title: Fast and highly efficient removal of dyes under alkaline conditions using magnetic chitosan-Fe(III) hydrogel.
abstract: The dyeing effluent of high alkalinity, which could not be treated efficiently by traditional wastewater technologies, highlighted the need to explore a technically feasible, highly efficient and cost effective method. Thus, a fast and highly efficient method for the removal of dyes under alkaline conditions using magnetic chitosan-Fe(III) hydrogel was proposed. Firstly, chitosan-Fe(III) hydrogel was prepared by a chelation procedure with cheap and environmentally friendly chitosan and iron salts. We characterized the sorption and desorption of C. I. Acid Red 73, a common type of anionic dye, on magnetic chitosan-Fe(III) hydrogel, to understand its availability for alkaline dyeing wastewater. Sorption of dye to chitosan-Fe(III) hydrogel was fast (adsorption could reach equilibrium in less than 10 min) in a wide pH range, and agreed well to the Langmuir-Freundlich adsorption model with a high maximum adsorption capacity of 294.5 mg/g under pH = 12. Meanwhile, 1 mol/L NaOH was used to desorb the dye efficiently (desorption efficiency 94.4%) and 0.1 mol/L HCl was applied to regenerate the chitosan-Fe(III) hydrogel. The results showed that the chitosan-Fe(III) hydrogel could retain its high efficiency after the desorption and regeneration. The common coexisting ions almost had no negative effect on the dye adsorption of chitosan-Fe(III) and the removals of a variety of anionic dyes suggest that the magnetic chitosan-Fe(III) hydrogel could efficiently adsorb both the acid and reactive dyes under alkaline condition. Overall, the results reported herein indicated that magnetic chtisoan-Fe(III) with high adsorption efficiency and strong magnetic property is very attractive and implies a potential of practical application for alkaline dyeing effluent treatment.
authors.affiliation: Institute of Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Chensi
authors.initials: C
authors.lastname: Shen
authors.forename: Yu
authors.initials: Y
authors.lastname: Shen
authors.forename: Yuezhong
authors.initials: Y
authors.lastname: Wen
authors.forename: Hongyu
authors.initials: H
authors.lastname: Wang
authors.forename: Weiping
authors.initials: W
authors.lastname: Liu
mesh_terms: D000327:Adsorption; D000468:Alkalies / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D004396:Coloring Agents / Q000302:isolation & purification*; D005290:Ferric Compounds / Q000737:chemistry*; D020100:Hydrogels; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008280:Magnetics; D008855:Microscopy, Electron, Scanning; D013816:Thermodynamics; D013818:Thermogravimetry
chemical_list: D000468:Alkalies; D004396:Coloring Agents; D005290:Ferric Compounds; D020100:Hydrogels; D048271:Chitosan