| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 86 === This research investigated the effect of synthesized zeolite
on stabilizing Cd, Cu, and Zn contaminated soil and also developed
model for simulating metal transport in soil columns. The
experimental work addressed adsorption equilibrium of metals
on soils, metal leaching from soil columns, and metal transport
model in soil environment. Specifically, four soil samples
, Pinchen, Jente, Erlin, and Chengchung, were obtained as represe
ntatives of local soil series.
In batch adsorption experiments, metals in solution phase
will compete for the reacting sites in soil surfaces. In system contain
ing all three metal ions, Cu preferentially outcompetes Zn and Cd for s
orption on soils. Sorption of Cd exhibits the weakest affinity for the su
rface reactions. Thus, in the presence of Cu and Zn, the sorption dens
ity of Cd is dramatically reduced by the competition among metals.
Adding zeolite in soil mixtures will greatly
enhance the holding capability of soils on metals, specifically Cd on Jente so
il samples. However, zeolite addition provides less significant effect on
Cu as well as Zn sorption. The effects of zeolite addition on metal sorpti
on onto soils can be modeled using Freundlich isotherm by considering the al
ternation of soil cation change capacity (CEC). The linear relationshi
p between Freundlich adsorption constant K and soil CEC at various zeolite add
ition was developed. THis linear equation is very useful in predicting adsorp
tion ability of soil with some amounts of zeolite addition in terms of Freu
ndlich K. Thereafter, the parameters necessaryfor pollutant advection-dispers
ion-adsorption model is obtainable. The model isthen used for simulating Cd (
30 mg/kg-soil) , Cd, and Zn (300 mg/kg-soil) migration in zeolite amende
d soil columns. The model outputs provides reasonable data for under
standing the reaction as well as metal transport in soil column, especially
for metal contamination level in the range of 30 to 300 mg/kg-soil. Neverthe
less, this model was unable to offer acceptable results f or the system with
high metal concentration such as 100 mg-Cd/kg-soil and 1000 mg-Cu-Zn/kg-soil.
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