Arsenic. An environmental problem limited by solubility*
M.Clara F.Magalhães
Department of Chemistry, University of Aveiro, P-3810-193
Aveiro, Portugal
Abstract: Arsenic is a toxic element for animals and the majority
of plants, in spite of evidence that it is also an essential element.
The long-term intake of small doses of arsenic has a carcinogenic effect.
There are well-identified regions where arsenic ground water concen-
trations can reach values higher than 2 mg/L. Water purification and
waste treatment techniques based on (1) precipitation of calcium, magnesium,
and iron(III) arsenates, and/or (2) adsorption or coprecipitation of
arsenic oxyanions are unlikely to produce aqueous solutions with arsenic
concentrations below the guideline values proposed for arsenic dissolved
in potable water and treated sewage effluents. As(III) species are more
toxic than As(V) species. Arsenate species are predominant at moderate
and high redox potentials, while arsenite species occur under more reducing
conditions. Metal arsenites are much more soluble than the corresponding
metal arsenates, and arsenites are adsorbed less by solid phases. Remediation
techniques must consider the available information on solubility and
adsorptive properties of As(III) and As(V). The less-soluble lead and
barium arsenates are not suitable for arsenic decontamination. New remediation
methods must consider solubility data for arsenic-containing materials
and minerals.
> erratum
* Lectures presented at the 10th International Symposium
on Solubility Phenomena, Varna, Bulgaria, 22 -26 July 2002. Other
lectures are published in this issue, pp. 1785-1920.
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