Lead Oxide Enhances the Leaching of Gold in Cyanide Tailings​

Introduction

Cyanidation is a widely used process for extracting gold from ores. However, cyanide tailings often contain a certain amount of residual gold, which is difficult to recover due to the influence of associated minerals. Improving the leaching efficiency of gold from cyanide tailings is of great significance for resource recycling and economic benefits. In recent research, it has been found that lead oxide can play a positive role in enhancing the leaching of gold in cyanide tailings.

The Problem of Low Gold Leaching Rate in Cyanide Tailings

The main challenge in recovering gold from cyanide tailings lies in the complex mineralogical composition. Residual cyanide in the tailings can cause gold to react with sulfides of associated iron (such as pyrrhotite). This reaction forms an Au/Sx passivation film on the surface of gold particles. This passivation film acts as a barrier, preventing the effective contact between gold and cyanide solution, thus resulting in a low conventional leaching rate of gold.

How Lead Oxide Enhances Gold Leaching

Chemical Reaction Mechanism

Lead oxide participates in multiple chemical reactions during the leaching process. Firstly, lead oxide can react with the passivation film formed on the gold surface. This reaction breaks down the passivation film, converting it into soluble salts. As a result, the gold surface is exposed again, allowing cyanide to react with gold. Secondly, lead oxide can act as an oxidant in the leaching system. In the presence of lead oxide, the oxidation potential of the system is adjusted, which is beneficial for the oxidation of gold to form soluble gold cyanide complexes.

Electrochemical Mechanism

There is an electric potential difference between gold and the reduction product of lead oxide. This potential difference enables the formation of a primary battery within the leaching system. In this primary battery, gold serves as the anode and undergoes oxidation, while the reduction product of lead oxide acts as the cathode. This electrochemical process, known as contact corrosion, effectively accelerates the dissolution of gold, thereby improving the gold extraction rate.

Experimental Verification

Experimental Materials and Methods

Researchers selected representative cyanide tailings samples for experiments. The tailings samples were first characterized to determine their mineral composition and gold content. Then, different amounts of lead oxide were added to the cyanide leaching system. The leaching conditions, such as leaching time, temperature, and cyanide concentration, were carefully controlled. A series of parallel experiments were carried out to ensure the accuracy of the results. In addition, advanced analytical techniques, such as scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were used to analyze the surface morphology and chemical composition changes of gold particles before and after leaching.

Experimental Results

The experimental results showed that the addition of lead oxide significantly increased the leaching efficiency of gold in cyanide tailings. Compared with the control group without lead oxide addition, the gold leaching rate increased by a remarkable percentage. For example, in some experiments, the gold leaching rate increased from a relatively low value to over [X]%. At the same time, the consumption of Sodium Cyanide was also reduced to a certain extent. SEM and XPS analysis further confirmed that lead oxide indeed reacted with the passivation film on the gold surface, and new chemical substances appeared on the surface of gold particles after the addition of lead oxide, which was consistent with the proposed reaction mechanism.

Application Prospect

The discovery of using lead oxide to enhance the leaching of gold in cyanide tailings has broad application prospects. In the mining industry, this technology can be applied to existing cyanide tailings treatment plants. By simply adding lead oxide to the leaching process, the recovery rate of gold can be improved without major equipment upgrades. This not only increases the economic value of tailings resources but also reduces the environmental impact caused by the long-term storage of tailings containing gold. Moreover, this method can also be extended to the treatment of some refractory gold ores, providing a new solution for the efficient extraction of gold resources.

In conclusion, lead oxide shows great potential in enhancing the leaching of gold in cyanide tailings. Through in-depth understanding of its enhancement mechanism and continuous optimization of experimental conditions, this technology is expected to play an important role in the future development of the gold mining industry.