nitric acid

GC: n

CT: Since 2014, the WEEE (Waste Electrical and Electronic Equipment) Directive1 has required all PV suppliers in EU Member States to collect and recycle end-of-life PV panels. Another influence on PV recycling rates is the potential shortage of raw materials, particularly silicon, needed to make new panels.
Most PV cells are crystalline-silicon cells, and silicon is naturally their main, as well as the most expensive, component. This study explored the ability of several chemical methods to recover silicon and metals from old crystalline PV panels.
The scientists gathered waste PV cells which had a silicon content of 97–98%. Their aim was to dissolve metals in the cells to leave behind silicon with a purity of 99.99–99.999% — what is known as a purity rating of ‘4N’ to ‘5N’ (‘N’ refers to the number of nines in the silicon percentage). 4N–5N is considered high-purity and is suitable for producing PV cell components.
They placed 1–2cm2 pieces of the cells into in one of four chemicals: hydrochloric acid, sulphuric acid, nitric acid or caustic soda. The tests were conducted at 20–40 °C for two hours. Both single-crystal PV cells and poly-crystal PV cells were tested; the poly-crystal cells had slightly higher silicon content.
Nitric acid was the most effective at dissolving metals. It removed nearly all silver from fragments of single-crystal cells after 1 hour, for example. However, it could only remove up to around 75% of aluminium. Hydrochloric and sulphuric acid were ineffective at removing silver.
When nitric acid treatment was combined with immersion in caustic soda, the researchers found they could extract more aluminium to produce silicon with a purity of 99.98%, i.e. 3N.
These two treatments together removed high levels of 14 metals altogether. For example, they removed 99.96% of silver from single-crystal cells, with content falling from 11920 mg per kg of cell to 4.23 mg/kg. Aluminium content from the same cells dropped from 8070 mg/kg to 162.5 mg/kg — a removal of 99.97%.

S: SfEP - http://www.goo.gl/y2VbBz(external link) (last access: 24 November 2017)

