Bleach is the name given to a group of chemicals, used industrially and domestically to whiten clothing, brighten hair color and remove stains. Many bleaches have broad-spectrum bactericidal properties, making them useful for disinfection and sterilization and are used in pool sanitation to control bacteria, viruses, and algae and in many places where sterile conditions are required. They are also used in many industrial processes, especially in bleaching wood pulp. Bleach is also used to remove fungi, kill weeds, and increase the longevity of cut flowers.
The bleaching process has been known for thousands of years, but the chemicals currently used for bleaching result from the work of some 18th-century scientists.
Chlorine is the basis of chlorine bleach: for example, the simplest ubiquitous sodium hypochlorite solution calls it "bleach", and calcium hypochlorite, the active compound in "bleach powder".
An oxidation-containing bleaching agent containing no chlorine is usually based on peroxides such as hydrogen peroxide, sodium percarbonate, and sodium perborate. This bleach is called non-chlorine bleach, Oxygen bleach, or safe color bleach. While most bleaches are oxidizing agents, some reducing agents such as sodium dithionite and sodium borohydride.
Video Bleach
Health risks
The digestive process can cause damage to the esophagus and stomach, possibly causing death. When left on the skin, it will cause irritation, drying, and potentially burning. Inhaling bleach smoke can damage the lungs. Bleach splattered in the eyes will also cause damage.
Maps Bleach
History
The earliest form of bleaching involves spreading fabrics and fabrics in bleachfield to be bleached by the action of the sun and water. Modern bleach is produced from the work of 18th-century scientists including the Swedish chemist Carl Wilhelm Scheele, who discovered chlorine, the French scientist Claude Berthollet, who admitted that chlorine can be used to whiten the fabric and which first makes sodium hypochlorite ( Eau de Javel, or Javel water, named after a quarter in Paris where it was produced) and Antoine Germain Labarraque, which discovers the hypochlorite disinfectant ability. Scottish chemist and industrialist Charles Tennant first produced a calcium hypochlorite solution, then calcium hypochlorite solid (bleach powder).
Louis Jacques ThÃÆ' Â © nard first produced hydrogen peroxide in 1818 by reacting barium peroxide with nitric acid. Hydrogen peroxide was first used for bleaching in 1882, but did not become commercially important until after 1930. Sodium perborate as a laundry bleach had been used in Europe since the early twentieth century, but did not become popular in North America until the 1980s.
Action mechanism
Bleaching
Colors usually arise from organic dyes and pigments, such as beta carotene. Chemical bleach works in one of two ways:
- The oxidizing bleach works by breaking the chemical bonds that make up the chromophore. It converts molecules into different substances that do not contain chromophores, or contain chromophores that do not absorb visible light. This is a chlorine-based bleaching mechanism.
- The reducing bleach acts by converting the double bond in the chromophore into a single bond. This removes the ability of the chromophore to absorb visible light. This is a bleaching mechanism based on sulfur dioxide.
Sunlight acts as a bleach through a process that leads to the same result: high light energy photons, often in violet or ultraviolet ranges, can disrupt the bonds in the chromophore, resulting in a colorless substance produced. Expanding exposure often causes enormous color changes that typically reduce color to a normally faded blue spectrum.
Antimicrobial efficacy
The broad spectrum effectiveness of bleach, especially sodium hypochlorite, is due to its chemical reactivity properties with microbes. Instead of acting inhibitory or toxic by way of antibiotics, fast bleach reacts with microbial cells to change properties and restore many pathogens. Bleach, especially sodium hypochlorite, has been shown to react with microbial heat shock proteins, stimulating their role as an intra-cellular companion and causing bacteria to form into clumps (like boiled eggs) that will eventually die. In some cases, acidity of the bleach base damages the bacterial lipid membrane, a reaction similar to that of a balloon. The range of micro-organisms that are effectively killed by bleach (especially sodium hypochlorite) is vast, making it a very versatile disinfectant. The same study found that at low levels of sodium hypochlorite (micromolar), E. coli and Vibrio cholerae activates a defense mechanism that helps protect bacteria, although the implications of this defense mechanism have not been fully investigated.
In response to infection, the human immune system will produce powerful oxidizing, hypochlorite acid, which is produced in neutrophils that are activated by peroxidation of chloride ions mediated by myeloperoxidase, and contribute to bacterial destruction.
