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Activated carbon for gold recovery

2022-01-12 09:49
1.Experiment
1.1Experimental materials
 
The tested raw gold ores was taken from one mine in northeast China. The raw ore pretreatment, element analysis, and the taste detection of gold and silver in the poor grade liquid involved in this article are all entrusted to Jilin Metallurgical Research Institute. The element analysis results of the raw gold mine are shown in Table 1. Coconut-shell activated carbon and coal-based activated carbon for the test were taken from Jiapigou Gold Mine and our company, Taixi Town, Shizuishan City, Ningxia. The main technical indicators are shown in
 
 
 
 
 
Table 2.
Table1 Elemental analysis data of raw gold ore
Element Au(g/t) Ag(g/t) Cu Pb Zn Fe As
Content% 37.10 119.83 0.031 2.11 0.53 18.94 4.89
Element S C Bi CaO MgO SiO2 Al2O3
Content% 22.35 0.23 0.022 1.29 1.10 44.76 2.05
 
 
1.2 AC(activated carbon) Mechanical wear comparison experiment
 
Taking Taixi coal based carbon and coal-shell carbon with the same particle size, using the WEMCO flotation test machine under the same conditions. The mixing tank diameter of the flotation test machine is 120mm, mixing wheel diameter is 50mm,. The mixing speed is 950r/min, the activated carbon mass concentration is 10%, and the mixing time is 6h. The experiment process is shown in Figure 1.
 
The mechanical wear of coconut shell and coal quality activated carbon is listed in Table 3 with the wear rate of 20% for coal shell activated carbon and 28%.
Table 2 Technical index between coconut shell activated carbon
No. Project Coconut shell Activated carbon Taixi coals Activated carbon Standard
Sample A Sample B Sample A Sample B  
1 Iodine value（mg/g） 1073 1043 1016 1056 ASTM D4670
2 CCl4(%) 61.3 56.5 55.4 61.1 ASTM D3467
3 Dry dosing strength% 97.3 97.8 97.3 96.4 ASTM D3802
4 Ash(%) 2.08 2.02 4.19 4.5 ASTM D2866
5 Bulk density (g/L) 519 535 572 546 ASTM D2854
6 Granularity (mesh) 8-16 8-16 8-16 8-16  
 
 
 
 
 
Carbon
 
Mixing
 
Separation of carbon and liquid

 
 
Liquid after filtration    carbon
 
 
 
Flow chart
Ores   milling   soaking in alkaline liquid
 
CaO3
NaCN
Activated carbon
 
Table 3
Type Quality before wearing /g Quality after wearing /g Rate of wearing/%
Coals AC 100 80 20.00
Coconut AC 100 72 28.00
 
1.3 Comparative experiment of activated carbon
Under the same cyanidation and adsorption conditions, take coal-based carbon of the same particle size and weight, and put the coconut shell carbon into the carbon leaching stirred tank of the same specification for dynamic adsorption of the leached precious liquid, and then take the lean carbon at different times. The liquid sample is analyzed for the content of gold and silver. Figure 2 of the test flow chart. Test conditions: Grinding fineness required -0.071mm accounted for 90%, slurry concentration was 40%, alkali presoaking time was 2h, CaO dosage was 4kg/t (concentration 0.01%), and NaCN dosage was 1.5 kg/t (concentration 0.04%), cyanide in and out time is 24 hours, carbon slurry concentration is 0.67kg/m3, and the cumulative adsorption time is 100h and 120h.
Activated carbon adsorption gold saturation test results are shown in Table 4. The data shows that under the same adsorption conditions, the gold and silver adsorption saturation of coal-based activated carbon are 15.11kg/t and 4.61kg/t, respectively, which are more saturated than the gold and silver adsorption of coconut shell carbon. The amount is 2.02kg/t and 1.48kg/t higher respectively.
Table 4 Activated carbon adsorption gold saturation test results
 
 
 
 
Type adsorption time /
h		 Liquid rich Liquid lean Saturated gold loaded carbon grade
Au/
g/m3		 Ag/
g/m3		 Au/
g/m3		 Ag/
g/m3		 Au/
kg/t		 Ag/
kg/t		 Cu/
%		 Pb
%		 Zn/
%		 Fe/
%
Coal based C 100 17.5 11.6 7.50 8.50 15.11 4.61 0.02 0.47 0.054 0.58
120 7.41 8.40
Coconut
Shell C		 100 17.5 11.5 8.83 9.51 13.09 3.13 0.012 0.93 0.034 0.27
120 8.77 9.40
 
1.4 Comparative test of activated carbon adsorption speed
First, use cyanide leaching equipment to analyze the taste of gold and silver. Under the same adsorption conditions, conduct adsorption tests with coal-based charcoal and coconut shell charcoal. The result of the adsorption rate of coconut shell charcoal. Fig. 3 and Fig. 4 of the test process, the preparation conditions of cyanide precious liquid are the same as above, the concentration of carbon slurry is 5kg/m3
 
