Peracetic Acid


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Peracetic Acid

  1. 1. Peracetic Acid Background Since early 1900s chlorine is being used as water disinfectant. It was favorite to the industries like water and wastewater for disinfection until several harmful disinfection by-products (DBPs) in chlorinated water was discovered. Since then the water community started looking for alternative disinfectant such as ozone, UV, PAA, and Hydrogen Peroxide (HP)etc. Disinfection by-products (DBPs) form when organic and mineral materials in water react with chemical treatment agents when disinfecting water. For example Trihalomethanes (THMs) (haloforms), Haloacetic acids and and many others. Trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane (CH4) are replaced by halogen atoms. THMs are also environmental pollutants, and many are considered carcinogenic. Trihalomethanes with all the same halogen atoms are called haloforms. Molecular Formula IUPAC name Common name CHF3 trifluoromethane Fluoroform CHCl3 trichloromethane Chloroform CHBr3 tribromomethane Bromoform CHI3 triiodomethane Iodoform Currently chlorine is proven to be the main source for causing several harmful disinfection by products (DBPs). Studies are being done to find and eliminate the DBPs precursors and look for the alternative disinfectant. PAA, mostly known as a water & wastewater disinfectant in European countries, because of its similar disinfection abilities to chlorine, without producing any harmful DBPs. The Peracetic Acid (PAA) is a chemical product belonging to the peroxide compounds as Hydrogen Peroxide (HP). But unlike HP, it is a more potent antimicrobial agent, being rapidly active at low concentrations against a wide spectrum of microrganism. It is sporicidal even at low temperatures and it remains effective also in the presence of organic matter. Peracetic Acid has high germicidal efficiency and sterilizant capability and his degradation residuals are not dangerous for environment or toxic for human health. Until 1960 it has a little application; though, from these years the Peracetic Acid has found special interests in the food processing industry, and actually is considered the only agent able to replace the glutaraldehyde in the surgical, medical and odontoiatric instruments sterilization. The core of actual medical applications of Peracetic Acid is its potent antimicrobial action, also at low temperatures, and the total absence of toxic residuals. Physical and Chemical Properties Peracetic acid (also known as peroxyacetic acid, or PAA), is a organic peroxide, explodes at 110 C. It should be is transported and stored in diluted solutions to prevent explosions. 1
  2. 2. Molecular CH3COOOH formula Molar mass 76.05 g/mol Appearance Colorless liquid Odor Strong like vinegar Density and phase 1.13 g/ml, liquid Solubility in water 10 g/100 ml (19 °C) Boiling point 105°C Production There are several methods to produce peracetic acid. 1. PAA is produced by reacting acetic acid and hydrogen peroxide. The reaction is allowed to continue for up to ten days in order to achieve high yields of product according to the following equation: 2. An additional method of preparation is the oxidation of acetaldehyde. 3. Alternatively, it is produced as an end product of the reaction of acetic anhydride, hydrogen peroxide, and sulfuric acid. 4.Recently a solid powdered form of PAA involves the reaction of TAED in the presence of an alkaline hydrogen peroxide solution. Mechanism of the perhydrolysis 2
  3. 3. On dissolving the persalts (percarbonates) in water, Hydrogen peroxide is released, which rapidly dissociates under the alkaline conditions of the washing liquor. The formation of perhydroxyl anions necessary for the perhydrolysis stage is promoted by a high pH value. Two molecules of peracetic acid are released by nucleophilic attack of the OOH– ions on the instable imide bonds of the TAED molecule . Since the perhydrolysis takes place much more quickly than a hydrolysis reaction, this side reaction can be largely excluded, providing the pH value is below 11. Mechanism of action PAA kills microorganisms by oxidation and subsequent disruption of their cell membrane, via the hydroxyl radical (OH·). As diffusion is slower than the half-life of the radical, it reacts with any oxidizable compound in its vicinity. It damages virtually all types of macromolecules associated with a microorganism: carbohydrates, nucleic acids (mutations), lipids (lipid peroxydation) and amino acids. The mechanism of oxidation is the transfer of electrons, therefore the strong oxidizer will produce faster killings or inactivation of the microorganism. The primary mode of action is oxidation. PAA disinfects by oxidizing of the outer cell membrane of vegetative bacterial cells, endospores, yeast, and mold spores. The mechanism of oxidation is the transfer of electrons, therefore the stronger the oxidizer, the faster electrons are transferred to the microorganism and the faster the microorganism is inactiviated or killed. It has also been reported to be virucidal. Oxidation Capacity of Selected Sanitizers Sanitizer eV* Ozone 2.07 Peracetic Acid 1.81 Chlorine Dioxide 1.57 Sodium Hypochlorite (chlorine bleach) 1.36 *electron-Volts 3
  4. 4. Therefore PAA has a higher oxidation potential than chlorine sanitizers but less than ozone. Application EPA had registered PAA as an antimicrobial in 1985 for indoor use on hard surfaces. It is being used in following industries as disinfectant: • Meat, Poultry, Seafood, processing and packaging plants. • Food processing industries. • Hospitals and Healthcare facilities as sterilant. • Paper and pulp Industries. • Water and wastewater industries • Plumbing disinfectant. • Water reuse applications such as cooling tower water disinfectant where it prevents bio film formation and effectively controls Legionella bacteria. Advantages: • No mutagenic DPBs. The absence of persistent toxic or mutagenic residuals or by- products. The disinfection end products like carboxylic acids and water are harmless to humans. • Synergic effect of PAA and UV has greater effects (can save lot of cost caused by using PAA alone). • No alteration in disinfection tank required. • pH, hardness, and presence of organic matters has no or little effect on biocidal activity of PAA. • Easy implementing treatment (without the need for expensive capital investment) • Broad spectrum of activity even in the presence of heterogeneous organic matter • No quenching requirement (i.e., no dechlorination) • Short contact time Conclusion: There are no doubts about PAAs bactericidal, virucidal, fungicidal abilities. Usages in food processing and medical facilities itself is a kind of approval of harmless end products. The cost factor (production, storage and transportation) can be reduce by local manufacturing and a much stable percentage of quaternary solution of PAA (PAA, Acetic acid, H2O2 and Water). Furthermore powdered non-active peracetic acid based disinfectants change the cost factor. Storage and transportation is not problem anymore. 4