Cefalexin crystallization residual liquor separation via nanofiltration based multistage process

Pharmaceuticals manufacture is of importance to human life and health. Great amount of pharmaceuticals crystallization residual liquor was produced in the pharmaceuticals manufacture, which lead to adverse influence on the green chemical engineering and environment. Herein, we proposed a multistage separation process based on nanofiltration technology to recover cefalexin crystallization residual liquor separation. The influence of membranes, pH value, concentration as well as separation stages on the separation performance was explored. The nanofiltration membrane (NF-200D) with strong electronegative charge showed a high rejection of 74.00% for 7-amino-3-desacetoxycephalosporanic acid (7-ADCA) and low rejection of 7.06% for D-phenylglycine in mixed solution. The increase in the electronegative charge of NF membranes could enhance the repulsion between membrane and solute molecules. The separation factor of nanofiltration membrane for 7-ADCA and D-phenylglycine reached a peak value of 3.06 at pH 8.0 and concentration of 10 mmol L−1. Using three stage separation, the concentrated 7-ADCA (C7-ADCA = 23.12 g L−1) and the permeate D-phenylglycine (CD-phenylglycine = 0.19 g L−1) were obtained. Further improved separation sequence should focus on the preparation of nanofiltration membranes with strong electronegative charge and acid-base tolerance, and the nanofiltration process design with enhanced efficiency of separation process.