Patent ID: 7686865

Claim:
A method, comprising: exposing a metal-containing material to an extractant comprising a liquid or supercritical-fluid solvent and an acid-base complex comprising an oxidizing agent and a complexing agent, thereby forming an extract, the extract comprising at least a portion of the liquid or supercritical-fluid solvent and a metal-containing complex comprising at least a portion of the complexing agent and at least a portion of a metal from the metal-containing material; and exposing at least a portion of the extract to a stripping agent in a stripping process to form a strip product and a raffinate, where the strip product comprises at least a portion of the metal and at least a portion of the stripping agent, and the raffinate comprises at least a portion of the liquid or supercritical-fluid solvent and at least a portion of the complexing agent, where exposing the extract to the stripping agent comprises introducing at least a portion of the extract into a first end of a countercurrent stripping column, introducing at least a portion of the stripping agent into a second end of the countercurrent stripping column, collecting at least a portion of the stripping agent near the first end of the stripping column as the strip product, and collecting at least a portion of the extract near the second end of the stripping column as the raffinate.