Abstract: A process is described for the substantially complete recovery of cyanide reagent and metal forming water soluble metal-cyanide complexes contained in mill effluents and waste waters. The process is comprised of a loading cycle wherein the metal-cyanide complexes are adsorbed onto a basic ion exchange resin and the free cyanide containing column effluent is returned to the mill. The metal ions, which are usually mostly copper, nickel and zinc, and the complexing cyanide are eluted in the subsequent regenerant cycle by an acid solution having controlled pH and controlled redox potential, the latter being measured against the saturated calomel electrode. The preferred oxidant to control the redox potential of the regenerant solution is hydrogen peroxide. The generated hydrogen cyanide is sparged with air, or removed by subatmospheric pressure from the regenerant solution, and dissolved in an alkaline scrubber solution for reuse. The metal ions are recovered from a bleed solution.

Abstract: High purity iron powder may be obtained by treating an iron bearing source which contains impurities such as silica along with minor amounts of aluminum, calcium and magnesium to a series of steps which include grinding the iron bearing source followed by subjecting the ground source to a caustic leach at an elevated temperature and pressure. Thereafter the soluble impurities may be separated from the residue, the latter then being reduced by treatment with hydrogen at an elevated temperature and pressure to convert the iron to the metallic form.