Adsorption and Desorption of Pb(II) on L-Lysine Modified Montmorillonite and the simulation of Interlayer Structure

Herein, we reported the adsorption and desorption of Pb(II) on L-lysine modified montmorillonite (L-Mt) with molecular dynamics simulation. L-lysine (Lys) modified montmorillonite (L-Mt) was prepared, characterized by various analytical techniques, and the simulation studies were performed to evaluate the interlayer structure and interaction properties of L-lysine and L-Mt. The results of X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectrum suggested that Lys⁺ was intercalated into the interlayer of Na-montmorillonite (Na–Mt) successfully. The batch adsorption experiments were implemented to study the adsorption capacity of Pb(II) on L-Mt in water. The maximum adsorption capacity of Pb(II) on the L-Mt (up to 43.3 mmol/100 g) were considerably higher than that on Na–Mt (up to 15.3 mmol/100 g), at room temperature. The adsorption isotherms of both, L-Mt and Na–Mt can fit the Langmuir isotherm. The adsorption experiments showed that Pb(II) removal efficiency of L-Mt is better than Na–Mt in acidic solution. The simulation results revealed the micro-mechanism of Lys⁺ inserted into the interlayer gallery of Na–Mt. It can be deduced that lysine interacted with montmorillonite surface mainly through the protonated side-chain amino group rather than through the protonated main-chain amino group or deprotonated carboxyl group. These consequences are expected to elucidate the adsorption mechanisms occurring at the water/clay minerals interface at atom level, providing significant insight into the adsorption and retention of Pb(II) on L-Mt composite, and lead to relevant engineering applications while treating heavy metals of wastewater.