Reusable Green Aerogels from Cross-Linked Hairy Nanocrystalline Cellulose and Modified Chitosan for Dye Removal

Abstract

A novel biopolymer-based aerogel was developed by freeze-drying a hydrogel, synthesized from cross-linking bifunctional hairy nanocrystalline cellulose and carboxymethylated chitosan through a Schiff base reaction. The nanocelluloses, bearing aldehyde and carboxylic acid groups, facilitated the cross-linking with chitosan through imine bond formation while providing negatively charged functional groups, and chitosan was modified to accommodate carboxylic acid. The potential of this bioaerogel in environmental remediation was examined in a model system comprising methylene blue, a cationic dye. Electrostatic complexation between acidic groups on the anionic aerogel with the dye resulted in time-dependent dye adsorption, with long-time equilibrium dye concentration fitting well to the Langmuir isotherm, yielding a maximum adsorption capacity of ∼785 mg g and equilibrium constant K ∼ 0.0089 at room temperature. Dynamics of adsorption was modeled by numerically solving the unsteady-state diffusion-adsorption mass balance in a 1D spherical coordinate, which attested to a diffusion-controlled process with a Langmuir adsorption time constant τ ∼ 7.6 s. To the best of our knowledge, this bioaerogel exhibits the highest removal capacity as yet for any reusable adsorbents prepared from biopolymers. Successful adsorption-regeneration cycles proved an excellent reusability, and the adsorption capacity remained constant over a wide pH range (e.g., pH > 7). This work may pave the way toward ultralight green functional materials.

Facile Preparation of Nanofibrillar Networks of “Ureido‐Chitin” Containing Ureido and Amine as Chelating Functional Groups

“…demonstrated that highly porous chitosan foams with chelating amine functional groups can be a promising adsorbent material for anionic dyes from which the elution of dyes have been accomplished with alkaline treatment of the foams. Yang et al . reported reusable hybrid (cellulose and chitosan‐based) foams for the removal of cationic dyes.…”

“…In this case the dye molecules were desorbed by treating the hybrid foams in 0.1 m HCl, followed by washing with 0.1 m NaOH solution. Both of these studies, proved the excellent functional properties of foams for many cycles.…”

Novel superabsorbent materials from bacterial cellulose

“…A greater charge of the polymer network gives better water absorbency including saline solution. Due to the high swelling capacity and user‐friendliness, such superabsorbent materials have been extensively used in various applications such as biomedicine, drug delivery, heavy metals removal, personal care products and agriculture …”

Gelation of crystalline nanocellulose in the presence of hydroxyethyl cellulose

“…Depending on the chemical treatment applied to the wood pulp, hairy nanoparticles can either have cationic charges, anionic charges, or no charges at all . The anionic form of this hairy nanocellulose is called electrosterically stabilized cellulose nanocrystals (ECNCs) and has been targeted for different uses such as heavy metal ions capture, biomimetic mineralization of calcium carbonate, and reusable green aerogels . In a previous work, both the dilute and the semi‐dilute regime of ECNC aqueous suspensions were studied.…”