Optimization of solid-liquid extraction: Solvent effects on the fatty acid composition and physicochemical properties of Argemone mexicana seed oil and valorization of seed residue
Blen Weldegebreal Gebreegziabher, Muyiwa S. Adaramola, John Morken, Amare Aregahegn Dubale
Abstract
Oil extraction from underutilized plants like Argemone mexicana (AM) is essential for biofuel and biochemical production. However, the effects of solvent choice and seed origin on oil yield, parametric optimization, oil quality, and seed residue valorization remain underexplored in the existing literature. This study employed Soxhlet extraction using three selected solvents: petroleum ether, dichloromethane, and n-hexane to extract oil from AM seeds. Response Surface Methodology with a Box-Behnken Design (RSM-BBD) was applied to optimize the key extraction parameters, achieving a maximum oil yield of 40.1 % using n -hexane at a temperature of 71.3 ˚ C, solvent-to-seed ratio of 5.22, and 270-minutes extraction time. Additionally, an oil yield ranging from 34.34 – 39.60 % was obtained from seeds collected from four localities. Most physicochemical parameters of the oil fall within the standard range reported for various oils, although it showed high free fatty acid (FFA) content. Major fatty acids identified were linoleic (58.6–64.3 %), oleic (21.5–25.4 %), palmitic (9.9–10.7 %), and stearic acids (2.20–2.65 %). ANOVA results (α = 0.05) demonstrated that both solvent type and seed collection sites significantly influenced oil yield and composition. The macro-elemental composition of de-fatted AM seeds contained 0.60 % Phosphorus, 1.40 % Calcium, 1.50 % Potassium, 3.88 % Nitrogen, and 46.8 % Carbon, with a calorific value of 17.7 MJ/kg and a C/N ratio of 12.07. The traits suggest that AM seed oil has the potential for producing biodiesel, provided the FFA content is lowered to comply with standard requirements. Moreover, the seed residue could be utilized as an energy co-substrate or organic soil nutrient stabilizer.