In the leaching operation, gold reacts with cyanide to form a gold cyanide complex dissolved in the solution. When zinc acts on the gold-containing solution, the gold is replaced by zinc to be converted into a metal state, and at the same time, the zinc is dissolved in the alkaline cyanide solution. Tree Swing, Saucer Swing,tree swing for adults,Garden tree swing Jiangsu Baoxiang Sports Equipment Co., Ltd , https://www.skyboundbx.com
The process of zinc substitution is an electrochemical reaction process. The precipitation of gold is the result of the formation of a galvanic couple. The electrode is a zinc- lead electrode couple, zinc is an anode, and lead is a cathode. Under the action of the galvanic current, the gold cyanide ion will inevitably move toward the anode and act with the plate, so that the zinc enters the solution in the state of cyanide complex ion, and the gold is reduced and precipitated. The response is:
2Au(CN) 2 - +Zn=2Au↓+Zn(CN) 4 2-
Zinc is dissolved at the same time, and the reaction process is:
Zn+4CN - =Zn(CN) 4 2- +2e
Zn+4OH - =ZnO 4 2- +2H 2 O+2e
ZnO 4 2- +4CN - +2H 2 O=Zn(CN) 4 2- +4OH
The hydrolysis process produces H + , and its reaction formula is:
H 2 Oâ†â†’H + +OH -
H + reduces the precipitation of H 2 at the cathode, and the reaction formula is:
2H + +2e=H 2 ↑
Combine the above reactions, namely:
4CN - +Zn+2H 2 O=Zn(CN) 4 2- +2OH - +H 2 ↑
When oxygen is present in the solution, the zinc is oxidized: 
Zn(OH) 2 +4CN - =Zn(CN) 4 2- +2OH -
In the low concentration cyanide solution, the cyanide complex decomposes and forms insoluble zinc cyanide. The reaction formula is:
Zn(CN) 4 2- +Zn(OH) 2 =2Zn(CN) 2 ↓+2OH -
The precipitation of Zn(OH) 2 and Zn(CN) 2 formed by the above reaction will deposit on the surface of zinc to hinder the replacement of gold. Therefore, in the replacement process, it is necessary to maintain a certain concentration of cyanide and alkali in the solution to avoid Zn. The formation of (OH) 2 and Zn(CN) 2 allows the gold replacement process to proceed smoothly.