| abstract |
AS PART OF A CYCLIC, LEACHING-PRECIPITATION PROCESS FOR COPPER VALUES, A REDUCTANT, SUCH AS A REDUCING GAS OR REDUCING IONS SELECTED FROM THE GROUP CONSISTING OF SULFITE ION AND BISULFITE ION, IS INJECTED INTO A BODY OF COPPERMINERAL-BEARING MATERIAL. THE INJECTION SITE OR SITES ARE REMOVED FROM ACCESS OF ATMOSPHERIC AIR, AND INJECTION IS CARRIED OUT IN THE ABSENCE OF OXYGEN TO PREVENT AUTOOXIDATION OF THE REDUCING AGENT. WHEN INJECTED IN AN AREA ADJACENT THE EMERGENCE FROM SUCH BODY OF AN APPLIED ACIDIC LEACH SOLUTION CONTAINING FERRIC IONS AND PREGNANT WITH COPPER VALUES, IN ORDER TO REDUCE FERRIC IONS IN SUCH LEACH SOLUTION TO FERROUS IONS SO DIFFICULTY, E.G. USELESS CONSUMPTION OF METALLIC IRON PRECIPITANT, IN THE COPPER RECOVERY STAGE IS AVOIDED, SUCH REDUCTANT ALSO ACTS AS A BACTERICIDE TO ELIMINATE BOTH AUTOTROPIC AEROBIC BACTERIA, WHICH OXIDIZE FERROUS TO FERRIC IRON IN PRESENCE OF OXYGEN, AND ANEROBIC HYDROGENASE-PRODUCING STRAINS OF BACTERIA, WHICH REDUCE SULFATES IN THE ABSENCE OF OXYGEN AND PRODUCE HYDROGEN SULFIDE THAT UNDESIRABLY PRECIPITATES SOLUBLE COPPER INTO INSOLUBLE COPPER SULFIDE. IF SUCH AN AREA IN THE BODY OF MATERIAL OR IF OTHER AREAS THEREIN HAVE BECOME, EITHER NATURALLY OR FROM APPLIED LEACHING PRACTICES, SUBSTANTIALLY IMPERVIOUS TO THE CONTINUED PERCOLATION OF A LEACH SOLUTION THERETHROUGH, THEY ARE RENDERED HIGHLY PERVIOUS BY THE INJECTION THEREINTO OF SUCH REDUCTANT. A CONCOMITANT EFFECT OF THIS TREATMENT IS THE RELEASE OF EATER, RICH IN COPPER VALUES, THAT HAD BEEN IMPOUND IN MINE WASTE DUMPS OR OTHER BODIES OF MATERIAL PREVIOUSLY SUBJECTED TO LEACHING. THE REDUCING IONS MAY BE CONVENIENTLY INJECTED AS A SULFITE OR BISULFITE SOLUTION. WHEN THE REDUCTANT IS A REDUCING GAS, SUCH AS SULFUR DIOXIDE OR CARBON MONOXIDE, IT IS PREFERABLY INJECTED DIRECTLY INTO THE MATERIAL CONCERNED. |