Bleach class
Chlorine-based bleach
Chlorine-based bleach is found in many household cleaners. Chlorine-based bleach concentrations are often expressed as active chlorine percent where one gram of 100% active chlorine bleach has the same bleaching power as one gram of chlorine. This bleach can react with other ordinary household chemicals such as vinegar or ammonia to produce toxic gases. Labels on sodium hypochlorite bleach warn about this interaction.
Chemical interactions
Mixing hypochlorite bleach with acid can liberate chlorine gas. Hypochlorite and chlorine are in equilibrium in water; the equilibrium position depends on pH and low pH (acid) supports chlorine,
- Cl 2 H 2 O? H Cl - HClO
Chlorine is a respiratory irritant that attacks the mucous membranes and burns the skin. At least 3.53 ppm can be detected as a smell, and 1000 ppm is likely to be fatal after several deep breaths. Chlorine exposure is limited to 0.5 ppm (weighted average 8 hours - 38 hours per week) by OSHA in the US.
Sodium hypochlorite and ammonia react to form a number of products, depending on the temperature, concentration, and how they are mixed. The main reaction is chlorination of ammonia, first giving chloramine (NH 2 Cl), then dichloramine (NHCl 2 ) and finally nitrogen trichloride (NCl 3 ). These materials are very irritating to eyes and lungs and toxic over certain concentrations; Nitrogen trichloride is also a very sensitive explosive.
- NH 3 NaOCl -> NaOH NH 2 Cl
- NH 2 Cl NaOCl -> NaOH NHCl 2
- NHCl 2 NaOCl -> NaOH NCl 3
Additional reactions produce hydrazine, in a variety of Raschig Olin processes.
- NH 3 NH 2 H NaOH -> N 2 H 4 NaCl H 2 O
The resulting hydrazine can react with more chloramine in an exothermic reaction to produce ammonium chloride and nitrogen gas:
However, the place of atomic oxygen in accounting for chlorine formation does not make sense like other theories based on the so-called 'chloride system' used in modern hydrometallurgy to dissolve the ore with weak acids in highly ionic and concentrated salt solutions. Salt is very effective, in this case, including MgCl 2 , CaCl 2 , FeCl 3 and, to a lesser extent, NaCl mono-valent. This is, essentially, the application of the theory of non-common ions, or as discussed in Wikipedia under the Solubility Equilibrium as the 'salt effect'. With respect to bleaching powder, which has been described as a compound salt of the form , the presence of CaCl 2 in a highly concentrated solution can greatly increase the 'activity level' of the weak acid. Thus, in this particular proposed application, H 2 CO 3 of CO 2 and moisture on the bleaching powder, acting on CaCl 2 to release some HCl acting on HClO releasing Chlorine:
- HClO HCl -> H 2 O Cl 2
or, increased acidity creates more HClO that drives a known equilibrium reaction (and long, see Watt's Dictionary of Chemistry) on the right:
- CaCl 2 2 HClO? Ca (OH) 2 2 Cl 2
Sodium hypochlorite
Sodium hypochlorite is the most common bleaching agent, usually as a dilute solution (3-6%) in water. This sodium hypochlorite solution, commonly referred to as "bleach", is also one of the first mass-produced bleaches. This is produced by passing the chlorine gas through dilute sodium hydroxide solution (a) NaClO (aq) H 2 O (l) 2 <
or by electrolysis of brine (sodium chloride in water).
- 2 Cl - -> Cl 2 2 e -
- Cl 2 H 2 O? HClO Cl - H
Dilute sodium hypochlorite solutions are used in many households to whiten laundry, disinfect hard surfaces in kitchens and bathrooms, treat water for drinking and keep swimming pools free of infectious agents.
In addition, due to transport and handling of security concerns, the use of sodium hypochlorite is preferred over the chlorine gas in water treatment, which is a significant potential market expansion.
Bleaching powder
Bleach powder is one of a variety of calcium hypochlorite, lime (calcium hydroxide), and calcium chloride mixtures. Also known as "chlorinated lime", is used in many of the same applications as sodium hypochlorite, but is more stable and contains more chlorine available. Usually white powder. A purer, more stable form of calcium hypochlorite is called HTH or high test hypochlorite. Whitening tablets contain calcium hypochlorite and other ingredients to prevent the tablet from collapsing. A mixture of calcium hypochlorite and lime (calcium oxide) supposedly more stable is known as "tropical bleach". The percentage of active chlorine in this material ranges from 20% to bleaching powder up to 70% for HTH.
