Boron in water

Boron Removal. Boron [7440-42-8] is occasionaHy present in water suppHes at an unacceptable level. It cannot be removed with the standard anion-exchange resins unless the water is deionized. Selective removal is possible by using an anion exchanger functionalized with /V-methy1g1ucamine [6284-40-8]. This resin is in limited commercial supply. The borate form of conventional strong base anion exchangers is used in some nuclear reactors to adjust the concentration of boron in water used as a moderator. The resin releases boron as the water temperature rises. 

In situ densitometry has been the most preferred method for quantitative analysis of substances. The important applications of densitometry in inorganic PLC include the determination of boron in water and soil samples [38], N03 and FefCNfg in molasses [56], Se in food and biological samples [28,30], rare earths in lanthanum, glass, and monazite sand [22], Mg in aluminum alloys [57], metallic complexes in ground water and electroplating waste water [58], and the bromate ion in bread [59]. TLC in combination with in situ fluorometry has been used for the isolation and determination of zirconium in bauxite and almnimun alloys [34]. The chromatographic system was silica gel as the stationary phase and butanol + methanol + HCl -H water -n HF (30 15 30 10 7) as the mobile phase. 

Green, G.H. and H.J. Weeth. 1977. Responses of heifers ingesting boron in water. Jour. Anim. Sci. 46 812-818. 

The curcumin method (in either the rosocyanin or rubrocurcumin version) has been applied for determining traee amounts of boron in biologieal materials [10], soils and plants [17], waters [51], silicon [52], chlorosilanes [20], uranium [1,53], zirconium and its alloys [53,54], nickel [55,56], copper alloys [56], cast iron and steel [12,57-59], beryllium and magnesium [53], and phosphates [2]. This method was also used for determining boric acid admixtures (about 0.05%) in powdered boron [11]. Some synthetic compounds having the structure similar to that of curcumin, were used in determining boron in water [60]. 

Boron in water was determined by the Azomethine-H method [1]. The detection limit was... 

Boron in the soil and water exists either as boric acid or as the borate ion. Although the levels generally present pose no problems to animal life, in many areas, present levels of boron in water supplies can be deleterious to agricultural crops. Boron is a typical case in which there exists a small difference between a deficiency level and a toxicity level in the water used for agricultural purposes. Boron phytotoxicity can occur with levels above 2 ppm, and deficiency can occur for many plant species if the levels are below 0.5-1.0 ppm of B. 

This is an exothermic process, due largely to the large hydration enthalpy of the proton. However, unlike the metallic elements, non-metallic elements do not usually form hydrated cations when their compounds dissolve in water the process of hydrolysis occurs instead. The reason is probably to be found in the difference in ionisation energies. Compare boron and aluminium in Group III ... 

Boron trioxide is not particularly soluble in water but it slowly dissolves to form both dioxo(HB02)(meta) and trioxo(H3B03) (ortho) boric acids. It is a dimorphous oxide and exists as either a glassy or a crystalline solid. Boron trioxide is an acidic oxide and combines with metal oxides and hydroxides to form borates, some of which have characteristic colours—a fact utilised in analysis as the "borax bead test , cf alumina p. 150. Boric acid. H3BO3. properly called trioxoboric acid, may be prepared by adding excess hydrochloric or sulphuric acid to a hot saturated solution of borax, sodium heptaoxotetraborate, Na2B407, when the only moderately soluble boric acid separates as white flaky crystals on cooling. Boric acid is a very weak monobasic acid it is, in fact, a Lewis acid since its acidity is due to an initial acceptance of a lone pair of electrons from water rather than direct proton donation as in the case of Lowry-Bronsted acids, i.e. 

Table 1 Hsts some of the physical properties of duoroboric acid. It is a strong acid in water, equal to most mineral acids in strength and has a p p o of —4.9 as compared to —4.3 for nitric acid (9). The duoroborate ion contains a neady tetrahedral boron atom with almost equidistant B—F bonds in the sohd state. Although lattice effects and hydrogen bonding distort the ion, the average B—F distance is 0.138 nm the F—B—F angles are neady the theoretical 109° (10,11). Raman spectra on molten, ie, Hquid NaBF agree with the symmetrical tetrahedral stmcture (12).

