CN106830091B - A kind of precipitation from arsenic containing solution obtains the high method for leaching stability scorodite - Google Patents

Abstract

The present invention relates to a kind of precipitations from arsenic containing solution to obtain the high method for leaching stability scorodite, this method adds in ferrous salt solution as heavy arsenical in a manner of continuous charging, add in certain density neutralizer simultaneously, it is ferric ion that oxygen, which is continually fed into, by ferrous ions, then the high scorodite for leaching stability of generation is reacted with the arsenic in solution.Gained scorodite can stablize stockpiling under the conditions of pH value range is 2~11 and strong reducing property.

Description

A method for obtaining scorodite with high leaching stability by precipitation from arsenic-containing solution

technical field

The invention belongs to the technical field of mineral arsenic fixation, and relates to an arsenic fixation method for treating arsenic-containing waste liquid produced in the metallurgical process of nonferrous metals.

Background technique

Arsenic is a highly toxic element with high carcinogenicity, and is widely associated in various non-ferrous metal smelting process systems. In the past 30 years, with the rapid development of my country's nonferrous metal industry, the problem of arsenic pollution has become more and more serious, seriously threatening people's lives and health. Therefore, the research on arsenic pollution control is an urgent and significant topic.

At present, arsenic fixation technologies mainly include encapsulation and mineral arsenic fixation. Encapsulation is to use cement, glass and other materials to coat arsenic-containing materials so that they can be stored stably. This method has a large amount of solid waste and high cost, making it difficult to be widely used. Mineral arsenic fixation is to convert arsenic into highly stable arsenic-containing mineral deposits. The selection of arsenic-fixing minerals should be comprehensively weighed from many aspects such as leaching stability, arsenic content in minerals, toxicity of leaching products, preparation difficulty, and cost. Although there are more than 300 primary and secondary arsenic minerals in total, it is rare to find a "satisfactory choice" for arsenic fixation. In the Ca(II)-As(V)-H ₂ O system, a series of calcium arsenate minerals can be synthesized under different conditions, and their stability is high; however, calcium arsenate has a high solubility under acidic conditions, and The Ca(II) ions can react with dissolved CO ₂ to form calcium carbonate and re-release arsenic. Therefore, calcium arsenate minerals are not suitable for arsenic-fixing minerals. In the Fe(III)-As(V)-H ₂ O system, changing the reaction conditions can prepare a series of iron arsenate precipitates with different compositions, crystal forms and crystallinity. Among them, scorodite (FeAsO ₄ 2H ₂ O) is currently recognized as the best arsenic fixation due to its high stability, theoretical arsenic content as high as 32%, easy liquid-solid separation in a crystalline state, and low water content in slag. mineral.

At present, the preparation methods of scorodite are mainly divided into three categories: hydrothermal method, atmospheric method and improved atmospheric method. Among them, the hydrothermal method is difficult for industrial application because of the high temperature and high pressure required, and the energy consumption is large; the normal pressure method prepares scorodite under normal pressure, but its cycle is long; Under the control of supersaturation by slowly oxidizing ferrous ions, scorodite with high crystallinity was prepared within 7 hours, which is currently recognized as the best preparation method. Scoorite has strong stability. In previous studies, the leaching concentration of arsenic was as low as 0.5 mg/L, but this was only limited to weakly acidic (pH 2-6) and oxidative conditions, while it was not stable under strong acidic or alkaline conditions. The leaching stability is poor in the neutral region or under reducing conditions. Therefore, further studies on the preparation of scorodites that are stable in alkaline and strongly reducing environments are necessary.

Among the currently published patents, the invention patent (CN 102153145 A, CN101952204 A) of Dowa Mining Co., Ltd. of Japan proposed for the first time to use ferrous iron as the iron source to process the arsenic-containing solution and prepare scorodite and iron arsenate powder. The arsenic precipitation is thorough, simple and convenient, but the prepared scorodite and ferric arsenate can only be stored stably in a narrow pH (2-6) range, and the toxicity of arsenic leaching under alkaline or strong reducing conditions far exceeds that of GB5085 .3-2007 national standard limit value (<5mg/L). The present invention improves the feeding method on the basis of the above, and adopts a continuous neutralization method to prepare scorodite that can be stored stably in a pH range of 2-11 and under strong reducing conditions.

Contents of the invention

The purpose of the present invention is to provide a method for obtaining scorodite with high leaching stability by precipitating from arsenic-containing solution, which can prepare scorodite which is stable under alkaline and strong reducing conditions. The process of the invention is simple, the operation is convenient, the prepared scorodite has high arsenic content, very low toxicity leaching concentration, wide stable area, and can be stably stockpiled under strong reducing conditions.

