the St of PAHs.In this case,it is also feasible to evaluate the St of PAHs in the mixed Tween 80/SDS solution by chemical shift.In the Tween 80/SDS mixed solution,the ternary solubilization system also has a relatively high St value.