Ion exchange treatment for removing toxic metals and cyanide values from waste waters

A method for the ion exchange treatment of waste water, comprising:

• flowing a feed waste water through a multi-level ion exchange resin bed having a strong base anion exchange resin layer, a weak acid cation exchange resin layer and a strong acid cation exchange resin layer;
• and
• regenerating said multi-level ion exchange resin bed by the steps of:
• (a) backwashing said multi-level bed by passing a rinse liquid through said multi-level bed and a bed expansion volume to form a liquid layer;
• (b) passing an acidic regeneration fluid through said multi-level bed;
• (c) flowing a pressurized gas into said bed expansion volume while generally concurrently flowing a rinse liquid through said multi-level bed to remove acidic regeneration fluid from said multi-level bed;
• (d) removing residual acidic regeneration fluid from said bed by flowing a rinse liquid through said multi-level bed in a direction generally opposite to that of said generally concurrent flow of pressurized gas;
• (e) passing a caustic regeneration fluid through at least said strong base anion resin layer and said weak acid cation resin layer;
• and
• (f) flowing a rinse liquid through at least said strong base anion resin layer and said weak acid cation resin layer.

Apparatus for removing cyanide values from acidic waste water, comprising:

• a stripper tank having heating means for driving off hydrocyanic gas from waste water including acid cyanide values therewithin;
• a reactor means having circulation between a holding tank and an inclined, closed passageway, said inclined closed passageway being both compact and elongated by including an inclined tube having a series of interconnected vertical levels;
• conduit means for passing said hydrocyanide gas from said stripper tank into said reactor means and generally upwardly within said inclined passageway;
• a column in fluid passing communication with the reactor holding tank, said inclined, closed passageway opening at one end thereof into said reactor holding tank and at the other end thereof into said column;
• means for circulating caustic fluid from said holding tank of the reactor means and generally downwardly within said inclined passageway and back to said holding tank generally countercurrently of said hydrocyanide gas flow therewithin to form a cyanide salt compound;
• and
• exit conduit means for removing said cyanide salt compound from said circulating reactor.

A method for removing cyanide values from acidic waste waters, comprising:

• heating a cyanide-containing waste water to drive off hydrocyanide gas therefrom;
• directing the driven off hydrocyanide gas into a reactor means having a caustic fluid therewithin;
• circulating said caustic fluid through the reactor means into and through an inclined, enclosed path, the caustic fluid flowing generally downwardly while within the inclined path, said inclined path being both compact and elongated by including a series of interconnected vertical levels;
• circulating said hydrocyanide gas through at least a portion of said reactor means into and through said inclined closed path, the hydrocyanide gas flowing generally upwardly while within the inclined path, said generally upward flowing of hydrocyanide gas within the inclined path and said generally downward flowing of the caustic fluid within the inclined path combining to provide countercurrent impingement and turbulence between the hydrocyanide gas and the caustic fluid, which countercurrent impingement and turbulence minimizes foaming between the hydrocyanide gas and the caustic fluid;
• whereby said caustic fluid and said hydrocyanide gas react with each other during their respective circulation steps to form a cyanide salt compound while minimizing foaming during the reaction;
• and
• recovering the cyanide salt compounds.