Safranin adsorption onto Acasia plant derived activated carbon: Isotherms, thermodynamics and kinetic studies

Abdulfattah Mohammed Alkherraz, Khaled Muftah Elsherif and Najah A. Blayblo

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This study aimed to evaluate the effectiveness of three surfaces derived from the Acasia plant - specifically, dry powder (DAM), hot activated carbon (HAC), and acid activated carbon (AAC) - in removing safranin dye from aqueous solutions. The experiment examined various parameters, including time, pH, adsorbent dose, initial dye concentration, and temperature, to determine their impact on safranin adsorption by the prepared surfaces. Results indicated that adsorption uptake increased with initial concentration but decreased with temperature, while pH remained relatively constant. The experiment data was then analyzed using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models, with the Freundlich model proving to be the best fit for the equilibrium data. The pseudo-second-order equation was found applicable, and the negative ΔG values at 25°C suggested the adsorption process was spontaneous and exothermic. The thermodynamic parameters (ΔG, ΔH, and ΔS) were calculated and explained based on the adsorbate's chemical structure.