The toxicity of heavy
metals in water is typically related to the concentration of the metals in water. However, it is known that apart from the
concentration the speciation of the heavy metals is also a critical factor. In this study, the concentration and type of species
(ionic form) of Cu, Co, and Pb from two different soil samples on the Copperbelt Province in Zambia were investigated by modeling using Visual MINTEQ
software. The concentration and the conductivity of the sample from ore-dump
site were higher
than that of the second site further away owing to the higher mineral content
in the waste ore-dump site. Modeling by Visual
MINTEQ uses defined parameters such as concentration, ionic conductivity and pH
of the sample solutions to analyze the
free metal ion and bound-metal distribution as a function of pH. The results of the model showed that Cu2 , Pb2 and Co2 ions thrive in aqueous acidic solutions up to pH 6.5. At higher pH, formation of the hydroxo and
bicarbonate species leads to a decline in the concentration of the divalent
ions. Interestingly, the Co2 ion
persists in solution up to pH 8.5 with little formation of the hydroxo or
carbonate forms. Finally,
the results show that without elaborate analytical tools, speciation modeling
can be used to ascertain the availability of metal ions in soils/aqueous solutions
when chelating and competing metal ions are taken in consideration.
Cite this paper
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