Repurposing waste cooking oil: A mini review

Abstract Waste cooking oil (WCO) contains high levels of free fatty acids (FFA) and other degradation by‐products, making it harmful to both human health and the environment if improperly disposed of or reused. Currently, WCO is utilized at the industrial scale for the production of biofuels and energy, thereby contributing to environmental sustainability through waste valorization. Adsorption serves as an alternative method for reducing the FFA content of WCO by selectively removing FFA through physical and chemical interactions with the adsorbent surface, achieving effective removal and high oil recovery. The adsorption of WCO using ash results in a 61% reduction in FFA content and an 80% oil recovery. In addition to its use as a biofuel feedstock, WCO has also been explored as an adsorbent for removing water pollutants, such as dyes and toxic heavy metals. It can be used as an alternative feedstock for producing adsorbents because of its high carbon content. The WCO‐based activated carbon with specific surface of ~2 m 2 /g yields an acceptable adsorption capacity of 5.52 mg/g congo red. This mini review explores both pathways: purifying WCO through adsorption and repurposing WCO into new carbon‐based adsorbents. It summarizes the preparation, properties and adsorption performance of oil‐derived adsorbents, offering insights into the potential of WCO‐based adsorbents for wastewater treatment.