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Abstract
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A magnetically separable MgFe-LDH/Fe₃O₄/Biochar nanocomposite was synthesized as an efficient adsorbent for
methylene blue (MB) removal. The biochar precursor was derived from Hordeum murinum (wild barley). XRD,
FTIR, Raman, BET, FESEM–EDS, and XPS analyses confirmed the successful integration of LDH nanosheets and
Fe₃O₄ nanoparticles onto a porous carbon matrix, providing abundant active sites, surface heterogeneity, and
magnetic recoverability. Process optimization using Central Composite Design (CCD) revealed significant effects
of pH, adsorbent dosage, temperature, and contact time. The quadratic model (R2 = 0.95) predicted optimum MB
removal of 93.8%, experimentally validated at 94.2% under optimal conditions (dosage = 168.3 mg L 1, pH =
5.7, time = 104 min, temperature = 35.05 ◦C). Kinetic data followed the pseudo-second-order model (R2 > 0.99),
while the Freundlich isotherm (R2 = 0.91, n = 3.23) confirmed multilayer adsorption on a heterogeneous surface.
Thermodynamic parameters (ΔH◦ = 2.18–13.89 kJ mol 1, ΔS◦ = 9.9–64.9 J mol 1 K 1, ΔG◦ < 0) indicated
a spontaneous, endothermic, physisorption-driven process. The nanocomposite retained >80% of its removal
efficiency after five cycles and achieved >81% removal for MB, Acid Red 14 (anionic dye), and Cd2+ (heavy
metal) in real groundwater. The estimated E-factor was ≈31, within the fine chemicals range (5–50). Overall, the
synergistic interplay between MgFe-LDH, Fe₃O₄, and biochar results in a stable, recyclable, and versatile
adsorbent for decentralized wastewater treatment.
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