CN106075800A - A kind of ferric arsenate/goethitum material utilizing arsenic containing solution preparation to have nucleocapsid structure realizes the method for solid arsenic - Google Patents

Abstract

The invention discloses a method for preparing ferric arsenate/goethite materials with a core-shell structure by using an arsenic-containing solution to realize arsenic fixation; after adjusting the pH of the arsenic-containing solution to acidity, adding Iron salt and oxygen-containing gas are introduced, and the reaction is stirred under heating conditions to obtain iron arsenate precipitation; the iron arsenate precipitation is immersed in an alkaline solution for reaction, and iron arsenate/goethite with a core-shell structure is obtained Material, the method can make the arsenic in the arsenic-containing solution through a simple and low-cost process into an iron arsenate/goethite material with particularly good stability and a core-shell structure, so as to realize the permanent fixation of the arsenic.

Description

A kind of ferric arsenate/goethite material with core-shell structure prepared by using arsenic-containing solution A method to achieve arsenic fixation

technical field

The present invention specifically relates to a method for preparing an arsenic-containing core-shell structure material; in particular, it relates to a method for using arsenic-containing waste liquid or arsenic-containing leaching liquid to prepare iron arsenate/goethite materials with a core-shell structure to achieve arsenic fixation, which belongs to the environmental governance area,

Background technique

Arsenic is a toxic element that exists stably in rock formations and soils mainly in the form of low-toxic calcium, iron, manganese, aluminum and other insoluble arsenates, and sulfides such as realgar, orpiment and arsenopyrite in the earth's crust. In the process of human development and utilization of mineral resources, the natural stable form of arsenic is destroyed and highly toxic water-soluble arsenic is released, especially the high-concentration arsenic-containing wastewater produced in the non-ferrous metal smelting process has become the main source of highly toxic arsenic. one of the ways. In recent years, a number of regional arsenic poisoning incidents have occurred in my country's Hunan, Guangxi, Guizhou, Yunnan and other areas where the non-ferrous smelting industry is concentrated, and arsenic pollution has become a sensitive issue of widespread concern to the society. For this kind of high-arsenic metallurgical wastewater, the treatment methods reported in the literature include chemical precipitation, ion exchange, adsorption, extraction, and biochemical methods [etc., but only chemical precipitation can be applied on an industrial scale. The basic principle of the chemical precipitation method is to convert highly toxic arsenic in solution into low-toxic insoluble arsenate, and return it to nature through safe landfill. The chemical precipitation method requires insoluble arsenate precipitation to have high arsenic removal efficiency, good arsenic fixation safety, and the lower the cost, the better. According to my country's national standards, in terms of arsenic removal efficiency, the residual arsenic concentration in the aqueous solution after arsenic removal is required to be reduced to 50 μg/L, and the safety of arsenic fixation is evaluated by toxic leaching test (TCLP), which requires the arsenic concentration in the leaching solution to be less than 5 mg/L.

At present, only calcium arsenate and iron arsenate two types of insoluble arsenate can better meet the above requirements. Calcium arsenate and ferric arsenate are basically similar in arsenic removal process. Add lime or ferric sulfate and other iron salt precipitants according to a certain Ca/As ratio or Fe/As ratio, and add neutralizer to adjust the pH value to obtain insoluble Precipitation of calcium arsenate and iron arsenate. For arsenic-containing wastewater with high acid concentration, using lime as a neutralizer and using the generated calcium arsenate to fix arsenic is a commonly used method in enterprises at present, but the content of CaSO ₄ in the aqueous solution after arsenic removal is high, and subsequent treatment is very troublesome . Generally, the comprehensive operating cost of calcium arsenate for arsenic removal is lower than that of iron arsenate, but iron arsenate has obvious advantages in the high efficiency of arsenic removal and the safety of arsenic fixation. The solubility of iron arsenate in water (AB type insoluble electrolyte, solubility product is about 10 ^-21 ~ 10 ^-24 , solubility is about 10 ^-11 mol.L ^-1 ) is higher than calcium arsenate (A ₂ B ₃ type insoluble Electrolyte, solubility product 10 ^-18 ~ 10 ^-21 , solubility about 10 ^-5 mol.L ^-1 ) is about 1 million times smaller, and calcium arsenate salt forms calcium carbonate and water-soluble arsenic after contacting with carbon dioxide in the air Acid, resulting in the "anti-dissolution phenomenon" of arsenic, which has potential safety hazards. Due to the cost barriers in the promotion and application of iron arsenate, most domestic metallurgical enterprises prefer to choose calcium arsenate which has potential safety hazards for arsenic removal. In order to greatly reduce the arsenic removal cost of iron arsenate to the same level as that of calcium arsenate, it is necessary to reduce the consumption of iron salt precipitant by more than half, that is, it is necessary to reduce the Fe/As ratio from about 4 in the process to within 2.

