Regeneration Potential of Eggshell Adsorbent on Spent Vegetable Oil: A Mean to Achieving Global Sustainability

Abstract

The regeneration potential of activated eggshell adsorbent (AESA) on spent vegetable oils (SVOs) is a promising approach to realizing global sustainability. Eggshell, which are typically discarded, was converted into an effective adsorbent in removing impurities from spent vegetable oil. This involved the cleaning and drying of eggshell followed by pulverization and chemical treatment for better modification, and improved adsorption capacity. Batch adsorption method was adopted at dosage range of 4 to 20 g at 4 g interval, and optimum time and temperature of 80 min and 50 oC respectively. Oil and adsorbents were mixed using magnetic stirrer and heated for 80 minutes at 50 oC. The adsorbent was separated from the oil by filtration of hot suspension on Buchner’s funnel with filter paper in a vacuum at (10-15 mm Hg) for 2 hours. The cool filtrates were stored in sealed bottles for further analysis. The results revealed that at the optimum dosage of 16 g, the percentage recovery of free fatty acids (FFA) and peroxide (PO) was 91.63 and 87.11 % respectively. The adsorbent was able to turn the dark brown colour of SVOs to golden brown, and the objectionable odour becomes less objectionable. Overall, the adsorbent was able to regenerate the SVOs close to the original status, thereby providing an innovative solution that contributes to global sustainability, by reducing waste, conserving resources, and promoting circular economy.

Introduction

Vegetable oil, composed mainly of triglycerides from plant seeds, deteriorates in quality when heated or stored due to oxidation, polymerization, and isomerization, producing harmful compounds and reducing nutritional value. Spent vegetable oils (SVOs), commonly used in frying at high temperatures (150–190°C), pose health risks when reused continuously.

Eggshells (EGS), primarily calcium carbonate with minor proteins and minerals, protect eggs and have porous surfaces allowing gas exchange. Beyond biological functions, eggshells are utilized in calcium supplements, fertilizers, crafts, traditional medicine, and environmental remediation—such as adsorbing pollutants from wastewater.

This study investigates the use of modified eggshell adsorbents (MESA) derived from eggshell waste to remediate spent vegetable oils. Eggshells were collected, cleaned, dried, ground, and chemically treated with phosphoric acid to enhance adsorption properties. The modified adsorbent was characterized by physicochemical properties, FTIR (identifying functional groups like OH, N-H, C=O), SEM (revealing porous structure), and EDX (elemental composition dominated by carbon and calcium).

Batch adsorption experiments showed that increasing the adsorbent dosage improved removal efficiency of free fatty acids (FFA) and peroxide value (PV) from spent oil, reaching maximum removal (~91.6% PV, 87.1% FFA) at 12 g dosage. The study suggests that MESA is an effective, low-cost adsorbent for improving the quality of used vegetable oil by reducing impurities and oxidation products.

Conclusion

The MESA possesses high fixed carbon content and surface areas together with well-developed pore structures. The presence of functional groups like OH, N-H, C?N, C=O, CH3 and CH boosts its good surface chemistry for adsorption of FFA and PV from SVOs. The adsorption cycle was reliant upon dosage at the optimum condition of 12 g until a marginal decrease sets in.

References

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Copyright

Copyright © 2025 Abidemi Anthony Sangoremi , Oluwayemi Olanike Onawumi , Olugbenga Solomon Bello. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.