CN100537798C - A kind of method of dearsenification from trioxygen-containingization two arsenic flue dust - Google Patents

Abstract

The invention relates to a method for removing arsenic from dust containing arsenic trioxide, which is suitable for the removal of arsenic from materials such as dust mainly in the form of As ₂ O ₃ . Sodium hydroxide, sodium carbonate or ammonia water is used to adjust the pH value of the leaching solution to 5-12, the liquid-solid weight ratio is 2-10:1, and hydrogen peroxide is added under stirring conditions for leaching, and the amount of hydrogen peroxide added is 100 of the chemical reaction measurement ~300%, the leaching temperature is 20~100℃, and the leaching time is 1~10 hours, so that the arsenic is dissolved into the solution, and the arsenic removal rate can reach more than 80%. The concentration of valuable elements in the solution is very low, and most of them remain in the slag. middle.

Description

A method for removing arsenic from dust containing arsenic trioxide

technical field

The invention relates to a method for removing arsenic from flue dust by non-roasting method.

Background technique

In the industrial production of zinc extraction, the dust produced by the fuming furnace contains zinc, lead, germanium, arsenic, etc., and the arsenic mainly exists in the form of As ₂ O _3. In order to recover zinc, lead and germanium, the dust is usually Returning to the sintering process for batching, resulting in the continuous enrichment of arsenic in the system, so how to remove arsenic damage is an urgent problem to be solved in production.

At present, there are some methods for removing arsenic from arsenic-containing materials. As disclosed in the Chinese patent CN96112949.2, "the process of removing arsenic from high-arsenic materials" introduces the method of using sodium hydroxide reagent to process high-arsenic materials. It is to mix the NaOH aqueous solution with the high-arsenic materials, and the solid weight ratio of the mixture is High-arsenic material: NaOH=1:0.3-1; said mixture is roasted at 300-650°C for 2-10 hours at medium temperature after drying; The time is 1-2 hours; then the arsenic in the obtained arsenic-containing solution is precipitated with a compound containing Ca ²⁺ or a compound containing NH ⁴⁺ +Mg ²⁺ until no precipitation occurs. Since the method includes a pyrotechnic process, the process is complicated, the processing time is long, and the cost is high.

In addition, Chinese patent CN02110552.9 "A method for removing arsenic from copper-zinc-cobalt material" is to impregnate the copper-zinc-cobalt material particles with sodium hydroxide solution, the concentration of sodium hydroxide solution is 80-160 g/liter, and the sodium hydroxide solution The mass ratio with solid material is 3-7:1, the leaching time is 0.5-2 hours, and the leaching temperature is 80-95°C. The removal rate of arsenic and sulfur in the method is extremely high, and the obtained leaching residue product contains very little harmful impurities. However, the arsenic contained in the solution obtained by this method is still highly toxic +3-valent arsenic, and the process is relatively complicated, and further oxidation treatment is required in the subsequent lime arsenic precipitation treatment.

Contents of the invention

The purpose of the present invention is to effectively remove +3 valent arsenic in materials by non-roasting method under the premise that the loss of valuable elements is as small as possible.

According to the solution of the present invention, sodium hydroxide, sodium carbonate or ammonia water is used to adjust the pH value of the leachate in the range of 5 to 12, the weight ratio of the leachate to the solid material is 2 to 10:1, and hydrogen peroxide is added for leaching under stirring conditions. The addition of hydrogen peroxide The amount is 100-300% of the stoichiometric amount, the leaching temperature: 20-100°C, and the leaching time: 1-10 hours.

A further approach is to use cyclic leaching to enrich the arsenic in the leaching solution to a value close to saturation.

The arsenic-containing leaching solution adopts a known method, adding lime to precipitate arsenic, controlling the arsenic precipitation temperature to 20-100°C, the reaction time is 3-10 hours, and the Ca/As molar ratio is 1-5:1.

The method of the present invention converts arsenic into pentavalent arsenic and dissolves it into the solution, and the arsenic removal rate can generally reach more than 80%; valuable elements remain in the slag, and when returning to the sintering ingredients, most of the arsenic has been removed and effectively eliminated The arsenic damage in production is eliminated; the concentration of valuable elements in the solution is very low, and after leaching, the solution can be used as a leaching solution after the arsenic sinks, and there is basically no waste water discharge, which greatly reduces the pollution to the environment. The present invention uses weak caustic alkali solution for oxidative leaching, and the process flow is simple, and the leached arsenic can be quickly made to exist in the solution in the form of sodium arsenate with high solubility without heating, which is beneficial to its further treatment, such as adding milk of lime Causticization converts sodium arsenate into calcium arsenate and precipitates into a more stable and less toxic form of pentavalent arsenate, which is removed after liquid-solid separation.

Detailed ways

Table 1, Table 2, and Table 3 are the raw material conditions of soot (sub-zinc oxide) in a zinc smelter.

Table 1 Contents of different forms of arsenic in materials

Table 2 Material chemical composition (average value)

Table 3 Material particle size composition

Note: The average particle size of the material is 1.72 μm (laser particle size analyzer).

In the embodiment of the method of the present invention, according to the average value of As ₂ O ₃ contained in 100 grams of zinc oxide materials, the trivalent arsenic therein is converted into pentavalent arsenic, and the theoretical consumption of hydrogen peroxide is 7.5 ml. In order to improve the leaching efficiency and make up for the loss caused by decomposition, the amount of hydrogen peroxide added is preferably 120-200% of the stoichiometric amount. If it is higher, the leaching efficiency will only increase and the consumption will be too large.

