Experimental report on the production of copper sulfate from copper slag

I. Introduction

Metals Inc. Bayannaoer Zijin design production capacity of 100,000 tons of zinc ingots, production process as follows: zinc oxide concentrate Fusing - hot acid leaching - A pollution yellow iron jarosite. Company treated feedstock is a high Marmatite, high cobalt, dross, antimony salts copper sulfate, lead sulfate cobalt removal process integrated net fluid used in the process. Therefore, the long-term purification process requires a large amount of copper sulfate to be consumed as an auxiliary material. Therefore, from the end of 2008, in order to respond to the slogan of “Study Jinshan, reduce costs”, and actively participate in the “small reforms” to promote efficiency and reduce costs, the Ministry of Technology set up a project team to produce copper sulfate using copper slag. Conducted a comprehensive and systematic study.

Second, test drugs and instruments

Copper slag: concentrated sulfuric acid (98%), 1 pumping pump, 1 agitator, 1 electric furnace, 1 each of 2000 mL and 4000 mL beakers; 1 1000 mL measuring barrel: one micro-bubble box;

Third, the experiment

(1) Experimental materials

The test raw materials are copper slag produced by our company's cadmium section. The main elements of copper slag are shown in Table 1.

Table 1 Content of major elements in copper slag (%)

(two) experimental principle

2Cu+1/2 O ₂ =Cu ₂ O (1)

Cu ₂ O+H ₂ SO ₄ =Cu ₂ SO ₄ +H ₂ O (2)

Cu ₂ SO ₄₊ H ₂ SO ₄ +1/2O ₂ =2CuSO ₄ +H ₂ O (3)

Total reaction formula:

Cu+O ₂ +H ₂ SO ₄ =CuSO ₄ +H ₂ O (4)

(3) Experimental methods

In this experiment, the "single factor analysis" method was used to analyze the amount of copper sulfate, sulfuric acid concentration, reaction temperature and reaction time. The specific operation of the test is as follows: prepare a certain concentration of sulfuric acid solution, add air, stir, and heat to a certain temperature, add the required copper slag at a time, stop heating and stirring after a certain period of time, filter the mixed liquid, and obtain the filter residue and filtrate. Perform elemental analysis.

Fourth, the results and discussion

(1) Determination of reaction temperature

Under the conditions that the other conditions are constant, the relationship between the conversion rate and the temperature change at the same time is obtained by changing the temperature. The experimental results are shown in Table 2.

Table 2 Relationship between reaction temperature and conversion rate

Reaction conditions: copper slag: industrial sulfuric acid = 1:1 (mass); concentration of dilute sulfuric acid: 10%; reaction time: 6 h.

It can be seen from Table 2 that when the reaction temperature is below 60 °C, the conversion rate is low and does not change much with the increase of temperature. Only when the temperature exceeds 60 °C, the conversion rate rises rapidly. When the temperature exceeds 80 ° C, the increase in conversion is not as significant as between 60 and 70 ° C. This is because at low temperatures, the overall reaction rate is controlled by the chemical reaction rate, the temperature is low, the reactivity is low, and the reaction rate is slow; and at higher temperatures, especially near the boiling temperature of water, the overall reaction rate Controlled by the solubility of air in water and physical diffusion rate, the temperature rises too high. Although the chemical reaction activity is large, the diffusion resistance of air in the acid solution is large, so the solubility of air decreases rapidly, resulting in no conversion rate. Significantly increased. In summary, the reaction temperature was determined to be between 80 °C.

(2) Determination of reaction time

The oxidation time was determined mainly based on the relationship between the measurement time and the conversion rate under the same initial reaction conditions (see Table 3).

Table 3 Relationship between reaction time and conversion rate

Reaction conditions: copper slag: industrial sulfuric acid = 1: 1 (mass); concentration of dilute sulfuric acid: 10%; reaction temperature: 80 ° C

It can be seen from Table 3 that when the reaction time reaches 7h, the conversion rate has reached more than 50%. Although the 7h conversion rate increased, it was not significant. In addition, the long-term bubbling reaction water evaporates more rapidly, and when the reaction reaches about 6 h, the volume of the reaction liquid is reduced to less than one-half of the volume of the initial solution. Although the conversion time is prolonged, the copper slag suspension is difficult due to the small volume and concentration of the solution, and copper crystallization may occur, which brings certain difficulties to the separation of unreacted copper slag and mother liquor. . During the reaction, the rate of evaporation of water is not only related to the reaction temperature and reaction time, but also to the shape of the reactor. The same ratio of raw materials and the volume of the reaction solution were respectively placed in 2000 mL and 4000 mL beakers, and after about 7 hours, the reaction liquid in the 2000 mL beaker did not need to be replenished in the whole reaction process, and 4000 mL was the least during the reaction. Need to add 100mL of water. Therefore, considering the comprehensive consideration, the reaction time should be 6h, and the reactor should be a container with a larger depth and a plane in the same volume.

