A Leaching Test for Self-management of Toxic Metals in Wastes

Tomohiro Tasaki* and Kohei Urano**
* Research Center for Material Cycles and Waste management, National Institute for Environmental Study
** Graduate School of Environment and Information Sciences, Yokohama National University
+ Correspondence should be addressed to Tomohiro Tasaki:
(16-2, Onogawa, Tsukuba, Ibaraki 305-8506 Japan)

Abstract
In order to propose a leaching test for precautionary self-management of leachable toxic metals from wastes, highly leachable conditions at landfill sites were investigated regarding pH, kind and concentration of leachant, and contact time, which mainly influence metal leaching from wastes.
It was confirmed that the range of pH from 4.0 to 9.5 should be taken into account, and the amounts of metals leached at pH 4.0 were mostly the largest within this pH range. The amounts of metals leached with both 0.4M acetic buffer solution as the representative fatty acids and 0.005M phthalic buffer solution as the representative aromatic carboxylic acids were compared to that with nitric acid at pH 4.0 by considering various leachate, and the amounts with 0.4M acetic buffer solution were mostly the largest. The equilibrium of metal leaching was not achieved in 6 hours in many cases, but in fewer cases in 24 hours and 48 hours. Emphasizing the importance of workability, it was considered that 24 hours of contact time was preferable.
Based on these results, we proposed a leaching test where wastes were in contact with 0.4M acetic buffer solution at pH 4.0 at 10mL/g of the liquid to solid ratio for 24 hours.

Key words: leaching test, metals, pH, acetic acid, contact time