Abstract

The use of granular activated carbon (GAC) is a typical and sustainable technique for recovering precious metals from a cyanide leaching solution (CLS). The level of GAC activity is a fundamental factor in assessing the rate of precious metal adsorption; thus, it is essential to determine the efficiency of carbon elution for reproducing GACs. Since mercury (Hg) adsorption plays a critical role, economically and environmentally, in GAC efficiency, we conducted various laboratory and industrial experiments to explore the effect of different rates of GAC activation (10%, 35%, 70% and 100%) on Hg adsorption from CLS. Assessments of laboratory test results showed a direct relationship between the Hg adsorption and GAC activity; by increasing the GAC activity from 10% to 100%, the recovery of Hg was increased from 20% to 41%. Kinetic modeling results indicated that the Hg adsorption for all GAC activities followed chemisorption mechanisms. There was good agreement between the laboratory test results and the results of experiments on the industrial scale (that used a continuous circuit). These outcomes indicate that by increasing the frequency of carbon reactivation and using GAC with a high level of activity in the first tank, Hg desorption was meaningfully decreased and recovery was improved (for 10% GAC activity vs. 35% GAC activity, recovery was 40% vs. 90%, respectively).

Highlights

  • Recovery of precious metals from cyanide leaching solution (CLS) by granular activated carbon (GAC) is a typical process in gold processing plants [1,2]

  • This study explores the effect of various rates of GAC activity (10%, 35%, 70% and 100%) on recovery of Hg from CLS on two different scales

  • The first tank was selected to study the effect of GAC activity on an industrial scale because, as mentioned, the plant works in a countercurrent format, and the concentrations of metals in this tank are significantly higher than those in other tanks

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Summary

Introduction

Recovery of precious metals from cyanide leaching solution (CLS) by granular activated carbon (GAC) is a typical process in gold processing plants [1,2]. Elution is a process that desorbs metals from the GAC surface to reactivate it. It is essential to understand the effect of the frequency of carbon reactivation on precious metals adsorption in gold extraction plants. Understanding adsorption rates onto GAC with different activities may help processors to strike an economical–technical balance in precious metals recovery in CLS plants. It is essential to study Hg removal from CLS by using GAC with different levels of activity. This study explores the effect of various rates of GAC activity (10%, 35%, 70% and 100%) on recovery of Hg from CLS on two different scales. The second is Hg adsorption onto GAC at a continuous circuit in a plant (industrial scale)

Ore and Adsorbent
Laboratory Tests
Modeling
Industrial Scale Test
Laboratory-Scale Studies
Industrial-Scale Studies
Conclusions

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