COPPER RECOVERY FROM PREGNANT LEACH SOLUTION USING COMBINATION OF ION EXCHANGE,SOLVENT EXTRACTION AND ELECTROWINNING
(Combined L/IX/SX/EW process )
For nearly thirty years, solvent extraction process has been the most prevalent technique of copper recovery in mining industry. It is an efficient and economically attractive way to recover copper from pregnant leach solutions.
Despite, the obvious advantages of the solvent extraction, it does have several shortcomings,namely leach solutions containing large quantities of suspended solids are unsuitable for solvent extraction processing ,large plant “footprint” of SX circuits, large volumes and cost of organic compounds.
The combined L/IX/SX/EW process using Ion Exchange and Solvent Еxtraction, developed by IONTECH, offers a method , which overcomes a negative characteristics shown above. This method may be excellent for processing of pregnant leach solutions (PLS) as well as in the decommissioning of spent copper heaps and dumps, acid mine drainage /AMD/ аnd other industrial streams without any preconditioning.
The IONTECH L/IX/SX/EW process is very promising in the recovery of copper from different chemical solutions .Figure I depicts the overall process. It shows clearly that the IX process can be successfully included in the L-SX-EW scheme. As the name suggests the method involves four major stages-Leaching ,Ion exchange ,Solvent Extraction and Electrowinning.
Metal recovery by Solvent Extraction (SX) process is a well-known technique that is practiced commercially for the recovery of copper,uranium,nickel,cobalt,molybdenum and other metals..The main advantages of the Solvent Extraction process are:
- A possibility to process a poor quality, oxidized and mixed sulfide ores
- An absence of using a high temperatures (process temperatures is not more that 50oC)
- Recycling of barren solutions
- Very high selectivity at removal and purification of metals
- Removal of desirable metal(s) without impurities
- Concentration of the desirable metal in order to reduce further operating costs; The concentration of the substance in the “new” aqueous solution may be increased, often to 10-100 times that of the original aqueous solution, through adjustment of the liquid flow rates
- Metal conversion to a form ,suitable for easily recovery
- Low capital cost and operating cost
- Exceptionally high quality of the final product
Despite the wide acceptance of SX, it does have some shortcomings that have several negative impacts. SX employs large quantities of volatile organic substances. SX extractants are potential toxins and certainly pose an environmental concern .Crud generation, which is “fact of life” in SX process requires special facilities and causes economic losses and downtimes.The organic losses resulting from the liquid organic phase are an environmental hazard to ground water and lead to economic losses and EW operating problems. Solvent extraction is very sensitive to low temperatures. This causes bad phase disengagement times and therefore poor process performance.
The combined L/IX/SX/EW process using Ion Exchange and Solvent Еextraction, developed by IONTECH, offers a method, which overcomes SX negative characteristics shown above. The key findings of the process are:
- The process is suitable for recovery of copper from PLS with metal concentrations, varying on a broad range
- Can be operate effectively with very low-graded copper pregnant leach solutions. This results in prolonged projects life ,compare to solvent extraction recovery only
- The construction of large ponds for pre-filtration of the PLS is not necessary. In this case, very sensitive solvent extraction process can be work properly even at intensive rainfalls;
- There is possibility to work with turbid solutions and solutions containing large quantities of suspended solids
- Winter operation without troubles. SX can be work properly i.e. with good phase disengagement times, even at low temperatures. This is due to high temperatures of IX regenerate used as a SX feed
- Combining of ion exchange and solvent extraction improves the Cu/Fe ratio in treated solutions.
- Combining of ion exchange and solvent extraction greatly reduces crud formation and thence crud handling requirements
- Combining of ion exchange and solvent extraction significantly reduces downtimes
- Integration of the sorption process in SXEW scheme can be used for control of metal/acid ratio ,which is very important for SX process
- Combining of ion exchange and solvent extraction strongly reduces organic losses
- Combining of ion exchange and solvent extraction reduces EW organic problems and thence improved copper cathodes quality
- Ion Exchange -Solvent Extraction-Electrowinning technological approach lead to SX plant sizes reducing. Thus ,minimizes the floor space requirements for SX “footprint “
- The IX-SX combination is suitable for treatment of solutions in the decommissioning of spent copper dumps, acid mine drainage /AMD/ аnd ammoniacal etch solutions.
- The process can be fully automated
- The process is cost effective and environmentally friendly .The IX-SX combination is characterized with similar capital cost and lower operating cost compare to solvent extraction process only
- Ion Exchange -Solvent Extraction-Electrowinning technological approach offers short construction times
- By combining of correctly selected reagents, good operation conditions and adequate flow rates is possible to ensure flexible and fully optimized plant circuit using technological approach Leaching-Ion Exchange-Solvent Extraction-Electrowinning