Desorption kinetics of ciprofloxacin in municipal biosolids determined by diffusion gradient in thin films

E. D'Angelo, D. Starnes

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Ciprofloxacin (CIP) is a commonly-prescribed antibiotic that is largely excreted by the body, and is often found at elevated concentrations in treated sewage sludge (biosolids) at municipal wastewater treatment plants. When biosolids are applied to soils, they could release CIP to surface runoff, which could adversely affect growth of aquatic organisms that inhabit receiving water bodies. The hazard risk largely depends on the amount of antibiotic in the solid phase that can be released to solution (labile CIP), its diffusion coefficient, and sorption/desorption exchange rates in biosolids particles. In this study, these processes were evaluated in a Class A Exceptional Quality Biosolids using a diffusion gradient in thin films (DGT) sampler that continuously removed CIP from solution, which induced desorption and diffusion in biosolids. Mass accumulation of antibiotic in the sampler over time was fit by a diffusion transport and exchange model available in the software tool 2D-DIFS to derive the distribution coefficient of labile CIP (Kdl) and sorption/desorption rate constants in the biosolids. The Kdl was 13 mL g−1, which equated to 16% of total CIP in the labile pool. Although the proportion of labile CIP was considerable, release rates to solution were constrained by slow desorption kinetics (desorption rate constant = 4 × 10−6 s−1) and diffusion rate (effective diffusion coefficient = 6 × 10−9 cm2 s−1. Studies are needed to investigate how changes in temperature, water content, pH and other physical and chemical characteristics can influence antibiotic release kinetics and availability and mobility in biosolid-amended soils.

Original languageEnglish
Pages (from-to)215-224
Number of pages10
StatePublished - Dec 1 2016

Bibliographical note

Funding Information:
The authors would like to express appreciation for research support from the Hatch Multistate Research Fund (MRF) provided by the National Institute of Food and Agriculture for the project W3170-Beneficial Reuse of Residuals and Reclaimed Water: Impact on Soil Ecosystem and Human Health . The authors would also like to express their sincere gratitude to Dr. Niklas Lehto for sharing the software tool 2D-DIFS that was essential for determining the kinetic parameters in this study.

Publisher Copyright:
© 2016 Elsevier Ltd


  • DGT
  • Desorption kinetics
  • Diffusion coefficient
  • Sorption isotherm

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry (all)
  • Pollution
  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis


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