Factors affecting the rate of leaching

Wangcheng Yan, Qiu Ding-fan, etc. The factors influencing the leaching rate bismuthinite. Studies have shown that under the test conditions, stibnite is easily leached, and the leaching rate of bismuth can reach more than 96% during the theoretical leaching electrolysis time of bismuth. Through the optimization of the leaching process and the design of the rotational regression test, the optimal conditions for the leaching process are as follows: the iron ion concentration is 4g ∕L, the leaching temperature is 75 ° C, and the leaching time is 1.5 times the theoretical amount. The relationship between stibnite and elemental sulfur during leaching is shown in Figure 1. The ordinate in the figure is the corresponding diffraction intensity of the strongest diffraction angle of the mineral.

Fig.1 Variation of stibnite and elemental sulfur during leaching

First, the leaching temperature

Temperature is an important factor affecting the leaching kinetics of the crucible. The test results in the temperature range of 323 to 353 K are shown in Fig. 2. The mathematical results were substituted into three mathematical models of unreacted contracted nuclei. The results are shown in Figures 3 and 4.

Figure 2 Relationship between leaching rate and time at different temperatures

Fig. 3 Relationship between 1-(1-α) ^{1 ∕3} and time of 铋 at different temperatures

Figure 4 1- at different temperatures Α-(1-α) ^{2 ∕3} and time diagram

Figure 3 shows that during the leaching theoretical leaching electrolysis time, the leaching process of hydrazine is controlled by chemical reactions, and Figure 4 shows that it is controlled by the diffusion step later.

Second, the stirring speed

The effect of the stirring speed on the leaching rate is shown in Figure 5.

Figure 5 shows that the leaching rate of bismuth in the ore sample does not change significantly in the range of 350-700 mm ^-1 , and the leaching process is controlled by chemical reaction.

Third, the iron ion concentration

The test results are shown in Figure 6. The results show that the leaching rate is faster when the concentration of iron ions in the leachate is 6g ∕L, and the leaching rate is lower when 8.5g ∕L. The leaching rate of stibnite is lower than that under high ferric ion concentration at low iron ion concentration. The rate is very different, indicating that iron ions are also involved in the leaching reaction process of stibnite.

When Dutrizac when using ferric chloride leaching of galena found iron concentration in solution is less than 5.6g / L, the leaching rate increases with increased concentration of iron ions. K∝[FeCl ₃ ] ^1.9 ; When the iron ion concentration is greater than 5.6g ∕L, the leaching rate decreases with the increase of iron ion concentration, k∝[FeCl ₃ ] ^-0.27 . Kolodziei found at acidic ferric chloride solution impregnated silver, when iron ions varied within 0.56 ~ 5.6g / L concentration range, the initial leaching rate is substantially the same, and further increase the concentration of iron leaching agent, the initial leaching results in The rate is reduced. When leaching Bobeck sphalerite same system is observed when increasing the concentration of iron ions to 5.6g / L, no further change in the rate of leaching. In the study of the mechanism of leaching sphalerite by this system, Warren found that in the low concentration of ferric chloride and chloride solution, the leaching reaction rate is proportional to the 0.5th power of the ferric iron concentration, and the chloride ion concentration is 0.45 times. The square is proportional; when the concentration of ferric chloride and chloride is high, the reaction rate decreases with the increase of the concentration of ferric and chloride ions. Kolodziej calculated the contribution rate of FeCl ₃ concentration to the presence of free oxygen ions at room temperature according to the corresponding equilibrium equilibrium constant of iron chloride complex ions (see table below). This result again shows that the total amount of iron in the system should not exceed 6g∕L.

Figure 5 Relationship between leaching rate and time at different stirring speeds

Fig. 6 Relationship between leaching rate and time under different iron ion concentrations

Effect of FeCl ₃ Concentration on the Presence of Free Chloride Ion

Substituting the test results into a mathematical model of the unreacted nucleus (Fig. 7) indicates that the leaching process is controlled by the chemical reaction step.

Fig. 7 Relationship between 1-(1-α) ^{1 ∕3} and time of bismuth under different iron ion concentrations

Fourth, the concentration of chloride ions

铋 exists in the form of ruthenium chloride complex in the chloride salt solution. The increase of chloride ion concentration will increase the solubility of ruthenium in the solution, contribute to the formation of elemental sulfur, and reduce the oxidation rate of elemental sulfur, but it is too high. The oxygen ion concentration will result in a decrease in free ferric iron in the solution. Kim has conducted a special study on this (Figure 8). Fuerstenau calculated that the diffusion rate of iron chloride ion in the solution of 180g ∕L NaCl is only half of the NaCl-free solution. When the concentration of ferric iron increases to 5.6g ∕L, the diffusion rate no longer follows. The concentration of iron changes; as the temperature increases, the rate of diffusion increases.

The test results of the influence of chloride ion concentration are shown in Fig. 9.

(20 ° C, Fe ^{3 +} = 10 ^-3 mol∕L)

Fig. 8 Relationship between distribution of iron chloride and chloride complexes and hydrochloric acid concentration

Figure 9 Relationship between leaching rate and time under different chloride ion concentrations

Five, hydrochloric acid concentration

Thermodynamic analysis shows that the increase of acidity of the solution can increase the solubility of cerium in solution and contribute to the improvement of leaching rate. The effect of the effect of hydrochloric acid concentration is shown in Figure 10.

Figure 10 Relationship between leaching rate and time under different hydrochloric acid concentrations

The results show that acidity has a great influence on the leaching rate of stibnite; the initial leaching rate under low acid and high acid is almost doubled.

Through the above tests and analysis, the following conclusions can be drawn:

1. The strontium concentrate is treated by slurry electrolysis. Under the experimental current intensity and during the theoretical leaching electrolysis time of hydrazine, the leaching of hydrazine is controlled by the electrochemical reaction step, and the reaction is controlled by the diffusion step.

2. The leaching reaction rate of strontium ore concentrate is very fast. At 60 °C, 铋 can reach 98% leaching rate in the theoretical leaching electrolysis time.

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