Benzotriazole

Adsorption / desorption

Description of key information

Based on available information worst case K_oc was selected.

Key value for chemical safety assessment

Koc at 20 °C:

77.62

Additional information

Sorption behaviour of 1H-Benzotriazole was investigated in several studies during the last decades showing a high mobility in soil. Motivated by findings at an abandoned airport in Norway Breedveld et al. performed a sorption study in six different soils according to OECD 106 (Breedveld et al., 2003). The study gave indications showing very little sorption in different soil matrices increasing with gradient organic carbon content. The maximum adsorption was found in peat at pH 3.0 and an organic carbon content of 47.4 % (estimated log K_oc 1.4). Experimental observations were supported by field studies detecting 1H-Benzotriazole in various soil samples from the surroundings of the airport at 1.2 m depth.

Hart et al. examined the sorption behaviour of 1H-Benzotriazole in short-term batch method according to an ASTM standard method in four different soil matrices with low organic carbon content (Hart et al., 2004). Results from the experiment were fitted by Langmuir, Freundlich and linear isotherms giving indications on different factors affecting the sorption behaviour of both substances. As all members of Benzotriazoles show a strong dipole moment (polar character) binding to soil is a complex combination of molecular driving forces with different binding sites for adsorption, absorption and hydrogen bonding. From the experimental results, a maximum log K_oc of 1.89 for 1H-Benzotriazole was calculated.

In addition, Jia et al. also observed non-linear sorption of 1H-Benzotriazole in mineral soils (Jia et al., 2007). A significant increase of sorption of Benzotriazole was detected when in situ pH of soil was in the range of pK_a of Benzotriazole. This may indicate ionic interactions between triazole molecules and binding sites in soil matter. Furthermore increased sorption has been found when zerovalent Fe(0) has been present indicating multi-layer coverage.

Mazioti et al. (2015) investigated the sorption behaviour of 1H-Benzotriazole in laboratory experiments using activated sludge from a municipal STP. The sludge was washed, dried and frozen before the tests. In addition, the samples were heat sterilized. The tests (six concentrations) were performed in the dark, for 24 hours at 22.0 ± 1.0 °C and pH 7.3 ± 0.2. Based on the findings a distribution coefficient K_d of 220±9 L/kg was calculated.

Experimental findings for Benzotriazole were supported by QSAR calculations using KOCWIN v.2.00 (log K_oc 1.72). In a second estimation according to Schüürmann (Schüürmann et al., 2006) a log K_oc of 1.69 for BTA was achieved.

Wu et al (2020) investigated the role of humic and tannic acid on the sorption behaviour of BTA to sandy loam soil in batch equilibrium experiments. The addition of increasing concentrations of both DOM representatives, gradually increased the sorption of Benzotriazole with tannic acid being the more relevant factor. Furthermore, the influence of the pH value on the sorption of BTA was examined. The deprotonated form (pH 10.5) showed a decreased sorption tendency. This is assumed to electrostatic repulsion of the anionic BTA- and the negatively charged soil surface.

All available information is adequate to assess the behaviour of BTA in soil. Therefore, no need for further testing was assumed. In summary, all results show a log K_oc < 3 indicating a high mobility in soil.

Breedveld GD, Roseth R et al. (2006) Persistence of the de-icing additive benzotriazole at an abandoned airport, Water Air Soil Pollut: Focus 3: 91 -101.

Hart DS, Davis LC et al. (2004) Sorption and partitioning parameters of benzotriazole compounds, Microchem J, 77, 9 -17.

Jia Y, Breedveld GD et al. (2007) Column studies on transport of deicing additive benzotriazole in a sandy aquifer and a zerovalent iron barrier, Chemosphere, 69, 1409 -1418.

Jia Y, Breedveld GD et al. (2007) Sorption of triazoles to soil and iron minerals, Chemosphere, 67, 250 -258.

Mazioti et at. (2015), Sorption and biodegradation of selected benzotriazoles and hydroxybenzothiazole in activated sludge and estimation of their fate during wastewater treatment, Chemosphere 131 (2015) 117–123

Schüürmann G, Ebert R, Kühne R (2006) Prediction of the Sorption of Organic Compounds into Soil Organic Matter from Molecular Structure, Environ. Sci. Technol., 40, 7005 -7011.

Wu et al (2020), Roles of dissolved humic acid and tannic acid in sorption of benzotriazole to a sandy loam soil, Ecotoxicology and Environmental Safety 204 (2020) 111088