Sustainable and low-cost protic ionic liquid-based recovery of oil from agricultural wastes “date pits” for biofuel production

Several studies revealed that date pits, often regarded as agro-industrial waste, possess the potential to be upgraded to value-added products like biofuels. Yet, the majority of the oil extraction studies from date pits relied on the use of environmentally harmful organic solvents which are highly flammable and toxic. Thus, for the first time, this paper is aimed at developing a cost-effective, green, and novel technology for the extraction of oil from date pits using protic ionic liquids. The date pits of eight distinct varieties were structurally characterized, determining their composition of oil (7.6–10.9%), carbohydrates (80.8–84.6%), protein (4.8–8.8%), and ash (1.1–1.7%) based on dry biomass. The quality of oil across these date pits was found to be comparatively similar and well-suited for biofuel production, with oleic, lauric, myristic, and palmitic acid being the most abundant constituents. The screening of six unique protic ionic liquids indicated that Triethylammonium dihydrogen phosphate [TEA][H₂PO₄] exhibited the highest oil extraction of 91.3 mg/g biomass (84% of total oil) from Majdool dates. The investigation of process parameters disclosed that temperature significantly affected oil extraction performance, whereas the reaction duration's impact was found to be minor. The recycling and reuse of [TEA][H₂PO₄] for the extraction of oil from Majdool date seeds throughout four cycles were promising in terms of performance stability, thereby promoting process viability. The outcomes obtained through this study endorse the capacity of low-cost protic ionic liquids to efficiently extract oil from date pits, presenting a viable alternative to toxic organic solvents in this context.