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Recovery of hydrofluoric acid (HF) from waste semiconductor acid solution by ion exchange was investigated. Strong base anionic and strong acid cationic ion exchange resins were involved in the recovery process. The former was used to capture the fluoride in the waste acid solution while the latter was employed for exchanging hydrogen ion for sodium in the NaF solution resulting from regeneration of the anion exchanger with NaOH. The ion exchange process consisted of two ion exchange steps and two regeneration steps. Batch experiments were conducted to determine the equilibrium ion exchange capacities and to develop ion exchange isotherms. Column tests were made to examine the performances of continuous ion exchange operations under conditions of different feed flow rates and inlet acid concentrations. A simplified model based on the general logistic function was adopted and tested for describing the solute breakthrough behaviors of the exit aqueous solution. Regeneration of exhausted ion exchange resins was also examined to test their effectiveness for repeated use. The hydrofluoric acid recovered by the ion exchange process would be available for reuse. It could also be converted by calcium chloride to high-purity calcium fluoride. CE Database subject headings: Acids; Ion exchange; Waste treatment; Recycling; Electronic equipment.

The 2,3,4,5,6,7,8,9,10,11,12-undecabromocarborane anion, 1-HC[B.sub.11][Br.sub.11.sup.-] (UB[C.sup.-]) has been evaluated for its suitability as an ion exchanger in solvent polymeric membrane electrodes and bulk optodes. Experiments comparing the chemical stability of the perhalogenated carborane anion to that of the best lipophilic tetraphenylborate, 3,5-[bis(trifluoromethyl)phenyl]borate (TFP[B.sup.-]), demonstrated that in the presence of 0.2 M acetic acid TFP[B.sup.-] was completely lost within 6 h, while the concentration of UB[C.sup.-] decreased by less than 10% in the same time period. Thin-film bulk optodes containing BME-44 as potassium-selective ionophore, ETH 5294 as chromoionophore, and UB[C.sup.-] as ionic sites exhibited a [K.sup.+] response similar to analogous optodes containing TFP[B.sup.-], with comparable selectivities over [Na.sup.+] and [Ca.sup.2+]. Potentiometric measurements evaluating the selectivity behavior of UB[C.sup.-] in both ionophore-free and ionophore-containing electrodes were performed. Ionophore-free PVC membranes containing UB[C.sup.-] as ion exchanger and either DOS or NPOE as plasticizer also demonstrated selectivity similar to TFP[B.sup.-]-containing membranes. Sodium-selective membranes containing the ionophore 4-tertbutylcalix[4]arenetetraacetic acid tetraethyl ester (sodium ionophore X) and UB[C.sup.-] as ionic sites showed a Nernstian response for sodium and selectivity comparable to that found in analogous electrodes containing TFP[B.sup.-].

The electrokinetic chromatographic separation of a series of inorganic and organic anions was achieved by utilizing an electrolyte system comprising a cationic soluble polymer (poly(diallydimethylammonium chloride, PDDAC) and a neutral [beta]-cyclodextrin ([beta]-CD) as pseudostationary phases. The separation mechanism was a combination of electrophoresis, ion-exchange (IE) interactions with PD-DAC, and hydrophobic interactions with [beta]-CD. The extent of each chromatographic interaction was independently variable, allowing for control of the separation selectivity of the system. IE interactions could be varied by changing either the PDDAC concentration or the concentration of a competing ion (e.g., chloride) in the BGE, while the hydrophobic interactions could be varied by changing the concentration of [beta]-CD. The separation system was very robust, with the reproducibility of the migration times being

A research was conducted to examine how the energetics of individual regions react to the presence of denaturant in the molten globule condition of Escherichia coli ribonuclease H1. Quenched hydrogen exchange reactions and nuclear magnetic resonance sample preparation were utilized at 4 degrees C. Protonated solutions were also used to evaluate which protons could serve as probes of the molten globule structure. Results showed that the free energy of hydrogen exchange declined linearly with increases in denaturant concentrations.

Allowable deviations in index profiles, dopant distributions, and concentration dependence of diffusion coefficients are determined for collimating microlenses. Examples of high (and low) numerical aperture lenses are given for silver/sodium (and lithium/sodium) ion exchanges. Using the full lens aperture, one can ensure diffraction-limited performance only when the index is measured to within 1.0 x [10.sup.-4] (4.3 x [10.sup.-5]) of the optimum values. Fabrication tolerances for diffraction-limited performance over 80% of the numerical aperture are expressed in terms of the concentration-dependent diffusion coefficient, which typically must be held to within [+ or -]4.7% ([+ or -]11.5%) of ideal values. Key words: Micro-optics, self-focusing lenses, gradient index, ion exchange.

