Chemical beneficiation of zinc ore

1 Development of acid leaching technology

Zinc acid leaching can generally be divided into direct acid leaching and pressurized acid leaching. Direct acid leaching is commonly used to treat zinc oxide ore such as smithsonite, while pressurized acid leaching is used to treat refractory zinc iron spinel and zinc silicate ore.

A direct acid leaching

Direct acid leaching of zinc ore is a common chemical dressing method. The researchers have a deeper understanding and elaboration of the reaction and mechanism of the leaching process by analyzing the thermodynamics and kinetics of the direct acid-free process.

Tang Shuanghua analyzed the thermodynamics and kinetics of the acid leaching process of zinc oxide and found that the acid leaching of zinc oxide is an exothermic reaction with great thermodynamic driving force. Yang Dajin et al. also analyzed the main chemical reactions of low-grade zinc oxide ore in the acid leaching process, and found that the reaction can proceed to the direction of zinc sulfate formation. The leaching rate of low-grade zinc oxide ore is mainly from low-grade zinc oxide ore. Determined by physical and chemical properties. Yan Wenqing et al. analyzed the acidity, acid addition, solid-liquid ratio, and kinetics of the high-silicon natural zinc oxide ore in the conventional acid leaching of the refractory pulp, the liquid-solid ratio is too small, and the zinc leaching recovery rate is low. The effect of particle size and temperature on zinc leaching rate.

In addition, researchers have made some progress in the study of the effects of factors in the direct acid leaching test. Yan Shaojuan et al. conducted an acid leaching test on zinc calcine and found that the initial acidity and liquid-solid ratio are the most important factors affecting leaching. He Shanming and others have done similar work. Zhou Jun by oxidation leaching zinc sulfate diafiltration resources associated directly with the metal germanium through research found that under optimal conditions the leaching rate with a higher germanium, and iron, silica leaching rate in the whole course of the experiment Lower. Li Rongxing et al. conducted a study on the leaching performance of low-grade zinc oxide ore at room temperature. The leaching rate of zinc reached 95.23% to 93.80%, reaching the theoretical leaching rate of zinc.

The zinc sulphate method has also been reported. The process of zinc sulphate smelting process is to decompose zinc ferrite in zinc baking sand by high temperature and high acid leaching, and to improve the leaching rate of zinc, so that the leaching rate of zinc is more than 98%, and the leaching rate of iron reaches 70%. ~90%, the content of iron in the leachate reaches about 30g / L. Cheng Liu et al. carried out a leaching test on the slag produced by the zinc sulphate method in a domestic factory. The concentrated sulphuric acid did not contain zinc, and the leaching rate of zinc finally exceeded 98%.

B is not pressurized

Pressurized acid leaching is another common method of acid leaching of zinc concentrate. Pressurized acid leaching has the advantages of shortening the leaching time, enhancing the leaching process, and increasing the leaching rate. Advances major pressure acid leaching process are: (1) described for the treatment of high oxygen pressure leaching of sulfide concentrates superiority of iron, zinc and lead oxide was confirmed HPAL process follows the "core from unreacted thermodynamically Reduced model; (2) For the problems of low leaching rate, poor selectivity and difficult handling of objects in pressurized acid leaching, various methods such as dilute with dilute acid and two-stage pressure leaching are used. A good result.

Xie Keqiang analyzed the thermodynamics of the oxygen-free acid in the high-iron zinc sulfide concentrate. He Shanming studied the leaching kinetics of zinc in pressurized acid leaching of high-silicon oxide lead-zinc ore. It was found that the pressurized acid leaching process of lead-zinc ore followed the “unreacted nuclear reduction” model, and the leaching process belongs to solid film diffusion control. .

The researchers solved the problems of low leaching rate, poor selectivity and difficult to handle objects in the leaching by using pressurized acid leaching. Š.Langová et al. studied the selective leaching of zinc in zinc iron spinel with hydrochloric acid. It was found that the leaching rate of zinc in the leaching of pressurized dilute acid was up to 93%, and the stronger acid leaching had certain advantages.