For realizing the purpose of the present invention, provide following technical scheme:

A method for obtaining scorodite with high leaching stability by precipitation from arsenic-containing solution, comprising the following steps:

(1) Oxidize As ³⁺ in the arsenic-containing solution to As ⁵⁺ ; then adjust its pH value to 1.5-3, preheat to 75-90°C and stir;

(2) Add ferrous salt solution and neutralizer in the reaction system obtained in step (1) at the same time in the form of drops, control the Fe/As molar ratio in the reaction system to be 2～5:1, and adjust the pH value to 1.5～3; Oxygen is continuously introduced during the reaction process for oxidation reaction;

(3) After the reaction, the solution is filtered, washed and dried to obtain crystalline scorodite.

The above method of obtaining scorodite with high leaching stability by precipitation from arsenic-containing solution of the present invention, wherein:

The arsenic-containing solution described in step (1) includes copper, lead, zinc and other heavy metal smelting, gold smelting, realgar and orpiment ore smelting arsenic-containing waste liquid and leachate of high-arsenic materials; preferably, the arsenic-containing solution The arsenic content in the medium is 30-70g/L.

The oxidation of As ³⁺ in the arsenic-containing solution to As ⁵⁺ in the step (1) can be performed by a conventional method in the prior art; for example, a hydrogen peroxide oxidation method is used.

The ferrous salt described in the step (2) includes: one or more mixtures of ferrous sulfate, ferrous chloride and ferrous nitrate. Step (2) can directly add ferrous salt, preferably add the solution of ferrous salt.

The neutralizing agent described in step (2) comprises: the mixture of one or more in sodium carbonate, sodium bicarbonate, sodium sulfite, or the mixture containing one or more mixtures in sodium carbonate, sodium bicarbonate, sodium sulfite solution. In step (2), the neutralizing agent can be added directly, preferably a solution of the neutralizing agent.

Preferably, the adding rate of the ferrous salt described in step (2) is 5-30 g/min.

The purpose of adding the neutralizing agent is to neutralize the proton released by the reaction, so the addition amount of the neutralizing agent is to neutralize the proton released by the reaction.

Preferably, the addition rate of the neutralizing agent described in step (2) is 0.1-1.0 g/min.

Preferably, the oxygen flow rate in step (2) is 1-20 L/min; preferably, the reaction time is 5-24 hours.

In the method of the present invention, ferrous salt solution is added as an arsenic precipitating agent in a continuous feeding mode, and at the same time, a certain concentration of sodium carbonate or other alkaline compound solution is added as a neutralizing agent, and oxygen is continuously fed to oxidize ferrous ions into ferric ions , and then react with arsenic in the solution to form scorodite with high leaching stability.

Advantage of the present invention:

(1) The process of the present invention is simple and easy to operate. The reagents used, ferrous salt and oxygen, are commonly used experimental materials in laboratories. The reaction conditions are mild and the requirements for equipment are low.

(2) The scorodite prepared by the present invention has high crystallinity and is easy to separate solid and liquid.

(3) The scorodite prepared by the present invention is not only stable under acidic (pH value 2～6) conditions, but also can be stored stably under strong alkaline (pH value 8～11) and strong reducing conditions. The leaching concentration is lower than 0.5mg/L, which is lower than the provisions of GB5085.3-2007 (Standard for identification of solid waste - identification of leaching toxicity), and can be safely stockpiled. It solves the problem that scorodite is difficult to store stably under alkaline and reducing conditions.

Description of drawings

Fig. 1 schematic diagram of the technical process of the inventive method;

Fig. 2 obtains the XRD figure of scorodite for embodiment 1;

Fig. 3 is the SEM picture that embodiment 1 obtains scorodite.

Detailed ways

The present invention provides a method for obtaining scorodite with high leaching stability by precipitation from arsenic-containing solution. In order to further explain the technical scheme and effect of the present invention, the following examples are given. It should be understood that the described embodiments are for illustration only and are not intended to limit the present invention. If no specific technique or condition is indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field, or according to the product specification. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that can be purchased through formal channels.

Example 1

Preparation of scorodite

Take 100g of arsenic trioxide, add 200g of hydrogen peroxide solution with a mass fraction of 30%, add distilled water to 500ml, heat and boil until the solid particles are completely dissolved, then continue to boil for 2h, titrate the concentration of trivalent arsenic ions in it by titration, if There is also trivalent arsenic, then continue heating until all trivalent arsenic is oxidized to pentavalent. Add water to make up the volume until the concentration of arsenic is 30g/L, and measure it by ICP-AES, the obtained solution is 30g/L arsenic acid solution.