Boron, in the form of boric acid, is used in the PWR primary system water to compensate for fuel consumption and to control reactor power (3). The concentration is varied over the fuel cycle. Small amounts of the isotope lithium-7 are added in the form of lithium hydroxide to increase pH and to reduce corrosion rates of primary system materials (4). Primary-side corrosion problems are much less than those encountered on the secondary side of the steam generators. 

The tri-, tetra-, penta-, and hexahydrates of boron phosphate have been reported. AH of these decompose rapidly in water to give solutions of the parent acids. Anhydrous boron phosphate hydroly2es in a similar fashion, though the reaction proceeds quite slowly for material that has been ignited at high temperatures. 

The triaLkoxy(aryloxy)boranes are typically monomeric, soluble in most organic solvents, and dissolve in water with hydrolysis to form boric acid and the corresponding alcohol and phenol. Although the rate of hydrolysis is usually very fast, it is dependent on the bulk of the alkyl or aryl substituent groups bonded to the boron atom. Secondary and tertiary alkyl esters are generally more stable than the primary alkyl esters. The boron atom in these compounds is in a trigonal coplanar state with bond hybridization. A vacantp orbital exists along the threefold axis perpendicular to the BO plane. 

AsH, primary and secondary amines, and lower alcohols, BCl, BBr, and BI react to hberate the corresponding hydrogen hahde. Tertiary alcohols and the boron tnhahdes yield the alkyl hahde and boric acid. The boron tnhahdes hydrolyze readily in water or moist air to produce boric acid and hydrogen hahdes. 

The method has been applied to the determination of boron in river water and sewage,16 the chief sources of interference being copper(II) and zinc ions, and anionic detergents. The latter interfere by forming ion-association complexes with ferroin which are extracted by chloroform this property... 

Standard boron solution. Dissolve 0.7621 g boric acid in water and dilute to 1 L. Take 50 mL of this solution and dilute to 1 L the resulting solution contains 6.667 Ug B per mL. 

Procedure (boron in steel). Dissolve about 3g of the steel (B content >0.02 per cent), accurately weighed, in 40 mL dilute sulphuric acid in a 150mL Vycor or silica flask fitted with a reflux condenser. Heat until dissolved. Filter through a quantitative filter paper into a 100 mL graduated flask. Wash with hot water, cool to room temperature, and dilute to the mark with water. This flask (A) contains the acid-soluble boron. 

A substance employed to slow down the neutrons in a nuclear reactor in order that they can be captured by the nuclei. Boron, heavy water (D20) and graphite are commonly used moderators. 

Metallic elements with low ionization energies commonly form basic ionic oxides. Elements with intermediate ionization energies, such as beryllium, boron, aluminum, and the metalloids, form amphoteric oxides. These oxides do not react with or dissolve in water, but they do dissolve in both acidic and basic solutions. 

This was one of the great shocks of my life and was the way we discovered that sodium borohydride possesses a remarkable stability (for a simple boron-hydrogen compound) in water. 

As mentioned several times Lewis acids are highly valuable catalysts but the most commonly used ones such as aluminium chloride and boron trifluoride are highly water sensitive and are not usually recovered at the end of a reaction, leading to a significant source of waste. In recent years there has been much research interest in lanthanide triflates (trifluoro-methanesulfonates) as water stable, recyclable Lewis acid catalysts. This unusual water stability opens up the possibility for either carrying out reactions in water or using water to extract and recover the catalyst from the reaction medium. 

CVD diamond films can be used for electrochemical applications, especially in harsh or corrosive environments. Conducting diamond electrodes, made by adding boron to CVD diamond films, are very inert compared to other electrode materials (such as platinum). Such diamond electrodes may find applications in analysis of contaminants, such as nitrates, in water supplies, and even in the removal of those contaminants. 

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