Bleaching of crude palm oil using Kirfi adsorbent: Optimum conditions, adsorption isotherm, Thermodynamics, and Kinetics

Abstract

Bleaching, a critical step that significantly reduces color impurities to improve palm oil quality, is essential for refining this globally produced edible oil. This study explores Kirfi adsorbent, a promising locally sourced alternative to conventional bleaching clays, for a more sustainable and cost-effective process. Several batch experiments were conducted to determine the optimum parameters for the adsorptive bleaching process.  The variables considered were temperature, contact time, and adsorbent dosage, all under room pressure conditions. The optical absorbance of the oil samples, both crude and bleached palm oil, was measured at 445 nm using a UV-Vis spectrometer. The results revealed that the optimum conditions for achieving a bleaching performance of 95.61% were a contact time of 20 minutes, a temperature of 90 °C, and an adsorbent dosage of 1.5 g/10ml. Adsorption isotherms were plotted to evaluate the applicability of the Freundlich and Langmuir equations. The Freundlich isotherm, with a regression coefficient of 0.9556, provided a better fit for the isotherm data, suggesting a multilayer adsorption process. Thermodynamic analysis revealed that the process is endothermic and entropy-driven, with a rate constant of 0.0546 S^-1, an enthalpy change (∆H) of 26.678 kJ/mol, and an entropy change (∆S) of 92.260 J/molK. The Gibbs free energy (∆G) values, ranging from -4447.0 J/mol to -9511.2 J/mol, increase negatively with temperature (70 ^oC—120 ^oC), indicating the process becomes more feasible at higher temperatures. These findings have potential implications for sustainable and cost-effective practices in the palm oil refining industry.