Novel Biosorbents Based on Carboxyethyl Chitosan for Allura Red Dye Contaminated Water Treatment

Abstract

Low biodegradability of several dyes leads to their accumulation in water, causing ecological and health damage. The adsorption and, in particular, biosorption processes are widely applied for the wastewater treatment. This article presents the first comparative study of the Allura red dye removal under neutral pH at 25 oC applying novel biosorbents: carboxyethyl chitosan hydrogel (CEC) and cryogel of carboxyethyl chitosan cross-linked with butanediol-1,4 diglycidyl ether (DEB-CEC). The gels were synthesized in “green” manner, and the characterization revealed porous structure and high swelling for both biopolymer compositions, which are the properties important for adsorption. The kinetic studies demonstrated that the adsorption rate for DEB-CEC is better represented by pseudo-second-order, while CEC followed better pseudo-first-order kinetics. The adsorption isotherm of Allura Red suited the Temkin model for both samples, with the maximum adsorption capacity of 22.523 mg/g (45.4 μmol/g) and 10.482 mg/g (21.1 μmol/g) for CEC and DEB-CEC, respectively. The results demonstrated that CEC and DEB-CEC polymers can be used as biodegradable and eco-friendly biosorbents for Allura Red dye removal from aqueous solutions, making these biosorbents promising for wastewater treatment and prevention of the azo-dye environmental pollution.