Thallium removal method for zinc hydrometallurgy system

Abstract

The invention discloses a thallium removal method for a zinc hydrometallurgy system, which comprises the following steps: 1) in a neutral leaching supernatant purification process, adding potassium permanganate and ferrous sulfate in a first purification stage of a liquid purification process, and reacting for 1-2 hours; 2) adding zinc powder into the solution, adding activated carbon, and reacting for 1-2 hours; 3) adding lead acetate, and reacting for 1-2 hours; and 4) carrying out solid-liquid separation through a plate filter press, and removing purified residues. A combined thallium removal mode is adopted, so that the thallium content of the purified solution is low, the requirement of electrolytic zinc can be met, and electrolytic'plate burning 'caused by thallium is avoided; according to the thallium removal method for the zinc hydrometallurgy system, additional reaction time does not need to be increased, the thallium removal method can be synchronously carried out with the original neutral leaching supernatant liquid purification process, the production period is not prolonged, additional equipment investment is not increased, the cost is low, and the effect is good.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical zinc refining technology, specifically relating to a method for removing thallium from a hydrometallurgical zinc refining system. Background Technology

[0002] Thallium is harmful to the electrolytic deposition process of wet zinc smelting, easily causing severe "plate burning" and inducing other impurities to "burn" the plates, which has an adverse effect on zinc sheet yield and technical indicators, leading to continuous fluctuations in production and making it impossible to operate normally.

[0003] Thallium is an impurity with a higher potential than zinc in zinc electrowinning systems. When the thallium content in the new solution exceeds the standard, a galvanic cell is formed due to the potential difference between thallium and zinc, causing the zinc cathode to undergo re-dissolution. Pitting appears on the surface of the zinc deposited on the cathode. As the thallium content increases or the operation continues, the re-dissolution intensifies, the pitting increases, and it develops into through-holes, eventually leading to the phenomenon of zinc cathode permeating through acid and forming continuous sheets with blackening of the inner surface. In severe cases of plate burning, the zinc cathode exhibits large-area through-holes, overall blackening, and automatic peeling, resulting in a significant decrease in electrolytic current efficiency.

[0004] In the hydrometallurgical zinc smelting process, thallium is naturally present in the raw zinc concentrate. Some zinc concentrates from certain ore sources have high thallium content, becoming one of the main sources of impurities in subsequent electrolysis processes. After roasting, thallium exists in the roasted ore as variable-valence oxides Tl₂O₃, TlO, and Tl₂O. During leaching, these thallium oxides dissolve into the system solution under acidic conditions.

[0005] The main reactions are as follows: Tl2O3+ 6H + = 2Tl 3+ + 3H2O; TlO + 2H + = Tl 2+ + H2O; Tl2O + 2H + = 2Tl + + H2O; During the neutral leaching stage, the endpoint pH was controlled at 5.2–5.4, Tl 3+ Hydrolyzed to Tl(OH)3, which enters the bottom slag stream along with the precipitated Fe(OH)3. The main reactions are as follows: Tl 3+ + 3OH - = Tl(OH)3↓; And Tl 2+ 、Tl + It does not hydrolyze and enters the supernatant of the intermediate leaching. During the acid leaching stage, some thallium in the bottom stream is leached out by acid and returned to the supernatant of the intermediate leaching.

[0006] In existing technologies, the purification process of intermediate leaching supernatant includes three stages: the first stage uses zinc powder replacement to remove copper and cadmium, the second stage uses zinc powder replacement to remove cobalt, and the third stage uses zinc powder replacement to remove residual copper, cadmium, and other impurities. However, how to remove thallium from the intermediate leaching supernatant is a pressing technical problem that needs to be solved. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for removing thallium in a wet zinc smelting system.

[0008] The objective of this invention is achieved through the following technical solution: a method for removing thallium from a hydrometallurgical zinc smelting system, comprising the following steps: 1) During the purification process of the intermediate leaching supernatant, in the first purification stage of the purification process, add a potassium permanganate solution of 77 g / m³ and a ferrous sulfate solution of 38 g / m³, and react for 1-2 hours to remove most of the Tl from the solution. 2+ 、Tl + Oxidation to produce Tl 3+ Tl 3+ Hydrolysis produces Tl(OH)3 precipitate, which enters the purification residue; 2) Add 420 g of zinc powder per cubic meter of solution and 40 g of activated carbon per cubic meter of solution. The activated carbon has an iodine adsorption value greater than 400 mg / g. React for 1-2 hours. The residual Tl 2+ 、Tl + Tl is generated by Zn substitution, and part of Tl is generated. 2+ 、Tl + Ti is removed by activated carbon adsorption, and the remaining Ti enters the purification residue; 3) Add 200 g of lead acetate solution per cubic meter and react for 1-2 hours. The lead acetate reacts with thallium ions to form thallium acetate precipitate, which enters the purification residue. 4) Solid-liquid separation is performed using a plate filter press to remove the purified residue.

