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Phototransformation in air

The atmospheric oxidation potential (AOP) predicted from the Epiwin program indicates that cyanuric chloride is not photolytically reactive (degradation half-life of > 15 year).


Measurements revealed a fast and stepwise hydrolysis of cyanuric chloride. The intermediate and final degradation products of cyanuric chloride were identified as 2,4-dichlor-6-hydroxy-1,3,5-triazine (first intermediate, DT50(pH 7.0, T=298.15 K = 0.52 h = 31.5 min), 2-chlor-4,6-dihydroxy-1,3,5-triazine (also named 6-chloro-1,3,5-triazine-2,4(1H,3H)-dione, sodium salt) (second intermediate, CAS no.: 32998-00-8, DT50 (pH 7.0, T=298.15 K)= 3.98 h =239.0 min ) and cyanuric acid (final degradation product, CAS no: 108 -80-5), respectively.

In this non guideline study the half-times for the first hydrolysis step of cyanuric chloride were determined to be

- DT50(pH 2.0, T=298.15 K = 1.2 min

- DT50 (pH 4.0, T=313.15 K)= 1.65 min

- DT50(pH 7.0, T= 298.15 K) = 3.47 min.

The rates of hydrolysis rise significantly for all three steps at acidic medium and are slower at basic pH (for T = constant).

The activation energy is idependent from pH and equal for the three hydrolysis steps.

Phototransformation in water

Cyanuric acid (concantration: ca. 275 mg/L) was treated both with UV radiation and with UV-irradiated H2O2. After 30 minutes treatment the concentration of the the test item (cyanuric acid) that was treated with UV radiation and with UV-irradiated H2O2 was determined to be ca. 225 mg/L and ca. 275 mg/L, respectively. Since these concentrations do not differ strongly from the initial test item concentration, photodegradation of the test item is not considered.