Rice Straw as an Adsorbent for Reducing the Peroxide and Acid Values of Used Cooking Oil

Rice straw is an abundant by-product of rice harvest, which can be developed into an adsorbent to remove contaminants from liquid and gaseous substances. The objectives of this study were to develop an adsorbent from rice straw, determine its characteristics, and test its performance in improving the quality of used cooking oil. Rice straw was collected and developed into an adsorbent based on its ability to reduce the peroxide value (PV) of used cooking oil (UCO). The particle size, adsorption capacity, functional groups on adsorbent surface, surface morphology, and pore size of the adsorbent were determined, and its performance on improving the quality of used cooking oil in terms of peroxide value, acid value (AV), and color were tested. Results showed that the best preparation of rice straw adsorbent (RSA) was through activation with 0.5 M NaOH at a particle size of 355 µm. The RSA had an adsorption capacity of 5% by weight for PV reduction in used cooking oil. The FTIR analysis showed the presence of O-H and C-O functional groups, while SEM analysis revealed porous structure and pointy nodules, at the surface of RSA. The RSA improved the quality parameters of used cooking oil through reducing PV and AV by 5.05 – 5.37% and 40.78%, respectively, and improving the lightness of the oil.