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Environmental fate & pathways

Hydrolysis

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Description of key information

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.

Key value for chemical safety assessment

Half-life for hydrolysis:
31.7 h
at the temperature of:
25 °C

Additional information

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 (Anonymous, 1995).

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).