The peracetic acid is a liquid organic compound whose chemical formula is CtwoH4OR3. It is the peroxide of acetic acid, which is why it is also known as peroxyacetic acid. Its molecule is similar to that of acetic acid CH3COOH but with an additional oxygen on the carboxyl.
It belongs to the class of organic peroxides, which are man-made molecules. The germicidal and sterilizing properties of its aqueous solutions have been known since 1902. This action can in some cases be exerted at concentrations as low as 0.001%..
This property makes it widely used in clinics and hospitals to sterilize medical equipment, with the additional advantage that its decomposition products are not toxic to humans..
PAA solutions are strongly oxidizing, a characteristic that has been used to bleach paper pulp or in laundries. It is also applied for the execution of chemical reactions in which this property is required, such as epoxidation and hydroxylation..
Its oxidizing and disinfectant action is used in cleaning equipment where food and beverages are processed. In addition, it is corrosive to some metals and when stored it must be kept away from organic or easily oxidizable compounds..
Note that its concentrated solutions can be explosive, which is why it should preferably be prepared diluted and stored in cold places. Its corrosive force also applies to human skin, mucosa and tissues, so it must be handled with caution and with protective equipment.
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Peroxyacetic acid has a molecule very similar to acetic acid but with an additional oxygen in the structure of the -COOH group, since it has 3 oxygen atoms instead of two.
- Peracetic acid
- Peroxyacetic acid
- Ethanoperoxoic acid
- PAA PeroxiAcetic Acid).
Clear colorless liquid with a pungent vinegar odor.
76.05 g / mol
110 ºC (with explosion)
40.5 ºC (open cup method)
200 ºC (it is the temperature at which it burns spontaneously)
1,226 g / cm3 at 15 ºC
3,280 cP at 25.6 ° C
1.3974 at 20 ºC
It is miscible with water in any proportion. It is soluble in polar organic solvents, such as ethanol. Slightly soluble in aromatic solvents. Very soluble in ether and sulfuric acid.
Less than 2.
pKto = 8.20 at 25 ºC (it is weaker than acetic acid that has pKto = 4.8)
As an acid, PAA is much weaker than the acid from which it comes, acetic acid..
It has a high potential as an oxidant. It is highly reactive making it difficult to store and this has limited its use..
Its degradation products are acetic acid CH3COOH, oxygen Otwo, hydrogen peroxide HtwoORtwo and water HtwoO. The HtwoORtwo in turn it degrades to water and oxygen. All of these compounds are environmentally safe.
It is an epoxidizing and hydroxylating agent for olefinic bonds (C = C double bonds). This means that it actively participates in the formation of epoxides in double bonds of organic molecules and in the addition of -OH groups in these..
PAA is corrosive to some metals such as smooth steel, galvanized iron, copper, brass, and bronze. Other metals are resistant such as stainless steel, pure aluminum and tinned iron.
Attacks synthetic and natural rubbers and extracts the plasticizer from some vinyl polymers.
It has a pungent and pungent odor reminiscent of acetic acid (acetic acid is the main component of vinegar).
By reacting glacial acetic acid (anhydrous, i.e. without water) with hydrogen peroxide HtwoORtwo in the presence of a mineral acid (such as sulfuric acid HtwoSW4), part of the acetic acid is oxidized and aqueous solutions of peracetic acid, acetic acid and H are obtainedtwoORtwo.
The HtwoSW4 acts as a catalyst or accelerator of the reaction. Stabilizing agents are used, such as pyridine-2,6-dicarboxylic acid.
If these solutions are distilled, a higher concentration of peracetic acid can be obtained..
It can also be obtained by oxidation of acetaldehyde CH3CHO with ozone O3, or by reaction of acetic anhydride (CH3CO)twoOr with HtwoORtwo.
Another way to get it right where it is needed is by adding tetra-acetyl-ethylenediamine (TAED) to an alkaline solution of HtwoORtwo.
PAA acts as a disinfectant for medical equipment in clinics, hospitals, medical and dental offices.
Some sources report that its action against microorganisms can be classified in a general way as follows: bacteria> viruses> bacteria spores> protozoan cysts. This means that it is more effective against bacteria and less effective against protozoan cysts..
In studies carried out on the bactericidal action of PAA and other high-level disinfectants against Staphylococcus aureus Y Pseudomonas aeruginosa in endoscopy equipment, PAA proved to be the fastest in its microbicidal effect.
The Staphylococcus aureus It can cause soft tissue infections, skin infections, pneumonia, and heart tissue infection. The Pseudomonas aeruginosa can lead to pneumonia.
Bacteria form biofilms that protect them from external stimuli or stress, through a thick layer of extracellular proteins, polysaccharides and nucleic acids..
These biofilms are highly resistant to common antibiotics and disinfectants. In equipment such as endoscopes, they tend to form in the narrow channels of these, due to inadequate or ineffective cleaning and disinfection routines.
PAA attacks these biofilms probably by oxidation of the more sensitive molecular bonds of proteins, enzymes and other metabolites. This leads to the breakdown of the cell walls of germs, their spores and cysts..
In addition, by penetrating into the cell PAA can oxidize essential enzymes, impairing the transport of molecules and vital biochemical processes.
Disinfection times have been established for some years, but during certain studies it was observed that treatment with PAA caused changes in the shape of cells after only 5 minutes, with the formation of pockets or bulges in the cell wall of the cells. bacteria, and collapse of the cellular structures of the microorganisms after 30 minutes.
