Peracetic acid

Peracetic acid (also known as peroxyacetic acid, or PAA), is an organic compound with the formula CH₃CO₃H. This organic peroxide is a colorless liquid with a characteristic acrid odor reminiscent of acetic acid. It can be highly corrosive.

Peracetic acid is a weaker acid than the parent acetic acid, with a pK_a of 8.2.^[1]

Production

Peracetic acid is produced industrially by the autoxidation of acetaldehyde:^[1]

O₂ + CH₃CHO → CH₃CO₃H

It forms upon treatment of acetic acid with hydrogen peroxide, with the equilibrium constant dependent on the concentrations and conditions of reaction:^[2]

H₂O₂ + CH₃CO₂H

CH₃CO₃H + H₂O

As an alternative, acetyl chloride and acetic anhydride can be used to generate a solution of the acid with lower water content.

Peracetic acid is generated in situ by some laundry detergents. This route involves the reaction of tetraacetylethylenediamine (TAED) in the presence of an alkaline hydrogen peroxide solution. The peracetic acid is a more effective bleaching agent than hydrogen peroxide itself.^[1]^[3] PAA is also formed naturally in the environment through a series of photochemical reactions involving formaldehyde and photo-oxidant radicals.^[4]

Peracetic acid is always sold in solution with acetic acid and hydrogen peroxide to maintain the stability of the peracid. The concentration of the acid as the active ingredient can vary.

Uses

The United States Environmental Protection Agency first registered peracetic acid as an antimicrobial in 1985 for indoor use on hard surfaces. Use sites include agricultural premises, food establishments, medical facilities, and home bathrooms. Peracetic acid is also registered for use in dairy/cheese processing plants, on food processing equipment, and in pasteurizers in breweries, wineries, and beverage plants.^[5] It is also applied for the disinfection of medical supplies, to prevent bio film formation in pulp industries, and as a water purifier and disinfectant. Peracetic acid can be used as a cooling tower water disinfect, where it prevents bio film formation and effectively controls Legionella bacteria. A trade name for peracetic acid as an antimicrobial is Nu-Cidex.^[6]

Epoxidation

Although less active than more acidic peracids (e.g., MCPBA), peracetic acid in various forms is used for the epoxidation of various alkenes. Useful application are for unsaturated fats, synthetic and natural rubbers, and some natural products such as pinene. A variety of factors affect the amount of free acid or sulfuric acid (used to prepare the peracid in the first place).^[1]

Niche uses

Peracetic acid will oxidize many metals, and is used for cleaning or creating a patina for artistic or protective purposes.

Safety

Peracetic acid is a strong oxidizing agent (E = 1.762 V vs Ag/AgCl)^[7] and a primary irritant. Exposure to peracetic acid can cause irritation to the skin, eyes and respiratory system and higher or long-term exposure can cause permanent lung damage. In addition, there have been cases of occupational asthma caused by peracetic acid.^[8] The ACGIH has published (spring 2014) a STEL TLV for peracetic acid of 0.4 ppm, calculated as a 15 minute time weighted average. Currently there is no US-OSHA permissible exposure limit for peracetic acid. In 2010, the US-EPA published Acute Exposure Guidelines (AEGL) for peracetic acid.

eight-hour TWA AEGL	Definition	mg/m³	ppm
1	The concentration at which the general population will experience transient and reversible problems, such as notable discomfort, irritation, or certain asymptomatic non-sensory effects.	0.52	0.17
2	The concentration that results in irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.	1.6	0.52
3	The concentration that results in life-threatening health effects or death	4.1	1.3

In comparison, the OSHA PEL for hydrogen peroxide (8 hour TWA) is 1.0 ppm.^[9] Peracetic acid has found widespread use in healthcare, food processing, and water treatment because of its broad antimicrobial properties. In order for employers to meet the ACGIH STEL TLV and comply with the General Duty Clause^[10] to provide a safe work environment, it is recommended that facilities using peracetic acid solution employ continuous monitors to provide an alert to employees if the concentration exceeds safe levels. This monitor is designed and installed so that it can automatically turn on additional ventilation as needed.

Concentrated peroxyacetic acid, an organic peroxide, explodes at 110 °C.

References

↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Herbert Klenk, Peter H. Götz, Rainer Siegmeier, Wilfried Mayr (2005), "Peroxy Compounds, Organic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a19_199
↑ RANGARAJAN, B., HAVEY, A., GRULKE, E. & CULNAN, P. D. 1995. Kinetic parameters of a two-phase model forin situ epoxidation of soybean oil. Journal of the American Oil Chemists’ Society, 72, 1161-1169.
↑ United States Department of Agriculture. Agriculture Marketing Service Peracetic acid. (PDF document). URL accessed on 11 November 2006.
↑ U.S. National Library of Medicine. Hazardous Substances Data Bank. URL accessed on 11 November 2006.
↑ U.S. Environmental Protection Agency. Hydrogen Peroxide and Peroxyacetic Acid. URL accessed on 11 November 2006.
↑ Lynam, P. A.; Babb, J. R.; Fraise, A. P. (1995). "Comparison of the mycobactericidal activity of 2% alkaline glutaraldehyde and 'Nu-Cidex' (0.35% peracetic acid)". The Journal of hospital infection 30 (3): 237–240. PMID 8522783.
↑ Awad, Mohamed Ismail; Denggerile, Ao; Ohsaka, Takeo (2004). "Electroreduction of Peroxyacetic Acid at Gold Electrode in Aqueous Media". Journal of the Electrochemical Society 151: E358. doi:10.1149/1.1812733.
↑ E.C. Marquand et al. (2007). "Asthma Caused by Peracetic Acid-Hydrogen Peroxide Mixture". J. Occup. Health 49 (2): 155–158.
↑ 29 CFR 1910.1000 Table Z-1
↑ US – Occupational Safety and Health Act (1970), sec. 5