1-Ethyl-3-methylimidazolium benzoate

Biodegradation in water: screening tests

Description of key information

not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

No data on the biodegradability of 1H-imidazolium, 3-ethyl-1-methyl-, benzoate are available. However, the test substance is an ionic liquid and dissolves in water to its ionic components benzoate and 3-ethyl-1-methyl-imidazolium. There are studies available which evaluate the biodegradability of these single ionic components. Those were assessed in a WoE appraoch and further described below.

The ready biodegradability of 1 -ethyl-3-methyl imidazolium chloride was examined in a test according to the OECD 301 A (Ready Biodegradability: DOC Die Away Test) (BASF SE, 2003). The biodegradation of the test substance was followed by exposing it to the non-adapted, activated sludge of a municipal waste water treatment plant. The activated sludge concentration was 30 mg/L/dry weight. An inoculum blank and a reference substance control were conducted in parallel. After 28 days, the test substance was biodegraded by an average of ~ 10 % CO2, therefore the test substance was found to be not readily biodegradable under the test conditions.

The ready biodegradability of 1-ethyl-3-methyl imidazolium sulfate was examined in a test according to the OECD 301 B (Ready Biodegradability: CO2 Evolution Test) (NOTOX, 2005). The biodegradation of the test substance was followed by exposing it to the activated sludge of a municipal waste water treatment plant (Waterschap de Maaskant, 's-Hertogenbosch, Netherlands). The activated sludge concentration was 4.5 g/L/dry weight. An inoculum blank, a toxicity control and a reference substance (acetic acid, sodium salt) control were conducted in parallel. After 29 days, the test substance was biodegraded by an average of < 10 % CO2, therefore the test substance was found to be not readily biodegradable under the test conditions.

The ready biodegradability of 1-ethyl-3-methyl imidazolium sulfate was additionally examined in a test according to the OECD 301 F (Ready Biodegradability: Manometric Respirometry Test) (BASF SE, 2014). The biodegradation of the test substance was followed by exposing it to the non-adapted activated sludge of a municipal waste water treatment plant (Liede Sewage Treatment Plant of Guangzhou, China). The activated sludge concentration was 3.7 g/L/dry weight. An inoculum blank, a toxicity control and a reference substance (benzoic acid, sodium salt) control were conducted in parallel. After 28 days, the test substance was biodegraded by an average of > 10 - < 20 % CO2, therefore the test substance was found to be not readily biodegradable under the test conditions.

The inherent biodegradability of 1-ethyl-3-methyl imidazolium sulfate was examined in a test according to the OECD 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test) (BASF SE, 2011). The biodegradation of the test substance was followed by exposing it to the non-adapted activated sludge of a municipal waste water treatment plant (Liede Sewage Treatment Plant of Guangzhou, China). The activated sludge concentration was 4.0 g/L/dry weight. An inoculum blank, an abiotic sterile control, a toxicity control and a reference substance (diethylene glycol) control were conducted in parallel. After 28 days, the test substance was biodegraded by an average of < 30 % CO2, therefore the test substance was found to be not inherently biodegradable under the test conditions.

The readily biodegradability of sodium benzoate was examined in a test according to the OECD 301 D (Ready Biodegradability: Closed Bottle Test) (BASF SE, 1998). The biodegradation of the test substance was followed by analysis of dissolved oxygen over a 30-day period. The micro-organisms in this test origin from the effluent of a municipal sewage treatment plant. After 5 days, a %-BOD/COD of 69 % was reached, therefore the test substance was found to be readily biodegradable under the test conditions.

The ready biodegradability of sodium benzoate was further examined in a test according to the OECD 301 E (Ready Biodegradability: Modified OECD Screening Test) (BASF SE, 1982). The biodegradation of the test substance was followed by analysis of DOC degradation over a 21-day period. The origin of the inoculum was not specified. An inoculum blank was conducted in parallel. After 14 days, a %-degradation (DOC removal) of 98 % was reached. According to the evaluation criteria of this study, test substance was found to be readily biodegradable under the test conditions.

Under the presumption, that the corresponding anionic substance components (sulfate or chloride for 1-ethyl-3-methyl imidazolium) or cationic component (sodium for benzoate) do not influence the degradability, the results of the studies indicate no readily degradability for 1-ethyl-3-methyl imidazolium and a readily degradability for benzoate.

In conclusion, the test substance 1H-imidazolium, 3-ethyl-1-methyl-, benzoate has to be regarded as not readily degradable.