Macromolecular Sorbent Materials for Urea Capture

Three types of chitosan-glutaraldehyde (Chi-Glu) crosslinked copolymer materials were prepared at various Chi-Glu weight ratios (i.e., 1 : 0.0835, 1 : 0.334, and 1 : 0.585) and variable reaction times. The corresponding Chi-Glu copolymer materials were imbibed in CuSO4 solution to yield impregnated materials in the form of copolymer/Cu(II) complexes. The copolymer materials were characterized using FTIR spectroscopy and thermogravimetry analysis. Urea sorption isotherms were obtained in aqueous solution at 295 K and pH 7 with pristine chitosan, Chi-Glu copolymers (i.e., 1 : 0.0835 and 1 : 0.585), and the corresponding Chi-Glu/Cu(II) complexes. The concentration of unbound urea was monitored indirectly using a colorimetric method with p-dimethylamino-benzaldehyde. The equilibrium adsorption data were analyzed using the Sips isotherm model. The uptake of urea with pristine chitosan was 4.7% w/w, whereas Chi-Glu copolymers display increased sorption (Q(m) 10.6-17.1% w/w) with increasing glutaraldehyde content. Urea sorption is further enhanced (Q(m) 16.3-26.4% w/w) for copolymer Chi-Glu/Cu(II) complexes. The preparation of Chi-Glu copolymers at various conditions illustrates that the sorption capacity and molecular recognition of urea can be systematically tuned via crosslinking and the formation of copolymer/Cu(II) complexes, and these results are related to a previously reported study (Shimizu and Fujishige, J. Biomed. Mater. Res. 1983, 17, 597). (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 128: 667-675, 2013