Influence of operating parameters on separation of green syrup colored matter from sugar beet by ultra- and nanofiltration

The interest in membrane filtration in the sugar industry has recently increased. In sugar beet processing, the main problem is the separation of non-sucrose compounds, especially of colored matter. Separation of colored matter from green syrup was examined by ultra- and nanofiltration of a solution with 39.2% d.m. content. In the process of ultratiltration (UF), two polymer membranes were used: membrane I with an MWCO (molecular weight cut-off) value of 15-20 kDa and membrane II with MWCO of 6-8 kDa. Nanofiltration (NF) was carried on a polymer membrane with MWCO of 0.5 kDa (membrane III). Effects of UF at 30 and 60 degreesC, in the range of transmembrane pressure of 1-4 bar, and NF at 30 and 50 degreesC, in the range of 5-30 bar were examined. In the course of experiments, interdependence between the permeate flux, transmembrane pressure, and volume concentration ratio were followed. The influence of operating parameters (transmembrane pressure, temperature and flow rate) on the efficiency of colored matter removal was examined. Highest separation effects by UF on the examined membrane, were achieved for the transmembrane pressure in the range of 2.5-4.0 bar at flow rates ranging from 220 to 360 l/h. Under these conditions, the permeate color was lower by about 55%nd 58% compared with the feed, when using membrane I and membrane 11, respectively. Separation of colored matter on membrane III was most efficient when the pressure was held on the level of about 30 bar and at a flow rate ranging from 300 to 400 l/h. Under these conditions, the permeate color decreased by 76%. (C) 2004 Elsevier Ltd. All rights reserved.