Poly(vinylalcohol) coated/Cibacron Blue F3GA-attached polypropylene hollowfiber membranes for removal of cadmium ions from aquatic systems

Dye-affinity adsorption is increasingly used for heavy metal removal from a quatic systems. Synthetic hollow fiber membranes have advantages as support matrices in comparison to conventional microbead adsorbents because they a re not compressible and they eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyvinyl alc ohol coated/Cibacron Blue F3GA-attached polypropylene hollow fibers for rem oval of Cd(II) ions. The internal matrix was characterized by scanning elec tron microscopy. Commercially available polypropylene hollow fiber membrane s were coated with polyvinyl alcohol (PVA). The PVA adsorption conditions w ere optimized to increase the amount of PVA by changing the initial concent ration of PVA, and adding NaCl. The maximum PVA adsorption capacity was 22. 6 mg/g. These hollow fiber membranes carrying Cibacron Blue F3GA (87.9 mu m ol/g) were used in the Cd(II) removal from aqueous solutions containing dif ferent amounts of ions (10-500 mg/l) and at different pH values (2.0-8.0). Cd(II) adsorption capacity increased with time during the first 40 min and then leveled off coward the equilibrium adsorption capacity. Adsorption of Cd(II) ions on the PVA coated polypropylene hollow fiber membranes was 1.2 mg/g. Cibacron Blue F3GA-attachment significantly increased the Cd(II) adso rption (46 mg/g polymer). The adsorption of Cd(II) ions increased with incr easing pH and reached a plateau value at around pH 5.0. Competitive heavy m etal adsorption from aqueous solutions containing Cd(II), Cu(II), Pb(II) an d Hg(II) was also investigated. The adsorption capacities are 1.75 mg/g for Cu(II); 3.46 mg/g for Hg(II); 5.86 mg/g for Pb(II) and 18.35 mg/g for Cd(I I) ions. These results may be considered as an indication of higher specifi city of the Cibacron Blue F3GA-attached polypropylene hollow fibers for the Cd(II) comparing to other ions. Modified hollow fibers, can be regenerated by washing with a solution of nitric acid (0.1 M). The maximum regeneratio n value was as high as 95%. These modified membranes are suitable for repea ted use for more than three adsorption-desorption cycles without considerab le loss of Cd(II) adsorption capacity. (C) 2001 Elsevier Science B.V. All r ights reserved.