Inco Limited

Justin Raskauskas

Eberhard Krause

Reichel A Tenbergen

Yoshiaki Okita

Brian Charles Blakey

Brian Charles Blakely

An aqueous solution, for example, effluent from an off-gas scrubber, is treated to remove metal and metalloid ions by in situ precipitation of ferrous ions by the addition thereto of a ferrous ion-containing solution, salt or other such ferrous ion-containing source and a hydroxyl-yielding base in the presence of the metals and metalloids. The reaction conditions include a temperature of at least about 60&deg; C., and a pH of from about 6 to about 10.

Process for reducing the concentration of dissolved metals and metalloids in an aqueous solution

The process provides a method of removing arsenic from solutions containing sulfur dioxide in an environmentally acceptable manner. This process first oxidizes arsenic, iron and sulfur dioxide contained in an aqueous solution to prepare the solution for precipitation and to improve process control. Recycled neutralized precipitate seeds the oxidized aqueous solution. A calcium-containing base precipitates products of neutralization on the seeds. The final neutralized precipitate contains a stable ferric arsenate compounds.

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Mississauga, Canada

Justin Raskauskas