Carbon column process
The carbon column method is a method for recovering gold cyanide complex from solution. Coconut shell ctivated carbon is placed in several tanks connected in series, and the solution flows upward through the carbon layer.
This method of recovering gold cyanide complex has been used for grinding cyanidation. Cyanide is fed into the grinding circuit together with the ore. Since the surface of gold particles is always fresh and highly reactive in the grinding circuit, and the diffusion rate of various ions in the slurry is also high, the dissolution rate of gold is quite fast, and the leaching rate of gold in the grinding circuit can reach more than 50%. The carbon column method is to recover this part of dissolved gold from the overflow of the thickener in the grinding circuit. The advantages of this method are: due to the lack of stirring and grinding of the slurry, the loss of carbon is very low; since the mass transfer in the solution is faster than in the slurry, the adsorption rate and gold loading of carbon will be higher. If the adsorption time of the carbon column method is the same as that of the carbon slurry method, the tail liquid discharged by the carbon column method will be lower.
Most carbon column methods are one-stage adsorption. The column is a suspended bed, and the use of a fixed bed is being studied. One of the reforms of the carbon column method is to use a movable carbon adsorption column. The carbon stringing method of this adsorption column is to move the adsorption column instead of transporting the carbon from one adsorption column to another. Finally, the gold-loaded carbon moves to the desorption and acid washing operation together with the adsorption column. This minimizes the wear of the carbon.
Factors affecting gold adsorption
1. Ionic strength
The ionic strength of the solution has a great influence on the carbon load. The carbon load in the gold solution of deionized water is very low. The ionic strength of the gold solution plays an important role in the adsorption mechanism. The degree of adsorption of various cyanide complexes of gold on activated carbon depends on their cations. Calcium cyanide is the most strongly adsorbed complex, and the order is as follows: Ca2+>Mg2+>H+>Li+>Na+>K+.
2. Effect of pH value
Because both hydrogen ions and hydroxide ions are adsorbed by carbon, the pH value affects the adsorption capacity of carbon. As the pH value decreases, the equilibrium amount of gold loaded on carbon increases. In fact, the effects of calcium cations and hydroxide anions are just opposite. They are added when adjusting the pH value with lime. High calcium concentration will promote the adsorption of gold, while high pH value will reduce the adsorption of gold.
3. Effect of particle size
The size of activated carbon particles has a great influence on the adsorption rate. For activated carbon of the same quality, the smaller the particle size, the greater the adsorption rate of gold.
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