Wang Jikun et al. studied the extraction of zinc and indium by high- indium and high-iron zinc sulfide concentrate by pressure acid leaching. The two-stage pressure leaching can ensure high zinc and indium leaching rate and selective leaching of zinc, indium and iron. , reduce the acidity of the leachate. In addition, Xu Hongsheng et al. tested the pressurized acid leaching of zinc silicate ore and found that the acid concentration is the most important parameter in the process of zinc silicate. The leaching rate of zinc, iron and silicon will vary with the concentration of sulfuric acid. The increase is gradually increasing. Wei Wei et al. tested the parameters affecting the leaching rate of zinc and silicon during the leaching of zinc silicate ore by pressurized sulfuric acid. Under the optimal conditions, the leaching rate of zinc can be as high as 99.25%, while only 0.20% of silicon is Leaching. Li Cunxiong and others used pressurized acid leaching technology to treat high-silicon zinc oxide ore in a certain area of ​​Guangxi. Under the optimal conditions, the zinc leaching rate can reach over 97%, and the SiO ₂ rejection rate is greater than 99.2%.

2 Development of alkali leaching and ammonia leaching technology

For the highly alkaline gangue type complex low-grade zinc oxide ore, the acid leaching process is difficult to treat the minerals cost-effectively. For this reason, researchers have developed ammonia leaching and alkali leaching processes, using the formation of complexes in alkaline The system selectively immersed zinc to avoid a large amount of leaching of alkaline gangue and achieved good results. In recent years, the main progress of ammonia leaching and alkali leaching are: (1) the “Zinc Bayer method” proposed to treat zinc ore has obtained better indicators; (2) The ligands that have changed the ammonia leaching and alkali leaching processes are limited to NH. ₃ , Cl ^- , OH ^- the status quo, proposed a variety of new ligands, such as alkaline lda ^2-- Glu ^2-- H ₂ O mixed system, alkaline sodium glutamate system.

In recent years, the alkaline leaching process of zinc has also been rapidly developed, and researchers have made a lot of improvements in the alkali leaching process. Zhao Zhongwei of Central South University has achieved a lot of results in the research of zinc alkaline leaching process. He mineral processing Bayer alumina transplanted to wet oxidation treatment to form a zinc "Zinc Bayer", zinc oxide leached with concentrated alkali, and then lowering the temperature or concentration of the zinc precipitated as zinc hydroxide, precipitated mother liquor After concentration treatment, the leaching ore is returned, the leaching rate of zinc reaches 95.1%, and the leaching rate of silicon is 45.5%. He also found that the formation of the insoluble product Na ₂ ZnSiO ₄ by zinc oxide ore at high temperature, long time and strong mechanical activation is the main reason for the decrease of zinc leaching rate. He also studied the leaching of zinc from refractory zinc silicate (heteropolar ore) by mechanical activation in sodium hydroxide solution. It was found that the addition of calcium oxide can effectively inhibit the leaching of silica, but the absence of zinc Almost unaffected.

In addition, Dou Aichun proposed a new process for treating zinc oxide ore with alkaline lda ^2- -Glu ^2- -H ₂ O mixed system for low-grade refractory high-alkaline gangue-type zinc oxide ore. Ren Jin is aiming at the current situation that traditional metallurgy is difficult to treat low-grade zinc oxide ore. A new process for treating zinc oxide ore with alkaline sodium glutamate system is proposed.

Ammonia leaching is also a relatively common method of chemical beneficiation of zinc. It has the advantages of wide raw materials, light purification burden and short process flow. In recent years, the ammonia leaching method has been vigorously developed.

There are many factors affecting the ammonia leaching method, and researchers have conducted a lot of research in this area. Yang Jianguang et al. studied the leaching kinetics of low-grade zinc oxide ore in NH ₃ -NH ₄ Cl-H ₂ O system, and found out the leaching efficiency of zinc by ore particle size, reaction temperature, ammonium ion concentration and ammonia concentration. Influence the regular model. Yang Shenghai et al. studied the effect of reaction conditions on the leaching rate of zinc in the process of leaching zinc oxide ore with ammonium chloride solution. It was found that zinc in the form of rhombohedrite, hydrozinc or the like was substantially completely leached, and zinc silicate was used. The presence of the zinc ferrite form cannot be leached. Liu Zhixiong, Ling Jianghua and others have also done similar work. Zhang Yumei et al. studied the effect of ultrasonic radiation on the ammonia leaching process of Lanping low-grade zinc oxide ore. The research shows that when the reaction temperature and leaching agent concentration are low, the molar concentration of NH ₄ C1 and NH ₄ OH is relatively large, ultrasonic The strengthening effect of radiation is remarkable.

