Iron sulfate is an important chemical raw material, and water purification is an important agent of hydrometallurgical. At present, the industrial production method of iron sulfate mainly oxidizes or catalyzes the oxidation of ferrous sulfate in an aqueous solution of sulfuric acid, and some is oxidized by bacteria with ozone or oxygen. For example, Canadian Patent CA-1018774 discloses a continuous process for producing iron sulfate. Bacterial oxidation process and equipment can convert ferrous sulfate into sulfuric acid by reacting with sulfuric acid and oxygen under the action of bacteria. In addition, the iron ore or a mixture thereof with the metal iron is leached with an aqueous solution of sulfuric acid, such as H 2 O 2 , KC1O 3 , KMnO 4 , O 2 , etc., such as Japanese Patent No. J61-286228, 286229, which is made of sulfuric acid and iron. In the oxide reaction, Fe 2 + in the obtained leachate is oxidized with O 2 or air, H 2 O 2 , MnO 2 , NaC1O 3 oxidant, or catalytically oxidized to Fe 3 + with a nitro oxide. The above-mentioned prior art, because it reacts sulfuric acid with ferrous iron, requires equipment to have good corrosion resistance, so equipment investment and maintenance cost are high, and oxidant and catalyst are consumed in a large amount, and the process is complicated, thereby limiting the production of ferric sulfate. And application. In this experiment, iron ore is used as raw material to prepare iron sulfate. Since iron ore contains many organic impurities, if it is directly acid leached, it will affect the quality of iron sulfate. Therefore, the iron ore was first satin fired and then acid leached. At the same time, the effects of calcination temperature, calcination time, sulfuric acid concentration, acid leaching time and liquid-solid ratio (sulfuric acid to iron ore mass ratio) on iron leaching rate were investigated. And determine the reasonable production process and operating conditions. The method has the characteristics of simple process, low investment and low cost, and can effectively utilize iron ore comprehensively to control environmental pollution.
First, the experimental part
The iron ore was taken from a steel plant in Xiangtan. After analysis, its chemical composition was: TFe 63.3%, FeO 0.25%, Fe 2 O 3 89.94%, Al 2 O 3 2.08%, SiO 2 4.16%, CaO 0.4%, The other 3.17%.
Main instrument. DBJ-621 six-time timing variable speed mixer; CS-501SP super quantity thermostat; muffle furnace.
experimental method. The iron ore fines ground to -200 mesh are placed in a muffle furnace and calcined at 600 ° C, 700 ° C, 800 ° C, and 900 ° C for a certain period of time. After cooling, they are taken out for use. Under normal temperature and pressure, a certain proportion of iron ore fines and diluted concentrated sulfuric acid are placed in a 500ml flask with a stirring device, and then reacted at 100 ° C for a period of time, cooled, filtered, and then contains Fe 2 (SO 4 ) 3 solution. The concentration of Fe 2 + was determined by titrating with KMnO 4 using H 3 PO 4 as a masking agent, and the concentration of Fe 3 + was determined by EDTA complexometric titration with sulfosalicylic acid as an indicator.
Second, the results and discussion
(1) Effect of calcination temperature on iron leaching rate
The calcination time was controlled to 2 h, the sulfuric acid concentration was 5 mol/L, the liquid-solid ratio was 6:1, and the acid leaching time was 3 h. The effects of different calcination temperatures on the iron leaching rate were investigated. The results are shown in Table 1. It is known from Table 1 that when the calcination temperature is lower than 800 °C, the iron leaching rate increases with the increase of temperature; but when the calcination temperature exceeds 800 °C, the iron leaching rate does not change significantly with the increase of temperature. Therefore, the preferred calcination temperature is 800 °C.
Table 1 Effect of calcination temperature on iron leaching rate
Calcination temperature / °C | 600 | 700 | 800 | 900 |
Iron leaching rate /% | 53.1 | 69.2 | 79.5 | 80.3 |
(2) Effect of calcination time on iron leaching rate
The calcination temperature was controlled at 800 ° C, the sulfuric acid concentration was 5 mol/L, the liquid-solid ratio was 6:1, and the acid leaching time was 3 h. The effects of different calcination times on the iron leaching rate were examined. The results are shown in Table 2. It can be seen from Table 2 that the leaching rate of iron increases with the increase of calcination time; however, after the calcination time exceeds 2 h, the iron leaching rate does not increase significantly. Therefore, the calcination time is preferably 2h.
