Investigation of the adsorption performance and mechanism of 2-mercaptoethane sulfonic acid intercalated modified layered double hydroxide on heavy metal ions

In the adsorption process of functionalized layered double hydroxide (LDH) to target pollutants it, is essential to investigate the role of functional groups. In this work, 2‑mercaptoethane sulfonic acid (MS) was used as an intercalation modifier to prepare functionalized NiFe-LDH by solvothermal method. The interfacial interaction between the functional groups and the NiFe-LDH surface was studied via molecular dynamics simulation. During the intercalation process, the more negatively charged sulfonic acid group tends to self-assemble electrostatically with the LDH laminate, while the sulfhydryl group is involved in complexing heavy metal ions. The adsorption experiments showed that the adsorption performance of the adsorbent for the three ions of Cd2+, Mn2+, and Co2+ at 298.15 K was 266.16 mg/g, 175.60 mg/g, and 106.56 mg/g, respectively, which were 10 times, 8.7 times, and 4.9 times higher than that of unmodified NiFe-LDH. Meanwhile, Multiwfn wavefunction analysis combined Visual Molecular Dynamics (VMD) was applied to analyze and visualize the reaction active sites & the interactions between MS and NiFe-LDH, and the complexation of the functional group of MS with metal ions, to insight the role of the functional groups in MS molecule, and to reveal the cause that the adsorption capacity of modified NiFe-LDH for heavy metals greatly improves from the view of atoms.