New poly(N-δ-acryloyl ornithine) gels cross-linked with N,N′-methylenebisacrylamide. Sorption properties

To make a polymer from ornithine the acryloyl group was added to δ-amino group of the amino acid and N-δ-acryloyl ornithine was polymerized. The presence of α-amino acid groups attached to the polymeric network of the gels enables the complexation of some di- and trivalent metal cations. Copper ions, which can form two complexes of different stoichiometry (1:1 and 1:2) with amino acids, were used to investigate the influence of the complexation process on the swelling behavior and sorption properties of the obtained gels. The swelling ratio decreased as copper ion concentration increased. The poly(N-δ-acryloyl ornithine) gel was most sensitive to the copper ions in the concentration range of 1–100 mg/mL. The obtained UV–Vis spectra indicated that the copper ions mainly formed complexes of stoichiomery 1:2 with the α-amino acid group. Copper ion uptake was found to exceed 94% in a wide pH range (4–10). The maximum sorption capacity calculated by applying the Langmuir equation was 18.0 mg/g. Kinetic data showed that the sorption process reached equilibrium within 30 min and indicated the importance of the intraparticle diffusion step.