Peracetic acid, 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 pKa of 8.2.
Production Peracetic acid is produced industrially by
the autoxidation of acetaldehyde: 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:
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 in the presence of an alkaline hydrogen peroxide
solution. The peracetic acid is a more effective bleaching agent than hydrogen peroxide itself.
PAA is also formed naturally in the environment through a series of photochemical reactions
involving formaldehyde and photo-oxidant radicals. 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. 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. Epoxidation
Although less active than more acidic peracids, 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. 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 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. The ACGIH has published 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 for peracetic acid. In comparison, the OSHA PEL for hydrogen peroxide
is 1.0 ppm. 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 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.
See also Disinfection
Hydroxyl Organic peroxide
Peroxy acid Cetophenicol
References