Chitosan scaffold as an alternative adsorbent for the removal of hazardous food dyes from aqueous solutions.
OBJECTIVE
The dye adsorption with chitosan is considered an eco-friendly alternative technology in relation to the existing water treatment technologies. However, the application of chitosan for dyes removal is limited, due to its low surface area and porosity. Then we prepared a chitosan scaffold with a megaporous structure as an alternative adsorbent to remove food dyes from solutions.


METHODS
The chitosan scaffold was characterized by infrared spectroscopy, scanning electron microscopy and structural characteristics. The potential of chitosan scaffold to remove five food dyes from solutions was investigated by equilibrium isotherms and thermodynamic study. The scaffold-dyes interactions were elucidated, and desorption studies were carried out.


RESULTS
The chitosan scaffold presented pore sizes from 50 to 200 μm, porosity of 92.2±1.2% and specific surface area of 1135±2 m(2) g(-1). The two-step Langmuir model was suitable to represent the equilibrium data. The adsorption was spontaneous, favorable, exothermic and enthalpy-controlled process. Electrostatic interactions occurred between chitosan scaffold and dyes. Desorption was possible with NaOH solution (0.10 mol L(-1)). The chitosan megaporous scaffold showed good structural characteristics and high adsorption capacities (788-3316 mg g(-1)).
Unit Operation Laboratory, School of Chemistry and Food, Federal University of Rio Grande, FURG, Engenheiro Alfredo Huch Street, 475, 96201-900 Rio Grande, RS, Brazil. Electronic address: nessafurg@gmail.com.
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Esquerdo
Unit Operation Laboratory, School of Chemistry and Food, Federal University of Rio Grande, FURG, Engenheiro Alfredo Huch Street, 475, 96201-900 Rio Grande, RS, Brazil. Electronic address: titoeq@gmail.com.
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Cadaval
Chemical Engineering Department, Federal University of Santa Maria, UFSM, Roraima Avenue, 1000, 97105-900 Santa Maria, RS, Brazil. Electronic address: guilherme_dotto@yahoo.com.br.
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Dotto
Unit Operation Laboratory, School of Chemistry and Food, Federal University of Rio Grande, FURG, Engenheiro Alfredo Huch Street, 475, 96201-900 Rio Grande, RS, Brazil. Electronic address: dqmpinto@furg.br.
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Pinto
D000327:Adsorption; D048271:Chitosan / Q000737:chemistry*; D005505:Food Coloring Agents / Q000302:isolation & purification*; D016062:Porosity; D012996:Solutions; D013816:Thermodynamics; D014867:Water / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
D005505:Food Coloring Agents; D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; D048271:Chitosan
Chitosan scaffold; Dyes; Thermodynamic; Two-step Langmuir model