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Solution purification and metals recovery

Outotec® Solution Purification Process offers a low investment cost and is well suited to retrofit projects.

During leaching, other metallic components nobler than zinc like copper, cobalt, nickel and cadmium are also leached and must be removed before electrowinning. Outotec is able to engineer the purification process by using either arsenic or antimony chemicals in cobalt and nickel removal. Outotec’s advanced chloride removal process can be combined with both arsenic and antimony processes.

The chemistry of the Outotec® Solution Purification Process based on arsenic was developed during the early 1970s. The investment required for the process is low. The three-stage process has been tested and proven on an industrial scale. The process yields a pure, high-quality zinc solution for the electrowinning process.

The antimony process is also three-stage, consisting of copper-cadmium removal and separate cobalt-nickel removal followed by polishing. Cobalt and nickel are precipitated using antimony chemical and zinc dust.

Based on Outotec’s experience, the arsenic process has advantages over the antimony process, such as lower zinc dust consumption and a purer product solution. The arsenic process is described in more detail in the Application section.

Solvent extraction is an alternative for solution purification by precipitation and cementation reactors. It is an especially good choice for high chloride and fluoride raw materials, such as electric arc furnace dusts. Solvent extraction is especially suitable for raw materials when zinc concentration in leach liquor needs to be increased before electrowinning.