Wet defluorination and dechlorination process for zinc oxide powder

Abstract

The invention provides a wet-process fluorine and chlorine removal process of zinc oxide powder, which comprises the following steps: S1, carrying out wet ball milling on secondary zinc oxide smoke dust to form ore pulp, pumping the ore pulp into an ore pulp transfer tank, and homogenizing, S2, carrying out stirring reaction on the ore pulp in an alkali-resistant stirring tank at the speed of 85r / min for 1.5 hours under the conditions that the temperature is 80-90 DEG C, the liquid-solid ratio is 5: 1 and the pH value is 10-11, so that fluorine and chlorine are converted into soluble NaF / NaCl, according to the method, an alkali washing-goethite-copper slag three-stage synergistic removal system is utilized, a copper slag resource directional chlorine precipitation technology is adopted, active components in the waste copper slag react with chloride ions to generate stable precipitates, high-added-value copper resources are synchronously recycled, and the problems that a traditional chlorine removal process is high in cost and serious in secondary pollution are thoroughly solved; and deep fixation of fluorine ions is realized by combining a goethite lattice fluorine fixation mechanism, the quality of cathode zinc is remarkably improved, the anode corrosion risk is greatly reduced, and the destructive influence of cyclic accumulation of fluorine and chlorine impurities in zinc hydrometallurgy on an electrolysis process is fundamentally eliminated.

Description

Technical Field

[0001] This invention relates to the field of zinc oxide powder processing technology, specifically a wet defluorination and dechlorination process for zinc oxide powder. Background Technology

[0002] my country is the world's largest producer and consumer of refined zinc, with domestic consumption exceeding domestic production. However, my country's zinc concentrate resources are already scarce. After years of intensive mining, high-quality zinc resources are dwindling. In 2024, domestic zinc concentrate production fell to its lowest level in nearly a decade, with a national output of 4 million tons, a decrease of 60,000 tons year-on-year. As zinc sulfide ore resources become increasingly scarce, the utilization rate of secondary zinc-containing resources, represented by zinc oxide dust, is rising year by year. Examples include zinc oxide powder produced from the volatilization of zinc-containing dust and sludge in rotary kilns at steel plants, zinc oxide dust obtained from the volatilization of zinc leaching slag in rotary kilns or fuming furnaces, and zinc oxide dust generated during the recycling of hot-dip galvanizing ash and galvanized steel scrap. In this type of zinc oxide powder, the content of zinc oxides (ZnO, Zn2O, etc.) fluctuates between 20% and 50%, and is accompanied by impurities such as fluorine (0.1%-0.5%), chlorine (0.2%-1.2%), lead (5%-30%), and arsenic (0.05%-0.3%). The hazards of fluorine and chlorine impurities are particularly prominent. Fluorine and chlorine mainly exist in complex forms such as lead chloride, zinc chloride, lead fluoride, and lead fluoride chloride in the flue dust. During acid leaching of zinc oxide powder, fluorine and chlorine ions also enter the solution and continuously accumulate. The increased concentration of fluorine ions makes it difficult to peel off zinc sheets, and the increased concentration of chloride ions leads to anodic corrosion and reduces the quality of cathode zinc. Therefore, how to efficiently remove fluorine and chlorine in the hydrometallurgical zinc smelting process is an important technical challenge. Summary of the Invention

[0003] (a) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, this invention provides a wet defluorination and dechlorination process for zinc oxide powder, solving the problem of how to efficiently remove fluoride and chlorine in the existing wet zinc smelting process.

[0005] (II) Technical Solution

[0006] To achieve the above objectives, the present invention provides the following technical solution: a wet defluorination and dechlorination process for zinc oxide powder, comprising the following steps:

[0007] S1. The zinc oxide dust is wet-milled to form a slurry, which is then pumped into a slurry transfer tank for homogenization.

