Functionality and mechanistic parametric study of the potential of waste plantain peels and commercial bentonite for soybean oil refining

Abstract

The consumption of unrefined vegetable oil poses acute and chronic health issues, yet improper disposal of waste plantain peels is not environmentally sustainable. This research investigates the feasibility, mechanism and thermodynamics of waste plantain peels, and commercial bentonite clay for soybean oil refining. Experiment was carried out using masses (1–4 g) of commercial bentonite clay, and unripe plantain peel ash (UPPA) to degummed and neutralized free fatty acid (FFA) contents in crude soybean oil at varying temperatures (50–120 °C), and time (15–35 min) for treatment of soybean oil. FTIR spectroscopy, SEM, and XRF techniques were applied to characterize the sample. The results established that at optimum 4.0 g dosage, the UPPA (97.73%) was more effective in the removal of FFA from oil at 50 °C and 20 min, while the clay (90%) was more effective in the removal of colour pigment from the vegetable oil 100 °C, and 25 min. The optimum efficiency of Clay-Ash-composite (70:30) in adsorbing pigment from soybean oil corresponds to 80%. The impact of changing viscosities, densities, and acid values on the performance of UPPA, clay, and clay-UPPA composite was investigated. Mechanistic studies confirmed the pseudo-second-order kinetics at 5 × 10–2 g/mg min−1 and 1.87 × 10–1 g/mg min−1, with corresponding adsorption capacity of 30.40 mg/g and 4.91 mg/g, at R2 ≤ 0.9982. The UPPA-driven sorption of FFA occurred as a physisorption and exothermic process (− 620.60 kJ/mol), while colour pigment removal occurred by chemisorption and endothermic process (22.40 kJ/mol). The finding recommends UPPA and composite as economically feasible for refining soybean oil.