Contents of the invention

In view of the defects of high arsenic fixation cost and poor arsenic fixation effect in the existing arsenic fixation technology, the purpose of the present invention is to provide a low-cost and high-efficiency arsenic fixation method, which can pass arsenic in arsenic-containing solution through simple, The low-cost process produces iron arsenate/goethite materials with particularly good stability and a core-shell structure to achieve permanent fixation of arsenic.

In order to achieve the above technical purpose, the present invention provides a method for preparing iron arsenate/goethite materials with a core-shell structure by using an arsenic-containing solution to fix arsenic. After adjusting the pH of the arsenic-containing solution to acidity, the Add ferrous salt and oxygen-containing gas into the solution containing arsenic, stir and react under heating condition to obtain ferric arsenate precipitate; the ferric arsenate precipitate is immersed in alkaline solution to react to obtain the product.

The key to the technical solution of the present invention is to convert arsenic into iron arsenate with better stability, and then further form a dense goethite layer on the surface of iron arsenate to protect iron arsenate, forming a special core-shell The structural material can effectively realize the permanent fixation of arsenic in the arsenic-containing waste liquid or arsenic-containing leaching solution, and prevent secondary pollution caused by the dissolution of fixed arsenic.

In a preferred solution, the arsenic-containing solution is arsenic-containing wastewater produced in the metallurgical industry, or arsenic-containing leaching solution of arsenic-containing fumes and/or slag. It is generally applicable to various arsenic-containing smelting waste liquids, or high-arsenic dust generated in the smelting process of lead, zinc, antimony, copper, tin, etc., and high-arsenic anode slime generated in the electrolysis process of crude lead, silver, copper, etc. Arsenic-containing leachate of waste materials.

In a preferred solution, the arsenic content in the arsenic-containing aqueous solution is 5-50 g/L.

More preferably, the pH of the arsenic-containing solution is adjusted to 1-3. Adjust pH with sulfuric acid solution and/or sodium hydroxide solution.

In a preferred solution, the amount of ferrous salt added to the arsenic-containing solution is 1.2 to 5 times the molar amount of arsenic in the arsenic-containing solution.

More preferably, the ferrous salt is at least one of ferrous sulfate, ferrous chloride and ferrous nitrate.

In a preferred solution, the flow rate of the oxygen-containing gas is 0.1-5 liters/minute; the oxygen-containing gas is oxygen and/or air.

A more preferred solution is to add ferrous salt and oxygen-containing gas into the arsenic-containing solution, then heat to 70-95° C., and stir for 6-12 hours to react.

In a preferred solution, the pH of the alkaline solution is 10-14.

More preferably, the time for the iron arsenate precipitate to immerse into the alkaline solution to react is 1 to 24 hours.

Compared with the prior art, the beneficial technical effect brought by the technical solution of the present invention:

The technical solution of the present invention uses arsenic-containing waste liquid as a raw material for the first time to prepare an iron arsenate/goethite material with a core-shell structure to achieve permanent fixation of arsenic. The technical scheme uses ferrous salt as raw material, converts arsenic into insoluble iron arsenate precipitate through acid oxidation, and the iron arsenate precipitate further reacts in alkaline solution to form a layer of dense needles on the surface of iron arsenate. The iron ore layer provides secondary protection to iron arsenate, which greatly improves the stability of iron arsenate/goethite materials. Through the toxic leaching test (TCLP), the test was carried out in accordance with the provisions of the "Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillating Method HJ 557-2010", and the results showed that the concentration of arsenic in the leach solution was lower than the "Hazardous Waste Identification Standard Leaching Toxicity Identification GB 5085.3-2007" The 5 mg/L specified in the standard meets the standards for safe arsenic-fixing compounds.

