Performance of polyamide and polyethersulfone membranes in the nanofiltration of reactive dye-salt mixtures on pilot scale

Abstract

Thin film composite polyamide (PA-NF) and polyethersulfone (PES-NF) membranes were used to study their performance towards reclamation of an aqueous solution of reactive red 198 and NaCl in a nanofiltration pilot plant. It was found that there were significant differences between the performance of the two membranes, and that the membrane properties played an important role in the dye removal rate, stable permeate flux, and salt rejection of the membrane. The experimental results showed that both the permeate flux and observed rejection decreased with an increase in dye as well as salt concentration in the feed. The maximum flux obtained with PA-NF membrane at 12.5 mg/l feed concentration was 11.4 × 10−6 m3/m2 s, whereas with PES-NF the flux was 5.5 × 10−6 m3/m2 s. The flux decline as a function of time for PES-NF membrane was much less compared to PA-NF. The contact angles of PA-NF and PES-NF membranes were found out to be 52o and 73o, respectively. Atomic force microscopy images revealed that the PA-NF membrane surface had more roughness than that of PES-NF.