Chemically Modified Allium cepa Peel as a Low-Cost Adsorbent for Methylene Blue Removal: Kinetics, Isotherms, and Thermodynamic Analysis

• Author(s): Isaac, Ibidun Blessing; Oyewole, Toyib Seun; Osundiya, Medinat Olubunmi; Olowu Rasaq Adewale; Adetunji, Bamidele Shadiat; Yekini, Aishat Olamitudun; Abdulganiyu, Abdulrasaq Olakuleyin; Idowu, Owoyemi Fatai
• Paper ID: 1712430
• Page: 2677-2691
• Published Date: 08-12-2025
• Published In: Iconic Research And Engineering Journals
• Publisher: IRE Journals
• e-ISSN: 2456-8880
• Volume/Issue: Volume 9 Issue 5 November-2025

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 (R² = 0.99), indicating heterogeneous adsorption with an adsorption energy constant BT of 0.22 J mol?¹. Kinetic analysis showed strong conformity to the pseudo-second-order model (R² ? 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?¹), demonstrating spontaneous adsorption, while the negative enthalpy change (?H° = ?44.53 kJ mol?¹) 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.

Citations

IRE Journals:
Isaac, Ibidun Blessing, Oyewole, Toyib Seun, Osundiya, Medinat Olubunmi; Olowu Rasaq Adewale, Adetunji, Bamidele Shadiat; Yekini, Aishat Olamitudun, Abdulganiyu, Abdulrasaq Olakuleyin; Idowu, Owoyemi Fatai "Chemically Modified Allium cepa Peel as a Low-Cost Adsorbent for Methylene Blue Removal: Kinetics, Isotherms, and Thermodynamic Analysis" Iconic Research And Engineering Journals Volume 9 Issue 5 2025 Page 2677-2691

IEEE:
Isaac, Ibidun Blessing, Oyewole, Toyib Seun, Osundiya, Medinat Olubunmi; Olowu Rasaq Adewale, Adetunji, Bamidele Shadiat; Yekini, Aishat Olamitudun, Abdulganiyu, Abdulrasaq Olakuleyin; Idowu, Owoyemi Fatai "Chemically Modified Allium cepa Peel as a Low-Cost Adsorbent for Methylene Blue Removal: Kinetics, Isotherms, and Thermodynamic Analysis" Iconic Research And Engineering Journals, 9(5)