Removal of copper(II) ions from aqueous solutions by complexation-ultrafiltration using rotating disk membrane and the shear stability of PAA-Cu complex

The stability of polymer-metal complex in the shear field is of great significance for the industrial applicaion of complex-ultrafiltration. The shear stability of PAA-Cu complex was investigated for the first time. Polyacrylic acid sodium (PAAS) was applied to remove Cu(II) from aqueous solutions by complexation-ultrafiltration using a rotating disk membrane. As important factors, solution pH and P/M (the mass ratio of polymer to metal ions) on the rejection of Cu(II) were investigated, and the rejection of Cu(II) could reach 99.6% at pH = 6.0, P/M = 25. The rotating disk was applied to generate shear rate on the membrane surface, and the radial distribution of shear rate on the membrane surface was calculated. The critical rotating speeds at which the rejection of Cu(II) begins to decrease were 1000, 900, 700 rpm at pH values 6.0, 5.0, 4.0, respectively, and the corresponding critical shear rates (gamma(c)) at which the PAA-Cu complex begins to dissociate were 8.0 x 10(4), 6.6 x 10(4) and 4.2 x 10(4) s(-1), respectively. Furthermore, the critical shear radius and the radial distribution of substances on the membrane surface were obtained using a segmentation model. The shear stability, especially the critical shear rate of the polymer-metal complex, can give guidance to the selection of the delivery pumps so that high removal efficiency can be obtained in the industrial application of complexation-ultrafiltration. In addition, shear induced dissociation and ultrafiltration was first applied to regenerate PAAS. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.