Separation efficiency and stability of thin-film composite nanofiltration membranes in long-term filtration of copper sulphate and sulphuric acid mixture

摘要

Separation efficiency and stability of two lab-fabricated polysulfonamide (PSA) and polypiperazineamide (PA) thin-film composite nanofiltration membranes in long-term filtration of copper sulphate and sulphuric acid mixture were evaluated and compared in this study. The PSA and PA membranes were fabricated through interfacial polymerization process and 60-day long-term filtration tests were carried out with an acidic aqueous solution containing 2.5% (w/v) CuSO4 and 8.0% (w/w) H2SO4 under 25.0 degrees C and 10.0bar. The separation efficiency was studied in terms of permeate flux and retentions to copper and acid. The change of separation efficiency with filtration time was investigated to evaluate the performance stability of the membranes studied. Attenuated total reflectance Fourier transform infrared, field emission scanning electron microscopy, streaming potential analyzer, and contact angle analyzer were also adopted to characterize the change of membrane surface property during filtration. It was found that the PSA membrane maintained its separation efficiency during the 60-day continuous filtration, exhibiting a copper retention of about 83.5% and a sulphuric acid retention of less than 5.0%. The PA membrane began to lose its selectivity after 20days of filtration due to the deterioration of its skin layer, which was confirmed by the change of membrane surface property.