Synthesis, characterization and evaluation of mesoporous silicates for adsorption of metal ions

—In this study mesoporous silicates MCM-41 and SBA-15 were investigated for their potential as metal ion-selective adsorbents. The greatest advantage of these materials is their large surface area, uniform pore size and controlled surface chemistry, and hence their potential for adsorption processes. The studies of the adsorption of transition metal ions onto MCM-41 examined the comparative adsorption behavior of Zn(II) and Cu(II), using acetylacetone (Hacac) as a chelating agent. The results showed that the MCM-41/Hacac system has potential as an ion-selective adsorbent material. However, due to the relatively small pore size and potential instability of MCM-41 when immersed in water for long time periods, a second mesoporous silicate, SBA-15, has been investigated. The SBA-15 was coated with octadecyltrichlorosilane (C18), and then loaded with a chelating agent (Cyanex 272) and assessed for its potential as an adsorbent material. The surface-modified SBA-15 has been found to have high metal ion selectivity and extractability, and hence good potential as an alternative to established solvent extraction systems.