Synthetically engineered chitosan-based materials and their sorption properties with methylene blue in aqueous solution

Chitosan (CS) and poly(acrylic acid) (PAA) were crosslinked by an ionic gelation method to form super absorbent polymers (SAPs). CS and PAA form amide bonds between the amino and carboxyl groups. The CS–PAA copolymers were synthetically engineered by varying the feed ratios of the prepolymer units. The copolymer materials possess tunable sorption and mucoadhesive properties with a backbone structure resembling proteinaceous materials. The sorption properties of the copolymers toward methylene blue (MB) in aqueous solution were studied using UV–Vis spectrophotometry at ambient pH and 295 K. The copolymers showed markedly varied interactions with MB, from physisorption- to chemisorption-like behavior, in accordance with their composition, surface area, and pore structure characteristics. The sorption isotherms were evaluated with the Sips model to provide estimates of the sorption properties. The sorbent surface area (271 and 943 m2/g) and the sorption capacity (Qm = 1.03 and 3.59 mmol/g) were estimated for the CS–PAA copolymer/MB systems in aqueous solution.

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► Chitosan–PAA copolymers display favorable sorption toward methylene blue (MB).
► Chitosan–PAA display synergistic equilibrium sorption behavior with MB.
► Monolayer sorption capacity (Qm) of copolymers rival the Qm values of activated carbon.
► Tunable sorption properties depend on copolymer composition.
► Chitosan–PAA display pH switchable recognition behavior toward MB.