GM-IX Gas Membrane-Ion Exchange
GM-IX Gas Membrane-Ion Exchange : A process for treating metal cyanide waste solutions, with recovery of both the metal and the cyanide. The solution is first passed through an anion exchange column, removing metal cyanide complexes and cyanide ion. Treatment of the column with 10 percent sulfuric acid releases the metal ions and hydrogen cyanide into solution. Passage of this solution through a gas membrane module, comprising thousands of hollow fibers of microporous polypropylene, strips the hydrogen cyanide gas from the solution. It not only removes the free hydrogen cyanide, it also forces the hydrolysis of metal cyanide complexes until all the cyanide has been removed from the system. The hydrogen cyanide is scrubbed by sodium hydroxide solution, with the resulting sodium cyanide solution being re-used. The metal is recovered from solution by electro-winning
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