Nitrate selective resins

To overcome these problems use is made of the now available nitrate-selective resins (Chapter 5, Dilute Solution Anion Exchange ) for which the anion affinity sequence is ... 

Figure 8.12 Leakage profile of ion residuals for chloride cycle anion exchange on a nitrate selective resin...

Advanced Condensate Polishing designs Sub-ppb ion residuals established for condensate treatments and Ultrapure water applications Nitrate selective resins Resin copolymerization - uniform bead size... 

In the ion-exchange part, the column is packed with nitrate-selective resin in a chloride form, which prevents treating waters with a concentration of nitrates exceeding 50 mg/L. 

Another method used for nitrate determination on dried and milled herbage employs the nitrate selective electrode. One of the first published methods was that of Paul and Carlson (1968). Other anions, especially chloride, can interfere. These authors removed chloride with silver resin, but Barker ef al. (1971) omitted the resin because it tended to foul the electrode and cause excessive drift. Normally the Cl N03 ratio is so low as not to interfere, but saline precipitation from coastal plots could affect this. The method was further modified to allow storage of extracts for up to 64 h by adding a preservative of phenyl-mercuric acetate and dioxane, both very toxic (Baker and Smith, 1969). This paper mentions the need to change the electrode s membrane, filling solution and liquid ion exchanger every 2 months to minimize chloride interference. It is easy to overlook electrode maintenance between batches of nitrate analyses, and this can lead to errors and sluggish performance. 

E. Lockridgeand. S. Fritz, Determination of water using nitrate selective ion-exchange resin, U. S. Patent... 

Selected alkyd resins are compatible with cellulose nitrate, amino resins, phenolic resins, epoxy resins, silicones, acrylics, chlorinated rubber, and styrene. When added to cellulose nitrate, short-oil alkyds improve gloss, adhesion, and flexibility of these commercial coatings. The chemical resistance of short-oil alkyds is improved when they are reacted with amino resins. Alkyds also react with phenolics to produce chroman-type alkali-resistant coatings. 

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

The same group also performed experiments with a continuous chromatographic reactor of the SMBR type [133,174]. The system used consisted of 12 columns with inner diameters of 5.4 cm and a length of 75 cm. Approximately 12 cycles were necessary for stabilization of the system. Complete inversion of sucrose even at feed concentrations of up to 55% w/v was achieved, while the product purity was over 90%. After prolonged usage, the system efficiency decreases due to the loss of the calcium ions from the matrix and a consequent decreased selectivity of the resin. However, this problem could be overcome by regeneration of the resin with calcium nitrate. 

In the method proposed by van Staden for the determination of three halides, these are separated in a short colunm packed with a strongly basic ion-exchange resin (Dowex i-X8) that is placed in an FI manifold. A laboratory-made tubular silver/silver halide ion-selective electrode is used as a potentiometric sensor. Van Staden compared the response capabilities of the halide-selective electrodes to a wide concentration range (20-5000 pg/mL) of individual and mixed halide solutions in the presence and absence of the ion-exchange column. By careful selection of appropriate concentrations of the potassixun nitrate carrier/eluent stream to satisfy the requirements of both the ion-exchange column and the halide-selective electrode, he succeeded in separating and determining chloride, bromide and iodide in mixed halide solutions with a detection limit of 5 /xg/mL [130]. 

A similar selectivity for copper over Fe3+ ions was observed for the recently described pyridyl-imidazole derivative resins, PI1 and PI2.384 There, too, iron is believed to be loaded onto the resin as the Fe(S04)2- anion, and it was shown383 that a six-fold improvement in the selectivity for copper over iron resulted when the aqueous-solution anion was changed from sulfate to nitrate, which does not form anionic complexes with Fe3+ ions. 

Ion exchange is widely used for the selective separa-tion/removal of metal ions from an aqueous medium either for environmental clean-up, for the removal of undesirable components, or for metal recovery. Other species that have been treated include nitrate, ammonia, and silicate. This process is normally based on the use of polymeric resins (typically styrene/divinylbenzene polymer backbones) that have chemically active groups attached to them. Sulfonic or carboxylate groups are regularly used for the removal of cations, and quaternary ammonium groups are used for the removal of anions. 

The partially demineralized water can be directly reused without furtlier polishing in some instances. This is not easy when the original condensate contains high concentrations of ammonium sulfate or nitrate, because strong acid resins are not highly selective for ammonium over hydrogen ions. To... 

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