Development and characterization of composite nanofiltration membranes and their application in concentration of antibiotics

Composite membranes for nanofiltration were prepared by interfacial polymerization of piperazine and trimesoyl chloride. The membranes were characterized by different inorganic salts, uncharged solutions, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) as well as atomic force microscopy (AFM). The separation performances of the prepared membranes are comparable to the commercial nanofiltration membranes. Some of the membranes were coated with polyvinyl alcohol (PVA). The coated surfaces were found to be smoother and more hydrophilic, which could reduce membrane fouling. The plate-and-frame and spiral-wound modules fabricated by the prepared membranes were used to concentrate antibiotics. The antibiotics solutions were concentrated from 12 000 to 110 000 U/ml in the lab scale experiments and from 80 000 to about 340 000 U/ml in pilot scale experiments. There was no apparent change in average processing capacity observed after nine batches operation in the pilot scale. This study shows that the nanofiltration is a promising technique for concentration of antibiotics.