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.
