Bio-originated mesosilicate SBA-15: synthesis, characterization, and application for heavy metal removal

Abstract

In the path of walking on the road of sustainable and eco-friendly production methods for manufacturing nanomaterials and utilizing them in environmental applications, this article deals with the prosperous synthesis of a biogenic cyclam-functionalized homologous SBA-15 (BCFH-SBA-15). For this purpose, the agricultural waste of the extensively consumed sorghum was used as a rich source of silica in the preparation of BCFH-SBA-15 with a bimodal micro-mesoporous architecture and a substantial surface area of 325 m2 g–1 through a simple one-pot environmentally friendly approach. The material was structurally characterized through the use of different instrumental analyses such as XRD, FTIR, FESEM, TEM, and nitrogen adsorption/desorption isotherms. BCFH-SBA-15 proved to be highly efficient in adsorbing Ni(II) in aqueous solutions, as confirmed by the most reliable classical models utilized for determining isotherm, thermodynamic, and kinetic adsorption parameters. The Langmuir isotherm model provided the most accurate representation of the experimental results, and it was used to calculate the maximum adsorption capacity of BCFH-SBA-15 under optimal conditions (pH = 6.0, adsorbent dose = 3.00 mg, contact time = 20 min). The maximum adsorption capacity at four temperatures of 298, 303, 308, and 313 K was estimated to be 243.36, 253.87, 260.95, and 266.28 mg g–1, respectively; surpassing most previously reported adsorbents for Ni(II) adsorption. The thermodynamic data of Ni(II) adsorption on the BCFH-SBA-15 indicated a strong chemisorption ( $${\triangle H}_{{\rm{ads}}.}^{\circ }$$  = +122.61 kJ mol–1) and spontaneous process ( $${\triangle G}_{{\rm{ads}}.}^{\circ }$$ .= −29.161 to −36.801 kJ mol–1) with a low degree of randomness ( $${\triangle S}_{{\rm{ads}}.}^{\circ }$$ . = 0.5093 kJ mol–1 K–1).