Investigatigation of chitosan-based materials for sorptive uptake of urea
Xue, Chen 1986-
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Three types of chitosan-glutaraldehyde (Chi–glu) cross-linked copolymer materials were prepared at various Chi–glu weight ratios and variable reaction times. Copper imbibed copolymers were prepared from the corresponding Chi–glu copolymer materials. The copolymer materials were characterized using FTIR spectroscopy and thermogravimetry analysis. Water swelling, urea sorption properties were studied at equilibrium and kinetic conditions for pristine chitosan, Chi–glu copolymers, and the copper imbibed copolymers. The uptake of urea with pristine chitosan was 4.7% w/w, whereas Chi–glu copolymers display increased sorption (Qm 10.6–17.1% w/w) with increasing glutaraldehyde content. Urea sorption is further enhanced (Qm 16.3–26.4% w/w) for copper imbibed materials. The kinetic results were fit with the Pseudo-First-Order and Pseudo-Second-Order models. Based on Pseudo-First-Order model, the time depend uptake (Qt) for the corresponding copolymers is consistent with the equilibrium uptake (Qe) estimated at similar initial urea concentration. In order to further study the sorption behaviour of urea on the sub-micron size materials, composite microparticles containing chitosan or modified (carboxymethyl) chitosan with polyanions such as alginate or tripolyphosphate were prepared in aqueous solutions. Several types of microparticles were prepared and their physicochemical properties were characterized by 1H/31P NMR spectroscopy, IR spectroscopy, and DLS. The average size and polydispersity index (in parentheses) are reported for the chitosan-based microparticles, 243.0±1 nm (0.3) to 424±14 nm (0.3), according to DLS measurements at ambient conditions. The stability of the microparticles is related to the composition of the system and the aqueous solution conditions, as evidenced by varying ionic strength with certain microparticle systems which display good stability over two weeks or more. The equilibrium uptake of urea for the most stable microparticle system was collected at ambient conditions using a one-pot dialysis tubing setup. The size and stability changes of microparticle during the adsorption were monitored using dynamic light scatter and NMR spectroscopy. Microparticles grow as the increase of the concentration of urea and the experiment time. After 36 hours, complete sedimentation was observed. Microparticles were shown to display good urea uptake (Qe ~36% w/w) that is comparable to chitosan based copolymers.
DegreeMaster of Science (M.Sc.)
CommitteeWilson, Lee d; Urquhart, Stephen
Copyright DateJanuary 2015
urea sorptive uptake properties