Preparation of diamine modified mesoporous silica on multi-walled carbon nanotubes for the adsorption of heavy metals in aqueous solution

An effective adsorbent of diamine functionalized mesoporous silica on multi-walled carbon nanotubes (NN-mSiO2@MWCNTs) has been prepared to remove heavy metals in aqueous solution. Structural characterization was conducted by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), N2 adsorption-desorption measurement and X-ray diffraction (XRD), which confirmed the successful grafting of organic moiety on mSiO2@MWCNTs. Metals removal from aqueous solution was examined for Cu(II), Ni(II), Pb(II) and Zn(II). In addition, Cu(II) adsorption process was thoroughly studied from both kinetic and equilibrium points of view. Adsorption kinetics could be well described by pseudo-second-order kinetic equation and exhibited 3-stage intraparticle diffusion mode. Adsorption isotherms fitted well with Langmuir model, exhibiting high adsorption capacity at low concentration. The thermodynamic analysis revealed that the adsorption of Cu(II) onto NN-mSiO2@MWCNTs was endothermic and spontaneous. The prepared adsorbent is expected to be a new material for the removal and recovery of heavy metals from contaminated water.