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Chemically Modified Allium cepa Peel as a Low-Cost Adsorbent for Methylene Blue Removal: Kinetics, Isotherms, and Thermodynamic Analysis
Subject area: Science,Engineering and Technology · Area of research: Environmental Chemistry & Engineering
Abstract
Synthetic dyes such as methylene blue (MB) are persistent water pollutants due to their structural stability, toxicity, and resistance to biodegradation. This study evaluates the adsorption efficiency of KMnO?/H?SO?-modified Allium cepa peels for MB removal from aqueous solutions. The adsorbent was characterized using SEM, FTIR, and XRD to confirm morphological modification, functional-group participation, and its predominantly amorphous structure. Batch experiments revealed that adsorption was highly pH-dependent, with optimal removal (91.3%) at pH 3, and equilibrium was attained at 100 min. The Temkin isotherm provided the best fit to the equilibrium data (R? = 0.99), indicating heterogeneous adsorption with an adsorption energy constant BT of 0.22 J mol??. Kinetic analysis showed strong conformity to the pseudo-second-order model (R? ? 0.99), with an adsorption capacity (Qe) closely matching experimental values, confirming chemisorption as the rate-determining step. Thermodynamic evaluation yielded negative ?G? values (-4.42 to ?26.59 kJ mol??), demonstrating spontaneous adsorption, while the negative enthalpy change (?H? = ?44.53 kJ mol??) confirmed exothermic interactions. Overall, the chemically modified onion peel exhibited strong potential as a low-cost, sustainable biosorbent for dye-laden wastewater treatment and offers a promising alternative to commercial activated carbon.
Keywords
Allium cepa peel, Adsorption, Methylene blue, Biosorption, Kinetics, Isotherms, Thermodynamics.
How to cite this paper
@article{1712430,
author = {Isaac, Ibidun Blessing, Oyewole, Toyib Seun, Osundiya, Medinat Olubunmi; Olowu Rasaq Adewale, Adetunji, Bamidele Shadiat; Yekini, Aishat Olamitudun, Abdulganiyu, Abdulrasaq Olakuleyin; Idowu, Owoyemi Fatai},
title = {Chemically Modified Allium cepa Peel as a Low-Cost Adsorbent for Methylene Blue Removal: Kinetics, Isotherms, and Thermodynamic Analysis},
journal = {Iconic Research And Engineering Journals},
year = {2025},
volume = {9},
number = {5},
pages = {2677-2691},
issn = {2456-8880},
url = {https://www.irejournals.com/formatedpaper/1712430.pdf},
abstract = {Synthetic dyes such as methylene blue (MB) are persistent water pollutants due to their structural stability, toxicity, and resistance to biodegradation. This study evaluates the adsorption efficiency of KMnO?/H?SO?-modified Allium cepa peels for MB removal from aqueous solutions. The adsorbent was characterized using SEM, FTIR, and XRD to confirm morphological modification, functional-group participation, and its predominantly amorphous structure. Batch experiments revealed that adsorption was highly pH-dependent, with optimal removal (91.3%) at pH 3, and equilibrium was attained at 100 min. The Temkin isotherm provided the best fit to the equilibrium data (R? = 0.99), indicating heterogeneous adsorption with an adsorption energy constant BT of 0.22 J mol??. Kinetic analysis showed strong conformity to the pseudo-second-order model (R? ? 0.99), with an adsorption capacity (Qe) closely matching experimental values, confirming chemisorption as the rate-determining step. Thermodynamic evaluation yielded negative ?G? values (-4.42 to ?26.59 kJ mol??), demonstrating spontaneous adsorption, while the negative enthalpy change (?H? = ?44.53 kJ mol??) confirmed exothermic interactions. Overall, the chemically modified onion peel exhibited strong potential as a low-cost, sustainable biosorbent for dye-laden wastewater treatment and offers a promising alternative to commercial activated carbon.},
keywords = {Allium cepa peel, Adsorption, Methylene blue, Biosorption, Kinetics, Isotherms, Thermodynamics.},
month = {November},
}