Dual cation systems

Table VII. Synergistic Relationships in Dual Cation Systems...

As pointed out above, IC is a well-established method for the analysis of inorganic anions and has become the method of choice in many application areas. Many techniques are available using singlecolumn [46] or dual-column systems with various detection modes. IC can be used both for analytical and preparative purposes. Large sample volumes, up to 1300 pul, can be injected to determine trace anions and cations and to attain detection limits of 10-400 ng/1. For determinations at a pig/1 to mg/1 level, a sample size of 10-50 xl is sufficient. Preconcentration is necessary for lower concentrations (an additional column, a sample pump, an extra valve and an extra time are the disadvantages of this approach [47]). With an IEC column and isocratic... 

Santhanam R, Noel M. Electrochemical intercalation of cationic and anionic species from a lithium perchlorate-propylene carbonate system—a rocking-chair type of dual-intercalation system. J Power Sources 1998 76 147-152. 

Flocculation of alumina suspensions obtained by the sequential addition of polystyrene sulfonate (M j, = 4600) and cationic polyacrylamide (M, = 4,000,000) at pH 4.5 is compared in Figure 7.33 with that obtained using single polymers. While the anionic polystyrene sulfonate had only a minor effect, cationic polyacrylamide did not produce any flocculation. However, when used together, both polymers adsorb completely. This coadsorption is attributed to the interaction of complexes between cationic polyacrylamide and the polystyrene sulfonate at the solid-liquid interface. The mechanism of the superior flocculation obtained with the dual polymer system is illustrated schematically in Figure 7.34. The anionic polystyrene sulfonate adsorbs on alumina surface and acts as an anionic anchor for the adsorption of the long-chain cationic polymer, which ultimately provides interparticle bridging and excellent flocculation. 

A dual column system has been described in which a complex mixture of saccharides from cell wall hydrolysates were separated on a chemically bonded amine colunm (Blaschek, 1983). The saccharides in the unresolved peaks were then further resolved by using cation-exchange chromatography which facilitated a baseline separation of all the carbohydrate components present in the extract. 

One of the more interesting possibilities of developing truly unique photocurable films lies in the ability of certain onium salts to generate both a reactive radical species and a strong acid upon photolysis. Indeed, several papers describe dual radical/cationic photocurable systems (16-18). The possibilities afforded by dual cure systems provide a unique mechanism for generating cured films with expanded properties for a number of applications. 

The use of anionic starches in the wet-end declined rapidly following the introduction of cationic starches and their use almost ceased with the subsequent move to neutral sizing. There has been a revival of interest in anionic products for use in dual-starch systems [5]. 

Battery cathodes provides an overview of the current cathode materials available for use in Li-ion batteries and a discussion of the various battery systems. Li-ion batteries are dual intercalation systems, in which both the cathode and the anode have structures that allow reversible insertion and extraction of lithium cations. In principle, there are numerous materials that undergo reversible intercalation and can serve as electrode materials. Hence, unlike the lead acid battery which describes a specific chemistry, the chemistry of the Li-ion battery is not fixed but determined by the choice of anode and cathode materials. 

Sang Y, Xiao H (2008) Clay flocculation improved by cationic poly(vinyl alcohol)/anionic polymer dual-component system. J Colloid Interface Sci 326 420... 

Examples can be cited for the mixed alkali metal and alkaline-earth metal borohydrides. It was reported that a Li-Mg borohydride could be formed by mechanical milling and subsequent heating of a mixture of LiBHj and Mg(BH4)2 in 1 1 mole ratio. This dual-cation borohydride exhibits a lower dehydrogenation onset temperature [82]. Also, composite materials made by combining LiBHj and Ca(BH4)2 are reported to show hydrogen release temperatures lower than for either component alone [83]. Composites of composition (LiBH4) (l - x)[Ca(BH4)2], where H2 capacity varies with x, were prepared. At intermediate compositions, such as x = 4, dehydrogenation was complete below 400°C with release of 10 wt% H2. Partial reversibility of this system was also reported. 

Starch is a polysaccharide found in many plant species. Com and potatoes are two common sources of industrial starch. The composition of starch varies somewhat in terms of the amount of branching of the polymer chains (11). Its principal use as a flocculant is in the Bayer process for extracting aluminum from bauxite ore. The digestion of bauxite in sodium hydroxide solution produces a suspension of finely divided iron minerals and siUcates, called red mud, in a highly alkaline Hquor. Starch is used to settle the red mud so that relatively pure alumina can be produced from the clarified Hquor. It has been largely replaced by acryHc acid and acrylamide-based (11,12) polymers, although a number of plants stiH add some starch in addition to synthetic polymers to reduce the level of residual suspended soHds in the Hquor. Starch [9005-25-8] can be modified with various reagents to produce semisynthetic polymers. The principal one of these is cationic starch, which is used as a retention aid in paper production as a component of a dual system (13,14) or a microparticle system (15). 

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