Sequestration of chromium(vi) and nickel(ii) heavy metals from unhygienic water via sustainable and innovative magnetic nanotechnology

Abstract

In a stride towards sustainable solutions, this research endeavors to address the critical issue of water pollution via heavy metals by coupling the power of magnetic nanotechnology, in combination with a green chemistry approach, to eliminate two noxious inorganic pollutants: chromium(VI) and nickel(II) from aqueous environments. The synthesis of magnetite (Fe₃O₄) nanoparticles was achieved using ferric chloride hexahydrate (FeCl₃·6H₂O) as a precursor, with the assistance of Ziziphus mauritiana Lam. leaves extract, known for its remarkable salt-reducing properties. A range of bio-adsorbents, derived from corncob biomass, corncob pyrolyzed biochar, and magnetite/corncob biochar nanocomposite (NC), were engineered for their eco-friendly and biocompatible characteristics. Extensive parametric optimizations, including variations in pH, contact time, dose rate, and concentration, were carried out to gain insights into the adsorption behavior and capacity of these bioadsorbents concerning Cr(VI) and Ni(II). Equilibrium and kinetic studies were undertaken to comprehensively understand the adsorption dynamics. In the case of Ni(II), the Freundlich isotherm model provided a satisfactory fit for all bio-adsorbents, demonstrating R² values of 0.91, 0.95, and 0.96 for BM, BC, and NC, respectively. Furthermore, the pseudo 1st order model emerged as the most suitable fit for Cr(VI) sequestration in corncob BM with an R² value of 0.98, while pseudo 2nd order models were robustly fitted for BC and NC, yielding R² values of 0.88 and 0.99, respectively. The magnetite/corncob nanocomposite outperformed other bioadsorbents in removing heavy metals from wastewater due to its environmental friendliness, larger surface area, reusability, and cost-effectiveness at an industrial scale.