Apatite and Phillipsite as Sequestering Agents for Metals and Radionuclides
A. S. Knox,* D. Kaplan, D. C. Adriano, G. Hinton, and M. D. Wilson
ABSTRACT
Laboratory and greenhouse studies were conducted to quantify apatite and
phillipsite (zeolite) sequestration of selected metal contaminants. The
laboratory batch study measured the sorption of aqueous Co2+,
Ba2+, Pb2+, Eu3+, and UO22+.
Apatite sorbed more Co2+, Pb2+, Eu3+,
and UO22+
from the spike solution than phillipsite, resulting in distribution coefficients
(Kd values) of >200 000 L kg-1. Phillipsite was
more effective than apatite at sorbing aqueous Ba2+. Results
from the laboratory study were used to design the greenhouse study that
used a soil affected by a Zn-Pb smelter from Pribram, Czech Republic.
Two application rates (25 and 50 g kg-1) of phillipsite and
apatite and two plant species, maize (Zea mays L.) and oat (Avena
sativa L.), were evaluated in this study. There was little (maize)
to no (oat) plant growth in the unamended contaminated soil. Apatite and,
to a slightly lesser extent, phillipsite additions significantly enhanced
plant growth and reduced Cd, Pb, and Zn concentrations in aU analyzed
tissues (grain, leaves, and roots). The sequestering agents also affected
some essential elements (Ca, Fe, and Mg). Phillipsite reduced Fe and apatite
reduced P and Fe concentrations in oat tissues; however, the level of
these elements in oat leaves and grains remained sufficient. Sequential
extractions of the soil indicated that the Cd, Pb, and Zn were much more
strongly sorbed onto the amended soil, making the contaminants less phytoavailable.
SREL Reprint #2667
Knox, A. S., D. I. Kaplan, D. C. Adriano, T. G. Hinton and M. D. Wilson. 2003. Apatite and phillipsite as sequestering agents for metals and radionuclides. Journal of Environmental Quality 32:515-525.
