Sequestration of Ni2+ and Zn2+ utilising agricultural biowaste-based amorphous M−SiO2 and modified green M−SiO2/Fe3O4 nano-adsorbents: Modelling and electroplating wastewater performance

Abstract

This work reports the synthesis of novel amorphous mesoporous silicon dioxide (M−SiO 2 ) nanoparticles and modified hybrid green mesoporous silicon dioxide embedded magnetite (M−SiO 2 /Fe 3 O 4 ) nanocomposite by one-pot co-precipitation green approach. The nano-adsorbents’ ability to sequester Ni 2+ and Zn 2+ ions was investigated in batch experiments using synthetic solutions. The M−SiO 2 /Fe 3 O 4, having specific surface area of 171.71 m 2 /g and mesoporous diameters of 6.281 nm, exhibits soft ferromagnetism with a saturation magnetisation of 35.45 emu/g. Specific surface areas and mesoporous diameters of 909 m 2 /g and 2.288 nm were recorded for M−SiO 2 . The Langmuir isotherm, pseudo second order kinetic, and Elovich kinetic were found to be best fitted to explain the highest capability of adsorption. The Langmuir monolayer coverage ( q max ) of 108.70 and 96.15 mg/g for Ni 2+ and Zn 2+ by M−SiO 2 /Fe 3 O 4, respectively, was notably higher than M−SiO 2 (80.65 and 72.46 mg/g). The best-fitted kinetics imply that chemisorption predominates on M−SiO 2 and M−SiO 2 /Fe 3 O 4 heterogeneous adsorption surfaces. Thermodynamic parameters confirm endothermic adsorption of cationic metals, and sequestration improved marginally at elevated temperatures. The lab scale cost estimation, magnetic separability and superior metal ions sequestration efficacy of M−SiO 2 /Fe 3 O 4 nanocomposite up to five ad-desorption cycles with > 90 % regenerability render it an economically feasible and recyclable nano-adsorbent. The feasibility of cationic metals sequestration from electroplating effluent confirms an effective and cost-efficient environmentally friendly nano-adsorbent (M−SiO 2 /Fe 3 O 4 ) for treatment of wastewater contaminated with potentially toxic metals.

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