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EC number: 201-186-8
CAS number: 79-21-0
Degradation half-life values: (0.001 mol/L = 95 mg/L; 25 °C): 48 or 46.7 (pH 4), 48 or 31.7 (pH 7) and 3.6 hours (pH 9)
Between pH 5.5 and 8.2, hydrolysis is negligible and peracetic acid degradation is mainly due to spontaneous decomposition (maximum at pH 8.2, which is equivalent to the pKa of peracetic acid). Between pH 8.2 and 9.0, the peracetic acid consumption is due to spontaneous decomposition and hydrolysis. Above pH 10.5, spontaneous decomposition is negligible and hydrolysis becomes dominant.
Hydrolysis of peracetic acid is strongly pH-dependent, which was found
in the study on abiotic degradation according to EU method C.7, where
degradation half-life values for peracetic acid (0.001 mol/L) were 48,
48 and 3.6 hours at temperature of 25 °C and at pH of 4, 7 and 9,
respectively, assuming a pseudo-first order kinetics. Additional
performed recalculation using the First Order Multi-Compartment model
revealed even lower values (46.7, 31.7 h at pH 4 and 7, respectively;
insufficient data points at pH 9). The study indicates that peracetic
acid is rapidly degraded in the environment and that decomposition is
faster at low concentrations and high pH values.
In a study by Yuan (1997), hydrolysis of peracetic acid is found to be
negligible between pH 5.5 and 8.2 where it mainly decomposes
spontaneously (maximum at pH 8.2, equivalent to the pKa of peracetic
acid). Between pH 8.2 and 9.0, the peracetic acid degradation is due to
spontaneous decomposition and hydrolysis. Above pH 10.5, spontaneous
decomposition is negligible and hydrolysis becomes dominant.
Other available data showed comparable values and a strong pH and
concentration-dependency for the degradation of peracetic acid
As a conclusion, the DT50 of 31.7 h at pH 7 determined for the peracetic
acid concentration of 95 ppm, was selected as input parameter for the
environmental exposure assessment (degradation in surface water).
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