The structures, syntheses and susceptibilities of Ga+-beta'-alumina and gaZr2(PO4)3 toward oxidation were discussed. The two compounds display a markedly different coordination environments for the Ga(I) cation. The similarity of the coordination chemistry for Ga(I) and alkali metal ions in the zirconium phosphate host is in contrast to the situation in the beta'-alumina system wherein the 3+0 coordination indicates the presence of stereochemically active lone pairs.

Ensembles of nanoscopic disk-shaped electrodes have been shown to offer enhancements in electroanalytical detection limits relative to electrodes of macroscopic dimensions (e.g., disk electrodes with diameters of [approximately]1 mm). Enhancements in electroanalytical detection limits have also been observed at macroscopic electrodes that have been coated with films of ion-exchange polymers. In this paper we combine these two concepts.. We demonstrate that a nanoelectrode ensemble (NEE) that has been coated with a thin film of the Kodak ion-exchange polymer AQ 55 shows enhanced electroanalytical detection limits relative to the uncoated NEE and to the coated macroscopic electrode. To our knowledge, this is the first investigation of the electrochemistry, and the electroanalytical advantages, of polymer film-coated NEEs.

The relationship between the characteristics of gradient-index rod lenses obtained by ion exchange and their mother glass compositions is studied. It is observed that [Li.sub.2]O content, [R.sub.2]O ([Li.sub.2]O + [Na.sub.2]O) content, and the [Li.sub.2]O/[Na.sub.2]O ratio are important factors in attaining a high acceptance angle and a small field curvature. Thus the gradient-index lens array is fabricated by the use of a newly developed glass composition and its optical performance; the modulation transfer function, luminous intensity, and chromatic aberration are precisely evaluated. The array is found to have a sufficiently high performance to be applicable for color use. Key words: Gradient-index, Li-containing glass, ion exchange, acceptance angle, field curvature, chromatic aberration.

A cation exchange ion exclusion HPLC technique was evolved to isolate and measure uronic acids of alginate or pectin added at different concentrations to lean ground pork. An Aminex HPX-87-H+ column, an isocratic 0.009N H2SO4 eluent and ultraviolet detection were used in this technique. The technique facilitated preferential measurement of uronic acids and ion exclusion column packing did not undergo rapid degeneration or contamination.

Ion exchange and immunoaffinity chromatography is used in the purification of an amiloride-inhibitable Na+ channel protein from the bovine renal papillae. Planar lipid bilayers were reconstructed from these purified Na+ channels to study the characteristics of single channels. The planar lipid channels have both large-and small-conductance Na+ selective ion-channels, which are blocked in a dose-dependent manner after the amiloride is applied.

We present the fabrication process and the optical characterization of waveguides made by an ion-exchange technique in high-index D0035 and D0042C Corning glasses. We fabricate monomode channel waveguides in both kinds of glasses by exchange through a metallic mask., A study on the manufacture of optical waveguides using a fabrication procedure based on ion exchange in opthalmic glasses is discussed. In the study, which used high-index D0035 and D0042C glasses made by Corning, monomode channel waveguides from such glasses were constructed by ion exchange via a metallic mask. A discussion of the fabricated optical waveguides's features is also given.

Ion exchange is often used to manufacture integrated optical waveguides in glasses and crystals. The manufacture of low-loss, compact, integrated optical waveguides can be achieved by varying the processing conditions (the temperature and the electric field) during the ion exchange. We have simulated the formation of waveguides in glass with a molten salt silver ion-exchange technique and have shown that, by simply linearly varying the temperature and electric field during processing of waveguides, one can tailor the refractive-index profiles to produce low-loss parabolic and hyperbolic secant dopant profiles or any other generic dopant profile. Key words: Ion-exchanged waveguides, diffusion optimization, profile control.

Silver-soda glass nanocomposites are prepared by using ion exchange method followed by thermal annealing. The studies have shown that the formation of Ag nanoparticles (NPs) in soda glass matrix has increased its insulating properties.

An inexpensive gradient maker can be put together for the biochemistry laboratory using two 25-mL plastic graduated cylinders or two plastic vials. They are connected to each other with tubing and connected to a mini-DEAE ion exchange column.