Preparation and sorption studies of glutaraldehyde cross-linked chitosan copolymers.

Chitosan-glutaraldehyde copolymer sorbents were synthesized by reacting variable weight ratios (low, medium, and high) of glutaraldehyde with fixed amounts of chitosan. Two commercially available chitosan polymers with low (L) and high (H) relative molecular weights were investigated. The chitosan-glutaraldehyde (Chi-Glu) copolymer sorbents are denoted as CPL-X or CPH-X where X denotes the incremental level (X=-1, -2, -3) of glutaraldehyde. The copolymers were characterized using FT-IR spectroscopy and TGA. The solid-solution sorption isotherms in alkaline aqueous solution for the copolymers were characterized using absorbance and emission based spectroscopic methods for p-nitrophenol (PNP) and the arsenate oxoanion HAsO4(2-) species, respectively. The Sips isotherm model was utilized to obtain sorption parameters at pH 8.5 and 295K (i.e. sorbent surface area, sorption capacity and removal efficiency) for each copolymer sorbent. The sorbent surface areas for the low molecular weight chitosan copolymers are listed in parentheses (m(2)g(-1)), as follows: CPL-1 (124), CPL-2 (46.7) and CPL-3 (31.6). The high molecular weight chitosan copolymers are as follows: CPH-1 (79.8), CPH-2 (64.7) and CPH-3 (96.3). The removal efficiencies depend on the pH, temperature, and the relative amounts of sorbate and sorbent. The sorbent removal efficiencies for p-nitrophenol ranged between 7.1% and 49%, and the values for H2AsO4(2-) ranged between 31% to 93% for the low and high molecular weight copolymers.

Preparation and sorption studies of ß-cyclodextrin-chitosan-glutaraldehyde terpolymers.

ß-Cyclodextrin-chitosan-glutaraldehyde terpolymers were synthesized by reacting variable weight fractions of ß-cyclodextrin (ß-CD) and chitosan (Chi), with a constant amount of crosslinker (glutaraldehyde). The ß-CD:Chi:Glu terpolymer sorbents were characterized by FT-IR spectroscopy and TGA. The solid-solution sorption isotherms in aqueous solution for the copolymers were characterized using two spectroscopic methods (UV-Vis and ICAP-OES) for p-nitrophenol (PNP) and the arsenate oxoanion (HAsO(4)(2-)) at alkaline pH conditions. The Sips isotherm model was utilized to obtain sorption parameters at pH 8.5 and 295 K (i.e. sorbent surface area, sorption capacity and removal efficiency) for each copolymer sorbent. The sorbent surface area estimates for the terpolymers at low (T1), medium (T2), and high (T3) weight fractions of ß-CD are listed in parentheses (m(2) g(-1)), as follows: T1 (161), T2 (51.2) and T3 (275). The removal efficiencies are dependent on the relative weight fraction of the polysaccharide components (i.e. ß-CD and Chi); whereas the removal efficiencies for p-nitrophenolate ranged between 7.3% and 28%, and H(2)AsO(4)(2-) ranged between 23% and 55%.

Sorption of agrochemical model compounds by sorbent materials containing beta-cyclodextrin.

Polymeric sorbent materials that incorporate beta-cyclodextrin (CD) have been prepared and their sorption behavior toward two model agrochemical contaminant compounds, p-nitrophenol (PNP) and methyl chloride examined. The sorption of PNP was studied in aqueous solution using ultraviolet-visible (UV-Vis) spectroscopy, whereas the sorption of methyl chloride from the gas phase was studied using a Langmuir adsorption method. The sorption results for PNP in solution were compared between granular activated carbon (GAC), modified GAC, CD copolymers, and CD-based mesoporous silica hybrid materials. Nitrogen porosimetry at 77 K was used to estimate the surface area and pore structure properties of the sorbent materials. The sorbents displayed variable surface areas as follows: copolymers (36.2-157 m(2)/g), CD-silica materials (307-906 m(2)/g), surface modified GAC (657 m(2)/g), and granular activated carbon (approximately 10(3) m(2)/g). The sorption capacities for PNP and methyl chloride with the different sorbents are listed in descending order as follows: GAC > copolymers > surface modified GAC > CD-silica hybrid materials. In general, the differences in the sorption properties of the sorbents were related to the following: (i) surface area of the sorbent, (ii) CD content and accessibility, (iii) and the chemical nature of the sorbent material.