The Efficacy of Three Diatomaceous Earth Sources for Removing Tylosin from Aqueous Systems

Abstract

Antibiotics used during animal production are the same or very similar to antibiotics used by humans. Tylosin, structurally similar to erythromycin prescribed to humans, is a common livestock antibiotic. Therefore, tylosin and other similar antibiotics present a potential threat of environmental buildup resulting in increased microbial resistance. To mitigate this potential impact, a remediation method for reducing the load of antimicrobials entering the environment is needed. The binding properties of different types of diatomaceous earth (DE) were investigated for maximum binding and the influencing physical characteristics to determine the potential use as a binding agent for wastewater treatment. Swimming pool DE was 99% crystalline silica and did not sorb any tylosin. Raw DE was 65% amorphous silica, 20% clay, and had 3% organic matter by weight. Langmuir isotherms predicted a maximum binding capacity of 49 ± 3 mg g−1 with a binding constant of 37,342 ± 5653 M−1. This was almost 3.3 times more than previously published work investigating the binding of tylosin to kieselguhr that is 96% amorphous silica with little to no clays or organic matter present. To determine the role of organic matter and clays in binding capacity, raw DE was digested with 3% hydrogen peroxide and adsorption isotherms were constructed. After removal of the organic matter, predicted maximum binding of tylosin increased to 88 ± 2 mg g−1, whereas the binding constant slightly decreased (23,482 ± 3264 M−1). It was concluded that the DE–clay matrix was responsible for high binding and therefore had the greatest potential for application in a wastewater treatment process.Core Ideas Tylosin binds to amorphous diatomaceous earth but not crystalline. The presence of clays in diatomaceous earth improves binding. Clay–diatomaceous earth matrix can be recycled by treatment with hydrogen peroxide.