Separation performance of multi-components solution by membrane technology in continual diafiltration mode

• A model was built to predict total retention in multi-components solution during diafiltration.
• A simplified binary system with membranes of different pore size was well verified the model.
• Commercial multi-component solution, soybean molasses, was well employed to verify the theory.
• The increment of total retentions was observed, and was testified by the model.
• The retention curve predicted by the model agreed well with the experimental data.

To investigate the membrane separation performance of multi-components solution throughout continuous volumetric diafiltration (CVD), sucrose and glucose were implemented as model solute. Two commercial nanofiltration (NF) membranes (QY-NF-1-SW with molecular weight cut-off [MWCO] of 150 Da and QY-NF-3-D with MWCO of 250 Da) were operated in batch recycling mode. Flux (Jv), trans-membrane pressure (ΔP), concentrations in feed (Cf) and permeate (Cp) were collected, and the retentions (R) were calculated. Based on the Spiegler and Kedem (S–K) equation, a theoretical R model was established. The model was employed to establish the mass balance equations in a feed tank during CVD. A novel revised retention equation was established to simulate CVD of sucrose and glucose mixture solution. Further, the model was popularly applied in ultrafiltration (UF) of the multi-components solution-soybean molasses by a commercial membrane (QY-UF-1-G with MWCO of 1 kDa). It was predicted in theory the total retention of multi-components increased, since the concentration of low retention solute declined with diafiltration process time when the flux was insignificantly changed which was then demonstrated by the experiment. The results showed that the retention curve predicted by the model agreed well with the experiment, and the revised retention equation was well designed for industrial food fluids.