Take 250ml of the 30g/L arsenic acid solution prepared by the above method, adjust the pH value to 1.5 with NaOH, preheat to 90°C, and stir; add ferrous salt solution and neutralizing agent sodium carbonate solution to it at the same time to control the reaction system The Fe/As molar ratio was 2:1, and the pH was adjusted to _1.5 with concentrated _H2SO4 . Wherein the adding rate of ferrous sulfate solution is to control adding 5.6g ferric ion (Fe ²⁺ ) in reaction system every minute; The adding rate of sodium carbonate solution is adding 0.1-1.0g in reaction system every minute for controlling

Sodium carbonate. The amount of sodium carbonate solution added is based on the proton released by the neutralization reaction. During the reaction process, 1 L/min of oxygen was continuously introduced for oxidation. After 7 hours of reaction, the precipitate was filtered, washed, and dried to obtain scorodite particles.

toxic leaching

(1) Carry out toxic leaching in accordance with GB5085.3-2007 (identification standard for solid waste—identification of leaching toxicity), the leaching concentration of arsenic is 0.10 mg/L, which is less than the limit value of the standard, and can be safely and stably stored;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of NaOH solution with a pH value of 10.05, and leach for 40 days at 25°C, and measure the leaching concentration of arsenic in it as 0.15mg/L.

Example 2

Preparation of scorodite

Scoorite was prepared according to the method of Example 1, wherein the concentration of arsenic acid was 40 g/L, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) Carry out toxic leaching in accordance with GB5085.3-2007 (identification standard for solid waste—identification of leaching toxicity), the leaching concentration of arsenic is 0.15mg/L, which is less than the limit of the standard, and can be safely and stably stored;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of NaOH+CaO mixed solution with a pH value of 9.67, leaching for 40 days at 25°C, and measure the content of arsenic in it. The leaching concentration is 0.26mg/L.

Example 3

Preparation of scorodite

Scoorite was prepared according to the method of Example 1, wherein the concentration of arsenic acid was 70 g/L, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) Toxic leaching is carried out according to GB5085.3-2007 (Standard for identification of solid waste - identification of leaching toxicity), the leaching concentration of arsenic is 0.20mg/L, which is less than the limit value of this standard, and it can be stored safely and stably;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of NaOH+CaO mixed solution with a pH value of 9.67, leaching for 40 days at 25°C, and measure the content of arsenic in it. The leaching concentration is 0.30mg/L.

Example 4

Scorodite was prepared according to the method of Example 1, wherein the molar ratio of Fe/As in the reaction system was controlled to be 3:1, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) Carry out toxic leaching in accordance with GB5085.3-2007 (identification standard for solid waste—identification of leaching toxicity), the leaching concentration of arsenic is 0.06mg/L, which is less than the limit value of this standard, and can be safely and stably stored;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of a mixed solution of NaH ₂ PO ₄ +NaOH with a pH value of 10.57 and an ORP of -213mV. Under leaching for 40 days, the leaching concentration of arsenic was determined to be less than 0.01mg/L.

Example 5

Scorodite was prepared according to the method of Example 1, wherein the molar ratio of Fe/As in the reaction system was controlled to be 5:1, and other conditions were kept unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) According to GB5085.3-2007 (identification standard for solid waste - identification of leaching toxicity), toxic leaching is carried out. The leaching concentration of arsenic is 0.11mg/L, which is less than the limit value of this standard, and can be safely and stably stored;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of tap water with a pH value of 5.40, and leach for 40 days at 25°C, and determine that the leaching concentration of arsenic is less than 0.01 mg/L.

Example 6

Scoorite was prepared according to the method of Example 1, wherein the neutralizing agent used was sodium bicarbonate solution, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) According to GB5085.3-2007 (identification standard for solid waste - identification of leaching toxicity), toxic leaching is carried out. The leaching concentration of arsenic is 0.08mg/L, which is less than the limit value of this standard, and can be safely and stably stored;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of a mixed solution of NaH ₂ PO ₄ +NaOH with a pH value of 9.69 and an ORP of -160mV. Under leaching for 40 days, the leaching concentration of arsenic was determined to be less than 0.01mg/L.

Example 7

Scorodite was prepared according to the method of Example 1, wherein the neutralizing agent was a mixed solution of sodium carbonate and sodium bicarbonate, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) Toxic leaching is carried out according to GB5085.3-2007 (Standard for identification of solid waste - identification of leaching toxicity), the leaching concentration of arsenic is 0.04mg/L, which is less than the limit value of this standard, and can be safely and stably stockpiled;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of a mixed solution of NaH ₂ PO ₄ +NaOH with a pH value of 9.69 and an ORP of -160mV. Under leaching for 40 days, the leaching concentration of arsenic was determined to be less than 0.01mg/L.

