In recent years, with the continuous expansion of the domestic electric zinc production scale and the depletion of zinc concentrate resources, the development and utilization of zinc-containing waste has attracted attention. Copper zinc waste containing elements Cu, Zn, Fe, Si, Cl, F , etc., but very difficult to handle a recovery value of zinc scrap, waste containing some copper-zinc higher iron content, zinc recovery when Separating iron is one of the most important issues. At present, most companies use sulfuric acid leaching-displacement-purification process to recover copper and zinc. The process places the removal of iron in a purification process, that is, when a copper-zinc is leached, a large amount of iron is simultaneously transferred into the solution, and then iron is removed by a yellow ammonium ferrite precipitation method, an iron hydroxide hydrolysis method, a goethite method, a solvent extraction method, or the like. For the copper-zinc waste residue with high iron content, the purification pressure of iron is relatively large. For this reason, the iron removal at the same time as leaching is studied, and the test is carried out by using the ferric hydroxide hydrolysis method and the yellow ammonium iron samarium precipitation method. First, the test part (1) Test materials The test raw material copper and zinc waste was taken from a copper smelting enterprise in Yunnan. The chemical analysis results of copper-zinc waste residue and iron-free leachate are shown in Table 1. Table 1 Chemical composition analysis results of copper-zinc waste residue and iron-free leachate Reagents: industrial grade H 2 O 2 , electrolytic zinc waste, industrial grade CaCO 3 , industrial grade NH 4 HCO 3 . Analytical method: When the iron concentration in the leachate is high, it is directly determined by titration; when the iron concentration is low, it is determined by spectrophotometry. A trace amount of Fe 2+ in the leachate, Fe is mainly Fe 3+ ; and the pH is 3.0 to 3.5. (2) Test methods 1. Ferric hydroxide hydrolysis method At room temperature, and the pH of the hydrolysis relationship leachate metal ions primarily in Table 2. It can be seen that the purpose of removing iron is easily achieved by the method of hydrolyzing iron hydroxide. In practice, it is only necessary to consider the filtration performance of the solution after de-ironing and to control the pH value to prevent simultaneous hydrolysis of Cu 2+ and Zn 2+ . Table 2 Relationship between metal ions and pH in solution Test procedure: Take 5L of copper and zinc waste leaching slurry, adjust the pH value, stir for 10 to 60 minutes, and filter to obtain the leaching solution after removing iron. 2, yellow ammonium iron sputum method to remove iron The basic reaction formula of the removal of iron by the yellow ammonium iron slag method is: Test procedure: Take 5L of copper and zinc waste leaching slurry, adjust the pH value, add ammonium hydrogencarbonate, stir, precipitate hydrazine, and filter to obtain leaching solution after removing iron. Second, the results and discussion (1) Ferric hydroxide hydrolysis method for removing iron 1. Effect of pH on iron removal effect Take 6 parts of the slurry and adjust the pH with CaCO 3 . The temperature was constant between 65 and 70 ° C. The test results are shown in Table 3. It can be seen that when the pH is lower than 4.0, the copper is not hydrolyzed, but the iron removal effect is not satisfactory; the pH is between 4.5 and 5.0, the iron removal effect is better, but the copper hydrolysis is more; the pH value is increased to 4.0 or more. As the copper is hydrolyzed, the solution filtration performance becomes better because a certain amount of copper hydroxide crystal grains are formed in the leaching slag. Table 3 Effect of pH value on iron removal efficiency of iron hydroxide hydrolysis 2. Effect of temperature on iron removal effect Take 4 parts of the slurry, control the pH between 3.5 and 4.0, stir for 3 hours, and test at different temperatures. The results are shown in Table 4. It can be seen that the temperature in the range of 65-100 °C has little effect on the hydrolysis of iron and copper; as the temperature increases, the solution filtration performance slightly improves. Table 4 Effect of temperature on iron removal efficiency of iron hydroxide hydrolysis (2) Removal of