MEND Project 3.21.1b
April 1995

EXECUTIVE SUMMARY

The extraction of Sb, Cd, Cu, Ni and Zn from acid mine drainage solutions using various ion exchangers was studied with batch and column tests. The extraction was studied at low pH, at mildly acidic pH and at neutral pH. The interference caused by the presence of Al, Ca, Mg and Fe was monitored.

It was found that most commercial ion exchangers do not exhibit a marked selectivity for the metals of interest. Consequently, the co-extraction of iron is a major obstacle for the application of ion exchange to acid mine drainage solutions. The selectivity did not improve significantly when Fe(III) was reduced to Fe(II). The co-extraction of calcium becomes a problem at higher pH when lime is used to neutralize the solution. The most promising results were obtained with copper and antimony, which were amenable to extraction even at low pH.

While the selective extraction of Cd, Ni or Zn was not feasible under most conditions, the simultaneous extraction of all three metals can be done at neutral pH using either a chelating resin or a synthetic zeolite. This fact could be used to reduce the amount of lime that is normally added to ensure the complete precipitation of metals.

Last Modified: 2003-11-26		Important Notices

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