Highly enhanced adsorption of Congo red onto dialdehyde cellulose-crosslinked cellulose-chitosan foam

The adsorption of Congo red (CR) was evaluated using cellulose-chitosan foam crosslinked via dialdehyde cellulose (DAC). DAC-crosslinked cellulose-chitosan foam (CCLBD) was obtained by dissolution/regeneration using a LiBr aqueous solution, followed by crosslinking between chitosan and DAC. CCLBD possessed a three-dimensional structure with 40–200 nm wide pores composed of nanofibrils with a width of 10–20 nm, resulting in a high specific surface area of 230 m2/g. CCLBD was highly stable even acidic conditions in spite of a low crosslinking degree of 10.3%, which induced a slight reduction in the amino groups that interact with CR. CCLBD showed a CR adsorption capacity of 1548.2 mg/g and the adsorption process followed the Sips isotherm and pseudo-second-order models.