Chlorine
Chlorine is produced by electrolysis of sodium chloride.
- 2 NaCl 2 H 2 O -> Cl 2 H 2 2 NaOH
Chlorine is used to prepare sodium and calcium hypochlorite. It is used as a disinfectant in water treatment, especially for making drinking water and in large public swimming pools. Chlorine is widely used to whiten wood pulp, but this use has decreased significantly due to environmental concerns.
Chlorine dioxide
Chlorine dioxide, ClO 2 , is an unstable gas and is used in place or stored as aqueous aqueous solution. Apart from these limitations, he found large-scale applications for bleaching wood pulp, fats and oils, cellulose, flour, textiles, beeswax, leather, and in a number of other industries. This can be prepared by oxidizing sodium chlorite with chlorine
- 2 NaClO 2 Cl 2 -> 2 ClO 2 2 NaCl
tetapi lebih umum disiapkan dengan mengurangi natrium klorat dengan zat pereduksi yang sesuai seperti methanol, hydrogen peroxide, asam hydrochlorat, atau sulphur dioxide.
where "R" is the reducing agent and "RO" is an oxidized form.
Peroxide-based bleaching
After chlorine-based bleaching, the most common peroxide bleach is encountered and is very common in detergent formulations. Peroxide is a compound containing a single oxygen-oxygen bond, O-O. This is a fairly weak bond so the peroxide reaction often involves breaking this bond, giving a highly reactive oxygen species. Most of the peroxide bleach is the addition of hydrogen peroxide. They contain hydrogen peroxide, HOOH in combination with other materials such as sodium carbonate or urea. The exception is sodium perborate, which has a cyclic structure containing two single O-O bonds. All peroxide based bleaches release hydrogen peroxide when dissolved in water. Bleaching peroxides are often used in conjunction with bleach activators, such as tetraacetylethylenediamine (TAED) or sodium nonanoyloxybenzenesulfonate (NOBS).
Hydrogen peroxide
Hydrogen peroxide is produced in very large quantities by several different processes. His action as an oxidizer is why he is made and used in large quantities. It is used by itself as a bleaching agent, for example to whiten wood pulp, hair and so on, or to prepare other bleaching agents such as perborates, peroxides, peracids, etc.
Sodium percarbonate
Natrium percarbonates the drip of secara industri denial to recover sodium carbonate under hydrogen peroxide, diikuti oleh kristalisasi. Juga, sodium carbonate kering dapat diperlakukan langsung dense larvae hydrogen peroxide peak.
Dissolved in water, it produces a mixture of hydrogen peroxide (see above) and sodium carbonate. It is generally regarded as an environmentally friendly cleaning agent.
Sodium perborate
Sodium perborate, Na 2 H 4 B 2 O 8 , dibuat dengan mereaksikan boraks dengan natrium hidroksida untuk memberi natrium metaborate (NaBO 2 ) yang kemudian direaksikan dengan hidrogen peroksida untuk memberikan natrium perborate terhidrasi.
- Na 2 B 4 O 7 2 NaOH -> 4 NaBO 2 H 2 O
Sodium perborate is useful because it is a stable source of anion peroxide. When dissolved in water form several hydrogen peroxide, but also an anion perborata (B (OOH) (OH) 3 - ), which is activated for nucleophilic oxidation.
Other bleach
Peracetic acid and ozone are used in the manufacture of paper products, especially newsprint and white Kraft paper. In the food industry, some organic peroxides (benzoyl peroxide, etc.) and other agents (eg, bromates) are used as bleach flour and ripening agents.
Reduce bleaching
Sodium dithionite (also known as sodium hydrosulfite ) is one of the most important reducing bleaching agents. It is a white crystalline powder with a weak sulfur smell. This can be obtained by reacting sodium bisulfite with zinc
- 2 NaHSO 3 Zn -> Na 2 S 2 O 4 Zn (OH) 2
It is used as in some industrial dyeing processes to remove excess dyes, residual oxides, and unwanted pigments and for bleaching wood pulp.
Reaksi sodium ditionit dengan formaldehyde menghasilkan Rongalite,
used in the bleaching of wood pulp, cotton, wool, leather and clay.
