Developing microfluidic purification techniques for biodiesel production from recycled grease trap waste

Abstract

This study aimed to investigate the desulphurisation process of model biodiesel containing thiophene (Th) using 3 different solvents (sulfolane, ionic liquids (ILs) – [BMIM]AlCl₄, [BMIM]MSA, and deep eutectic solvents (DESs) – choline chloride (ChCl) : phenol (Ph), ChCl : polyethylene glycol (PEG)). The investigation focused on evaluating the impact of solvent-to-fuel (S : F) ratio, mixture flow rate, and temperature to optimize the process using a central composite design. The results indicated that the optimal conditions for desulphurisation were achieved by employing ChCl : PEG at a high S : F ratio of 2 : 1, a low mixture flow rate of 1.55 mL min⁻¹, and a temperature of 30 °C, resulting in a removal efficiency of 65.81%. To meet the economical requirements, the desirability function suggested operating the system at a S : F ratio of 1.85, mixture flow rate of 1.77 mL min⁻¹, and temperature of 25 °C, with the predicted yield of 55.38%. The conditions were experimentally checked, resulting in 44% of removal for a single stage and 80% of removal for 5 stages. However, the chosen purification technique would increase the total operational cost by $12.77 per litre. This financial barrier can be overcome by further considering the ability to regenerate the solvent and the use of different configurations of the microfluidic device for higher efficiency.