Table 2 Effect of calcination time on iron leaching rate
Calcination time / h | 0.5 | 1 | 2 | 3 |
Iron leaching rate /% | 35.3 | 62.5 | 78.7 | 80.4 |
(III) Effect of sulfuric acid concentration on iron leaching rate
The calcination temperature was controlled at 800 ° C, the calcination time was 2 h, the liquid-solid ratio was 6:1, and the acid leaching time was 3 h. The effects of different sulfuric acid concentrations on the iron leaching rate were investigated. The results are shown in Table 3. As can be seen from Table 3, as the concentration of sulfuric acid increases, the leaching rate of iron increases. When the concentration of sulfuric acid exceeds 5 mol1/L, the leaching rate of iron decreases. This is because if the concentration of sulfuric acid is too high, the amount of water in the reaction system is less, the reaction is insufficient, and the leaching rate of iron is rather decreased. Therefore, it is preferred to control the sulfuric acid concentration to 5 mol/L.
Table 3 Effect of sulfuric acid concentration on iron leaching rate
Sulfuric acid concentration / (mol / L) | 3 | 4 | 5 | 6 |
Iron leaching rate /% | 44.8 | 70.6 | 79.5 | 78.2 |
(4) Effect of acid leaching time on iron leaching rate
The calcination temperature was controlled at 800 ° C, the calcination time was 2 h, the sulfuric acid concentration was 5 mol/L, and the liquid-solid ratio was 6:1. The effect of different acid leaching time on the iron leaching rate was examined. The results are shown in Table 4. It can be seen from Table 4 that the leaching rate of iron increases with the extension of the acid leaching time; however, the iron leaching rate does not increase significantly after the acid leaching time exceeds 3 hours. Therefore, the acid leaching time is preferably 3h.
Table 4 Effect of acid leaching time on iron leaching rate
Acid leaching time / h | 1 | 2 | 3 | 4 |
Iron leaching rate /% | 51.5 | 70.3 | 78.7 | 79.1 |
(5) Effect of liquid-solid ratio (mass ratio of sulfuric acid to iron ore) on iron leaching rate
The calcination temperature was controlled at 800 °C, the calcination time was 2 h, the sulfuric acid concentration was 5 mol1/L, and the acid leaching time was 3 h. The effects of different liquid-solid ratios (sulfuric acid and iron ore mass ratio) on iron leaching rate were investigated. The results are shown in Table 5. . It can be seen from Table 5 that the iron leaching rate increases with the increase of the liquid-solid ratio. As the liquid-solid ratio increases, the liquid-solid contact opportunity increases, but the rate increases, so the iron leaching rate increases, but the liquid-solid ratio exceeds 6:1. The increase in iron leaching rate is not obvious. Therefore, the liquid-solid ratio (sulfuric acid to iron ore mass ratio) is preferably controlled at 6:1.
Table 5 Effect of liquid-solid ratio on iron leaching rate
Liquid to solid ratio (mass ratio of sulfuric acid to iron ore) | 4 | 5 | 6 | 7 |
Iron leaching rate /% | 58.3 | 75.1 | 79.1 | 79.7 |
Third, the conclusion
(1) Since iron ore contains many organic impurities, if it is directly acid leached, it will affect the quality of iron sulfate. Therefore, the iron ore is first calcined and then acid leached, and the iron leaching effect is better.
(2) When the calcination temperature is 800 ° C, the calcination time is 2 h, the sulfuric acid concentration is 5 mol 1 /L, the acid leaching time is 3 h, and the liquid-solid ratio (sulfuric acid to iron ore mass ratio) is 6:1, the iron leaching rate highest.
(3) Using iron ore as raw material and preparing iron sulphate according to the above method, it has the characteristics of simple process, low investment and low cost, and can effectively utilize iron ore comprehensively to control environmental pollution.
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