[0008] S2. The slurry is placed in an alkali-resistant stirring tank and stirred at 85 r / min for 1.5 h at 80-90℃, liquid-solid ratio of 5:1, and pH of 10-11 to convert fluorine and chlorine into soluble NaF / NaCl.

[0009] S3. The reaction slurry is separated by a plate and frame filter press. The filtrate enters the filtrate storage tank A. When the chlorine content is <15g / L, it is returned to the first washing and recycling stage. When it is ≥15g / L, it is discharged to the water treatment center. The filter residue is transferred into the filter residue slurry tank A.

[0010] S4. The filter residue in filter residue slurry tank A is mixed with the three-stage recycled filtrate and stirred for 1.5 hours at room temperature, liquid-solid ratio of 6:1 and pH of 8.0-8.5 to further remove residual fluorine and chlorine.

[0011] S5. After the slurry is pressed and filtered, the filtrate enters the filtrate storage tank B, and the filter residue is transferred to the filter residue slurry tank B.

[0012] S6. The filter residue in filter residue slurry tank B is mixed with clean water and reacted for 1.5 hours at room temperature, liquid-to-solid ratio of 5:1 and pH 7.0-8.0 to complete deep washing.

[0013] S7. Detect the chlorine content of the filtrate - if <0.5g / L, return to this section for circulation; if ≥0.5g / L, pump into filter residue slurry tank A for reuse; the final filter residue enters the secondary ball mill for fine refining and is stored in the slurry mixing and storage tank for use in the zinc leaching process.

[0014] S8. The filtrate from filtrate storage tank B is pumped into the hydrolysis reactor, Fe2(SO4)3 solution is added, and the temperature is raised to 90-95℃, controlling the Fe... 3+ / F - When the molar ratio is ≥10, hydrolysis produces goethite, and F is absorbed through the lattice solidification effect. - The solid fluoride residue is fixed in the precipitate and separated by pressure filtration after the reaction.

[0015] S9. The low-fluoride filtrate is introduced into the chlorination reaction tower. Copper slag of 75-106μm is added according to an iron powder coefficient of 1.2. The sulfuric acid concentration is maintained at 20g / L, the temperature at 85℃, and the flow rate at 40mL / min. Air is introduced and stirred for 125 minutes to induce oxidation, resulting in the following reaction:

[0016] 2Cu 0 +O2+4H + +4CI - →4CuCl↓+2H2O

[0017] CuO + 2H+ + +2Cl - →CuCl₂ + H₂O → CuCl↓ + 1 / 2Cl2 is used to generate CuCl precipitate. After pressure filtration, copper-rich slag containing 56% copper is obtained, and the purified liquid is returned to the zinc electrolysis system.

[0018] Preferably, the washing sections in S1, S4, and S6 are enamel-lined reactors, the filter presses in S2, S5, and S7 are equipped with polypropylene filter plates, and the chlorination reaction tower in S9 is lined with a PTFE anti-corrosion layer and equipped with an air distributor to enhance oxidation.

[0019] Preferably, in step S2, NaOH solution and Na2CO3 solution are added to the slurry in stages to control the total alkalinity and stabilize the pH at 10-11. The fluorine and chlorine impurities in zinc oxide are converted into soluble NaF / NaCl through a metathesis reaction.

[0020] Preferably, in step S4, a 10% dilute sulfuric acid solution is slowly added dropwise to the slurry, and the pH value is monitored in real time until it reaches 8.0-8.5 to neutralize residual alkalinity and inhibit the redissolution of impurities. The dilute sulfuric acid is adjusted by adding a 10% H2SO4 solution in a gradient via a metering pump at a rate ≤2L / min, while the pH sensor feedback value is monitored simultaneously. When the pH drops to 8.3±0.2, the acid addition is stopped to prevent the redissolution of precipitated impurities due to excessively low pH.

[0021] Preferably, the high-temperature washing waste heat in S2 is used to preheat the copper slag reaction system, and the copper slag can replace the special dechlorination agent.

