Brief introduction of gold and silver extracted by thiourea method
In the past two or three decades, people have made great efforts in the research of non-toxic gold extraction technology, trying to find some non-toxic, efficient, cheap and feasible non-cyanide gold solvent, and achieved gratifying results. Among them, the thiourea method is the most promising one, such as thiourea electrowinning method, thiourea carbon slurry method, thiourea resin method, etc., all of which have undergone considerable scale expansion experiments and achieved initial success.
The characteristics of the thiourea method are: non-toxic (low toxicity); the rate of gold dissolution is fast, and some research results prove that it is 4-5 times faster than cyanide, and some even think it is 12 times faster. The leaching of silver sulfide is not only fast. And the leaching rate is also high; the selectivity is better than cyanide, and the sensitivity to copper , zinc , arsenic and antimony is significantly lower than that of the cyanidation method; when the solubility is high, Fe 3+ and the oxygen in the air are used as the mixed oxidant. It is cheaper and more effective than H 2 O 2 and NaO 2 , etc.; with H 2 SO 4 as a pH adjuster, the dissolution rate of gold is faster than that of HNO 3 and HCl as a pH adjuster; There are many methods for recovering gold and silver in the pulp, and the recovery rate is high. At the same time, the consumption of thiourea can be greatly reduced, and valuable metals such as copper can be comprehensively recovered. Other gold-loading materials such as anode mud, gold-bearing uranium ore, acid leaching residue can be treated. When it comes to bacterial leaching, it has certain advantages. However, its disadvantages are: the nature of thiourea is not very stable, the consumption is large, the price is high, the cost is high, and the economic competition is not the cyanidation method; while the thiourea method is carried out under acidic conditions (pH<4), the acidic environment The resulting corrosion of the equipment is another weakness of the thiourea process; and some believe that thiourea is carcinogenic.
In view of the fact that thiourea dissolves silver sulfide at a high rate and the leaching rate is much higher than that of cyanidation, the Colorado Colorado mine has used thiourea to leaching silver from silver-containing tailings since 1982. Since 1977, France has used thiourea to recover gold and silver from flotation tailings and zinc calcine. Australia's New England antimony mine has been treated with thiourea for strontium-containing concentrates since 1984. South German calcium cyanamide company (SKW), researched on the basis of the conventional thiourea method to introduce the reducing agent SO 2 into the leaching slurry, the supply rate of SO 2 to control 50% of the total thiourea in the slurry Dithiocarbamidine is good. Under this condition, the leaching rate of gold in the ore can reach more than 85%, and the consumption of thiourea can be reduced to 0.57kg per ton of ore, which can greatly reduce the consumption of thiourea, and promote the industrial application of thiourea gold extraction. There is also a South African gold mining company that slightly acidifies the thiourea leachate (pH 4-7) and adds Fe 3+ as an oxidant, which can leaching 95%-99% of the gold in the raw material within 2 hours to treat the mercury tailings. And low grade ore. The United States has also studied the fine-grained gold ore of Carlin-type carbonaceous ore and Chip Mining, and has tested the lean thiourea heap leaching.
The study of thiourea gold extraction in China began in the 1960s. Through nearly 30 years of hard work, it has entered the forefront of the world in the application research of thiourea gold. Among them, Beijing Nonferrous Metallurgy Design and Research Institute, Changchun Gold Research Institute, Jilin Metallurgical Research Institute and other units are even more advanced. In recent years, the thiourea leaching gold technology developed in China has been applied to the industrial production of gold deposits such as Yu'er Cliff, Zhangjiakou and Longshui.
The characteristics of the thiourea method are: non-toxic (low toxicity); the rate of gold dissolution is fast, and some research results prove that it is 4-5 times faster than cyanide, and some even think it is 12 times faster. The leaching of silver sulfide is not only fast. And the leaching rate is also high; the selectivity is better than cyanide, and the sensitivity to copper , zinc , arsenic and antimony is significantly lower than that of the cyanidation method; when the solubility is high, Fe 3+ and the oxygen in the air are used as the mixed oxidant. It is cheaper and more effective than H 2 O 2 and NaO 2 , etc.; with H 2 SO 4 as a pH adjuster, the dissolution rate of gold is faster than that of HNO 3 and HCl as a pH adjuster; There are many methods for recovering gold and silver in the pulp, and the recovery rate is high. At the same time, the consumption of thiourea can be greatly reduced, and valuable metals such as copper can be comprehensively recovered. Other gold-loading materials such as anode mud, gold-bearing uranium ore, acid leaching residue can be treated. When it comes to bacterial leaching, it has certain advantages. However, its disadvantages are: the nature of thiourea is not very stable, the consumption is large, the price is high, the cost is high, and the economic competition is not the cyanidation method; while the thiourea method is carried out under acidic conditions (pH<4), the acidic environment The resulting corrosion of the equipment is another weakness of the thiourea process; and some believe that thiourea is carcinogenic.
In view of the fact that thiourea dissolves silver sulfide at a high rate and the leaching rate is much higher than that of cyanidation, the Colorado Colorado mine has used thiourea to leaching silver from silver-containing tailings since 1982. Since 1977, France has used thiourea to recover gold and silver from flotation tailings and zinc calcine. Australia's New England antimony mine has been treated with thiourea for strontium-containing concentrates since 1984. South German calcium cyanamide company (SKW), researched on the basis of the conventional thiourea method to introduce the reducing agent SO 2 into the leaching slurry, the supply rate of SO 2 to control 50% of the total thiourea in the slurry Dithiocarbamidine is good. Under this condition, the leaching rate of gold in the ore can reach more than 85%, and the consumption of thiourea can be reduced to 0.57kg per ton of ore, which can greatly reduce the consumption of thiourea, and promote the industrial application of thiourea gold extraction. There is also a South African gold mining company that slightly acidifies the thiourea leachate (pH 4-7) and adds Fe 3+ as an oxidant, which can leaching 95%-99% of the gold in the raw material within 2 hours to treat the mercury tailings. And low grade ore. The United States has also studied the fine-grained gold ore of Carlin-type carbonaceous ore and Chip Mining, and has tested the lean thiourea heap leaching.
The study of thiourea gold extraction in China began in the 1960s. Through nearly 30 years of hard work, it has entered the forefront of the world in the application research of thiourea gold. Among them, Beijing Nonferrous Metallurgy Design and Research Institute, Changchun Gold Research Institute, Jilin Metallurgical Research Institute and other units are even more advanced. In recent years, the thiourea leaching gold technology developed in China has been applied to the industrial production of gold deposits such as Yu'er Cliff, Zhangjiakou and Longshui.
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