Cellulose-amine complexes

Water soluble derivatives of cellulose have also been made through the formation of sodium cellulose xanthate (Cell-O-CS Na ) ( 12) and copper amine complexes (that is, the cuprammonlum process) ( X3). Both these derivatives require regeneration of the Insoluble cellulose structure at the time of membrane formation. Strong salt and acid solutions are used to precipitate the soluble derivatives and simultaneously recover the cellulose structure. Residues of xanthate or cuprammonlum salt decomposition must subsequently be washed out of the resulting membrane. 

Adsorption by carbon, which is one of the oldest adsorption methods used, has been reviewed and evaluated for the preconcentration of trace metals (794). Many authors have discussed the preparation of activated charcoal and carbon from a wide variety of usually local sources. The applications to water treatment are far too numerous to mention other than a few. Jo (795) carbonized a resin and a gum and hydrated the residue above 600 C to produce an adsorbant selective for cadmium(II). Kuzin et al, 196) used deashed active carbon and oxidized carbon for the quantitative sorption of copper, lead, zinc, and nickel from nearly neutral solutions containing 1-2 M alkali-metal halide. Pearson and Siviour (797) converted the metal-ion species to amine complexes before adsorbing these onto carbonaceous materials such as brown charcoal char or cellulose. Mercury vapor can be removed from a solution by reduction followed by passage of a nitrogen stream and adsorption by activated charcoal (798). Activated carbon, which had been oxidized with nitric acid, has been used to extract several metals including divalent nickel, cadmium, cobalt, zinc, manganese, and mercury from fresh water, brine, and seawater (799, 200). 

Unit cells of pure cellulose fall into five different classes, I—IV and x. This organization, with recent subclasses, is used here, but Cellulose x is not discussed because there has been no recent work on it. Crystalline complexes with alkaU (50), water (51), or amines (ethylenediamine, diaminopropane, and hydrazine) (52), and crystalline cellulose derivatives also exist. Those stmctures provide models for the interactions of various agents with cellulose, as well as additional information on the cellulose backbone itself. Usually, as shown in Eigure la, there are two residues in the repeated distance. However, in one of the alkah complexes (53), the backbone takes a three-fold hehcal shape. Nitrocellulose [9004-70-0] heUces have 2.5 residues per turn, with the repeat observed after two turns (54). 

Mino and Kaizerman [12] established that certain. ceric salts such as the nitrate and sulphate form very effective redox systems in the presence of organic reducing agents such as alcohols, thiols, glycols, aldehyde, and amines. Duke and coworkers [14,15] suggested the formation of an intermediate complex between the substrate and ceric ion, which subsequently is disproportionate to a free radical species. Evidence of complex formation between Ce(IV) and cellulose has been studied by several investigators [16-19]. Using alcohol the reaction can be written as follows ... 

In a related application, polyelectrolyte microgels based on crosslinked cationic poly(allyl amine) and anionic polyfmethacrylic acid-co-epoxypropyl methacrylate) were studied by potentiometry, conductometry and turbidimetry [349]. In their neutralized (salt) form, the microgels fully complexed with linear polyelectrolytes (poly(acrylic acid), poly(acrylic acid-co-acrylamide), and polystyrene sulfonate)) as if the gels were themselves linear. However, if an acid/base reaction occurs between the linear polymers and the gels, it appears that only the surfaces of the gels form complexes. Previous work has addressed the fundamental characteristics of these complexes [350, 351] and has shown preferential complexation of cationic polyelectrolytes with crosslinked car-boxymethyl cellulose versus linear CMC [350], The departure from the 1 1 stoichiometry with the non-neutralized microgels may be due to the collapsed nature of these networks which prevents penetration of water soluble polyelectrolyte. 

The hemocompatibility of poly(amido-amine) polyelectrolyte complexes was recently studied by Xi, Zhang and coworkers [499, 500]. The poly(amido-amine) was based on piperazine and methylene bisacrylamide, and the polyelectrolyte complexes were obtained from the reaction of poly(amido-amine) with alginic acid, carboxymethyl cellulose or poly(methacrylic acid). Complexes of polyamido-amine and alginic acid with a 1 2 ratio gave the best hemocompatibility. Finally, the blood compatibility of polyelectrolyte complexes based on anionic and cationic cellulose derivatives were studied by Ito et al. [338], In vivo, good blood compatibility of complexes formed from quaternary hy-droxyethyl cellulose reacted with carboxymethyl cellulose and cellulose sulfate was observed. 

The first section covers the chemistry of cellulose solutions in an amine N-oxide solvent (NMMO), the so-called Lyocell chemistry, as encountered in the industrial production of cellulosic Lyocell material. The system is characterized by high reaction temperatures, the presence of a strong oxidant and high complexity by multiple (homolytic and heterolytic) parallel reactions. Trapping was used to address the questions that reactive intermediates are present in Lyocell solutions and are responsible for the observed side-reactions and degradation processes of both solvent and solute. 

Besides the cellulose structures I-IV and their subclasses, cellulose forms a variety of crystalline complexes. Soda celluloses were mentioned above, and there is an extensive array of complexes with amines [236]. Soda cellulose IV [237] is actually a hydrate of cellulose and contains no sodium (historically, cellulose hydrate meant cellulose II, which is now known to contain no water ). Many cellulose derivatives such as the nitrate (see above) and the triacetate [238] also give diffraction patterns. The most recent analysis of triacetate I shows a single-chain unit cell [239]. 

Decrystallization of cellulose by swelling agents or solvents can be brought about by concentrated sodium hydroxide amines me-tallo-organic complexes of copper, cadmium, and iron quaternary ammonium bases concentrated mineral acids (sulfuric, hydrochloric, phosphoric) concentrated salt solutions (beryllium, calcium, lithium, zinc) and a number of recently investigated mixed solvents (J6). 

Cellulose hydroxyl groups and the amino group of amines form a hydrogen bond which is mainly responsible for the complex formation162. 

Among various amines, the liquid ammonia appears to be unique in its swelling action on cellulose and its effect on crystal stmcture. Anhydrous liquid ammonia, being smaller molecule, penetrates cellulose very rapidly and complexes with hydroxyl groups of cellulose after breaking hydrogen bonds in crystalline regions and increases distance between cellulose chain in crystallites [109-115]. 

Microcrystalline cellulose triacetate, cyclodextrin- and crown ether-derived CSPs, as well as some chiral synthetic polymers, achieve enantiomer separation primarily by forming host-guest complexes with the analyte in these cases, donor-acceptor interactions are secondary. Solutes resolved on cyclodextrins and other hydrophobic cavity CSPs often have aromatic or polar substituents at a stereocenter, but these CSPs may also separate compounds that have chiral axes. Chiral crown ether CSPs resolve protonated primary amines. 

Figure 1. Equations for non-aqueous preparations of sodium cellulosate (1), diethylaminoethyl cellulose (DEAE) (2), monoquaternary ammoniun celluloses (3), where R varies from CH3 to 10 22 tliquaternary ammonium celluloses (4), where n varies from 2 to 10> complex formation between DEAE and Lewis base, BI (5), and coordination of tertiary amines of DEAE with a transition metal ion (6).

---