Bi-functionalized MCM-41 for heavy metal ions removal: synthesis, enhanced performance and mechanism study

This work reports the amine and mercapto bi-functionalized mesoporous silica MCM-41 for heavy metal ions removal from aqueous solutions. XRD, FTIR and N₂ adsorption–desorption analyses confirmed that a series of bi-functionalized mesoporous silica MCM-41 with huge specific surface area were successfully obtained. In aqueous solution, the adsorption performance were evaluated by the adsorption of Zn(II), Cu(II), Cr(III) and Pb(II). The obtained results indicate that synthesis process has no significant influence on the structure and the existence of functional group resulted in outstanding adsorption capacity. The methodology of pre-hydrolysis was one effective treatment for grafting useful functional group on to mesoporous silica. The adsorption reactions for the adsorption of heavy metal ions by bi-functionalized silica-based mesoporous materials were spontaneous adsorption processes over the range of experimental temperatures. The adsorption isotherm is consistent with the Freundlich adsorption isotherms model. The Freundlich parameters K_F and n indicated favorable adsorption. The adsorption kinetics of heavy metalions over these bi-functionalized mesoporous silica could be well described by pseudo-second-order models. Therefore, this bi-functionalized mesoporous material has promise for the removal and recovery of heavy metal ions from water.