The relationship curve between the first adsorption time and the adsorption rate is shown in Figure 5A. The newly prepared precious liquid contains 17.50g/m3 of gold and 11.48g/m3 of silver. It can be seen that the adsorption rate of coal-based activated carbon is higher than Coconut shell activated carbon, after 20 hours of adsorption, the gold adsorption rate of coal-based activated carbon reached 99.57%, the silver adsorption rate reached 89.90%, the 20-hour gold adsorption rate of coconut shell activated carbon reached 96.97%, and the silver adsorption rate reached 71.78%
The relationship curve between the second adsorption time and the adsorption rate is shown in Figure 5B. It can be seen that the adsorption speed of coal-based activated carbon is also higher than that of coconut shell activated carbon. After 20 hours of adsorption, the gold adsorption rate of coal-based activated carbon reaches 96.29%, and the adsorption of silver The rate reached 69.51%; the 20-hour gold adsorption rate of coconut shell activated carbon reached 86.86%, and the silver adsorption rate reached 40.77%
The relationship between the third adsorption time and the adsorption rate is shown in Figure 5C. It can be seen that the adsorption speed of coal-based activated carbon is higher than that of coconut shell activated carbon. After 20 hours of adsorption, the gold adsorption rate of coal-based activated carbon reaches 92.57%, and the adsorption rate of silver Reaching 38.33%, the 20-hour gold adsorption rate of coconut shell activated carbon reached 75.71%, and the silver adsorption rate reached 20.73%
□Coal Carbon-Au; △Coconut Shell Carbon-Au; ○Coal Carbon-Ag;▽Coconut Shell Carbon-Ag
 
1.5 Analysis test of gold-loaded activated carbon
The analytical solution is a mixed solution with a mass concentration of 1% NaOH and 1% NaCN, the analytical temperature is 98-100°C, the analytical time is 12 hours, the analytical solution volume is 1L, and the amount of gold-loaded activated carbon is 1g. Under these conditions, analytical tests were carried out on coal-based activated carbon and coconut shell activated carbon. The analytical test process is shown in Figure 6
 
 
Gold-loaded carbon
Parsing
Carbon liquid separation
Analytic charcoal analytic liquid
Figure 6: Analytical test process of gold-loaded activated carbon
The analysis test results of coal-based activated carbon and coconut shell activated carbon are shown in Table 5. It can be seen that the gold resolution rate of coal-based activated carbon reaches 99.50%, and the silver resolution rate reaches 97.72%; the gold resolution rate of coconut shell activated carbon reaches 99.43%, and the silver resolution rate The rate reaches 96.66%, and the resolution rate of coal-based activated carbon is slightly higher than that of coconut shell activated carbon.
 
 
Table 5 Gold-loaded activated carbon analysis test results
Type Gold-loaded activated carbon grade/（kg/t）
Au           Ag		 Separate carbon grade/（g/t）
Au          Ag		 Separate liquid/（g/m3）
Au          Ag		 Separate rate%
Au          Ag
Coal AC 15.11 4.61 75.31 105.19 15.03 4.51 99.50 97.72
Coconut AC 130.9 3.13 79.10 104.40 13.61 3.02 99.43 96.66
 
1.6 Specific surface area and pore size distribution of coal-based activated carbon
Use autosorb-1 specific surface and porosity analyzer to test the liquid nitrogen adsorption-desorption isotherm of coal-based activated carbon at a temperature of 76.71K (as shown in Figure 9), and use BET equation and BJH method to calculate the pore size distribution of activated carbon. Specific surface area and pore volume. The results show that the average particle size of coal-based activated carbon is 0.76nm, the specific surface area is 1017m2/g, the effective pore volume is 0.42cm3/g, and the mesopore distribution is narrow.
 
3. Conclusion
Coconut shell activated carbon is the most widely used activated carbon in the cyanide carbon slurry process for gold beneficiation, and it has a relatively good adsorption effect. The coal-based activated carbon used in this comparative test is made from high-quality Taixi anthracite raw materials to produce high-quality activated carbon. The results of the comparative experiment show that the wear rate, saturated gold loading and adsorption speed of activated carbon prepared from Taixi anthracite are significantly better than coconut shell activated carbon. The resolution rate is slightly higher than that of coconut shell activated carbon.
(1) Under the same conditions, the attrition rate of coal-based activated carbon is 20%, and the attrition rate of coconut shell activated carbon is 28%
(2) Under the same conditions, the saturated gold loading of coal-based activated carbon is 15.11kg/t and the silver loading is 4.61kg/t; the gold loading of coconut shell charcoal is 13.09kg/t, and the silver loading is 3.03kg /t.
(3) Under the same conditions, the first gold and silver adsorption rates of coal-based activated carbon reached 99.57% and 89.90%, the second gold and silver adsorption rates reached 96.29% and 69.51%, and the third gold and silver adsorption rates reached 92.57% and 38.33%; the first gold and silver adsorption rates of coconut shell activated carbon reached 96.97% and 7178%, respectively, the second gold and silver adsorption rates reached 86.86% and 40.77%, and the third gold and silver adsorption rates reached 75.71. % And 20.73%
(4) Coal-based activated carbon has an average particle size of 0.76nm, a specific surface area of ​​1017m2/g, and an effective pore volume of 0.42cc/g.
(5) Activated carbon prepared from Taixi anthracite has a significantly better gold extraction performance than coconut shell carbon, and has a wide range of coal sources and relatively low price. It has good research and promotion application value in gold beneficiation technology.
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