[0022] Preferably, compressed air is introduced into the chlorine precipitation reaction tower in S9 to maintain the oxygen partial pressure at 0.15-0.2 MPa, thereby promoting Cu precipitation. 0 Oxidized to Cu + After the reaction, the slurry is left to stand in an aging tank for 30 minutes to improve the integrity of CuCl grain growth.

[0023] Preferably, Fe in S8 3+ Before hydrolysis, the Fe / F molar ratio of the solution needs to be pre-adjusted to 12:1, and the hydrolysis temperature should be 90±2℃ for 40 min. XRD analysis of the solidified fluoride residue confirmed the α-FeOOH crystal form, ensuring the presence of F. - The fixed rate is >98%.

[0024] (III) Beneficial Effects

[0025] This invention provides a wet defluorination and dechlorination process for zinc oxide powder. It has the following beneficial effects:

[0026] 1. This invention utilizes a three-stage synergistic dechlorination system of "alkali washing-goethite-copper slag". Through the copper slag resource utilization directional chlorination technology, the active components in the waste copper slag react with chloride ions to generate stable precipitates, and high-value-added copper resources are recovered simultaneously, completely solving the problems of high cost and serious secondary pollution of traditional dechlorination processes. Combined with the fluoride fixation mechanism of goethite crystal lattice, it achieves deep fixation of fluoride ions, significantly improves the quality of cathode zinc and greatly reduces the risk of anode corrosion, fundamentally eliminating the destructive impact of the cyclic accumulation of fluoride and chloride impurities in hydrometallurgical zinc smelting on the electrolysis process.

[0027] 2. This invention utilizes a multi-stage intelligent filtrate diversion and reuse mechanism to form a near-zero wastewater discharge system in conjunction with the goethite purification unit, greatly reducing the treatment load of high-salt wastewater. At the same time, the copper slag dechlorination process replaces the high-energy-consuming traditional method, and combined with the waste heat cascade utilization technology, it significantly reduces the overall operating cost, forming a complete process solution that combines high efficiency, environmental protection and economic sustainability. Attached Figure Description

[0028] Figure 1 This is an overall flow chart of a wet defluorination and dechlorination process for zinc oxide powder proposed in this invention.

[0029] Figure 2 The figure shows the influence of multiple factors on the precipitation rate of copper, chlorine, and arsenic in a wet defluorination and dechlorination process of zinc oxide powder proposed in this invention.

[0030] Figure 3 The graph shows the influence of multiple factors on the precipitation rate of copper, chlorine, and arsenic in a wet defluorination and dechlorination process of zinc oxide powder proposed in this invention.

[0031] Figure 4 The graph shows the changes in copper, chlorine, and arsenic concentrations over time in two sets of reactions for a wet defluorination and dechlorination process of zinc oxide powder proposed in this invention.

[0032] Figure 5 This is a graph showing the precipitation rate and product content data of two sets of reactions in a wet defluorination and chlorination process of zinc oxide powder proposed in this invention.

[0033] Figure 6 This is a graph showing the change of redox potentials over time in two sets of reactions in a wet defluorination and chlorination process for zinc oxide powder proposed in this invention.

[0034] Figure 7 This is a particle size distribution diagram of four types of iron powder in a wet defluorination and chlorination process of zinc oxide powder proposed in this invention.

[0035] Figure 8 This is a schematic diagram of the contact angles of four types of iron powder in a wet defluorination and chlorination process for zinc oxide powder proposed in this invention.

[0036] Figure 9 This is a comparison diagram of the particle size distribution of four types of iron powder in a wet defluorination and chlorination process of zinc oxide powder proposed in this invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1:

[0039] like Figure 1 As shown, this embodiment of the invention provides a wet defluorination and dechlorination process for zinc oxide powder, including the following steps:

[0040] S1. The zinc oxide dust is wet-milled to form a slurry, which is then pumped into a slurry transfer tank for homogenization.

