Due to their use in various domestic and industrial formulations, benzalkonium compounds have been isolated in many environmental matrices. Sorption to soil components has been shown to play a key role in their environmental fate. Whereas sorption of benzalkonium compounds to soils is attributed to cation exchange and van der Waals forces, the relative contributions of these two mechanisms at environmental levels have not been clearly defined. In this study a previously reported algal toxicity assay-based method was employed to determine the distribution coefficients (Kd) of benzalkonium compounds between water and soil components, at environmental concentrations. Cation exchange capacity corrected Kd values for organic matter and clays were all within one order of magnitude. This implies that ion exchange is the dominant mechanism of sorption for benzalkonium compounds. When the sorption data were used to compute sorption energies for four homologues of benzalkonium ions, the magnitude of the free energy change of sorption increased with size of the molecule. The increase in sorption energy could be partly explained by increased energy of hydration with addition of methylene groups to the alkyl chain. A model that predicts sorption coefficients of benzalkonium compounds to soils using organic carbon content and cation exchange capacity was also defined. When tested using an artificial soil, the model estimates were all within one order of magnitude of the experimental values.
Bibliographical noteFunding Information:
This research was partly supported by the Ministry of Environment (MOE), Republic of Korea as “Technology Program for establishing biocide safety management” [ 2018002490001 ]. MN was supported by the Global Korea Scholarship Program . Appendix A
This research was partly supported by the Ministry of Environment (MOE), Republic of Korea as ?Technology Program for establishing biocide safety management? . MN was supported by the Global Korea Scholarship Program.
© 2020 Elsevier Ltd
- Cation exchange
- Distribution coefficient
- Hydration energy
- Organic cation
- Sorption energy
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- General Chemistry
- Public Health, Environmental and Occupational Health
- Health, Toxicology and Mutagenesis