From Waste to Value: Banana-Peel-Derived Adsorbents for Efficient Removal of Polar Compounds from Used Palm Oil

The banana chip industry generates significant quantities of waste, including banana peels and used palm oil, which present both environmental and economic challenges. This study explored converting banana peel waste into porous adsorbents via chemical and thermal activation using sulfuric acid (S-BP) and 5% w/v acetic acid (A-BP) as activating agents. Characterization using field emission scanning electron microscopy (FESEM) and Brunauer–Emmett–Teller (BET) analysis revealed notable morphological distinctions and enhanced porosity. The BET surface areas of S-BP and A-BP were 338.959 m²/g and 201.722 m²/g, respectively, significantly higher than that of calcined banana peel (C-BP) at 3.202 m²/g. Despite the higher surface area of S-BP, A-BP, prepared under milder acetic acid conditions, was further investigated for adsorption studies. A-BP effectively reduced the free fatty acids (FFAs) in used palm oil from 3.108% to 1.69% within 30 min. Adsorption isotherms favored the Freundlich model (R² = 0.9115), indicating multilayer adsorption behavior. The adsorption energy derived from the Dubinin–Radushkevich (D–R) model was determined to be 2.61 J/mol, indicating that the adsorption process primarily occurs through physisorption. This study highlights a sustainable approach to waste management and resource recovery, promoting circular economy principles in the banana chip industry.