[0041] S2. The slurry is placed in an alkali-resistant stirring tank and stirred at 85 r / min for 1.5 h at 80-90℃, liquid-solid ratio of 5:1, and pH of 10-11 to convert fluorine and chlorine into soluble NaF / NaCl.

[0042] S3. The reaction slurry is separated by a plate and frame filter press. The filtrate enters the filtrate storage tank A. When the chlorine content is <15g / L, it is returned to the first washing and recycling stage. When it is ≥15g / L, it is discharged to the water treatment center. The filter residue is transferred into the filter residue slurry tank A.

[0043] S4. The filter residue in filter residue slurry tank A is mixed with the three-stage recycled filtrate and stirred for 1.5 hours at room temperature, liquid-solid ratio of 6:1 and pH of 8.0-8.5 to further remove residual fluorine and chlorine.

[0044] S5. After the slurry is pressed and filtered, the filtrate enters the filtrate storage tank B, and the filter residue is transferred to the filter residue slurry tank B.

[0045] S6. The filter residue in filter residue slurry tank B is mixed with clean water and reacted for 1.5 hours at room temperature, liquid-to-solid ratio of 5:1 and pH 7.0-8.0 to complete deep washing.

[0046] S7. Detect the chlorine content of the filtrate - if <0.5g / L, return to this section for circulation; if ≥0.5g / L, pump into filter residue slurry tank A for reuse; the final filter residue enters the secondary ball mill for fine refining and is stored in the slurry mixing and storage tank for use in the zinc leaching process.

[0047] S8. The filtrate from filtrate storage tank B is pumped into the hydrolysis reactor, Fe2(SO4)3 solution is added, and the temperature is raised to 90-95℃, controlling the Fe... 3+ / F - When the molar ratio is ≥10, hydrolysis produces goethite, and F is absorbed through the lattice solidification effect. - The solid fluoride residue is fixed in the precipitate and separated by pressure filtration after the reaction.

[0048] S9. The low-fluoride filtrate is introduced into the chlorination reaction tower. Copper slag of 75-106μm is added according to an iron powder coefficient of 1.2. The sulfuric acid concentration is maintained at 20g / L, the temperature at 85℃, and the flow rate at 40mL / min. Air is introduced and stirred for 125 minutes to induce oxidation, resulting in the following reaction:

[0049] 2Cu0 +O2+4H + +4Cl - →4CuCl↓+2H2O

[0050] CuO + 2H+ + +2Cl - →CuCl₂ + H₂O → CuCl↓ + 1 / 2Cl2 is used to generate CuCl precipitate. After pressure filtration, copper-rich slag containing 56% copper is obtained, and the purified liquid is returned to the zinc electrolysis system.

[0051] The washing sections in S1, S4, and S6 use enamel-lined reactors. The filter presses in S2, S5, and S7 are equipped with polypropylene filter plates. The chlorination reaction tower in S9 is lined with a PTFE anti-corrosion layer and equipped with an air distributor to enhance oxidation.

[0052] In S2, NaOH and Na2CO3 solutions are added to the slurry in stages to control the total alkalinity and stabilize the pH at 10-11. Through a metathesis reaction, fluorine and chlorine impurities in zinc oxide are converted into soluble NaF / NaCl.

[0053] In S4, a 10% dilute sulfuric acid solution is slowly added dropwise to the slurry, with the pH value monitored in real time until it reaches 8.0-8.5. This neutralizes residual alkalinity and inhibits the re-dissolution of impurities. The dilute sulfuric acid is adjusted by adding a 10% H2SO4 solution in a gradient via a metering pump at a rate ≤2L / min. The pH sensor feedback value is monitored simultaneously. When the pH drops to 8.3±0.2, the acid addition is stopped to prevent the re-dissolution of precipitated impurities due to excessively low pH.

[0054] The waste heat from the high-temperature washing in S2 is used to preheat the copper slag reaction system, and the copper slag can replace the special dechlorination agent.

