Bi-porous bioinspired chitosan foams with layered structure and their adsorption for xylenol orange

Ordered bi-porous bioinspired chitosan foams were prepared by a unidirectional freeze-drying method, their structures and properties such as porosity were characterized. The adsorption performance of bioinspired chitosan foams for xylenol orange (XO) was studied. The bi-porous material has good adsorption performance for it. The porosity and adsorption efficiency are related to the amount of chitosan, pH, adsorbing time, degree of crosslinking in the foams and the content of ethyl acetate. When the pH was 3–9 at room temperature, the adsorption efficiency for XO reached 90% and the adsorption capacity achieved 122 mg/g that approached the calculated maximum value. The adsorption isotherms are fitted by both Freundlich equation and Langmuir equation, and the adsorption follows a pseudo-first-order kinetic model. Since the chitosan foams are nontoxic, biodegradable and efficient, they could be widely used in wastewater treatment as well as other areas, such as the purification of drinking water and the separation and recycling of small molecules and macromolecules.

► The bi-porous chitosan monoliths were prepared by unidirectional freeze-drying.
► The monoliths have two kinds of pores and a unidirectional porous structure.
► All the monoliths have a very high porosity (over 96%).
► Their adsorption capacity for xylenol orange reaches 122 mg/g (experimental data).
► The adsorption for xylenol orange follows a pseudo-first-order kinetic model.