R. Chantiwas et al., Evaluation of metal stabilization ability of adsorbents for toxic metals in solid waste by sequential extraction, J ENVIR S A, 35(6), 2000, pp. 849-867
Citations number
16
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A-TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING
The stabilization of toxic metals (Cd, Zn, Pb, Cu and Mn) in a solid waste
from a zinc refinery was studied by the addition of either a synthetic adso
rbent (zeolite A) or an organic adsorbent (dried water hyacinth and rice hu
ll carbon). The stabilization ability of an adsorbent was evaluated by mean
s of sequential extraction, which separated the metals into five fractions.
Metals extracted in the first two fractions by relatively weak solvents ar
e considered as mobile. These metal contents provide an estimation of the a
mount available for plant uptake. Metals extracted in the last three fracti
ons are considered to be immobile. Stabilization ability of an adsorbent wh
en mixed with solid waste can be considered as the transformation of a meta
l from mobile to immobile form.
In this work an index, the 'stabilization dose' (SD), is defined for use as
a measure of the stabilization ability of an adsorbent for a metal. SD50 v
alue is the percentage amount (w/w) of an adsorbent which, when added to so
lid waste, can reduce 50% of a metal formerly in the mobile fractions. The
lower the SD50 value the greater is the stabilization ability of the adsorb
ent. By comparing the SD values for four metals, zeolite and dried water hy
acinth are found to be more effective than rice hull carbon. The SD50 value
s of zeolite were 6.9, 18.6, 25.5, and 30.0 %w/w for Pb, Cd, Zn and Cu, res
pectively. The SD50 values of dried water hyacinth were 23.8 and 46.4%w/w f
or Cu and Zn. Only copper could be stabilized by rice hull carbon with SD50
value of 45.1%w/w.