Desorption of gold loaded carbon
【Principle of gold loaded carbon desorption】
The experimental study on the principle of gold loaded carbon desorption shows that the process of activated carbon adsorption is actually a reversible process. When the carbon adsorbs gold, the
high temperature, pressure, pH value and CN concentration will significantly reduce the amount of gold adsorption. Therefore, an effective method can be taken to make the gold on the gold loaded carbon be desorbed into the solution.
【Desorption method and technological conditions of gold loaded carbon】
Atmospheric heating desorption method
This is the first relatively simple method. Under the condition of 85 ~ 95 ℃, a mixed aqueous solution of 0.1% NaCN and 1.0% NaOH is used to make it pass through the gold loaded carbon bed. It takes about 28 ~ 70 hours to complete the desorption.
Pressure desorption method
When the temperature is 150 ~ 1700c, the pressure is 0.3432mpa, the mixed aqueous solution is 0.1% NaCN and 0.4 ~ 1.0% NaOH, and the desorption time is 4 ~ 6 hours, the gold content of decarbonization is less than 50 ~ 70g / T. The cycle of this method is not long, but the cost of equipment is high, and it must be cooled before the desorption of precious liquid is sent to electrowinning.
Alcohol desorption
The mixture of 1.0% NaCN and 1.0% NaOH is added with 20% volume of alcohol and desorbed at 800C under normal pressure for 5 ~ 6 hours. However, alcohol is flammable and volatile, which is not easy to control.
American British desorption method
The method is developed by Anglo American Research Institute of South Africa. The mixture of 5% and 1.0% of 0.5 volume of gold loaded carbon is used to pretreat the gold loaded carbon for 0.5 ~ 1 hour, and then the gold loaded carbon is desorbed with 5 volume of heated deionized water at a flow rate of 3 volume of gold loaded carbon bed per hour. The operating temperature is 1100c, the operating pressure was 0.5 ~ 1.0 kg / cm2, and the desorption time (including acid) is about 9 hours.
【Desorption equipment and operation precautions】
The desorption equipment of gold loaded carbon is usually connected with the electrodeposition equipment to form the unit of production cycle.
The prepared gold loaded carbon is loaded into the desorption tower (column), and then the prepared desorption solution is pumped into the desorption electrowinning system. The specific operation mode depends on the equipment and process used.
【Matters needing attention in desorption of gold loaded carbon】
When the length diameter ratio of desorption tower is greater than 6, the desorption effect is better, the operation is convenient and the desorption time is shortened. Therefore, the desorption tower with length diameter ratio higher than 6 is generally used.
The flow state of desorbed liquid in the tower should be as uniform as possible in the cross section of the tower, and fully contact with gold loaded carbon
In general, the longer the desorption time is, the higher the desorption rate is. However, if the desorption time is too long, the utilization rate of equipment will be reduced and the production cost will be increased.
The desorbing temperature should be strictly controlled according to the regulations, and the desorbing temperature should be evenly distributed at all points in the tower
Ensure that the composition of desorption solution meets the requirements
Pay attention to the flow rate of desorbing liquid, which can reach 1-5 carbon bed volume in 1 hour.
Pay attention to the impurity content and pore characteristics of gold loaded carbon. The removal of impurities (sawdust, plastics, coarse-grained ore, etc.) in advance will be beneficial to the improvement of desorption rate.
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