Example of resin in pulp - processing rich silver and gold -
2020-11-02 10:31Introduction：Example of resin in pulp- processing rich silver and gold -silver ore During cyanidation leaching, gold-silverore,naturalsliver and naturalgoldare easy to leach, and other silver minerals, especially silver sulfide, are difficult to leach.
Example of resin in pulp - processing rich silver and gold - silver ore
During cyanidation leaching, gold-silver ore , natural sliver and natural gold are easy to leach, and other silver minerals, especially silver sulfide, are difficult to leach.The cyanidation leaching reaction of silver sulfide is as follows:
The direction of the reaction depends on the ratio of sodium cyanide to sodium sulfide. When sodium sulfide accumulates to a certain value, leaching of silver sulfide stops.In order to improve the leaching rate of silver, it is necessary to increase the concentration of cyanide in the slurry and strengthen the aeration of slurry so that sodium sulfide is oxidized and decomposed. The oxidation reaction is as follows:
2Na2S+2O2+H2O=Na2S2O3+2NaOH
Na2S2O3+2O2+2NaOH=2Na2SO4+H2O
Therefore, the total reaction formula for leaching silver sulfide in a highly air-filled solution of high concentration cyanide is as follows:
Ag2S+4NaCN+2O2=2NaAg(CN)2+Na2SO4
Therefore, increasing the concentration of slurry cyanide and oxygen is the key to increasing the leaching rate of silver sulfide.
In the cyanidation of silver sulfide ore, except the higher cyanide concentration and oxygen concentration required, the cyanidation leaching time was longer, and the dynamic curve of cyanidation leaching of gold and silver ore in the former Soviet union was shown in figure 5-48.It can be seen from the curve in the figure that the leaching speed of gold and silver is the highest when the cyanide concentration is between 0.1% and 0.4%.The leaching time of natural gold is about 12 hours.The leaching rate of silver is only about 80% after 42-hour leaching. The leaching rate of silver is almost 50% within the first 2-3 hours, and the leaching time is 4 times longer than that of gold. The main reason is that gold and silver ore is easy to be cyanised and silver sulfide is difficult to be dissolved.
The order of AM-2B exchange resin for the adsorption of metal cyanide anions is: 【Au(CN)2】-＞【Zn(CN)4】2-＞【Ni(CN)4】2-＞【Ag(CN)3】2-＞【Cu(CN)4】3-＞【Fe(CN)6】4-. When the resin is saturated, the anions with weak affinity can be replaced by the anions with weak affinity.Therefore, gold and silver in cyanide slurry can be selectively recovered by two-stage cyanidation - adsorption process.
The technological process of recovering gold and silver in ore by two-stage cyanide-adsorption process is shown in figure 5-49.The original slurry was cyanided for 12 hours under conditions of 0.1% ~0.15%NaCN and 0.2% ~ 0.3% CaO. At this time, almost all the gold was leached, and the leaching rate of silver was about 50%.The cyanate slurry is sent to the first section for countercurrent adsorption, and the resin is added from the last adsorption tank. The resin absorbs more gold or silver than gold.With the reverse movement of the resin, the silver in the resin is gradually replaced by gold, saturated resin is rich in gold resin.The adsorption rate of gold in the first section is 98% ~ 99%.After the first stage of adsorption, the slurry was added with cyanide to reach 0.15% of NaCN, then the second stage of cyanidation leached silver sulfide, and cyanated slurry was sent to the second stage for countercurrent adsorption, and a saturated resin rich in silver and a small amount of redissolved gold was produced.
