Hybrid zipper-like chitosan-carboxymethyl cellulose-ferric adsorbents for tunable anion adsorption

Abstract

Composite materials (CCFe and CGCFe) were prepared from carboxymethyl cellulose, chitosan, glutaraldehyde, and iron III species. The composite materials were characterized by FTIR, TGA, ICP-OES and SEM studies that provided evidence of cross-linking between chitosan and glutaraldehyde, along with variable iron doping and morphology of the composites. The equilibrium uptake study indicates that CGCFe surpassed the adsorption capacity of CCFe, where greater uptake was noted at lower versus higher temperatures (283 – 303 K). The monolayer adsorption capacity (Qm; mg g−1) of CGCFe for 2-naphthoxy acetic acid (S6) was 263 mg/g and 484 mg/g at alkaline and acidic pH conditions, according to the Sips and Langmuir isotherm models. The composite materials show limited discrimination of OSPW naphthenate components. Regeneration studies revealed that CGCFe retained 95% of its adsorption capacity after 5 cycles via a “zippering effect” in the presence of saline water. The enhanced regeneration and zipper-like structural transition of CGCFe represents a unique application of saline responsive supramolecular function driven by changes in ionic strength. This study advances the design of modular polysaccharide adsorbents according to the insight on the role of Fe (III) species, cross-linking effects, and biopolymer structure that relate to anion binding properties in aqueous solution.

Keywords

• Carboxymethyl cellulose
• Chitosan
• Iron (III)
• Cross-linking
• Composites
• Biopolymer “zippering effect”