Mass transfer and transport during purification of fructooligosaccharides by nanofiltration

In this work, a process has been designed for the purification of fructooligosaccharides obtained by enzymatic transformation of sucrose from sugar cane molasses. The designed protocol includes two nanofiltration stages with the same membrane. The first one is a diafiltration process, at constant volume followed by concentration. The second stage consists in the nanofiltration of the permeate of the first stage to obtain a concentrate similar in its characteristics to the initial solution. The process allows getting purities over 90% in fructooligosaccharides with yields around 80%. These processes are studied and modeled, by taking into account the effects of the resulting osmotic pressure and the changes in resistance due to solute adsorption on the membrane. The transport is modeled by assuming that there are diffusion and convection but hindered by friction in the pore. The steric partitioning, along with an adequate mass balance for the differently sized molecules have also been considered leading to get the pore size distribution of the membrane.