Comparative Deacidification of High Free Fatty Acid Crude Palm Oil Using Activated Carbon, Zeolite, and Calcium-Based Adsorbents

Crude palm oil (CPO) is a promising renewable feedstock for high-value industrial applications; however, its high free fatty acid (FFA) content limits its physicochemical stability and subsequent processing. This study comparatively evaluated activated carbon, zeolite, calcium carbonate (CaCO₃), KOH-modified activated carbon, and KOH-modified zeolite for CPO deacidification through contact-time and vacuum–thermal treatments. Material characteristics were examined using SEM, EDX, and FTIR, while time-dependent FFA removal was evaluated using Weber–Morris and Elovich kinetic models. During the five-day treatment, CaCO₃ achieved the highest final FFA removal of 47.6%, whereas activated carbon and zeolite reached maximum removals of 43.9% and 40.1%, respectively, on day 4. KOH modification altered material characteristics but did not consistently improve FFA removal. Kinetic analysis revealed material-dependent behavior: KOH-modified activated carbon exhibited the highest apparent Weber–Morris diffusion slope, while unmodified activated carbon showed the strongest agreement with the Elovich model. Under vacuum–thermal treatment at 450 mmHg and 120–180°C, KOH-modified activated carbon exhibited the strongest temperature-dependent relationship (R² = 0.9356, p = 0.0327), with an apparent ΔH° of 29.64 kJ mol⁻¹. Overall, CPO deacidification was governed by material characteristics, mass transfer, contact time, and temperature, while KOH modification did not necessarily result in higher FFA removal efficiency.