clarification of apple juice with a scraped-surface membrane unit: the effect of system parameters on process efficiency

Apple juice can be clarified by ultrafiltration; however, fouling is a limiting factor against the industrialization of the process. a scraped-surface membrane unit was designed and constructed to reduce fouling during membrane clarification of apple juice using a polyether sulfone membrane with a pore size of 4 kda. the effects of blade rotation speed (0, 600, 1400, and 2200 rpm), transmembrane pressure (0.5, 1, and 1.5 bar), feed flow rate (10, 15, and 20 ml/s), and distance between the blade and the membrane surface (2 and 5 mm) were evaluated on the permeate flux. the results revealed that increasing the blade rotation speed up to 600 rpm would increase the permeate flux, but further elevation of rotation did not affect the permeate flux. the optimized operating condition was obtained at low transmembrane pressure, feed flow rate, and short distance between the blade edge and the membrane surface. the study of the physicochemical properties of apple juice during clarification indicated that the designed system could reduce the turbidity of the juice by more than 99%. other properties also changed to almost the same extent as in non-rotating systems.