iron by the method of yellow ammonium iron 1. Effect of temperature on iron removal effect Take 4 parts of the slurry, add NH 4 HCO 3 with a theoretical value of 1.5 times of precipitation, adjust the pH value to about 2.0 with electrolytic waste liquid, and stir for 3 hours at different temperatures. The test results are shown in Table 5. It can be seen that in the range of 65-100 °C, the effect of sedimentation increases with the increase of temperature; when the temperature reaches 95-100 °C, the mass concentration of iron in the solution drops to 0.13g/L; with the increase of temperature, the solution is filtered. The performance is getting better. Table 5 Effect of temperature on iron removal by ferric ammonium iron 2, the effect of pH on the effect of iron removal Take 5 parts of the slurry, add 1.5 times the theoretical value of NH 4 HCO 3 , maintain the temperature between 85 and 90 ° C, stir for 3 h, adjust the pH value of the slurry with electrolytic waste. The test results are shown in Table 6. It can be seen that when the pH value of the sinking point is lower than 1.5, the effect of sinking is slightly worse; as the pH value decreases, the effect of sedimentation deteriorates remarkably, and the filtration performance of the slurry deteriorates significantly; the pH value of the sinking point is 2.0-3.0. Between, the effect of sinking is better, and the filtration performance of the slurry is better. Table 6 Effect of pH value on iron removal effect of yellow ammonium iron samarium method 3. Effect of stirring time on iron removal effect Take 1 part of the slurry, add 1.5 times the theoretical value of NH 4 HCO 3 , and adjust the pH of the slurry to 2.0 with electrolytic waste to stir for different time. The test results are shown in Table 7. It can be seen that the stirring effect is better when the stirring is carried out for 1 to 5 hours, and the filtration performance of the slurry is also improved. Table 7 Effect of stirring time on iron removal effect of yellow ammonium iron samarium method 4, the effect of ammonium bicarbonate dosage on iron removal Take 4 parts of the slurry, add different amounts of NH 4 HCO 3 respectively , adjust the pH value of the starting point to 2.0 with the electrolytic waste liquid, maintain the temperature between 85 and 90 ° C, stir for 1 h, and the test results are shown in Table 8. It can be seen that the addition amount of NH 4 HCO 3 is better when the theoretical value of sinking is the theoretical value of sinking. Table 8 Effect of the amount of ammonium bicarbonate on the iron removal effect of the yellow ammonium iron samarium method 5, yellow ammonium iron sputum method iron removal industry practice In a copper-zinc waste leaching slurry of about 45 m 3 , a theoretical amount of 1.0 to 1.2 times of NH 4 HCO 3 was added , and the pH of the starting point was adjusted to 2.5 with the electrolytic waste liquid, the temperature was maintained above 85 ° C, and the mixture was stirred for 3.0 h. The test results are shown in Table 9. It can be seen that when leaching, the removal of iron by the yellow ammonium iron sputum method can simultaneously remove some other impurities, especially the F element, and the principle needs further study. Table 9 Chemical composition analysis results of copper and zinc slag leachate after iron removal g/L Third, the conclusion (1) In the process of leaching copper and zinc waste, iron removal by iron hydroxide hydrolysis method is adopted. When the pH value is low, the iron removal effect is poor; when the pH value is high, the iron removal effect is good, but the copper hydrolysis in the leachate is serious. (2) The method of removing iron by the yellow ammonium iron shovel method is better, and the copper recovery rate in the solution is high, and the preliminary iron removal in the process of treating the copper and zinc waste residue by the wet method is suitable. The suitable process conditions are: temperature above 85 ° C, pH between 2.0 and 3.0, stirring time of 3 to 5 h, and the amount of ammonium bicarbonate is more than 1.0 times the theoretical amount. Under the optimal conditions, the iron concentration in the copper-zinc waste leaching solution can be reduced to below 0.25g/L, and the pressure filtration performance of the slurry is good.
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