Cellulose Chelate complexes

A plot of the temperatures required for clouding versus surfactant concentration typically exhibits a minimum in the case of nonionic surfactants (or a maximum in the case of zwitterionics) in its coexistence curve, with the temperature and surfactant concentration at which the minimum (or maximum) occurs being referred to as the critical temperature and concentration, respectively. This type of behavior is also exhibited by other nonionic surfactants, that is, nonionic polymers, // - a I k y I s u I Any lalcoh o I s, hydroxymethyl or ethyl celluloses, dimethylalkylphosphine oxides, or, most commonly, alkyl (or aryl) polyoxyethylene ethers. Likewise, certain zwitterionic surfactant solutions can also exhibit critical behavior in which an upper rather than a lower consolute boundary is present. Previously, metal ions (in the form of metal chelate complexes) were extracted and enriched from aqueous media using such a cloud point extraction approach with nonionic surfactants. Extraction efficiencies in excess of 98% for such metal ion extraction techniques were achieved with enrichment factors in the range of 45-200. In addition to metal ion enrichments, this type of micellar cloud point extraction approach has been reported to be useful for the separation of hydrophobic from hydrophilic proteins, both originally present in an aqueous solution, and also for the preconcentration of the former type of proteins. 

Cellulose was the first sorbent for which the resolution of racemic amino acids was demonstrated [23]. From this beginning, derivatives such as microcrystalline triacetylcellulose and /3-cyclodextrin bonded to silica were developed. The most popular sorbent for the control of optical purity is a reversed-phase silica gel impregnated with a chiral selector (a proline derivative) and copper (II) ions. Separations are possible if the analytes of interest form chelate complexes with the copper ions such as D,L-Dopa and D.L-penicillamine [24], Silica gel has also been impregnated with (-) brucine for resolving enantiomeric mixtures of amino acids [25] and a number of amino alcohol adrenergic blockers were resolved with another chiral selector [26]. A worthwhile review on enantiomer separations by TLC has been published [27],... 

Our published articles focused on using carboxymethyl cellulose and hydroxyethyl cellulose, and cellulose acetate, as ligands for cellulose derivative-metal complexes. These derivatives are examples of water-soluble cellulose ethers and solvent-soluble cellulose esters, respectively. The micro-analyses, electronic and IR-spectra, and magnetic susceptibility measurements were used as tools for studying the nature of the chemical structures of cellulose ethers complexes with some transition metals [10-16], while electrical and thermal analyses were carried out to identify the functional properties of cellulose ether provided from chelation with metal ions [17-20]. 

Procedure for DTA peak analysis of dioxouranium [UO, [VI]] complexes with cellulose acetate [CA], using the equation of Prout and Tompkins [Table 7.9] showed that the increase of DS of cellulose acetate [from 2.2 to 2.86] and its chelation with uranium [VI] ions increased the activation energies for degradation. The increase in the thermal stabilities [activation energy] of cellulose acetate complexes can be attributed to the coordination bonds between dioxouranium and acetyl of cellulose acetate, i.e., to the formation of five-membered rings [14,29]. 

As early as 1884, Levallois [62] observed that cellulose dissolved in Schweitzer s reagent (an ammoniacal solution of tetrammine copper [Cu(NH3)4] (OH)2) is strongly laevorotatory. Later, Hess [63] investigated the relationship between the optical rotation and the Cu-cellulose concentration, and found a maximum at 1 Cu atom per base unit. Today it is assumed that Cu forms a chelate complex with the OH groups at C2 and C3. 

Direct Dyes. These water-soluble anionic dyes, when dyed from aqueous solution in the presence of electrolytes, are substantive to, i.e., have high affinity for, cellu-losic fibers. Their principal use is the dyeing of cotton and regenerated cellulose, paper, leather, and, to a lesser extent, nylon. Most of the dyes in this class are polyazo compounds, along with some stilbenes, phthalocyanines, and oxazines. Aftertreatments, frequently applied to the dyed material to improve washfastness properties, include chelation with salts of metals (usually copper or chromium), and treatment with formaldehyde or a cationic dye-complexing resin. 

Koshijima, T., Tanaka, R., Muraki, E., Yamada, A., and Yaku, F. 1973. Chelating polymers derived from cellulose and chitin. I. Formation of complexes from metal ions. Cell Chem. Technol. 7, 197-205. 

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