Separation of Sulfoether Compounds in Garlic Oil by Integrated Membrane Technologies

This study investigated an integrated process to separate sulfoether compounds from garlic oil. The garlic oil was pretreated by vapor distillation and the oil–water mixture was treated with the combination of ceramic membrane microfiltration (MF) and poly(dimethylsiloxane)/poly(vinylidene fluoride) composite membrane pervaporation (PV). The optimum operating conditions with respect to sulfoether compounds' recovery were determined to be 1.8% feed concentration, 30C and 0.10 MPa for ceramic membrane MF; and 40C, 5 h, 0.24 MPa and 0.32 L/min for PV. It was found that the emulsified oil was effectively separated by ceramic MF membranes, and the rejection rates of diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS) were 91.11, 99.8 and 100%, respectively. In the subsequent process, PV membrane was used to recover the dissolved oil. PV membrane had a good enrichment effect on DAS and DADS in the penetrant permeate fluid, with separation factors of 6.31 and 5.45, respectively. Compared with oil–water mixture by vapor distillation, the yield of garlic oil is 99.6%. This study showed that MF and PV processes were attractive technologies for the recovery of garlic sulfoether compounds as they yield good separation and operate under mild conditions. Practical Applications: Researchers have reported that active components of garlic have beneficial effect on human's health; in particular, the sulfoether compounds of garlic oil. However, the development of process technology and high value-added products of garlic is lacking. The present study provides an integrated process to separate sulfoether compounds from garlic oil. The results indicated that microfiltration and pervaporation processes were effective technologies for the recovery of garlic sulfoether compounds. These processes should be taken as good examples for extraction of plant essential oil and the treatment of oily wastewater generated by the industry to achieve oil–water separation.