Study on the precipitation of indium from pressurized infiltration solution of indium-rich high-iron zinc sulfide concentrate by iron shovel method

The recovery methods of ruthenium mainly include oxidative slagging method, electrolytic enrichment method, ion exchange method, sulphation roasting method, hot acid leaching iron shovel method, and hot acid leaching goethite method. Iron removal by iron method has been widely used at home and abroad. However, there are few reports on sinking indium from pressurized indium -rich high-iron leaching solution. This paper attempts to find a process for sinking indium from a rich indium-rich high-iron pressurized leachate. Both to better enrichment of indium, iron while allowing the body to obtain zinc metal separation, reducing production cost of the process.

First, the experiment

(1) Formation of iron and vanadium and the principle of sinking indium

The formation of iron bismuth compounds is a slow formation of a poorly soluble complex and a crystalline potassium sulphate (sodium sulphate) from a weakly acidic sulphate solution at a relatively high temperature and in the presence of an alkali metal ion or NH ₄ ⁺ . , ammonium) and other double salt compounds. This precipitate is very stable, has low solubility, and is easy to settle for filtration and washing. The reaction mechanism is as follows: 3Fe ₂ (S0 ₄ ) ₃ + lOH ₂ 0+2NH ₃ · H ₂ 0 = (NH ₄ ) ₂ Fe ₆ (S0 ₄ ) ₄ (OH) ₁₂ + 5H ₂ S0 ₄ is known from the reaction formula, in order to complete the reaction, It is necessary to neutralize the sulfuric acid formed by hydrolysis. The neutralizing agent used herein is analytically pure ZnO.

In addition to strong adsorption properties, the iron bismuth compounds have a wide range of crystal isomorphisms, such as K ⁺ , Fe ³⁺ , and S0 ₄ ^2- , which can cause In to be adsorbed or replaced. Way to enter the iron oxide compound.

For the interaction mechanism between In and iron shovel, this paper believes that the following reactions may occur:

In ₂ (S0 ₄ ) ₃ +36H ₂ O+9Fe ₂ (S0 ₄ ) ₃ =3In _2/3 Fe ₆ (S0 ₄ ) ₄ (OH) ₁₂ +18H ₂ S0 ₄

In ³⁺ replaces the positions of Na ⁺ , K ⁺ , and NH ⁴⁺ to enter the iron sputum and form a precipitate.

(2) Experimental materials and reagents

The experimental raw material is an indium-rich high-iron bowl zinc-zinc concentrate pressurized leachate, and its composition is (g/L): In O.045～0.14, Fe10～15, Fe ³⁺ 4.6～6.O, H ₂ S0 ₄ 40～50 , CuO.4-0.5, PbO.7~1.0, As O.4~0.5, CdO.3~0.40 The experimental reagent is analytical pure iron sulfate, zinc oxide, ammonia water, potassium sulfate and the like.

(three) experimental steps

The Fe ²⁺ in the leachate was oxidized to Fe ³⁺ with an appropriate amount of H ₂ O ₂ in a glass reactor thermostated in a water bath. The solution was continuously stirred with a power agitator at a stirring speed of 40 r/min. The pH of the solution was measured with a pH meter, and after the temperature was raised to the desired temperature, the time was started. Since the H+ concentration in the reaction is constantly increasing, it is necessary to continuously add ZnO for neutralization, and attention should be paid to controlling the slow neutralization speed. In order to study the effect of the iron slag method on the indium in different initial concentrations of In ³⁺ and Fe ³⁺ , it is necessary to concentrate, dilute or add a certain amount of In ³⁺ and Fe ³⁺ to the leachate.

Second, the results and discussion

(1) Effect of iron-indium molar ratio on jarosite precipitation

The iron-indium molar ratio is an important condition that affects the precipitation rate of indium. The iron-indium molar ratio is too low, and the indium in the leachate cannot be completely precipitated; on the contrary, if the iron-indium molar ratio is too high, the post-treatment amount is increased, resulting in an increase in cost. Fixation conditions: pH=1.75, temperature 96-98 ° C, time 3 h, adding jarosite seed crystal, the experimental results are shown in Figure 1.

Fig.1 Effect of iron/indium molar ratio on sinking In

Fig.1 Effect of Fe/In mole ratio on indium precipitation rate

It can be seen from Fig. 1 that the precipitation rate of indium increases with the increase of the molar ratio of iron to indium. When the molar ratio of iron to indium reaches 140, the rising trend of indium precipitation rate begins to become gentle, and the molar ratio of iron to indium reaches 200. The change is not obvious. Therefore, the optimum iron to indium molar ratio is 200. At this time, the precipitation rate of indium can reach 98% or more.

(2) Relationship between iron precipitation rate and indium precipitation rate in solution

Fixation conditions: pH=1.75, temperature 96-98 ° C, time 3 h, iron concentration 4.8 g / L, iron indium molar ratio 200, adding jarosite seed crystal, the experimental results are shown in Figure 2.

Figure 2 Relationship between iron precipitation rate and indium precipitation rate

Fig.2 Relationship between indium and iron precipitation rate

It can be seen from Fig. 2 that the indium precipitation rate shows a significant upward trend with the increase of the iron precipitation rate in the solution. The lower the initial concentration of indium in the solution, the better the precipitation effect of indium. When the initial concentration of indium in the solution is 0.045 g/L, the indium precipitation effect is the best, and the indium precipitation rate is over 95%.

