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The rates of pH during elution when were studied from 2 to 12 showed small variation. The ph value apparently has little effect on the rate of elution and small variations can be occurred by secondary aspects such as contamination of recycled solution due to corrosion. Thus, a good ph value for the elution should be major than 10. As can be appreciated application of strong base resins is feasible. Once eluted the resin, the obtained solution with high gold concentration can be sent to electrowinning.
Weak base resin are selective and can be eluted easily but have low capacity, approximately 25-50% of a strong base resin. Loading and selectivity are depended of pH. Selectivity improves with increasing pH; however, both the capacity and adsorption rate are reduced markedly as the pH is increased above 8. These resins can be eluted by simple hydrolysis with sodium hydroxide, the rate increases with increasing the NaOH concentration to an optimum concentration of 0.5 M. At higher concentrations the rate is reduced, maybe to the precipitation of some hydroxides. Then
weak base resins can be employed in the gold recovery from cyanidation.
Some pilot tests were carried out at Mintek some time ago. Some results are presented in Table 3. The performance of the RIP and CIP plants are very similar, with stage efficiencies of between 70 and 75% under the chosen operating conditions. This is interesting, since one of the claimed disadvantages of the resin for gold is its non-selectivity.
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