Lead hydroxide structure, properties, uses, risks

The lead hydroxide It is a white inorganic solid in which lead (Pb) is in the 2+ oxidation state. Its chemical formula is Pb (OH)_two. According to some sources of information, it can be prepared by adding an alkali to a solution of lead nitrate (Pb (NO₃)_two). It can also be obtained by electrolysis of an alkaline solution with a lead anode..

However, there is a contradiction between the various authors, since it has long been affirmed that there is only one stable solid form of lead (II) hydroxide, formulated as 3PbO.H_twoO, or lead (II) oxide hydrate.

Lead hydroxide is very poorly soluble in water. Its uses include its usefulness to remove chromium (VI) ions from wastewater, as a catalyst in chemical reactions or to increase the efficiency of other catalysts..

It has also been used as a pH stabilizer in mixtures for sealing permeable formations, as an ingredient in heat-sensitive paper, and as an electrolyte in sealed nickel-cadmium batteries..

Another of its uses is in protective screens against radiation in buildings and to stabilize plastic resins against degradation..

Exposure to Pb (OH) should be avoided_two since all lead compounds are toxic to a greater or lesser degree.

Article index

• 1 Structure
• 2 Electronic configuration
• 3 Nomenclature
• 4 Properties
  • 4.1 Physical state
  • 4.2 Molecular weight
  • 4.3 Melting point
  • 4.4 Solubility
  • 4.5 Other properties
• 5 Uses
  • 5.1 In catalysis of chemical reactions
  • 5.2 In the treatment of water contaminated with chromium (VI)
  • 5.3 In the preparation of photothermographic copies
  • 5.4 In mixtures for temporary sealing
  • 5.5 In various applications
  • 5.6 Recent studies
• 6 Risks
• 7 References

Structure

Pb (OH)_two it is an amorphous white solid. It does not have a crystalline structure.

Electronic configuration

The electronic structure of lead metal is:

[Xe] 4F¹⁴ 5d¹⁰ 6s^two 6p^two

Where [Xe] is the electronic configuration of the noble gas xenon.

Its most stable chemical form in solution is that of the Pb ion.^two+, what is a present in Pb (OH)_two, in which the two electrons of shell 6 are lostp, resulting in the following electronic configuration:

[Xe] 4F¹⁴ 5d¹⁰ 6s^two

Nomenclature

- Lead (II) hydroxide.

- Plumb hydroxide.

- Lead (II) dihydroxide.

- Lead (II) oxide hydrate.

Properties

Physical state

Solid white amorphous.

Molecular weight

241.23 g / mol.

Melting point

It dehydrates when it reaches 130ºC and decomposes when it reaches 145ºC..

Solubility

Weakly soluble in water, 0.0155 g / 100 mL at 20 ºC. Slightly more soluble in hot water.

It is soluble in acids and alkalis. Insoluble in acetone.

Other properties

Lead (II) ion, or Pb^two+ it is partially hydrolyzed in water. It has been experimentally verified by spectrometry of the UV-Visible region, that the species of Pb^two+ present in alkaline solutions of lead (II) perchlorate (Pb (ClO₄)_two) are as follows: Pb (OH)⁺, Pb (OH)_two, Pb (OH)₃^- and Pb (OH)₄^two+.

Applications

In catalysis of chemical reactions

Pb (OH)_two It is useful in the synthesis of carboxylic acid amides as it is used to incorporate a certain percentage of lead to the palladium (Pd) metallic catalyst. In this way, the catalytic efficiency of palladium is increased..

It has also been used as a catalyst for the oxidation of cyclododecanol.

In the treatment of water contaminated with chromium (VI)

The hexavalent chromium ion Cr⁶⁺ it is a polluting element because even in minimal concentrations it is toxic to fish and other aquatic species. Therefore, for water contaminated with Cr⁶⁺ can be disposed of into the environment, it must be treated until the complete removal of the chromium it contains.

Lead hydroxide has been used to remove Cr⁶⁺, even in very small quantities, as it forms an insoluble lead chromate compound (PbCrO₄).

In the preparation of photothermographic copies

Photothermographic copying has been used to make copies of documents.

It involves placing the original document in heat conductive contact with a blank sheet of paper and subjecting both to intense infrared radiation (heat).

This is done in such a way that the printed part of the original absorbs a portion of the radiant energy. This heat causes the image of the original to develop on the blank sheet..

In this process, the blank sheet of paper must be formulated in such a way that when heated it can change to a contrasting color. That is, the paper must be heat sensitive..

