Recovery of carotenoids from crude palm oil using organic solvent nanofiltration

Abstract

The recovery of carotene from crude palm oil prior to refining would add significant value to the country’s palm oil industry. Various methods are currently available to yield high concentrations of carotene. These methods however, have many disadvantages when factors such as cost, and energy consumption are weighed into consideration. This work presents the application of organic solvent nanofiltration membranes for the separation of carotene from a crude palm oil (CPO)/solvent system. Filtration tests were conducted using a dead-end filtration set-up, utilizing four different polyimide membranes and four different solvents. PuraMem™ 280 showed the best performance, with a selectivity of 1.25 when hexane was used as the solvent. Runs using DuraMem™ 150, DuraMem™ 300 and DuraMem™ 500 showed low or no selectivity between carotene and triglyceride in all solvents. It was found that rejection of carotene depends strongly on the type of solvents and membrane type and therefore is critical for carotene separation. Lower applied pressure and low feed concentrations improved the membrane selectivity. The effect of solute-solvent coupling was much higher towards lower molecular weight component (carotene) and at lower pressures. Theoretical pore size of the membrane was predicted using sets of equations relating the diffusivity of the solutes and the experimental rejection results. Results showed that the theoretical pore size of membrane PuraMem™ 280 was between 1.38 nm to 1.85 nm. The effect of concentration polarisation was predicted, and result showed that in this system, the effect of concentration polarization was very minimal, where cw/cb was only between 1.06 to 1.24. Generally, high feed concentrations increased the feed viscosity, resulting in significant osmotic pressures and reduces the permeate flux.