Various biomaterials have shown promise as sorbants to remove heavy me
tals from water. Several advantages of peat moss for such applications
include its abundance, low cost, and high metal capacity. A Ca-loaded
column of peat moss was therefore studied with mixtures of metals. Me
tals bind to anionic sites by displacing protons from acidic groups (K
-ex(H)) or existing metals from anionic sites at high pH (K-ex). These
ion-exchange equilibrium constants were determined in batch experimen
ts by direct measurement of species in solution and sorbed on the soli
d phase. The same K-ex values of Mg 0.342, Mn 0.862, Ca 1.00, Ni 1.42,
Zn 1.88, Cd 2.82, Cu 9.97, and Pb 26.7 relative to Ca were found for
a given metal alone or in the presence of a mixture, thus showing that
the metals function independently. Under conditions employed for a Mg
/Mn mixture, it was found that ion-exchange equilibria were maintained
along the column due to very fast rates for metal-metal exchange as m
easured in a separate kinetic study. A linear relationship for log K-e
x(H) vs pH over 10(6) was interpreted as due to metal binding to sites
of different acid strengths.