During leaching, although it can be carried out within a relatively large liquid-solid ratio range, when the concentration of the material is too low, the concentration of the material is too high, which is not conducive to the uniformity of the reaction system. /S is preferably 3-5:1.

Since the content of arsenic in the smoke is generally low, in order to reduce the treatment amount of the leaching solution, multiple cycles of leaching are used, and the number of cycles is generally 2 to 5 times, so as to increase the enrichment value of arsenic in the leaching solution until it is close to or reaches the saturation value. , plus a precipitant to precipitate arsenic, and the leached liquid after liquid-solid separation is returned as the leaching liquid.

For comparison, a comparative example without adding hydrogen peroxide was made under the same raw material conditions.

Comparative example: 100 grams of zinc oxide material, 0ml of hydrogen peroxide; leaching temperature: room temperature (30°C); leaching time: 3h; adjust the pH of the solution to 11 with NaOH; L/S is 5:1.

The arsenic removal rate is 13.4%, [Pb]<0.01g/L;[Zn]<0.01g/L;[Ge]<0.005g/L in the leached solution; but 91.7% of As is in the form of As ³⁺ exist.

The following are examples of the present invention:

Example 1: 100 grams of zinc oxide material, the amount of hydrogen peroxide added is 10ml; leaching temperature: 23°C; leaching time: 3h; pH value of the solution is adjusted to 11 with NaOH; L/S is 3:1.

The arsenic removal rate reaches 83.6%. [Pb]<0.08g/L;[Zn]<0.1g/L;[Ge]<0.005g/L; 98.8% of As exists in the form of As ⁵⁺ in the leaching solution.

Example 2: 100 grams of zinc oxide material, 20ml of hydrogen peroxide; leaching temperature: 29°C; leaching time: 3h; use Na ₂ CO ₃ to adjust the pH of the solution to 9; L/S is 5:1.

The arsenic removal rate reaches 83.3%. [Pb]<0.1g/L;[Zn]<0.2g/L;[Ge]<0.005g/L; 100% of As exists in the form of As ⁵⁺ in the leaching solution.

Example 3: 100 grams of zinc oxide material, 15ml of hydrogen peroxide; leaching temperature: 75°C; leaching time: 1h; adjust the pH of the solution to 5.0 with ammonia water; L/S is 4:1.

The arsenic removal rate reaches 84.1%. [Pb]<0.1g/L;[Zn]<0.2g/L;[Ge]<0.005g/L; 100% of As exists in the form of As ⁵⁺ in the leaching solution.

Example 4: 100 grams of zinc oxide material, the amount of hydrogen peroxide added is 15ml; leaching temperature: 75°C; leaching time: 10h; the pH of the solution is adjusted to 8.2 with NaOH; L/S is 4:1.

The arsenic removal rate reaches 84.4%. [Pb]<0.1g/L;[Zn]<0.3g/L;[Ge]<0.005g/L; 100% of As exists in the form of As ⁵⁺ in the leaching solution.

Add lime to the arsenic-containing leaching solutions in the above examples to precipitate arsenic, control the arsenic precipitation temperature to 60-90°C, the reaction time is 5-7 hours, the Ca/As molar ratio is 2-4:1, and the arsenic precipitation rate reaches 86.2- 89.3%.

Example 5: Three cycles of leaching are used, and the solid slag is separated from the leaching solution each time, and then the next batch of materials and hydrogen peroxide are added and the pH value is adjusted. 100 grams of zinc oxide material each time, the amount of hydrogen peroxide added for each leaching is 10ml; leaching temperature: room temperature (30°C); leaching time: 3h; use NaOH to adjust the pH value of the solution to 10-11.5; L/S is 5 : 1, the results are shown in Table 4.

Table 4 Effect of arsenic removal by leaching solution circulation

As shown in Table 2, the arsenic removal rate is stable above 80% every time, [Pb]<0.1g/L;[Zn]<0.1g/L; 100% of As in the leaching solution is in the form of As ⁵⁺ exist.

In Example 5, the leaching solution after 3 cycles contained arsenic 32.1g/L, added lime to precipitate arsenic, controlled the arsenic precipitation temperature at 90°C, and the reaction time was 5 hours, the Ca/As molar ratio was 3:1, and the arsenic precipitation rate reached 92.3 %.

Claims (2)

1. A method for removing arsenic from dust containing arsenic trioxide, comprising removing the 5-valent arsenic in the leached liquid with lime precipitation, characterized in that the pH value of the leached liquid is adjusted from 5 to 5 with sodium hydroxide, sodium carbonate or ammonia 12. The weight ratio of liquid to solid is 2-10:1. Add hydrogen peroxide for leaching under stirring conditions. The amount of hydrogen peroxide added is 100-300% of the stoichiometric reaction, the leaching temperature is 20-100°C, and the leaching time is 1-10 Hours; After each leaching liquid separates the solid slag, then add the next batch of materials and hydrogen peroxide and adjust the pH value for cyclic leaching. The number of cycles is 2 to 5 times. 2. The method for removing arsenic according to claim 1, characterized in that the liquid-solid weight ratio is 3-5:1, and the amount of hydrogen peroxide added is 120-200% of the stoichiometric amount.