[0055] Compressed air is introduced into the S9 chlorine precipitation reaction tower to maintain the oxygen partial pressure at 0.15-0.2 MPa, promoting Cu precipitation. 0 Oxidized to Cu + After the reaction, the slurry is left to stand in an aging tank for 30 minutes to improve the integrity of CuCl grain growth.

[0056] Fe in S8 3+ Before hydrolysis, the Fe / F molar ratio of the solution needs to be pre-adjusted to 12:1, and the hydrolysis temperature should be 90±2℃ for 40 min. XRD analysis of the solidified fluoride residue confirmed the α-FeOOH crystal form, ensuring the presence of F. - The fixed rate is >98%.

[0057] Example 2:

[0058] The effects of key factors such as iron powder type, iron powder addition coefficient, and sulfuric acid concentration on copper precipitation efficiency and impurity removal were systematically investigated. The composition and reaction pathway of the precipitated products were revealed. The experimental results are as follows: Figure 2 and Figure 3 As shown, the experimental results indicate that under the conditions of an iron powder addition coefficient of 1.2, a sulfuric acid concentration of 20 g / L, a reaction temperature of 85 °C, a reaction time of 25 min, and an iron powder particle size of 75-106 μm, the precipitation rates of copper, chlorine, and arsenic are 78.8%, 44.5%, and 13.4%, respectively. The contents of copper, chlorine, and arsenic in the precipitate are 55.4%, 18.28%, and 1.27%, respectively. The main phases in the precipitate are CuCl and CuCl2(Cu(OH)2)3, with a very small amount of Cu2O. Arsenic exists in the form of Cu3As and Cu2As2O7.

[0059] Two sets of continuous reaction experiments were conducted under the following conditions: an iron powder addition coefficient of 1.2, a sulfuric acid concentration of 20 g / L, a reaction temperature of 85℃, and an iron powder particle size of 75-106 μm. The total solution volume was 4 L, the flow rate was 40 mL / min, and the reaction continued for 25 min after the solution had completely drained, for a total reaction time of 125 min. A 20 mL sample was taken every 20 min for analysis, and the redox potential was measured every 10 min. The concentration changes of copper, chlorine, and arsenic over time in the two sets of continuous reaction experiments are shown in the graphs below. Figure 4 As shown in the figure, the redox potential change graph is as follows: Figure 6 As shown in Table 5, the experimental results of the two sets of experiments are presented. Figure 4 It can be seen that the concentration of copper in the solution showed a clear trend with the extension of reaction time: in the initial stage of the reaction (0-60 min), the copper concentration decreased rapidly, then rebounded slightly and tended to stabilize. The chloride concentration showed a continuous decreasing trend overall. The arsenic concentration changed relatively slowly, showing a characteristic of first decreasing slowly and then stabilizing. This phenomenon is mainly attributed to the change in the amount of iron powder added. In the first 60 min, due to the relatively excessive amount of iron powder added, the iron powder could fully reduce Cu2+ in the solution, causing it to precipitate as Cu in large quantities, resulting in a significant decrease in the copper ion concentration. Consequently, the chloride ion concentration decreased less in the early stage. At the same time, the excessive iron powder in the early stage was conducive to the precipitation reaction of arsenic. As shown in Table 3.20, the continuous reaction experiment was superior to the intermittent reaction experiment in terms of the removal effect of copper, chloride, and arsenic, as well as the grade of copper, chloride, and arsenic in the precipitate. In the continuous reaction, the precipitation rate of copper exceeded 83%, the precipitation rate of chlorine was about 53%, and the precipitation rate of arsenic was about 20%. Meanwhile, the content of copper in the precipitate was stable at about 56%, the content of chlorine was about 19%, and the content of arsenic was about 2%.