Although the PAA stood out for its speed, the researchers have recommended re-evaluating the times established in the cleaning and disinfection protocols, increasing them for most high-level antiseptics, to ensure their total effectiveness..
One of the negative aspects of PAA is that there are some pathogens against which it is not very effective, such as cysts of the Giardia lamblia and of Cryptosporidium parvum (parasites that can cause diarrhea or other intestinal conditions).
The disinfecting effect of PAA in municipal or industrial wastewater effluents has been investigated for more than 30 years.
Among its advantages is the broad spectrum of its germicidal activity even in the presence of organic matter, as well as the fact that it does not generate secondary products that are harmful to the environment..
The effectiveness of its action seems to depend, among other factors, on the amount of organic matter present in the effluent, the type and amount of microorganisms to be eliminated, the PAA concentration in the water to be treated, the pH and the duration of the treatment..
In some cases, PAA has been shown to be better than sodium hypochlorite for disinfecting wastewater in tropical climates and has been effective against the cholera virus, among many other pathogens..
However, one of the negative points is that due to the acetic acid remaining after disinfection, the water effluent is loaded with organic matter, which increases the risk of new growth of microorganisms..
On the other hand, it is an expensive product, so it is not yet very competitive, for example with sodium hypochlorite due to this aspect..
Because it is a strong oxidizing agent, it is very effective against microorganisms at low temperatures and this has led to its wide use as a bactericide and fungicide in food and beverage processing..
This includes meat and poultry processing plants, dairy, breweries, wineries or wineries, and soft drink manufacturing plants. In all these places the PAA is applied because it is ideal for cleaning in situ (in the place).
Enzymes found in some foods such as peroxidase and catalase, which deactivate hydrogen peroxide HtwoORtwo, they have no harmful effect on peracetic acid. Protein residues don't hurt you either.
Due to the fact that PAA in food breaks down into acetic acid and hydrogen peroxide, it is considered safe for use in applications where food is not rinsed..
It serves as a disinfectant and sterilant for stainless steel and glass tanks, pipes and tanker trucks, which serve for the transport and storage of beverages.
Its characteristic of generating non-toxic products and that in high dilution they do not produce flavors or odors, constitute time and money savings for these industries..
Peracetic acid is an important chlorine-free agent in bleaching technology in the paper pulp industry..
Some authors consider peracetic acid as an activated derivative of HtwoORtwo, where one of the hydrogens of this has been replaced by an acyl group CH3C (= O)-.
As a result of this, peracetic acid reacts with organic substrates to a greater degree than HtwoORtwo and that it can be used in oxidation reactions under more moderate conditions than with HtwoORtwo.
Under neutral or moderately alkaline conditions the peracetate ion CH3C (= O) OO- being a strong nucleophile (attracted by electron-deficient atoms), it selectively removes chromophores or colored compounds present in paper pulp.
This allows these industries to have a very effective bleach and whose residues do not contaminate their aqueous effluents..
Peracetic acid serves as an oxidant to prepare epoxy compounds, as a catalyst to make polyester resins and to obtain caprolactam and glycerol.
Some researchers have managed to recover useful materials by treating certain polymeric wastes with PAA solutions..
The process is carried out by oxidation of certain carbon fiber reinforced polymer waste from aerospace activities, with solutions of glacial acetic acid and hydrogen peroxide.
In this way, peracetic acid is generated. in situ, which breaks down the epoxy resin by 97% leaving the carbon fiber intact.
Then, by distillation, more than 90% of the acetic acid is recovered, resulting in further decomposition of the polymer that generates recoverable aliphatic and phenolic compounds..
Carbon fiber is obtained clean, and maintains its length and tensile strength comparable to virgin fibers.
The process is carried out under mild conditions, without gaseous emissions, which makes it environmentally friendly.
Due to its oxidizing power of colored compounds, peracetic acid is used in laundry bleaching. In these cases, the mixture of tetra-acetyl-ethylenediamine with HtwoORtwo in alkaline medium to obtain it on site.
Its range of application is very wide, as it can be used in hard waters or those containing a high proportion of calcium and magnesium salts, at pH between 3.0 and 7.5 and temperatures of 0 to 40 ºC..
Peracetic acid or PAA can be highly corrosive. It is strongly irritating to the skin and eyes.
If its solutions are ingested, it causes corrosion of the mucous membranes of the mouth, throat, esophagus and gastrointestinal tract, causing pain and difficulty in swallowing..
If its vapors are inhaled, irritation of the respiratory tract occurs and if inhalation is prolonged, edema in the lungs occurs..
Solutions containing more than 15% PAA begin to exhibit some degree of instability and explosiveness and shocks or shaking should be avoided. They can decompose explosively. If the concentration of PAA in solution exceeds 56% it can detonate due to the violent evaporation of acetic acid.
Heat should be avoided. It is considered a flammable liquid. Its decomposition is violent with an explosion at 110 ºC. It should be stored in cool places, preferably under refrigeration, or in very well ventilated places..
It is strongly oxidizing, therefore dangerous in contact with organic materials. When stored, it must be isolated from other compounds, especially organic, combustible, flammable or oxidizable compounds. It must be separated from acids, alkalis and heavy metals.
When heated to decomposition, it emits acrid and irritating fumes, which irritate eyes, nose and throat..
If spilled, it should not be allowed to flow into drains as they create a fire or explosion hazard..
As preventive measures for handling, we recommend rubber gloves and protective clothing, a face shield or eye protection (glasses or safety glasses), respiratory protection and do not eat, drink, or smoke while working with their solutions..
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