In this article, the permeation experiments by using a NF membrane were carried out for single component solutions of inorganic electrolytes (NaCl, KCl, MgCl2, Na2SO4 and MgSO4) and neutral organic solutes (glycerin, glucose, sucrose and raffinose) and a mixture solution of NaCl and glucose or sucrose. The effects of applied pressure and feed concentration and the coupling interaction between glucose or sucrose and NaCl on the separation performance (observed rejection and permeation flux) were investigated for single and mixture solutions, respectively. NF45 membrane is a negative charged membrane with the molecular weight (MW) cut-offs of about 300 Da, and it is available for the separation of saccharides or bivalent anion electrolytes and univalent anion electrolytes. An overall diafiltration process with a batch-wise mode was simulated for a model solution of soybean whey wastewater containing some saccharides and salts (such as NaCl), and the feasibility of the concentration of oligosaccharides and the removal of salts was also discussed.