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Guo, Lei, Shanhong Zhu, and Shengtao Zhang. Journal of Industrial and Engineering Chemistry 24 (2015): 174-180.
Benzalkonium chloride (BKC), a representative quaternary ammonium compound, demonstrates exceptional performance as a corrosion inhibitor for carbon steel exposed to acidic environments. In 0.1 M H₂SO₄, BKC exhibits high inhibition efficiency, with an optimal concentration of 300 mg/L. Electrochemical impedance spectroscopy confirms a significant increase in charge-transfer resistance, indicating that BKC effectively blocks active anodic and cathodic sites through strong surface adsorption. Potentiodynamic polarization further identifies BKC as a mixed-type inhibitor capable of suppressing both metal dissolution and hydrogen evolution reactions.
The adsorption of BKC onto steel follows the Langmuir isotherm, and the negative ΔG_ads values indicate that the process is spontaneous, driven by a synergistic combination of physical and chemical interactions. SEM analysis reveals the formation of a uniform, protective molecular film that isolates the steel surface from the corrosive medium.
Quantum chemical calculations provide molecular-level justification for BKC's high inhibition efficiency, linking its electronic properties to its adsorption behavior. Molecular dynamics simulations highlight a critical mechanistic role of chloride ions, which act as a bridging species between BKC cations and the negatively charged steel surface, thereby stabilizing the adsorbed inhibitor layer.
This study demonstrates that Benzalkonium chloride is highly effective for the corrosion protection of carbon steel, offering a robust, surface-active solution for industrial systems operating under acidic conditions.
Tandukar, Madan, et al. Environmental science & technology 47.17 (2013): 9730-9738.
This case study examines benzalkonium chlorides (BACs), a major class of quaternary ammonium disinfectants, as selective environmental stressors shaping microbial community structure and antibiotic resistance. Three long-term aerobic microbial consortia-BAC-unexposed (DP), BAC-exposed (DPB), and BAC-enriched (B)-were cultivated for over four years under systematically varied carbon and energy inputs. The BAC mixture (60:40 dodecyl and tetradecyl benzyl dimethyl ammonium chlorides) served either as an auxiliary substrate (DPB) or the sole carbon source (B), enabling evaluation of adaptive microbial responses under sustained disinfectant pressure.
Long-term BAC exposure induced pronounced reductions in microbial diversity alongside strong enrichment of BAC-tolerant taxa, predominantly Pseudomonas spp. Both DPB and B communities exhibited substantially decreased susceptibility not only to BACs but also to clinically relevant antibiotics such as penicillin G, tetracycline, and ciprofloxacin. Mechanistic analyses revealed that resistance to BACs and penicillin G was chiefly associated with biodegradation or transformation pathways, whereas increased resistance to tetracycline and ciprofloxacin arose from enhanced efflux pump activity. Quantification of multidrug resistance genes further confirmed significant enrichment of key efflux-associated determinants in BAC-exposed communities relative to the DP control.
Overall, this study demonstrates that benzalkonium chloride can drive adaptive microbial restructuring and promote cross-resistance to multiple antibiotics, highlighting important implications for environmental disinfection practices and antimicrobial resistance dissemination.
Kim, M., Weigand, M. R., Oh, S., Hatt, J. K., Krishnan, R., Tezel, U., ... & Konstantinidis, K. T. (2018). Applied and environmental microbiology, 84(17), e01201-18.
This case study highlights benzalkonium chloride (BAC), a widely used quaternary ammonium disinfectant, as a selective environmental stressor capable of promoting antibiotic resistance through multiple genetic and physiological pathways. Using BAC-fed bioreactors inoculated with river sediment, researchers demonstrated that sustained BAC exposure enriched for Pseudomonas aeruginosa and other taxa exhibiting markedly increased resistance to several antibiotics compared to communities grown without BAC.
Metagenomic sequencing revealed that integrative and conjugative elements (ICEs) carrying both BAC efflux determinants and antibiotic resistance genes coselected under BAC pressure, enabling simultaneous tolerance to BAC and structurally unrelated antimicrobials. Cloning experiments confirmed the functional contribution of these mobile elements. Moreover, adaptive evolution of P. aeruginosa isolates exposed to ascending BAC concentrations selected for mutations in the pmrB locus-an established polymyxin resistance determinant-thereby elevating tolerance to polymyxin B and rifampin. At subinhibitory BAC concentrations, isolates also exhibited strong induction of the mexCD-oprJ multidrug efflux pump system, further enhancing broad-spectrum resistance.
Notably, BAC-adapted P. aeruginosa populations tolerated concentrations up to 1,600 mg/L, exceeding common disinfectant usage levels. These findings underscore that BAC can drive coselection of antibiotic resistance via mobile genetic elements, point mutations, and efflux regulation. The study highlights the critical need for controlling BAC accumulation in environmental and engineered systems and emphasizes the importance of BAC degradation technologies to mitigate the spread of resistance determinants.
