Removal of alizarin red by supermacroporous cross-linked chitosan monolith sorbents

Abstract

Here, we report the fabrication of supermacroporous monolith sorbents for acidic dye removal via chitosan cross-linking with ethylene glycol diglycidyl ether (EGDGE) in acidic medium at sub-zero temperature. The developed porous structure with the thickness of polymer walls in the range of a few microns and a high content of primary amino groups determined the high sorption capacity of the sorbents toward Alizarin Red in a broad pH range (2-8). Due to the cross-linking via hydroxyl groups of the chitosan, the static sorption capacity of the fabricated materials was higher than that of chitosan flakes, even for sorbents cross-linked at EGDGE:NH2-chitosan with molar ratio 2: 1. The monolith sorbents were mechanically stable and supported flow rates up to 300 bed volumes per hour. The breakthrough curve of Alizarin Red sorption showed that the effective dynamic sorption capacity was 283 mg/g, and 100% of the dye could be removed from the solutions with concentration of 100 mg/L. The monoliths can be regenerated with 0.3s M NaOH solution and used in several consecutive cycles of sorption/regeneration without loss of efficacy.