[0009] Furthermore, after step 4), in the three-stage purification stage of the purification process, a potassium permanganate solution of 38 g / m³ and a ferrous sulfate solution of 19 g / m³ are added, along with a zinc powder solution of 420 g / m³, for deep purification, causing the residual thallium in the solution to oxidize to Tl. 3+ It hydrolyzes to form Tl(OH)3 precipitate, which is then separated into liquid, solid, and liquid components using a plate filter press to remove residual thallium from the solution. In the purification process of the intermediate immersion supernatant, this invention uses an oxidant to remove Tl from the solution. 2+ 、Tl + Oxidized to Tl 3+ , make Tl 3 +The precipitate generated by hydrolysis enters the purification residue, and the residual Tl 2+ 、Tl + By increasing the amount of zinc powder, it is replaced by Tl, which, combined with the adsorption of activated carbon, removes thallium from the solution. Then, lead acetate reacts with thallium to form thallium acetate precipitate. After liquid-solid separation, the thallium in the solution is removed, ensuring that the thallium content in the intermediate leaching supernatant is less than 0.1 mg / L.

[0010] The beneficial effects of this invention are: 1. The combined thallium removal method of the materials in this invention results in a low thallium content in the purified solution, which can meet the requirements of electrolytic zinc and avoid thallium-induced electrolytic "plate burning"; 2. The thallium removal method of the wet zinc smelting system of this invention does not require additional reaction time and can be carried out simultaneously with the original intermediate leaching supernatant purification process, without extending the production cycle or increasing additional equipment investment, resulting in low cost and good effect. Detailed Implementation

[0011] The present invention will now be described in detail.

[0012] This invention relates to a method for removing thallium from a hydrometallurgical zinc refining system, comprising the following steps: 1) During the purification process of the intermediate leaching supernatant, in the first purification stage of the purification process, add a potassium permanganate solution of 77 g / m³ and a ferrous sulfate solution of 38 g / m³, and react for 1-2 hours to remove most of the Tl from the solution. 2+ 、Tl + Oxidation to produce Tl 3+ Tl 3+ Hydrolysis produces Tl(OH)3 precipitate, which enters the purification residue (the purification residue contains copper, cadmium, excessive zinc powder and other impurities). The main reactions are as follows: 5Tl + + 2MnO4⁻ = 5Tl³⁺ + 2 Mn²⁺; 5Tl 2+ + MnO4⁻ = 5Tl³⁺ + Mn²⁺; Tl 3+ + 3OH - = Tl(OH)3↓; 2) In the original purification process of the supernatant from the immersion solution, 5500 g of zinc powder per cubic meter of solution was added; in this invention, 420 g of zinc powder per cubic meter of solution and 40 g of activated carbon per cubic meter of solution were added. The activated carbon has an iodine adsorption value greater than 400 mg / g. The reaction is carried out for 1-2 hours, and the residual Tl is reduced. 2+ 、Tl + Tl is generated by Zn substitution, and part of Tl is generated. 2+ 、Tl + Ti is removed by activated carbon adsorption, and the remaining Ti enters the purification residue; The main reactions are as follows: Zn + Tl 2+ = Zn 2+ + Tl↓; Zn + 2Tl + = Zn 2+ + 2Tl↓; 3) Add 200 g of lead acetate solution per cubic meter and react for 1-2 hours. The lead acetate reacts with thallium ions to form thallium acetate precipitate, which enters the purification residue. 4) Solid-liquid separation is performed using a plate filter press to remove the purified residue.

[0013] 5) In the three-stage purification process of the purified solution, add 38 g / m³ potassium permanganate solution and 19 g / m³ ferrous sulfate solution, and add 420 g / m³ zinc powder solution for deep purification, so that the residual thallium in the solution is oxidized to Tl. 3+ It is hydrolyzed to generate Tl(OH)3 precipitate, and then separated into liquid, solid and liquid by plate filter press to remove residual thallium from the solution.

[0014] After purification using the above thallium removal methods, the thallium content in the intermediate leaching supernatant is less than 0.1 mg / L, which can better meet the requirements of electrolytic zinc.

[0015] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for removing thallium from a hydrometallurgical zinc smelting system, characterized in that... Includes the following steps: 1) During the purification process of the intermediate leaching supernatant, in the first purification stage of the purification process, add a potassium permanganate solution of 77 g / m³ and a ferrous sulfate solution of 38 g / m³, and react for 1-2 hours to remove most of the Tl from the solution. 2+ 、Tl + Oxidation to generate Tl 3+ Tl 3+ Hydrolysis produces Tl(OH)3 precipitate, which enters the purification residue; 2) Add 420 g of zinc powder per cubic meter of solution and 40 g of activated carbon per cubic meter of solution. The activated carbon has an iodine adsorption value greater than 400 mg / g. React for 1-2 hours. The residual Tl 2+ 、Tl + Tl is generated by Zn substitution, and part of Tl is generated. 2+ 、Tl + Ti is removed by activated carbon adsorption, and the remaining Ti enters the purification residue; 3) Add 200 g of lead acetate solution per cubic meter and react for 1-2 hours. The lead acetate reacts with thallium ions to form thallium acetate precipitate, which enters the purification residue. 4) Solid-liquid separation is performed using a plate filter press to remove the purified residue.

2. The method for removing thallium from a hydrometallurgical zinc smelting system according to claim 1, characterized in that: Following step 4), in the three-stage purification process of the purified solution, a solution of 38 g / m³ potassium permanganate and 19 g / m³ ferrous sulfate are added, along with a solution of 420 g / m³ zinc powder, for deep purification, oxidizing the residual thallium in the solution to Tl. 3+ It is hydrolyzed to generate Tl(OH)3 precipitate, and then separated into liquid, solid and liquid by plate filter press to remove residual thallium from the solution.