Chitosan Interactions with Metal Ions and Dyes: Dissolved-state vs. Solid-state Application |
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Authors: | E Guibal E Touraud J Roussy |
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Institution: | (1) Ecole des Mines d’Alès, Laboratoire Génie de l’Environnement Industriel 6, avenue de Clavières, F-30319 ALES cedex, France |
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Abstract: | Summary Chitosan is an amino-polysaccharide with highly efficient properties for the binding of metal ions and anionic dyes. Uptake
may occur through chelation on free amino functions (at near-neutral pH) or by electrostatic attraction on protonated amino
groups (in acidic solutions). The polymer is soluble in acidic solutions and its binding properties can be used in both solid
form (sorption) and liquid form (ultrafiltration coupled with chelation, coagulation–flocculation). These properties have
been used for the recovery of mercury from dilute solutions at initial pH 5 (which reveals the most efficient pH in the range
pH 4–6) and for the recovery of Reactive Black 5 (RB5, anionic dye) at pH 3. While in the case of mercury binding saturation
of the biopolymer is only slightly higher when chitosan is used in the liquid form compared to solid-state adsorption, in
the case of the coagulation–flocculation of RB5 (using the liquid-form of chitosan) the saturation of the polymer (calculated
on the basis of molar ratio of dye vs. amino groups of the polymer) is reached at a significantly greater value than when
the polymer is used for the solid-state binding of the dye. There is a much more efficient use of amino groups when chitosan
is used in the liquid-form due to a better availability of amino groups (less hydrogen bonds between the chains of the polymer)
and to a better accessibility to internal sorption sites (lower diffusion control). |
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Keywords: | Adsorption chitosan coagulation– flocculation mercury reactive black 5 ultrafiltration |
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