Location: Livestock Bio-SystemsTitle: Tylosin sorption to diatomaceous earth described by Langmuir isotherm and Freundlich isotherm models
Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2017
Publication Date: 11/20/2017
Publication URL: https://handle.nal.usda.gov/10113/5869588
Citation: Stromer, B.S., Woodbury, B.L., Williams, C.F. 2018. Tylosin sorption to diatomaceous earth described by Langmuir isotherm and Freundlich isotherm models. Chemosphere. 193:912-920. https://doi.org/10.1016/j.chemosphere.2017.11.083.
Interpretive Summary: Tylosin is a widely used antibiotic fed to animals during livestock production. A majority of the antibiotic passes through the animal undigested and enters the environment where it could possibly contribute to antimicrobial resistance. In this paper, we added a common clay mineral to wastewater containing tylosin to determine if it could be removed. The binding of the Tylosin to the clay mineral was compared by looking at values from two different models that describe how they bind to each other. Various types of salt were added to the water to see how they impacted the binding of the Tylosin to the clay mineral. We concluded that one of the models was better at describing the binding. Also we found the amount of tylosin that binds to the clay mineral could be changed by the types of salts that were added or changing the temperature of the water. From previously reported data on the concentration of tylosin in beef cattle storage ponds, removal of tylosin by sorption to DE would cost $0.25 per Mega gallons of storage pond water.
Technical Abstract: Tylosin, an antibiotic used for livestock, is a macrolide structurally similar to a number of important, often prescribed human antibiotics. Because of this relationship, tylosin presents a potential threat of antimicrobial resistance from environmental buildup. This work investigated tylosin sorption to natural diatomaceous earth product (DE) and the types of physical interactions responsible for sorption. Most sorption processes were best described by the Langmuir model when compared with Freundlich model. Heat of sorption (delta H) was 1.14 kJ/mol-1 indicating a physisorption process. Change in entropy (delta S) was 119 J/mol-1. Sorption was evaluated from aqueous solution with various H+, KCl and Urea concentrations. In 0.01 M phosphate buffer (PB) pH 6.6, a maximum sorption capacity of 15 mg tylosin per g of DE was achieved. Changing the pH to 2.9 or 11.2 resulted in decreased sorption of tylosin (13 and 10 mg/g-1, respectively). Addition of 1 M KCl to 0.01 M PB pH 6.6 decreased sorption of tylosin to DE with the maximum binding capacity of 7 mg/g-1. Sorption in 1.0 M urea, 0.01 M phosphate buffer pH 6.6 showed a maximum sorption of 13 mg/g-1. Based on these results, the sorption of tylosin appears to be a physisorption process, with charge-charge interactions being the mode of sorption at neutral pH and small contributions from secondary interactions. This information will be useful for developing effective strategies for mitigating tylosin and other antimicrobial's impact on the environment.