Example 8

Scorodite was prepared according to the method of Example 1, wherein the ferrous salt was added at a rate of 21 g/min, and other conditions remained unchanged, and scorodite powder with a good crystallization state was obtained.

toxic leaching

(1) According to GB5085.3-2007 (identification standard for solid waste - identification of leaching toxicity), toxic leaching is carried out. The leaching concentration of arsenic is 0.13mg/L, which is less than the limit value of this standard, and can be safely and stably stored;

(2) According to the mass ratio of liquid to solid of 20:1, mix 1g of scorodite powder prepared above with 20ml of Mg(OH) ₂ solution with a pH value of 9.47, leaching at 25°C for 40 days, and measure the arsenic in it. The leaching concentration is 0.12mg/L.

Example 9

Scorodite was prepared according to the method of Example 1, wherein the molar ratio of Fe/As in the reaction system was controlled to be 3:1, the oxygen flow rate was 15 L/min, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) Toxic leaching is carried out according to GB5085.3-2007 (Standard for identification of solid waste—identification of leaching toxicity), and the leaching concentration of arsenic is 0.05mg/L, which is less than the limit value of this standard, and can be safely and stably stored;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of a mixed solution of NaH ₂ PO ₄ +NaOH with a pH value of 7.95 and an ORP of -55mV. Under leaching for 40 days, the leaching concentration of arsenic was determined to be less than 0.01mg/L.

Example 10

Scorodite was prepared according to the method of Example 1, wherein the molar ratio of Fe/As in the reaction system was controlled to be 3:1, the reaction time was 6 h, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) Toxic leaching is carried out according to GB5085.3-2007 (Standard for identification of solid waste—identification of leaching toxicity). The leaching concentration of arsenic is 0.09mg/L, which is less than the limit value of this standard, and can be safely and stably stored;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of tap water with a pH value of 5.40, and leach for 40 days at 25°C, and determine that the leaching concentration of arsenic is less than 0.01 mg/L.

Example 11

Scorodite was prepared according to the method in Example 1, wherein the concentration of arsenic acid was 40 g/L, the molar ratio of Fe/As in the reaction system was controlled to be 3:1, and other conditions remained unchanged, and scorodite powder with good crystallization state was obtained.

toxic leaching

(1) Toxic leaching is carried out according to GB5085.3-2007 (Standard for identification of solid waste - identification of leaching toxicity), the leaching concentration of arsenic is 0.04mg/L, which is less than the limit value of this standard, and can be safely and stably stockpiled;

(2) According to the liquid-solid mass ratio of 20:1, mix 1g of scorodite powder prepared above with 20ml of a mixed solution of NaH ₂ PO ₄ +NaOH with a pH value of 10.16 and an ORP of -188mV at 25°C After leaching for 40 days, it was determined that the leaching concentration of arsenic was less than 0.01mg/L.

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (5)

1. a kind of precipitation from arsenic containing solution obtains the high method for leaching stability scorodite, which is characterized in that including following step Suddenly：

(1) by the As in arsenic containing solution³⁺It is oxidized to As⁵⁺；Its pH value is adjusted again to 1.5~3, is preheated to 75~90 DEG C and is stirred；

(2) ferrous salt solution and neutralizer, control reaction are added in a manner of tear drop simultaneously into reaction system obtained by step (1) Fe/As molar ratios are 2~5 in system:1, and pH value is adjusted with acid to 1.5~3；Oxygen is continually fed into reaction process and carries out oxygen Change reaction；

The addition rate of the ferrous salt is 5-30g/min；

The neutralizer includes：The mixture of one or more of sodium carbonate, sodium bicarbonate, sodium sulfite or containing carbonic acid The solution of one or more of sodium, sodium bicarbonate, sodium sulfite mixture；

The addition rate of the neutralizer is 0.1-1.0g/min；

The oxygen flow is 1~20L/min；

(3) after reaction, solution is filtered, washed, dried, obtain crystalline state scorodite.

2. according to the method described in claim 1, it is characterized in that, arsenic content is 30~70g/L in the arsenic containing solution.

3. method according to claim 1 or 2, which is characterized in that step (1) will be in arsenic containing solution using hydrogen peroxide As³⁺It is oxidized to As⁵⁺。

4. method according to claim 1 or 2, which is characterized in that the ferrous salt described in step (2) includes：Sulfuric acid is sub- The mixture of one or more of iron, frerrous chloride, ferrous nitrate.

5. method according to claim 1 or 2, which is characterized in that the reaction time for 5~for 24 hours.