Flux Decline and Blocking Mechanism in Ultrafiltration of Glycerin-Rich Solution

Abstract

In the oleochemical industry, crude glycerin is a byproduct of biodiesel production. As a byproduct, crude glycerin has a low economic value and very limited applications. To improve these limitations, the purification of glycerin is required. One method for glycerin purification is a filtration process that uses ultrafiltration (UF) membranes based on polyethersulfone (PES). However, this process has several problems, particularly the flux decline that occurs during filtration. Thus, the aim of this study was to obtain a better understanding of the flux decline and blocking mechanism that occur in the UF of glycerin. In this work, the flux decline and blocking mechanism were observed by commercializing the UF of the PES membrane with a 1-kDa molecular weight cut-off. The investigated parameters were the pressure, temperature, and pH with ranges of 2-4 bar, 40-60oC, and 4-9, respectively. The results showed that the flux decline was significant due to the relatively small size of impurities, which clog the membrane's pores. Furthermore, the blocking mechanism was analyzed using Hermia's model, and it was found that the blocking mechanism was mostly dominated by cake formation, except at a pH of 7.