The heat-generated image can be formed both by a physical change in the blank sheet and by a heat-induced chemical reaction..

Lead hydroxide has been used in the preparation of special paper for photothermographic copies. It is applied to paper as a dispersion with a volatile organic solvent so that a coating is formed.

The lead hydroxide coating must be on the inside, this means that another coating is placed on top, in this case a thiourea derivative.

During the heating of the paper, a chemical reaction occurs in which dark-colored lead sulphides are formed..

Paper made this way produces well-defined prints where the graphic part is black in contrast to the whiteness of the paper..

In mixtures for temporary sealing

Sometimes it is necessary to temporarily seal permeable formations in which openings have been made. For this, mixtures are used capable of forming a mass that supports appreciable pressures and then liquefies so that the plug stops working and allows the flow of fluids through the formation..

Some of these mixtures contain gums derived from sugars, hydrophobic compounds, an organic polymer that keeps the ingredients in suspension, and a pH control agent..

Lead hydroxide has been used as a pH controlling compound in this type of mixture. Pb (OH)_two releases hydroxyl ions (OH^-) and helps maintain the pH between 8 and 12. This ensures that the hydrophobically treated rubber does not swell due to acidic conditions..

In various applications

Pb (OH)_two It serves as an electrolyte in sealed nickel-cadmium batteries. It has been used in electrical insulating paper, in the manufacture of porous glass, in the recovery of uranium from seawater, in lubricating greases and in the manufacture of radiation shields in buildings..

As a raw material to produce other lead compounds, particularly in the plastics industry, to produce stabilizers for polyvinyl chloride resins to resist thermal degradation and that caused by UV light.

Recent studies

The use of a derivative of Pb (OH) has been investigated_two, lead (II) hydroxychloride, Pb (OH) Cl, as a novel anode in lithium (Li) batteries or energy storage systems. The initial recharge capacity of Pb (OH) Cl was found to be high.

However, in the electrochemical process the formation of Pb (OH) occurs_two and PbCl_two at the expense of Pb (OH) Cl and the formation of holes on the surface of the electrode is observed. As a result, the cyclical charge and recharge property decreases due to damage to the PB (OH) Cl electrode during the repetition of these cycles..

Therefore, the use of these Pb (OH) Cl electrodes in lithium batteries should be reviewed to find a solution to this problem..

Risks

Lead is toxic in all its forms but to varying degrees depending on the nature and solubility of the compound. Pb (OH)_two it is very poorly soluble in water, so it is likely to be less toxic than other lead compounds.

However, the toxic effect of lead is cumulative, therefore prolonged exposure to any of its forms should be avoided..

The most common symptoms of plumbismus (lead poisoning) are gastrointestinal: nausea, diarrhea, anorexia, constipation, and colic. Lead absorption can affect hemoglobin synthesis and neuromuscular function.

In women, lead can decrease fertility and harm fetuses. In cases of high levels of Pb in the blood, encephalopathies occur.

To avoid this, in industries where there is a possibility of exposure, respiratory protection, protective clothing, continuous exposure monitoring, isolated canteens and medical supervision should be used..

References

1. Kirk-Othmer (1994). Encyclopedia of Chemical Technology. Volume 15. Fourth Edition. John Wiley & Sons.
2. Nimal Perera, W. et al. (2001). An Investigation of the Lead (II) -Hydroxide Inorg. Chem. 2001, 40, 3974-3978. Recovered from pubs.acs.org.
3. Jie Shu, et al. (2013). Hydrothermal fabrication of lead hydroxide chloride as a novel anode material for lithium-ion batteries. Electrochimica Acta 102 (2013) 381-387. Recovered from sciencedirect.com.
4. Cotton, F. Albert and Wilkinson, Geoffrey. (1980). Advanced Inorganic Chemistry. Fourth Edition. John Wiley & Sons.
5. Otto, Edward C. (1966). U.S. Patent No. 3,260,613. Heat-sensitive sheet for thermographic copying. July 12, 1966.
6. Nimerick, Kenneth H. (1973). Method for temporarily sealing a permeable formation. U.S. Patent No. 3,766,984. October 23, 1973.
7. Nieuwenhuls, Garmt J. (1974). Process for treating water contaminated with hexavalent chromium. U.S. Patent No. 3,791,520. February 12, 1974.
8. Nishikido Joji, et al. (nineteen eighty one). Process of preparing carboxylic acid amides. U.S. Patent No. 4,304,937. December 8, 1981.
9. .