In view of the characteristics of highly toxic sodium cyanide, it is important to study how to use physical or chemical methods for enhanced leaching, reduce the amount of sodium cyanide, and increase the leaching rate of gold to improve the economic benefits of enterprises. At present, a certain mine in Jiaodong has caused a sharp increase in the amount of sodium cyanide due to the treatment of some gold concentrate containing high copper and lead . Despite the leaching of ammonia cyanide, the working environment of the workshop deteriorates due to the high volatility of ammonia. Its utilization rate is also low. To this end for the characteristics of the high copper lead experiment, Alkaline Pretreatment taken, and the addition of the two agents suitable for such ores which instead of liquid ammonia leaching; not only strengthen the leaching of gold and silver, and sodium cyanide can be reduced The amount used.
   First, the nature of the ore
Comp ore concentrate experiment for a lead-containing copper gold mine 3 according to a certain proportion of the concentrate containing pyrite, galena, chalcopyrite, pyrrhotite, galena and some white secondary metal such as copper minerals, gangue minerals as quartz, illite and sericite, gold-bearing ore is a gold silver, gold-silver, gold fine particles to granules, micro-fine-based, copper was Secondary copper accounts for 30% to 50% of all copper. The secondary lead can be leached in 10% to 30%. The main chemical components in the mixed concentrate are shown in Table 1.
Table 1 Main chemical element content of mixed concentrate
element | Au/g·t -1 | Ag/g·t -1 | Cu/% | Pb/% | Zn/% | Fe/% | As/% |
grade | 49.79 | 245.43 | 1.29 | 4.17 | 1.2 | 36.37 | 0.34 |
   Second, the experiment and results analysis
In response to the influence of copper and lead and the actual production situation at the site, the first alkaline leaching pretreatment was carried out to remove some harmful impurities such as iron, copper, lead and sulfur. The second is to add strengthening agent and copper in the leaching operation. In combination, the consumption of sodium cyanide is reduced, and the leaching of gold and silver is accelerated, and the original ammonia water immersion agent which is volatile and affects the operating environment is replaced.
(1) Inflatable alkaline soaking. Adding lime before leaching, adding air to alkali leaching under the condition of pH≥11, the time is 2h, which can remove some harmful impurities and significantly reduce the amount of sodium cyanide. In addition, secondary lead can form lead in strong alkali conditions. The acid salt enters the solution and is dehydrated by pressure filtration to discharge the process flow, thereby reducing its influence on the subsequent cyanidation operation. The test results are shown in Table 2.
Table 2 Test results of cyanidation leaching after aerated alkali leaching
test | Raw ore grade / g·t -1 | Slag grade / g·t -1 | Leach rate /% | NaCN unit consumption / g·t -1 | Remarks |
1# 2# | 49.79 49.79 | 1.52 1.49 | 96.92 97.01 | 10.9 9.1 | Alkali dip Alkali dip |
From the above results, the alkali leaching can significantly reduce the amount of sodium cyanide. Under the condition that the cyanide leaching rate is close to each other, the sodium cyanide unit consumption is reduced by 1.8 kg/t.
(2) Since copper and lead consume a large amount of [CN - ] and O 2 in cyanide leaching, in order to reduce the influence of copper and lead, five kinds of agents were selected, and five kinds of agents were comprehensively tested, and finally determined 2 The combination of the agents was used as an infusion aid for cyanide leaching, and the results of the respective tests are shown in Table 3.
Table 3 Test results of cyanidation leaching after compounding
Pharmacy name | Na 2 CO 3 | CaO | Phosphate sodium hexametaphosphate | A | A+B | B | Conventional leaching |
Dosage / g·t -1 Dip grade / g·t -1 Au leaching rate /% | 2.5 1.39 97.21 | 0.5 1.4 97.19 | 0.8 1.5 96.99 | 0.48 1.41 97.17 | 0.3+1 1.29 97.41 | 1.0 1.35 97.29 | 1.51 96.92 |
Note: All the above experiments were carried out under alkaline leaching conditions.
In summary, various agents can improve leaching, but the synergistic effect of A and B agents can significantly improve the leaching of such ores, and the leaching rate can be increased by 0.49%.
(3) The effect of A+B interaction on the amount of cyanide is shown in Table 4.
Table 4 Results of cyanide leaching test after conventional leaching and addition of A and B agents
condition | NaCN unit consumption /kg·t -1 | [CN - ] concentration /mol·L -1 | Slag grade /g·t -1 |
Conventional leaching Add A and B leaching | 9.1 7.8 | 0.70×10 -2 to 0.75×10 -2 0.60×10 -2 to 0.65×10 -2 | 1.51 1.29 |
From the results of the table, the addition of two kinds of A and B leaching agents can significantly reduce the amount of sodium cyanide. Since the entire leaching [CN - ] concentration can be carried out at a lower level, the consumption of NaCN can be saved.
(4) After two months of comparison of production and application, the test results are shown in Table 5.
Table 5 Results of conventional leaching and cyanide leaching test
condition | NaCN unit consumption /kg·t -1 | [CN - ] concentration /mol·L -1 | Slag grade Au/g·t -1 |
Conventional leaching (April) Add A and B agent leaching (May) | 9.16 7.06 | 0.70×10 -2 to 0.75×10 -2 0.60×10 -2 to 0.65×10 -2 | 1.21 1.09 |
In summary, the use of A + B combination can significantly improve the effect of cyanide leaching, to a certain extent can replace the use of ammonia in the original production, one is to inhibit the leaching of Cu; the second is to reduce the impact of copper and lead leaching on gold cyanidation The third is to reduce the concentration of sodium cyanide in the leaching operation. More than one month of production practice has proved that the cyanide concentration in cyanide leaching operations can be reduced by 0.10%, the consumption of NaCN can be saved by 2.1kg/t, and the grade of cyanide slag can be reduced by 0.12g/t.
  Third, the benefit calculation
(1) The unit price of A medicine is 3.1 yuan per kilogram, the unit price of B medicine is 2.8 yuan per kilogram, and these two kinds of medicaments are easy to purchase. According to the experimental dosage, the cost of medicine is 3.1×0.3+2.8=3.73 yuan per ton. The saved amount of NaCN is 2.1kg/t, and the cost is 6.98×2.1=14.658 yuan per ton, and the cost per ton of mine can be 14.658-3.73=10.928 yuan.
(2) The benefit from the reduction of sodium cyanide concentration is that the moisture content of the effluent concentrate is 15%, the liquid-solid ratio is 0.18, the water volume outside the ton mine is 0.18t, and the concentration of sodium cyanide is decreased by 0.10%. , equivalent to a drop of 1kg / t, that is, the amount of sodium cyanide in the outer band of the ore is 0.18kg / t, and the cost of reducing sodium cyanide is 1.256 yuan per ton.
(3) The amount of volatilization reduced due to the decrease in concentration cannot be accurately calculated and will not be calculated.
According to the annual processing of 50,000 tons of concentrate, the annual profit can be (10.928+1.256)×5=60.92 million yuan.
 Fourth, the conclusion
The use of aerated alkali leaching of concentrates containing pyrrhotite, secondary copper and lead prior to leaching can save considerable amounts of NaCN.
For gold concentrates with relatively high copper and lead, adding a combination of A and B complexing agents for conventional cyanidation can significantly improve the leaching effect of such ores, increase the leaching rate, and reduce the amount of NaCN 2.1. Kg/t, which produces considerable economic benefits.
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