| Mineral resources are important natural resources for human live and development. With the development of society and technology, mineral processing technology gets also developed too. Because of human constantly exploiting and utilizing mineral resources, the gold mine reserves is decreasing, and tend to be "poor, fine and complex". Therefore reasonably exploiting on gold resources, and especially comprehensive utilization for low-grade and refractory gold ore has important economic and social significance.In this paper a low-grade and refractory gold ore in Qinghai was studied. The granularity of embedding is small, so the target mineral is difficult to separate from and when blending the cyanide, the impurity in the ore is deleterious for leaching, thus, the rate of gold leaching is low.This paper conducted spectral analysis, chemical analysis and phase analysis on that gold ore, and carried series exploring tests based on its character, then got the following conclusions:(1) The test result shows that:this ore belongs to quartz vein-type gold ore. The gold in this ore is 2.76 (10-6). It mainly exists as natural gold format, and in addition, there are few isomorphism gold. Natural gold mainly exist as Micro-fine-grain, especially for fissure-filling gold and wrapped gold. Fissure-filling gold shares more or less 41.7%in the gold, where wrapped gold mostly exist in feldspar, and shares 30.83%in the gold. Besides, there are a little wrapped gold existing in clay, and it shares17.68%in the gold. Isomorphism gold mainly exists in Metal sulfides, its grade is 13.2 (10-6), and shares 9.57%of total gold.(2) The test investigated the effect on cyanide leaching by the impact of grinding fineness, sodium cyanide concentration leaching time, hydrogen peroxide, bleaching powder, lead nitrate, ammonium and other aid infusion. It especially investigated the supplement role of some ammonium salts and their consumption for cyanide leaching of gold.(3) The experiment shows that, due to the presence of dissolubility copper in the ore, gold leaching has been restarted in the cyanide process. In the first 5 hours of leaching, the impure mineral consumed most of free sodium cyanide of the liquor, in that case, the rate of gold leaching is low. When the impurities nearly dissolved, the remaining solution of sodium cyanide gradually dissolves the gold of ore.(4) The test results showed that ammonia leaching-cyanide gold extraction technique has good leaching result for that gold ore. Adding ammonia increased the PH value of ore pulp, it promoted the formation of cupric hydroxide precipitation, and reduced the content of copper ions in solution. Ammonia and the Cu-CN"ions of solution cooperate together, and then promoted the dissolution of gold.(5) Synthesis considering the field of production, minerals characters and economic costs, we definitely confirm the best condition for the cyanide leaching of that gold mine as follows:grinding fineness:95%-200 mesh, pulp density:40%, pulp pH value:10-11, sodium cyanide concentration:12/10000, leaching time:24 hours, ammonia or ammonium chloride is more appropriate to be assist infusion, the sodium cyanide and ammonia molar ratio is 1:2, gold leaching rate obtained was 87.5%, sodium cyanide dosage at 1.53 kg/tore will get better leaching results.(6) It outlines the principle of dipping gold process by hydrogen peroxide, bleaching powder and lead nitrate, and emphasized the introduction of ammonia-cyanide gold extraction mechanism and characteristics. In the cyanide gold extraction process, the soluble copper in the ore will cause a large number consumption of cyanide, and affect the gold leaching. The ammonia leaching-cyanide gold extraction technology is the effective method to deal with a variety of copper gold ore. Ammonia can effectively reduce the impact of copper on the process of leaching gold and reduce the consumption of sodium cyanide, then improving gold leaching rate. |
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