Thermodynamic Modeling, Kinetic Runs, and Multilayer Adsorption of Acid Orange 7 Dye onto Modified Bentonite Clay

International Journal of Chemistry | Vol. 16, No. 6, June 2025 | pp. 41–48

DOI: 10.46882/2025/IJC/000200

Article Type: Original Research Paper

Title: Thermodynamic Modeling, Kinetic Runs, and Multilayer Adsorption of Acid Orange 7 Dye onto Modified Bentonite Clay

Names of Authors: A. D. Yusuf¹, M. A. Al-Ghamdi²*

Authors’ Affiliations:
¹Department of Industrial Chemistry, Federal University of Technology, Yola, Nigeria.
²Department of Chemistry, Qatar University, Doha, Qatar.

Abstract: The release of highly stable anionic azo dyes like Acid Orange 7 from textile processing factories causes significant environmental and toxicity hazards in surface water channels. This study examines the adsorptive uptake performance of a surfactant-modified bentonite clay (SMB) prepared via chemical functionalization with hexadecyltrimethylammonium bromide (HDTMA-Br). The structural parameters of raw and modified clays were characterized using X-ray diffraction (XRD) and FT-IR spectroscopy. Adsorption operations were conducted via batch runs, monitoring changes in contact time, solution pH, initial dye loading concentrations, and system temperatures. The equilibrium datasets fit closely with the Freundlich isotherm model, demonstrating successful multilayer dye attachment onto the hydrophobic surfactant bilayers. Kinetic parameters matched the intra-particle diffusion expressions alongside a pseudo-second-order mechanism, showing that chemisorption reactions controlled the mass transfer rates. Thermodynamic constants showed that the adsorption process was endothermic (delta H° = 22.4 kJ/mol) and caused an increase in system randomness at the solid-solution interface (delta S° = 74.2 J/mol K). Negative values of Gibbs free energy (delta G°) spanning from -2.4 to -5.8 kJ/mol across the 298 to 328 K range confirmed process spontaneity, positioning SMB as an affordable material for industrial dye wastewater treatment.

Keywords: Bentonite clay; Surfactant modification; Acid orange 7; Adsorption isotherm; Chemisorption; Thermodynamic parameters

Manuscript Timeline: Received: September 10, 2023; Revised: October 22, 2023; Accepted: November 15, 2023; Published: June 03, 2025.

Citation: Yusuf, A. D., & Al-Ghamdi, M. A. (2025). Thermodynamic Modeling, Kinetic Runs, and Multilayer Adsorption of Acid Orange 7 Dye onto Modified Bentonite Clay. International Journal of Chemistry, 16(6), 41–48.

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