Phosphorylated Chitins and Chitosans

Phosphorylated chitosans (12.255a) may be used for chelating alkaline earth cations or stabilising bleaching agents. Chitins of type (12.255b) are reported to improve the textile properties of co-spun alginate fibres [21]. 

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Beside kinetic and thermodynamic studies, equilibrium studies were done in order to determine the influence of the initial concentration of the metals ions upon the efficiency of the adsorption process and in order to determine the maximum adsorption capacities of the phosphorylated chitin and chitosan materials in the removal process of various metal ions from aqueous solutions. The experimental equilibrium data were fitted to the Langmuir and Freundlich isotherms. In all the cases the experimental results showed a better fit to the Langmuir than to the Freundlich equation. The maximum adsorption capacities obtained from the Langmuir isotherm plot in the... 

The maximum adsorption capacities of various phosphorylated chitins and chitosans in the removal process of different metal ions from aqueous solutions. 

Jayakumar, R., Reis, R.L., and J.F. Mano. 2006. Chemistry and applications of phosphorylated chitin and chitosan. E-Polymers 35 1-16. 

Metal Ion Adsorption onto Chitin and Chitosan Grafted with Different Phosphorylated Groups... 

As stated above, the present biomedical products utilize only the base materials. Chanical derivatization is the way forward to realize the fuU potential of chitin and chitosan (Alves and Mano 2008). The well-known C6-earboxymethyl-chitin and ehitosan would be an ideal starting place (Raimunda and Campana-Filho 2008). However, this work again started with the alkali-chitin process that is known to be ineffieient and associated with inhomogeneity eoncems. Another recent work is the preparation of Af-hydroxyacryl-chitosan that utilizes ehitosan from a commercial source without further treatment (Maa et al. 2008). Phosphorylated chitins and ehitosans are another example of chemical derivatization that yields soluble compounds (Jayakumar et al. 2008). 

Direct phosphorylation of chitin and chitosan has been reported but the degree of phosphorylation is uncertain. Such products are polyelectrolytes and may have medical or cosmetic applications. 

Figure 1. Some chemical reactions for the molecular design of chitin and chitosan. [1], chitin [2], chitosan [3], alkoxide (alkali chitin) [4] salt (carboxyl-ate) [5], chelation [6] Schiff s base [7], N-acylation [8], halogenation [9], N-alkylation [10], 0-alkylation [11], oxido-deaminative cleavage [12], 0-acylation [13], sulfonation [14], sulfation, phosphorylation and nitration.

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