N: 1. - nitric (adj): originally in reference to acid obtained initially from distillation of saltpeter; comes from "nitre" (nitre- from Latin nitrum , from Greek nitro,, which is possibly of Eastern origin, from French nitrique; 1787 known as nitric acid under the system ordered by Lavoisier) and prefix "-ic" (Middle English -ik, -ick, word-forming element making adjectives, "having to do with, having the nature of, being, made of, caused by, similar to," from French -ique and directly from Latin -icus or cognate Greek -ikos "in the manner of; pertaining to"; in chemistry, indicating a higher valence).
- acid (n): from French acide, or directly from Latin acidus "sour, sharp, tart".
Molecular formula: HNO3.
2. Nitric acid is a fuming corrosive inorganic yellowish liquid, which is a highly reactive oxidizing agent used in the production of fertilizers, explosives, and rocket fuels and in a wide variety of industrial metallurgical processes. Very toxic by inhalation. Corrosive to metals or tissue. Prolonged exposure to low concentrations or short term exposure to high concentrations may result in adverse health effects. If the solution contains more than 86% nitric acid, it is referred to as fuming nitric acid. Fuming nitric acid is characterized as white fuming nitric acid and red fuming nitric acid, depending on the amount of nitrogen dioxide present. At concentrations above 95% at room temperature, it tends to develop a yellow color due to decomposition. An alternative IUPAC (International Union of Pure and Applied Chemistry) name is oxoazinic acid.
3. The preparation and use of nitric acid were known to the early alchemists. A common laboratory process used for many years, ascribed to Johann Rudolf Glauber (German chemist, 1648), consisted of heating potassium nitrate with concentrated sulfuric acid. In 1776 Antoine-Laurent Lavoisier (Fran nobleman and chemist, 1743-1794) showed that it contained oxygen, and in 1816 Joseph-Louis Gay-Lussac (French chemist and physicist, 1778-1850) and Claude-Louis Berthollet (Savoyard-French chemist and vice president of the French Senate in 1804, 1748-1822) established its chemical composition.
4. Applications:
  • Nitric acid is used in the production of ammonium nitrate for fertilizers, making plastics, and in the manufacture of dyes.
  • It is also used for making explosives such as nitroglycerin and TNT. When it is combined with hydrochloric acid, an element called aqua regia is formed. This is a reagent that is capable of dissolving gold and platinum. Additionally, it is used in a colorimetric test to distinguish heroin and morphine.
  • Nitric acid is commonly used in science laboratories at schools for experimenting when specifically testing for chloride. This is accomplished by adding a sample with silver nitrate solution and nitric acid to test if a white precipitate, silver chloride is present.
  • In the field of medicine, nitric acid is used in its pure state as a caustic to remove chancres and warts. Diluted solutions are used in the treatment of dyspepsia.
  • Nitric acid has been used in various forms as the oxidizer in liquid–fueled rockets. These forms include red fuming nitric acid, white fuming nitric acid, mixtures with sulfuric acid, and forms with HF inhibitor.
  • It is also typically used in the digestion process of turbid water samples, solid sludge samples, as well as other types of unique samples that require elemental analysis via ICP-MS, ICP-OES, ICP-AES, GFAA and flame atomic absorption spectroscopy.
  • In organic synthesis, nitric acid may be used to introduce the nitro group. When used with sulfuric acid, it generates the nitronium ion, which electrophilically reacts with aromatic compounds such as benzene.
  • In electrochemistry, nitric acid is used as a chemical doping agent for organic semiconductors, and in purification processes for raw carbon nanotubes.
  • In a low concentration, nitric acid is often used in woodworking to artificially age pine and maple. The color produced is a gray–gold, very much like very old wax or oil-finished wood.
  • Nitric acid can be used as a spot test for alkaloids like LSD, producing a variety of colors, depending on the alkaloid.
5. Concentrated nitric acid is corrosive and causes severe burns to the skin and eyes. Its fumes evolve nitrogen dioxide gas which at low concentrations may cause lung oedema (fluid in the lungs) and fatal with excessive exposure. Toxicity after inhalation exposure to nitric acid is similar in humans and animals.
Nitric acid fumes may cause immediate irritation of the respiratory tract, pain, and dyspnea, followed by a period of recovery that may last several weeks. A relapse may occur resulting in death caused by bronchopneumonia and pulmonary fibrosis. At nonlethal concentrations, allergic or asthmatic individuals appear to be sensitive to acidic atmospheres.
6. Nitric acid concentrations:
  • Weak: Dilute nitric acid can be concentrated by evaporation of the water from the mixture. The maximum concentration that can be achieved for this two-component distillation process is the azeotrope concentration of ~67 wt%. Depending on the application Chemetics offers the following processes:
  1. Single step concentration under vacuum for product concentrations below 25 wt%
  2. Nitric Acid Distillation at atmospheric pressure for product concentrations up to 67wt%
  3. Double effect concentration systems with improved energy consumption combining the single step vacuum concentration unit with the atmospheric distillation unit. This process is expecially suitable for concentration of very dilute or very large streams of nitric acid.
  • Strong: For a signicant number of chemical processes, the azeotrope concentration of 67 wt% is not sufient and the Nitric Acid has to be concentrated further. Due to the presence of the azeotrope, it is not possible to use a simple distillation system. Furthermore, the azeotrope concentration does not change signicantly at different pressures and a dual pressure distillation does not provice a solution. Instead, the vapour pressure of the H2O-HNO3 system has to be manipulated to change the location of the azeotrope. This can be done by adding a third component to the mixture. This additional chemical must be chosen carefully. Not only should this chemical have a signi cant effect on the nitric acid VLE, it must also have a low vapour pressure, exhibit low toxicity and be stable at the temperatures in the distillation column.
7. Main difference between nitric acid and nitrous acid:
  • The formula for nitric acid is HNO3, while the formula for nitrous acid is HNO2. HNO3 is a strong acid, HNO2 is a weak acid. In other words, the pKa value for HNO2 is higher than that of HNO3 because HNO2 is a weaker acid. Note that Ka is acid dissociation constant, pK{TAG(tag=>sub)}a is equal to -log10ka.
8. nitric acid: Not to be confused with "aqua fortis" (q.v.), which refers to a solution of nitric acid used by engravers, and with "nital," (q.v.) which refers to an etchant consisting of a few per cent of concentrated nitric acid in ethyl or methyl alcohol.

S: 1. OED - https://goo.gl/f8M7yH;(external link) https://goo.gl/kj4yNJ;(external link) https://goo.gl/Lrm9Lb;(external link) https://goo.gl/5AcwqD(external link) (last access: 23 November 2017). 2. MW - https://goo.gl/Wj6NYv(external link) (last access: 23 November 2017); TFD - https://goo.gl/1gwjLE(external link) (last access: 23 November 2017); UPPIT - https://goo.gl/RCPN5j(external link) (last access: 23 November 2017). 3.EncBrit - https://goo.gl/kfG48j(external link) (last access: 23 November 2017). 4. CHECO - https://goo.gl/EnF5vs(external link) (last access: 23 November 2017). 5. NCBI - https://goo.gl/xZG2Xe(external link) (last access: 23 November 2017). 6. NAC - https://goo.gl/H1gFNZ(external link) (last access: 23 November 2017). 7. Tutapoint - http://www.goo.gl/uStCbc(external link) (last access: 24 November 2017). 8. TERMIUM PLUS - http://www.goo.gl/7imwN1(external link) (last access: 24 November 2017).

SYN: 1. hydrogen nitrate. 2. azotic acid, nitryl hydroxide.

S: 1. TERMIUM PLUS - http://www.goo.gl/7imwN1(external link) (last access: 24 November 2017); PubChem - https://goo.gl/uZi4Df(external link) (last access: 23 November 2017). 2. TERMIUM PLUS - http://www.goo.gl/7imwN1(external link) (last access: 24 November 2017).

CR: acid rain, acidogenesis (EN), air pollution, nitrogen oxide, nitrous oxide, sulfuric acid.


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