Adsorptive Exclusion of Lead and Chromium from Tannery Wastewater Using MgO Impregnated Biochar Derived from Co- Pyrolysis of Banana Peel and Rice Husk

Abstract

Heavy metal contamination from tannery effluents poses a significant threat to human health, wildlife, and the environment, necessitating effective and sustainable removal methods to mitigate this pollution. This study evaluated MgO-impregnated biochar (MgO@BC), synthesized from the co-pyrolysis of rice husks and banana peels, for the simultaneous removal of Pb (II) and Cr (VI) from effluents in both single solute and binary solute system. The physicochemical properties of the materials were comprehensively characterized through a multi-technique approach, encompassing X-ray diffraction, BET analysis, FTIR spectroscopy, SEM-EDX, and proximate analysis, to determine their structural, morphological, and textural attributes. In single solute system the results revealed that MgO@CBC achieved remarkable removal efficiencies of 94% for Cr (VI) at pH 2 and 100% for Pb (II) at pH 4, using a dosage of 2 g/L and an initial concentration of 20 mg/L. In binary solute systems, under the same initial concentration and dosage conditions, pH 2, Cr (VI) removal was 88.5% and Pb (II) removal was 99%. Notably, a synergistic effect was observed in the combined system at pH 2, wherein the enhanced removal efficiency of Pb (II) was facilitated by the surface properties and charge neutralization processes of MgO@CBC. The isotherm study found out that binary solute system data conform more closely to langmuir and freundlich models than the single solute system. Post-removal FTIR and XRD analyses suggest that charge neutralization, surface complexation, and metal ion exchange are the key mechanisms governing Pb (II) and Cr (VI) removal by MgO@CBC. Furthermore, MgO@CBC demonstrated recyclability over five regeneration cycles, with a gradual decline in removal efficiency (Pb (II) and Cr (VI)) due to active site deactivation and surface degradation. The results confirm its potential as a reusable adsorbent with active MgO sites for effective multi-metal removal from industrial wastewater.