[0060] according to Figure 6 The results showed that the redox potential decreased rapidly within the first 20 minutes as the reaction time increased, which was mainly attributed to the presence of Fe in the solution. 3+ Cu 2+This is due to the rapid reduction reaction of oxidizing substances under the action of iron powder. When the reaction time reaches 60 minutes, the redox potential gradually stabilizes, indicating that the redox reaction in the system is close to equilibrium. This shows that appropriate sulfuric acid concentration and reaction time can significantly improve the effect of copper precipitation in synergistic removal of chlorine and arsenic. Excessive sulfuric acid concentration will lead to a large amount of hydrogen evolution, affecting the reaction efficiency; while excessively long reaction time will cause CuCl to dissolve back, reducing the copper precipitation efficiency and the chlorine removal effect.

[0061] Example 3:

[0062] The effects of four types of iron powder on the synergistic effect of iron powder in copper deposition for chlorine and arsenic removal were investigated. Iron powder No. 1 was analytical grade reduced iron powder, while iron powders No. 2-4 were from different companies. The particle size distribution diagrams of the four types of iron powder are shown below. Figure 7 As shown, the particle size distribution is compared to... Figure 8 As shown, the contact angles of the four types of iron powder are as follows: Figure 9 As shown, the metallic iron contents of the four types of iron powder are 98%, 95.41%, 94.43%, and 93.25%, respectively.

[0063] The results show that the particle size distribution and wettability of iron powder affect the reaction efficiency. Iron powder with uniform particle size distribution and good wettability is more conducive to the simultaneous precipitation of copper, chlorine, and arsenic. Excessive iron powder leads to a lower Cu2+ concentration in the solution, inhibiting the formation of CuCl. Sulfuric acid concentration and reaction time have a significant impact on the reaction of copper precipitation and chlorine / arsenic removal. When the sulfuric acid concentration exceeds 30 g / L, the precipitation efficiency of copper, chlorine, and arsenic decreases due to the formation of side reactions caused by the large-scale evolution of hydrogen gas. In the process of iron powder precipitation and chlorine / arsenic removal reaction, copper precipitation is dominant in the initial stage, and the precipitation rates of chlorine and arsenic are low. When the reaction time is 20-25 min, the effect of copper precipitation and chlorine / arsenic removal is good. When the reaction time exceeds 25 min, CuCl in the precipitate begins to dissolve back, leading to a decrease in copper precipitation efficiency and a worse removal effect of chlorine and arsenic. The particle size of iron powder and the reaction temperature have little effect on the precipitation of copper, chlorine, and arsenic. Low chlorine concentration in the solution can promote arsenic precipitation, while high chlorine concentration can promote the formation of CuCl and increase the precipitation rate of copper.

[0064] In summary, controlling the particle size distribution and wettability of iron powder can improve reaction efficiency, thereby enhancing the simultaneous precipitation of copper, chlorine, and arsenic. Iron powder with a uniform and concentrated particle size distribution and good wettability is more conducive to the reaction.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the wet defluoridation and dechlorination of zinc oxide powder, characterized in that, The method comprises the following steps: S1, wet ball milling of zinc suboxide fume dust to form a slurry, and pumping the slurry into a homogenizing tank; S2, the slurry is stirred in an alkali-resistant stirring tank at 80-90℃, a liquid-solid ratio of 5:1, and pH 10-11, and 85r / min for 1.5h to convert fluorine and chlorine into soluble NaF / NaCl; S3, the reaction slurry is separated by a plate-and-frame filter press, the filtrate is returned to the first washing cycle when the chlorine content is less than 15g / L, and is discharged to a water treatment center when the chlorine content is greater than or equal to 15g / L, and the filter residue is transferred into the inside of a filter residue slurry tank A; S4, the filter residue in the filter residue slurry tank A is mixed with the three-stage recycled filtrate, and is stirred at room temperature, a liquid-solid ratio of 6:1, and pH 8.0-8.5 for 1.5h to further remove residual fluorine and chlorine; S5, after the slurry is filtered, the filtrate is introduced into a filtrate storage tank B, and the filter residue is transferred into a filter residue slurry tank B; S6, the filter residue in the filter residue slurry tank B is mixed with clean water, and is reacted at room temperature, a liquid-solid ratio of 5:1, and pH 7.0-8.0 for 1.5h to complete deep washing; S7, the chlorine content of the filtrate is detected, and the filtrate is returned to the present stage when the chlorine content is less than 0.5g / L, and is pumped into the filter residue slurry tank A for reuse when the chlorine content is greater than or equal to 0.5g / L; The final filter residue is stored in a slurry stirring tank after secondary ball milling for use in a zinc leaching process; S8, the filtrate in the filtrate tank B is pumped into the hydrolysis reactor, Fe2(SO4)3 solution is added and the temperature is raised to 90-95℃, the Fe 3 + / F - molar ratio ≥ 10, hydrolysis generates goethite, F - is fixed in the precipitate, and after the reaction, the solid fluorine-containing residue is separated by pressure filtration; S9, the low-fluorine filtrate is introduced into a chlorine precipitation reaction tower, 75-106μm copper residue is added according to an iron powder coefficient of 1.2, the sulfuric acid concentration is maintained at 20g / L, the temperature is 85℃, the flow rate is 40mL / min, air is introduced for oxidation and stirring for 125 minutes, and the following reaction occurs: 2Cu 0 + O2+ 4H + + 4Cl - → 4CuCl↓ + 2H2O CuO + 2H + + 2Cl - → CuCl2+ H2O → CuCl↓ + 1 / 2Cl2, CuCl precipitate is generated, copper-rich slag containing 56% of copper is obtained after pressure filtration, and the purified liquid returns to the zinc electrolysis system.

