Modeling of permeate flux decline and permeation of sucrose during microfiltration of sugarcane juice using a hollow-fiber membrane module

Microfiltration (MF) of centrifuged sugarcane juice was used as a pre-clarification step prior to further clarification. MF was performed with the objectives of achieving maximum flux, minimum retention of sucrose and maximum rejection of total solids as well as maximum removal of microorganisms from the permeate keeping the nutritional and physico-chemical profile intact. In this regard, experiments were done using a polyacrylonitrile-based MF membrane of filtration area 0.027 m2 and pore size of 0.1 μm. A detailed investigation of the effects of different operating conditions, namely transmembrane pressure TMP (35, 69, 104 and 138 kPa) and cross flow velocity CFV (0.123, 0.246 and 0.369 m/s) on membrane productivity and juice quality was undertaken. The steady-state permeate flux ranged from 5.41 to 6.23 l/m2∙h for the domain of the operating conditions studied herein. Profiles of permeate flux and sucrose concentration in permeate were modeled using a gel layer controlling model under the framework of boundary layer analysis. The optimized operating conditions were found to be TMP of 104 kPa and CFV at 0.369 m/s, yielding a flux of 6.04 l/m2∙h and having sucrose and polyphenols concentration of 104.8 g/l and 9.38 mg GAE/100 ml, respectively. Total solids (26%) and turbidity (98%) were removed to a great extent during MF along with remarkable improvement of clarity (3 times). Microbiological evaluation confirmed that, MF successfully reduced the total viable plate count by 5 log CFU/mL scale and yeast and mold count by 4 log CFU/mL scale.