Researchers have promoted the development of ammonia leaching technology through improvements in the ammonia leaching process. Wang Shumin et al. studied the optimum process conditions for high-oxygen catalytic oxidation of ammonia in high-iron sulfide zinc ore concentrate. The results show that the leaching rates of zinc, copper and cadmium by first-stage leaching can reach 93%, 94% and 91%, respectively. The iron is not contained in the liquid. After the second stage is not taken, zinc, copper and cadmium are effective. The leaching rate of the ingredients will achieve the desired results. Jiang Chongwen et al. used zinc-ammonium bicarbonate solution to extract zinc oxide from low-grade zinc oxide ore. The zinc oxide content of the purified liquid after evaporation and calcination was 99.53% (calculated as zinc oxide). The method has the advantages of simple process, low energy consumption, high leaching rate, and no process to be friendly to the environment. Liu Yachuan et al. studied the ammonia leaching of a difficult-to-select low-grade zinc oxide ore and found that the low-grade zinc oxide ore was leached under suitable conditions with NH ₃ -NH ₄ Cl as the leaching agent. The leaching rate of zinc can be Up to 87.51%. The temperature required for the leaching process is about 35 ° C, and the energy consumption is low. Le Weihe et al. leached a highly alkaline zinc oxide ore from Guangxi Hechi with NH ₃ -NH ₄ Cl system, and the zinc leaching rate reached 89.3%.

3 Progress in zinc leaching-extraction-electrowinning process

The new zinc leaching processes studied in recent years are mainly leaching-extraction-electrowinning and (circulation) leaching-purification-electrowinning (MACA method), roasting-water immersion, oxygen pressure catalytic enhanced leaching, combined application with precipitation, etc. .

Lingjiang Hua and others are difficult to economically use the valuable metals in ore for the traditional acid zinc smelting process, and the process of removing ammonia and silicon is complicated. The ammonia leaching-extraction-electrowinning process is used to treat Yunnan Lanping. Choose low grade zinc oxide ore. Lu Xingwu et al. used the “acid leaching (or two-stage leaching)-purification-extraction electrowinning” process to recover zinc from a medium-low grade zinc oxide ore, and the zinc leaching rate can reach over 92%. Wang Ruixiang first proposed a new process for the treatment of highly alkaline gangue zinc oxide ore by the (cycle) leaching-purification-electrowinning MACA method. The process can be electrowinned without enrichment, and the waste electrolyte is returned to the formulation leaching agent. And normal temperature operation, low DC power consumption, is a new method of wet zinc smelting that is clean and low energy consumption.

Zhang Yali proposed a process of “low temperature roasting-water leaching and zinc extraction” for silver ferrite zinc low-grade zinc oxide ore. The leaching solution was returned to the zinc smelting system purification process after iron removal, and the water immersion liquid was leached with lead chloride in one step. In the zinc extraction stage, the direct acid leaching and roasting-water immersion schemes were found to have better effect of using zinc by roasting-water leaching. Yang Long treats the oxidized minerals of high-impurity and low-grade zinc that are difficult to smelt, and is treated by solvent extraction-traditional wet process after leaching with sulfuric acid. In order to overcome the high extraction rate of zinc and the low extraction rate of iron, Wang Shumin et al. proposed a high-oxygen catalytic oxidation ammonia leaching process for high-iron sphalerite concentrate in order to overcome the high smelting process of high-speed sphalerite. Yu Xiaohua et al. proposed a process for treating high indium and high iron sulfide zinc sulfide concentrate by oxygen pressure catalytic acid leaching, which achieved the common leaching of zinc and indium, and achieved preliminary separation from iron.

In addition, Liu Qing et al. proposed a poor zinc oxide ore. The new process of zinc concentrate and lead concentrate was prepared by "alkali leaching-precipitation method", and the process parameters of lead and zinc precipitated by sodium sulfide were determined. The industrial feasibility of the process was verified by a small comprehensive test. Yang Jixing proposed to use the "sink zinc-calcium-re-leaching" process to treat low-concentration zinc-containing leaching solution.

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