2. A process for the removal of fluorine and chlorine from zinc oxide powder by wet process as claimed in claim 1 wherein: The washing stages in S1, S4 and S6 use enamel reaction kettles, the filter presses in S2, S5 and S7 are equipped with polypropylene filter plates, the chlorine precipitation reaction tower in S9 is lined with a PTFE anticorrosion layer and is equipped with an air distributor to strengthen oxidation.

3. A process for the removal of fluorine and chlorine from zinc oxide powder by wet process as claimed in claim 1 wherein: In S2, NaOH solution and Na2CO3 solution are added to the slurry in steps to control the total alkalinity so that the pH is stabilized at 10-11, and the fluorine and chlorine impurities in the zinc suboxide are converted into soluble NaF / NaCl through a metathesis reaction.

4. A process for the removal of fluorine and chlorine from zinc oxide powder by wet process as claimed in claim 1 wherein: In S4, 10% dilute sulfuric acid solution is slowly added to the slurry, the pH value is monitored in real time to be 8.0-8.5, residual alkalinity is neutralized, and impurities are inhibited from being redissolved, the dilute sulfuric acid is added by a metering pump at a gradient, the addition rate is less than or equal to 2L / min, the pH sensor feedback value is monitored synchronously, the acid addition is stopped when the pH drops to 8.3±0.2 to prevent the pH from being too low to cause the redissolution of precipitated impurities.

5. A process for the removal of fluorine and chlorine from zinc oxide powder by wet process as claimed in claim 1 wherein: The high-temperature washing residual heat in S2 is used to preheat the copper residue reaction system, and the copper residue can replace a special chlorine removal agent.

6. A process for the removal of fluorine and chlorine from zinc oxide powder by wet process as claimed in claim 1 wherein: The compressed air is introduced into the chlorine precipitation reaction tower in S9, so that the oxygen partial pressure is maintained at 0.15-0.2 MPa, and the Cu 0 oxidation is promoted + After the reaction, the slurry is placed in the aging tank for 30 min to improve the integrity of CuCl crystal grain growth.

7. A process for the removal of fluorine and chlorine from zinc oxide powder by wet process as claimed in claim 1 wherein: Fe in S8 3+ The Fe / F molar ratio of the pre-adjusted solution before hydrolysis was 12:1, the hydrolysis temperature was 90±2℃, and the hydrolysis was kept for 40 min; the solid fluorination slag was detected by XRD to confirm the α-FeOOH crystal form, and the F - The grid fixation rate was >98%.

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