Influence of process and operating variables on the performance and fouling behavior of modified nanofiltration membranes treating licorice aqueous solution

The main purpose of this study was to investigate the effect of different operational parameters on performance and fouling trends of unfilled- polyethersulfone, 0.5 wt.% boehmite-polyethersulfone, tannic acid coated boehmite-polyethersulfone nanofiltration membranes during filtration of Licorice aqueous solution as model foulant. The impact of hydrodynamic conditions (such as transmembrane pressure and cross-flow velocity) and feed composition on permeation, fouling trends and rejection capability were evaluated using lab-scale cross-flow filtration set-up. The applied transmembrane pressure and cross-flow velocity were various in range of 6-12 bar and 0.5-2.5 cm/s, respectively. The results indicated that although, increasing of operational pressure and cross-flow velocity can enhance the permeability and rejection capability of NF membranes also incur appearance of the more severe fouling phenomenon. The least fouling for NF membranes was occurred at the lowest licorice concentration of 0.1 g/l. The rejection percentage of unfilled and embedded nanofiltration polyethersulfone membranes was more than 92 %.