(III) Effect of endpoint pH on jarosite

The pH of the solution is a significant factor in the formation of jarosite, and it is related to the equilibrium iron ion concentration. The lower the equilibrium Fe ³⁺ concentration in the solution, the larger the pH range of jarosite formation. The Fe ³⁺ concentration used in this experiment was 4.8 g/L, and seed crystals were added. Selected conditions: temperature 96 ~ 98 ° C, time 3h, iron indium molar ratio of 200, adding jarosite seed crystal, the experimental results shown in Figure 3.

Figure 3 Effect of endpoint pH on jarosite

Fig.3 Effect of pH value on indium precipitation rate

It can be seen from Fig. 3 that as the pH of the solution end point increases, the precipitation rates of indium and iron increase significantly. When the solution pH=1.75, the indium precipitation effect is the best, the indium precipitation rate is above 98%, and the iron precipitation rate is above 95%. Continue to increase the pH, there is no significant change in the precipitation rate of indium and iron. From the hydrolysis equilibrium p of iron, it is known that when the concentration of iron in the solution is 4.0 to 5.6 g/L, the pH at which precipitation starts is 1.867 to 1.914. It is fully explained that Fe ³⁺ in the solution does not undergo hydrolysis to form a Fe(OH) ₃ precipitate. The XRD analysis results of the precipitated slag under the process conditions also showed that the precipitate was jarosite and had good crystallinity, and no Fe(OH) _{3 was} found.

(4) Effect of reaction time on indium precipitation

The prolongation of the reaction time can make Fe ^{3+ in the} solution fully react to form iron ruthenium, thereby ensuring that the In ^{3+ in the} solution is sufficiently adsorbed or displaced by the generated iron slag. Selected conditions: pH=1.75, temperature 96-98 ° C, concentration of Fe ³⁺ in the leachate 4.8 g / L, iron indium molar ratio of 200, adding jarosite seed crystal, the experimental results shown in Figure 4.

Figure 4 Effect of reaction time on indium precipitation rate

Fig.4 Effect of reaction time on indium precipitation rate

It can be seen from Fig. 4 that the precipitation rate of In increases with the increase of the reaction time regardless of whether or not the iron strontium seed crystal is added. After the addition of the iron sorghum seed crystal, the formation rate of the iron shovel was significantly faster than that of the iron sorghum seed crystal. After the seed crystal was added, the precipitation rate of In had reached 98% or more when the reaction was carried out for 3 hours. After 3 hours, the curve tends to be gentle, and the In precipitation rate does not change significantly, and the reaction reaches a chemical equilibrium. When the seeding reaction time was not added at 3 hours, the In precipitation rate was only about 80%. However, as the reaction time prolonged, the In precipitation rate of the two was almost the same, indicating that the addition and non-addition of iron strontium seeds had no significant effect on the precipitation rate of In, and the rate of formation of iron slag was affected.

(5) Effect of reaction temperature on precipitation rate of indium

The experimental results under the conditions of pH=.75, reaction time 3 h, iron-indium molar ratio 200, and addition of iron strontium seed crystals are shown in Fig. 5.

Figure 5 Effect of reaction temperature on indium precipitation rate

Fig.5 Effect of reaction temperature on indium precipitation rate

It can be seen from Fig. 5 that the reaction temperature has a great influence on the precipitation rate of iron and indium, and the precipitation rate of indium iron increases as the temperature increases. When the temperature is lower than 92 ° C, the precipitation rate of indium iron is low, and the precipitated crystals are not good, and the filtration performance is deteriorated. Therefore, in the process of sinking indium by iron, the temperature should be controlled above 92 °C. When the temperature is around 98 ° C, the precipitation rate of indium can reach 97% or more.

(6) Comparison of the method of yellow potassium iron sputum and yellow ammonium iron samarium

In order to investigate the difference in the precipitation rate of indole between the jarosite method and the yellow ammonium ferrite in the iron shovel method, the following experiment was performed. The fixing conditions were as follows: pH=1.73 to 1.75, an initial concentration of Fe ^{3+ of} 4.8 g/L, a molar ratio of iron to indium of 200, and a reaction temperature of 96 to 98 °C. The corresponding iron sorghum seed crystals were added to the two iron shovel methods, and the seed crystals were added in an amount of 1.5 times the amount of iron strontium. The experimental results are shown in Table 1.

Table 1 Precipitation effect of jarosite and yellow ammonium ferrite on indium

Table l Effect on indium precipitation rate by Jarosite and Ammonium jarosite

It can be seen from Table 1 that under the selected process conditions, the precipitation rate of the jarosite indium iron is higher than that of the yellow ammonium iron samarium method in the same reaction time. The yellow potassium iron sputum method reached a chemical equilibrium reaction time of 3 h, while the yellow ammonium iron sputum method was 6 h. When the equilibrium is reached, the indium indium rate of the jarosite method is 97.4%, and the yellow ammonium ferric niobium method is 94.23%, indicating that the jarosite method has a greater indium sinking capacity than the yellow ammonium ferrite method.

Third, the conclusion

(1) When pH=l.73～1.75, temperature 96～98°C, iron-indium molar ratio is more than 200, and the time should be 3h, when adding seed crystals is 1.5 times of the theoretical amount of iron sputum, use the jarosite method It is technically feasible to enrich indium from the pressurized leaching solution of indium-rich high-iron zinc concentrate, and the indium precipitation rate is about 98%;

(2) The precipitated compounds are jarosite and yellow ammonium ferrite, and no Fe(OH) _{3 is} formed. The reaction mechanism is: In ³⁺ replaces the positions of Na ⁺ , K ⁺ and NH ₄ ⁺ , thereby entering the iron sputum and forming a precipitate;

(3) The jarosite method has the ability to sink indium more than the yellow ammonium ferrite method, and the time for sinking indium is about 3 h.

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