Mesoporous silica-giant particle with slit pore arrangement as an adsorbent for heavy metal oxyanions from aqueous medium

Abstract

The incessant formation of chain-like IBN-4 mesoporous silica (ICMS-N) with long channels running along the length of hexagonal rods have been directly achieved by the co-condensation of 3-aminopropyltriethoxysilane (APTES) and tetraethylorthosilicate as the silica source in the presence of Pluronic P123 and fluorocarbon (FC-4) surfactants as structure directing agents. The newly synthesized materials were successfully characterized using SAXS, N₂-physisorption, FT-IR, XPS, ²⁹Si NMR, TEM, SEM and elemental analysis. TEM images confirmed the chain-like morphologies, whereas SEM studies showed that the synthesized ICMS-N particles possess length >10 μm. Moreover, the as-formed material was tested for the removal of oxyanions such as arsenate and chromate, and it exhibited the maximum adsorption capacity of 55 and 35 mg g⁻¹ for ICMS-N15, respectively. The formation of quaternary species of amine on the surface of the ICMS-N enhanced the adsorption capacity towards arsenate and chromate under acidic pH and the adsorption isotherm fits with Langmuir monolayer adsorption. Naturally, existing anions such as nitrate, sulfate, phosphate and chlorides with 1 × 10⁻² M have no significant effect on the adsorption of heavy metal ions; moreover, reusability tests were also carried out.