(3) The effect of the amount of sulfuric acid and the concentration of dilute sulfuric acid on the reaction.

1, the effect of sulfuric acid on the reaction

The effect of the ratio of the raw material of copper slag to sulfuric acid on the reaction results is shown in Table 4.

Table 4 Effect of the amount of sulfuric acid on the conversion of copper slag

Reaction conditions: reaction temperature: 80 ° C, reaction time: 6 h, copper slag was 200 g, reaction vessel: 2000 mL and 4000 mL beaker, the acid concentration was 10%.

As can be seen from Table 4, at the same reaction temperature and the same acid concentration, the conversion time of the copper slag was approximately the same under the same reaction time. In Table 4, Cu:H ₂ SO ₄ = 1:1. The reaction time was 6 hours, and the amount of copper slag conversion was low because the reaction was low in the initial stage. Copper slag air oxidation to produce copper sulfate is carried out in a concentration of dilute sulfuric acid solution. This is a three-phase reaction of gas, liquid and solid. The air must be fully bubbled in dilute sulfuric acid to suspend the copper residue. The suspended copper slag can only be oxidized in the dilute sulfuric acid to form cuprous oxide and not to form copper oxide. The cuprous oxide reacts with dilute sulfuric acid to form cuprous sulfate, and the cuprous sulfate reacts with dilute sulfuric acid to form Copper sulfate, the reaction formula is as follows:

2Cu+1/2 O ₂ =Cu ₂ O (1)

Cu ₂ O+H ₂ SO ₄₌ Cu ₂ SO ₄ +H ₂ O (2)

Cu ₂ SO ₄₊ H ₂ SO ₄ +1/2O ₂ ==2CuSO ₄ +H ₂ O (3)

Total reaction formula:

Cu+O ₂ +H ₂ SO ₄ =CuSO ₄ +H ₂ O (4)

Therefore, when copper sulfate is formed or a small amount of copper sulfate is put in at the beginning of the reaction, copper sulfate adsorbs copper slag to form cuprous sulfate, namely:

Cu+CuSO ₄ ==Cu ₂ SO ₄ (5)

Then, the reaction is further carried out in accordance with the reaction (3). Therefore, when the reaction proceeds to a certain extent, the raw material Cu is simultaneously reacted according to two different mechanisms. It can be seen from the reaction mechanism that the copper slag is directly oxidized in the dilute sulfuric acid to form copper sulfate, and the copper slag only indirectly reacts with sulfuric acid in a molar ratio of 1:1. Excessive sulfuric acid has little effect on the conversion of copper slag. On the contrary, it will cause the acid concentration in the reaction mother liquor to be too high, so that the copper sulfate is dark blue crystal of trihydrate, which affects the quality of the product. Excessive copper slag reduces the acid concentration in the reaction mother liquor, causing the copper sulfate to be brilliant blue or light blue pentahydrate crystals, which improves the quality of the product, so the copper slag is generally used in excess.

2. Effect of concentration of dilute sulfuric acid on the reaction

The effect of the concentration of dilute sulfuric acid on the reaction effect is shown in Table 5.

Table 5 Relationship between dilute sulfuric acid concentration and copper slag conversion rate

Reaction conditions: reaction temperature 80 ° C, reaction time: 6 h, copper slag are 200 g, industrial sulfuric acid 24 mL, reaction vessel: 1000 mL and 4000 mL beaker.

It can be seen from Table 5 that during the experiment, as the concentration of the acid increases, the conversion rate of the copper slag not only does not increase, but has a tendency to decrease. According to the reaction mechanism analysis, when the concentration of the acid increases, the density of the solution increases, the viscosity increases, and in the case where the total amount of the acid does not increase, the volume of the reaction liquid tends to decrease as the concentration of the acid increases, so Finally, the difficulty of suspending the copper slag. Since the copper slag cannot be fully suspended and the chance of gas, liquid and solid contact is reduced, the conversion rate of the copper slag tends to decrease.

V. Conclusion

In summary, the best experimental parameters of the experiment are: reaction time: 6h; reaction temperature: 70 ~ 90 ° C; copper slag: copper slag: industrial sulfuric acid = 1:1 (mass); dilute sulfuric acid concentration: 10%;

Six, postscript

After the experimental plan was determined, the experiment was applied to production practice and production was normal under the great attention of the company's leaders. The copper sulphate solution produced can completely replace the purchased copper sulphate (crystal) to meet the company's internal needs.

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