Electrochemical conversion to borax
Electrolysis
In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from n ...
of a concentrated solution of 20% ·4 with an anion exchange membrane
An anion exchange membrane (AEM) is a semipermeable membrane generally made from ionomers and designed to conduct anions but reject gases such as oxygen or hydrogen.
Applications
Anion exchange membranes are used in electrolytic cells and f ...
and inert anode (such as gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
, palladium
Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself ...
, or boron-doped diamond) converts the metaborate anion to tetraborate , and the sodium salt of the later (borax
Borax is a salt (ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular form ...
) precipitates as a white powder.[
: + 2 → + + 4 e−
]
Hydrolysis of sodium borohydride
Hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysi ...
of sodium borohydride with a suitable catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
gives sodium metaborate:
: + 2 → + 4 (Δ''H'' = -217 kJ/ mol)[
]
Reduction to sodium borohydride
Sodium metaborate can be converted to sodium borohydride by several methods, including the reaction with various reducing agents at high temperatures and pressure,[ or with ]magnesium hydride
Magnesium hydride is the chemical compound with the molecular formula MgH2. It contains 7.66% by weight of hydrogen and has been studied as a potential hydrogen storage medium.
Preparation
In 1951 preparation from the elements was first reporte ...
by ball mill
A ball mill is a type of grinder used to grind or blend materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering. It works on the principle of impact and attrition: size reduction is done ...
ing at room temperature, followed by extraction of the with isopropylamine.[
: + 2 → + 2 MgO
Another method is the electrolytic reduction of a concentrated sodium metaborate solution,][ namely
: + 6 + 8 e− → + 8
However, this method is not efficient since it competes with the reduction of ]hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. ...
, 4 → 2 + + 4 e−
Nanofiltration membranes can effectively separate the borohydride from the metaborate.[
]
Reaction with alcohols
Anhydrous sodium metaborate refluxed with methanol
Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is ...
yields the corresponding sodium tetramethoxyborate:[
: + 4 → + 2
The analogous reaction with ]ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
yields the tetraethoxyborate.[
]
Uses
Current and proposed applications of sodium metaborate include:
*Manufacture of borosilicate glasses, which are resistant to uneven or fast heating because of their small coefficient of thermal expansion.
*Composition of Herbicide
Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...
s.[
*Raising the pH of injected fluids for oil extraction.][
]
See also
* Borate
References
[P. A. Akishin and V. P. Spirtdonov (1962): "Electron Diffraction Study of the Structure Of LiBO2 and NaBO2 Metaborate Molecules in the Vapor State". ''Zhumal Struktumoi Khimii'', volume 3, issue 3, pages 267-269. ]
[Alfred Büchler and Edward P. Marram (1963): "Gaseous Metaborates. II. Infrared Spectraof Alkali Metaborate Vapors". ''Journal of Chemical Physics'', volume 39, page 292. ]
[Hasan K. Atiyeh and Boyd R. Davis (2007): "Separation of sodium metaborate from sodium borohydride using nanofiltration membranes for hydrogen storage application". ''International Journal of Hydrogen Energy'', volume 32, issue 2, pages 229-236. ]
[Fuzhen Chen, Hanqiao Jiang, Xiaohu Bai, Wei Zheng (2013): "Evaluation the performance of sodium metaborate as a novel alkali in alkali/surfactant/polymer flooding". ''Journal of Industrial and Engineering Chemistry'', volume 19, issue 2, 25 March , Pages 450-457. ]
[John Krc, Jr. (1951): "Crystallographic Data. 44. Sodium Metaborate Dihydrate". ''Analytical Chemistry'', volume 23, issue 5, page 806. ]
[BareSpot Monobor-Chlorate]
. Product safety data sheet at the BareSpot company website. Accessed on 2022-06-28.
[Sodium metaborate]
Substance page at the Chemister website. Accessed on 2022-06-28.
[Z. P. Li, B. H. Liu. K. Arai, N. Morigazaki, S. Suda (2003): "Protide compounds in hydrogen storage systems". ''Journal of Alloys and Compounds'', volumes 356–357, pages 469-474. ]
[T. Kemmitt and G. J. Gainsford (2009): "Regeneration of sodium borohydride from sodium metaborate, and isolation of intermediate compounds" ''International Journal of Hydrogen Energy'', volume 34, issue 14, pages 5726-5731. ]
[Lingyan Kong, Xinyu Cui, Huazi Jin, Jie Wu, Hao Du, and Tianying Xiong (2009): "Mechanochemical Synthesis of Sodium Borohydride by Recycling Sodium Metaborate". ''Energy Fuels'', volume 23, issue 10, pages 5049-5054. ]
[Eun Hee Park, Seong Uk Jeong, Un Ho Jung, Sung Hyun Kim, Jaeyoung Lee, Suk Woo Nam, Tae Hoon Lim, Young Jun Park, Yong Ho Yuc (2007): "Recycling of sodium metaborate to borax". ''International Journal of Hydrogen Energy'', volume 32, issue 14, pages 2982-2987. ]
[Nelson P. Nies and Richard W. Hulbert (1967): "Solubility isotherms in the system sodium oxide-boric oxide-water. Revised solubility-temperature curves of boric acid, borax, sodium pentaborate, and sodium metaborate". ''Journal of Chemical and Engineering Data'', volume 12, issue 3, pages 303-313. ]
[Ssu-Mien Fang (1938): "The Crystal Structure of Sodium Metaborate ". ''Zeitschrift für Kristallographie - Crystalline Materials'', volume 99, issue 1-6, pages 1–8, ]
[M. Marezio, H. A. Plettinger and W. H. Zachariasen (1963): "The bond lengths in the sodium metaborate structure", ''Acta Crystallographica'', volume 16, pages 594-595. ]
[Sandford S. Cole and Nelson W. Taylor, "The system -, IV: Vapor Pressures of Boric Oxide, Sodium Metaborate, and Sodium Diborate between 1150°C and 1400°C". ''Journal of the American Ceramic Society'', volume 18, issue 1‐12, pages 82-85 ]
[W. H. Zachariasen (1937): "The Crystal Structure of Potassium Metaborate, K3(B3O6)". ''Journal of Chemical Physics'', volume 5, issue 11, page 919. ]
{{Borates
Borates
Sodium compounds