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 HAsO42- species, respectively. 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 areas for the low molecular weight chitosan copolymers are listed in parentheses (m2 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 H2AsO42- ranged between 31% to 93% for the low and high molecular weight copolymers.

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► Chitosan-based copolymers exhibit tunable sorption properties.
► Tunability is afforded with variable chitosan and glutaraldehyde content.
► Tunable sorption occurs for p  -nitrophenolate (PNP) and arsenate HAsO42-.
► Tunable sorption relates to the copolymer composition and adsorbate concentration.