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Zinc leaching from tire crumb rubber
Emily P Rhodes1, Zhiyong Ren, David C Mays
1Department of Civil Engineering, University of Colorado Denver, Campus Box 113, PO Box 173364, Denver, Colorado, USA.
Environmental Science & Technology
|November 14, 2012
Summary
Zinc leaching from tire crumb rubber increases with smaller particle size and longer exposure. Washing reduces initial zinc pulses but not the long-term steady-state leaching concentration.
Area of Science:
- Environmental Engineering
- Geotechnical Engineering
- Materials Science
Background:
- Tire crumb rubber in civil engineering poses environmental concerns due to zinc leaching.
- Existing data show variability in zinc leaching, influenced by pH and time, but lack detail on crumb rubber size and flow dynamics.
Purpose of the Study:
- Investigate the impact of crumb rubber size on zinc leaching.
- Determine the effect of exposure time on zinc release.
- Characterize the dynamics of zinc leaching during flow through crumb rubber.
Main Methods:
- Synthetic Precipitation Leaching Procedure (SPLP) for size effects.
- Quiescent batch leaching tests for exposure time.
- Column tests to study leaching dynamics under flow.
- Modeling using a single-parameter model and HYDRUS-1D software.
Main Results:
- Zinc leaching increases with smaller crumb rubber size and longer exposure times.
- Leaching models predict a constant rate up to 96 hours.
- Column tests show an initial zinc concentration pulse (~3 mg/L) followed by a steady state (~0.2 mg/L).
- Washing reduces the initial pulse but not the steady-state leaching.
Conclusions:
- Crumb rubber size and exposure time are critical factors influencing zinc leaching.
- Initial zinc release is significant but diminishes to a stable leaching rate.
- Washing is ineffective in reducing long-term zinc leaching from tire crumb rubber.
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