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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Based on the currently available data on hydrolysis and biodegradation are imidazolines quickly hydrolyzed to amidoamines under ambient conditions. The (micro-organism mediated) hydrolysis of these amidoamines is probably the rate determining step. After breaking of the amido bond the substance is completely degraded to H2O, CO2 and the starting polyethyleneamine, with exception of DETA which is also completely biodegraded.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

Imidazoline DETA

Fatty acid C18 unsaturated diethylenetriamine imidazoline may be biocidal to micro-organisms and consequently inhibitory in all ready biodegradability tests. Reduction of the toxicity of fatty amine derivatives in ready biodegradability tests has therefore been achieved through the addition silica gel (van Ginkel et al, 2008). For toxic substances, the specified high test substance concentrations in ready biodegradability tests are controversial because substances are present in the environment in the sub μg/L range. Fatty acid C18 unsaturated diethylenetriamine imidazoline tested in the presence of silica gel was biodegraded 24% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test Fatty acid C18 unsaturated diethylenetriamine imidazoline was biodegraded 61% at day 60 (Akzo Nobel, 2010). The bio­degradation reached at the day 60 demonstrates that Fatty acid C18 unsaturated diethylenetriamine imidazoline is ultimately biodegradable and not persistent. In another Closed Bottle test a biodegradation of 17 % was reached at day 28 (Arkema, 2009). 

Complete (ultimate) degradation of tall oil diethylenetriamine imidazoline was also found in a semi continuously fed activated sludge (SCAS) test (van Ginkel et al, 2010). In this test removal percentages of organic carbon of >90% were achieved. Complete degradation of Fatty acids C18 unsat. diethylenetriamine imidazoline can also be concluded from the ready biodegradability of fatty acids and diethylenetriamine formed upon hydrolysis (Popp, 1977; van Ginkel et al 1995)

 

Imidazoline PEPA

In the semi-continuously-fed activated sludge (SCAS) test removal percentages of 100% were immediately accomplished for Fatty acids C18 unsaturated reaction products with polyethylenepolyamines. Removal percentages decreased to approximately 80% after a few weeks. This removal percentage was maintained throughout the remaining test period of more than 300 days. The ability of micro-organisms to completely biodegrade Fatty acids C18 unsaturated reaction products with polyethylenepolyamines may be demonstrated in a Closed Bottle test with adapted sludge from the SCAS unit (Table II).  In this test, 35 and 38% biodegradation was achieved after 28 and 56 days, respectively. The result in the SCAS test and Closed Bottle tests demonstrate that fFatty acids C18 unsaturated reaction products with polyethylenepolyamines are only partially degraded (van Ginkel et al, 2010).

Biodegradation percentages of <60% were always found in ready biodegradability test also showing that Fatty acids C18 unsaturated reaction products with polyethylenepolyamines are not ultimately biodegradable (IVL 1983; van Ginkel et al 2010). Partial degradation is attributed to the oxidation of the alkyl chains and the inability of microorganisms to grow on polyethylenepolyamines (necessary to acquire positive results in OECD test). The alkyl chains (fatty acids) linked with an amide bond to the polyethylenepolyamines is thought to be degraded after an initial biologically catalysed hydrolysis. Alkyl chains attached to the imidazoline ring are probably liberated as fatty acid after an initial chemical hydrolysis of the imidazoline ring followed by hydrolysis of the amide bond. Amide bonds are in general very easily cleaved by amidases present in the competent microorganisms. Fatty acids C18 unsaturated reaction products with polyethylenepolyamines are as a consequence readily converted into carbon dioxide, water and polyethylenepolyamines. Polyethylenepolyamines cannot be degraded in OECD 301 and 302 tests and are therefore considered to be persistent. It can however be concluded that Fatty acids C18 unsaturated reaction products with polyethylenepolyamines (parent compounds) are readily biodegradable. In other words, the alkyl chain of Fatty acids C18 unsaturated reaction products with polyethylenepolyamines is readily biodegradable.