Application of Nanofiltration in the Separation and Purification ofε-Poly-L-Lysine for Desalination

Abstract:

To develop the process of desalination in the separation and purification of ε-poly-L-lysine（ε-PL），the nanofiltration was used in this study. Firstly，several nanofiltration membranes were evaluated，，then the operation parameters were optimized through one-factor-at-a-time experiment using model solution as object. Finally，the eluent of ion exchange step was desalinated by nanofiltration at the optimal condition. The results showed that SP800 was the best choice used for desalination in terms of permeate flux，ε-PL retention ratio and NaCl removal ratio. Meanwhile，the optimal desalination conditions were as follows：the pH was 9.0，and the maximum ε-PL concentration was concentrated to about 100 g/L，while the permeate conductivity was controlled less than 300 μS/cm through adding deionized water. To evaluate the efficient of the developed desalination process，1 000 L ε-PL eluent of ion exchange step was employed for desalination by nanofiltration at the optimal condition. Finally，the NaCl removal ratio and the ε-PL loss ratio were reached 96.43% and 0.77%，respectively；and the ε-PL purity and ash content were attained 98.21% and 1.02%，respectively. This is the first report on the desalination of ε-PL solution using nanofiltration，it would be helpful to the production of ε-PL in industry.