Lead and zinc are important non-ferrous metals and have an irreplaceable role in the development of the national economy and industry. 80% of the world’s lead and zinc are obtained by smelting lead sulfide ore. However, with years of mining, the easy-to-select sulfide ore resources are increasingly depleted, and the lead-zinc ore resources are being continuously developed. However, due to the complex mineral composition of lead-zinc oxide ore, many associated minerals, fine particle size of embedding, serious sludge phenomenon, and high soluble salt content, various unavoidable ions have a great influence on the lead-zinc floatability. Therefore, at present, only a small part of high-grade lead-zinc oxide mines have mining value, and it is difficult to recover low-grade lead-zinc oxide mines using conventional beneficiation processes.
At present, lead-zinc oxide ores with industrial value mainly include white lead ore (PbCO3), lead alum (PbSO4), smithsonite (ZnCO3), heteropolar ore, etc. as a large country of lead-zinc oxide ore resources, China’s current domestic lead-zinc concentrate output can not meet the demand, and still relies heavily on imports, strengthening the research on the recovery and utilization of lead-zinc oxide ore is of great practical significance to alleviate the contradiction between supply and demand. On the basis of practice and theory for many years, fodamon engineers summarized the methods of treating oxidized lead-zinc ore from flotation process, leaching process and combined process of concentration and metallurgy as follows.
1. Flotation process
At present, the flotation process is usually used in lead-zinc concentrators. A single oxidized lead-zinc deposit is relatively rare. The oxidized lead-zinc ore mainly comes from the oxidized zone of sulfide ore, containing both oxidized ore and sulfide ore. There are two main flotation principles for lead-zinc oxide ores: one is “sulfur before oxygen”, i.e. flotation in the order of galena sphalerite lead oxide zinc oxide ore; the other is “lead before zinc”, i.e. flotation in the order of galena lead oxide sphalerite zinc oxide ore. At present, the flotation technology of lead-zinc oxide ore mainly includes sulfide flotation, fatty acid collector flotation, chelator flotation and flocculation flotation.
1.1 sulfuration xanthate flotation method
Sulfide xanthate method is an effective way to recover lead-zinc oxide. A lot of researches have been made on it by domestic and foreign concentrators. The mechanism of sulfurization xanthate method is to sulfurize the surface of lead-zinc oxide in advance, so that the surface of lead-zinc oxide is covered with a strong hydrophobic sulfide film, and then the xanthate collector is used for flotation. It was found in the early research that when the pulp temperature was increased to 50-60 ℃, it would be beneficial to the sulfidation of zinc oxide minerals and the adsorption of reagents, but the excessive amount of sulfidizer would inhibit the interaction between xanthate and mineral surface, and zinc oxide minerals need to be activated by adding copper sulfate after sulfidation before being collected by xanthate. In gorno concentrator in northern Italy, the lead tailings were flotation by heating sulfuration flotation method. The pH value of pulp was adjusted to 11, and the heated pulp was sulfurized at 45 ~ 50 ℃. After being activated by copper sulfate, the grade of zinc concentrate was up to 38% , zinc recovery 76.4% 。 Sun Wei et al. Studied the flotation process of a lead-zinc oxide ore in Cangyuan, Yunnan Province, by using sulfide xanthate flotation and sulfide thiophenol flotation. Using Na2S as sulfurizer, xanthate as lead collector, thiophene as zinc collector and oil No.2 as foaming agent, lead grade was obtained 53.93% , zinc 13.13% Lead concentrate, zinc grade 31.82% With lead 2.75% Of zinc concentrate and lead grade of 33.38% , zinc grade 19.10% The comprehensive recovery of lead and zinc is over 98%.
Sulfur xanthate method is widely used in lead oxide recovery, but its selectivity is generally poor, so it is difficult to obtain better beneficiation indexes for complex low-grade lead-zinc oxide ore. In addition, heating process and activation process are also needed, which are more complex and costly.
In the next part, Fodamon engineers continue to share the other four flotation methods.