Environmental impact
A RAR report conducted by the European Union on sodium hypochlorite conducted under EEC Regulation 793/93 concluded that this substance is safe for the environment in all current normal use. This is because of its high reactivity and instability. The loss of hypochlorite is practically direct in a natural aquatic environment, achieving in short time concentrations as low as 10 -22 ? G/L or less in all emissions scenarios. In addition, it was found that while volatile chlorine species may be relevant in some indoor scenarios, they have negligible impacts in open environment conditions. Furthermore, the role of hypochlorite pollution is assumed to be negligible in the soil.
Bleaching agents industry can also be a source of concern. For example, the use of chlorine elements in bleaching wood pulp produces organochlorines and persistent organic pollutants, including dioxins. According to industrial groups, the use of chlorine dioxide in this process has reduced the generation of dioxin to a level that can be detected. However, the respiratory risk of chlorine and chlorine by-products is highly toxic.
A recent European study showed that sodium hypochlorite and organic chemicals (eg, surfactants, fragrances) contained in some household cleaning products can react to produce chlorinated volatile organic compounds (VOCs). This chlorinated compound is emitted during cleaning applications, some of which are toxic and possible human carcinogens. This study showed that indoor air concentrations increased significantly (8-52 times for chloroform and 1-1170 times for carbon tetrachloride, respectively, above the baseline quantity in the household) during use of bleach-containing products. Increased concentrations of chlorinated volatile organic compounds are the lowest for plain bleach and the highest for products in the form of "thick liquid and gel". Significant improvements observed in indoor air concentrations of some chlorinated VOCs (especially carbon tetrachloride and chloroform) suggest that the use of bleach may be a potentially important source of inhalation exposure to these compounds. Although the authors suggest that using these cleaning products may increase cancer risk significantly, this conclusion appears to be hypothetical:
-
- The highest level mentioned for the concentration of carbon tetrachloride (which seems most important) is 459 micrograms per cubic meter, translated to 0.073 ppm (parts per million), or 73 ppb (parts per billion). The weighted average concentration of OSHA time allowed during the eight hour period is 10 ppm, almost 140 times higher;
- The highest peak concentration allowed by OSHA (5 minutes exposure for five minutes in a 4 hour period) was 200 ppm, twice as high as the highest peak rate reported (from the main room of the bleach sample bottle plus detergent)).
Disinfection
Sodium hypochlorite solution, 3-6%, (ordinary household bleach) is usually diluted for safe use when disinfecting surfaces and when used to treat drinking water.
The weak solution of 2% household bleach in warm water is typical to clean the smooth surface before brewing a beer or wine.
The US Government Regulation (21 CFR Part 178) allows food processing equipment and food contact surfaces to be cleaned with a bleach-containing solution, provided that the solution is allowed to flow sufficiently before contact with food, and that the solution does not exceed 200 parts per million (ppm) of available chlorine ( for example, one tablespoon of typical household bleach containing 5.25% sodium hypochlorite, per gallon of water).
Dilution of 1-in-5 household bleach with water (1 part bleach to 4 parts water) is effective against many bacteria and some viruses, and often a disinfectant of choice in cleaning surfaces in hospitals (especially in the United States). Even "scientific-class", commercially produced disinfection solutions such as Virocidin-X usually have sodium hypochlorite as their only active ingredient, although they also contain surfactants (to prevent beading) and fragrances (for hide bleach odor).
See Hypochlorous acid for a discussion of the mechanisms for disinfecting action.
Treatment of gingivitis
Sodium hypochlorite dilute at the level of 2000-1 (0.05% concentration) can represent a efficacious, safe and affordable antimicrobial agent in the prevention and treatment of periodontal disease.
Secure bleach color
Safe color bleach is a chemical that uses hydrogen peroxide as an active ingredient (to help remove stains) rather than sodium hypochlorite or chlorine. It also has chemicals in it that help brighten the color. Hydrogen peroxide is also used for sterilization and water treatment purposes, but the ability of disinfectants may be limited because of the concentration in the bleach solution of color compared to other applications.
See also
- Teeth whitening
References
Further reading
- Bodkins, Dr. Bailey. Bleach . Philadelphia: Virginia Printing Press, 1995.
- Trotman, E.R. Scouring and Textile Bleaching . London: Charles Griffin & amp; Co., 1968. ISBNÃ, 0-85264-067-6.
External links
- Bleach at Britannica
- Bleach (MSDS)
Source of the article : Wikipedia
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