Construction of carboxymethyl chitosan @ sodium oxide alginate aerogel for efficient adsorption of malachite green

Water pollution has emerged as a formidable issue of utmost concern in the world, and the design of three-dimensional porous, high adsorption performance, and sustainable adsorbent materials is of great significance for wastewater purification. Naturally abundant sodium alginate was used to prepare oxidized sodium alginate (OSA), a biomass macromolecule containing an aldehyde group. A double network interpenetrating structure based on carboxymethyl chitosan (CMS) and OSA was constructed without any small molecule cross-linking agent throughout, and a Schiff base reaction occurred at room temperature to prepare chemically stable CMS@OSA aerogels, which contain a continuous and dense porous structure inside the aerogel. CMS and OSA both contain an anionic reactive group, carboxyl, which makes them both matrix and functional materials, enabling selective adsorption of malachite green (MG) dyes. The prepared aerogel adsorbent showed a high adsorption capacity (302 mg/g) for MG at room temperature. The adsorption mechanism between the aerogel adsorbent and the adsorbent mass was investigated, and the effect of different factors on the adsorption performance was analyzed. The fitting coefficients of both the adsorption kinetic model and the isotherm model reached 0.99. The ingenious preparation method and excellent adsorption performance offer great prospects for chitosan biomass aerogels to play a role in environmental protection and economy. Highlights: An interpenetrating structure based on the Schiff base reaction. Construction of three-dimensional porous structures. Pure ecological raw materials without toxic crosslinkers. High adsorption capacity at 302 mg/g for malachite green. © 2023 Society of Plastics Engineers.