Simple and facile synthesis of amino functionalized hollow core-mesoporous shell silica spheres using anionic surfactant for Pb(II), Cd(II), and Zn(II) adsorption and recovery

In this work, amino functionalized hollow core-mesoporous shell silica spheres (NH2-HCMSSs), which are expected to have a significant tendency for heavy metal removal, are synthesized by ultrasonic assisted soft-templating method using anionic surfactant. Ultrasonic waves, have produced bubbles on which the anionic surfactant micelles have assembled and thereafter the silica nuclei have precipitated to form hollow core structure. Co-structure directing agent, 3-aminopropyltrimethoxysilane (APMS), was used to assist the electrostatic interaction between the partially negatively charged silica particles and the negatively charged surfactant molecules through S-N+I- pathway. Upon the surfactant removal by solvent extraction, amino groups of APMS have then functionalized the mesoporous shell of hollow core structure. Various synthesis parameters, such as sonication time, solvent type, and acid concentration, have been investigated to synthesize HCMSSs spheres with superior textural properties (e.g., total pore volume and surface area). Furthermore, the impact of these parameters on the removal of heavy metal cations from polluted water was evaluated accordingly. HCMSSs were characterized by low-angle X-ray diffraction (Lo-XRD), transmission electron microscopy (TEM), and N-2 sorption analysis. In this study, the variation of synthetic parameters have led to a considerable increment of the surface area and pore volume from 319.44 to 718.024 m(2)/g and 3.309 x 10(-1) to 1.190 cm(3)/g, respectively. HCMSSs samples have shown heavy metal adsorption capacity of 194.4, 190.5 and 193 mg/g for Pb(II), Cd(II), and Zn(II) metal cations, respectively.