The technical scheme of the present invention realizes the fixation of arsenic through a two-step method, the reaction conditions are mild, and the steps are simple; and the raw materials for arsenic fixation adopted are ferrous salt, air or oxygen, etc., which are cheap and are conducive to popularization and application; the prepared arsenic has a core-shell The structure of the iron arsenate/goethite material is safe and reliable through the toxicity leaching test, and can be used as an ideal arsenic fixation material to solve the current arsenic pollution problem in metallurgical enterprises.

Description of drawings

[Fig. 1] is a specific flow chart of the present invention;

[Fig. 2] is the X-ray powder diffraction pattern of the core-shell structure arsenic-fixing material in Example 1 of the present invention;

[ Fig. 3 ] is a scanning electron microscope image of the core-shell structure arsenic-fixing material in Example 1 of the present invention.

detailed description

The following examples are intended to illustrate the content of the present invention, rather than to further limit the protection scope of the present invention.

The raw material arsenic-containing aqueous solution used in the present invention is obtained from a high-arsenic soot leachate produced by a copper smelter in Hunan, and the leachate is prepared according to the patent "a method for gradient arsenic removal of high-arsenic metallurgical waste" (patent number 201110379510). The arsenic content in the solution was determined by ICP, and the concentration of arsenic in the solution was adjusted by evaporation or dilution with water.

Toxic leaching experiment (TCLP), according to the provisions of "Solid Waste Leaching Toxic Leaching Method Horizontal Oscillating Method HJ 557-2010", the prepared iron arsenate/goethite core-shell structure material was added to distilled water, and the solid-liquid ratio was 1:10, shake horizontally for 8 hours, and after standing still for 16 hours, filter and collect the leaching solution, and use the plasma direct reading spectrometer (ICP) to test the concentration of arsenic in the leaching solution.

Example 1

Prepare 1 liter of 30 g/L arsenic-containing solution according to the above method, and adjust the pH of the solution to 1 with concentrated sulfuric acid. Weigh 166.83 grams of ferrous sulfate heptahydrate according to the molar ratio of iron to arsenic of 1.5, add it into the solution and keep the solution stirring. Oxygen was bubbled into the solution at a flow rate of 0.5 L/min. The solution was heated to 90 degrees Celsius, kept stirring and reacting with oxygen for 7 hours. After the solution was cooled, it was filtered, the precipitate was washed with deionized water, and dried to obtain a light green powder solid. And the arsenic content in the solution after the reaction was tested by direct reading plasma spectrometer (ICP), and the arsenic deposition rate was calculated to be 99.6%. Soak the obtained solid powder in a sodium hydroxide solution with a pH of 11 for 12 hours, filter, wash, and dry to obtain a khaki powder, which is the target product. Finally, the product was tested by X-ray powder diffraction and field emission scanning electron microscope. Figure 2 is the X-ray powder diffraction pattern of the core-shell structure arsenic-fixed material. It can be seen from the figure that the prepared material is indeed iron arsenate dihydrate and needle iron ore composite; Figure 3 is a scanning electron microscope image of arsenic-fixed material with a core-shell structure. From the figure, the core and shell of the material can be clearly seen, indicating that our material is indeed a core-shell structure material.

Example 2

Prepare 1 liter of 10 g/L arsenic-containing solution according to the above method, and adjust the pH of the solution to 1 with concentrated sulfuric acid. Weigh 74.15 grams of ferrous sulfate heptahydrate according to the molar ratio of iron to arsenic of 2, add it into the solution and keep the solution stirring. Oxygen was bubbled through the solution at a flow rate of 2 liters/minute. The solution was heated to 80 degrees Celsius, kept stirring and reacted with oxygen for 9 hours. After the solution was cooled, it was filtered, the precipitate was washed with deionized water, and dried to obtain a light green powder solid. And the arsenic content in the solution after the reaction was tested by direct reading plasma spectrometer (ICP), and the arsenic deposition rate was calculated to be 99.4%. Soak the obtained solid powder in a sodium hydroxide solution with a pH of 13 for 6 hours, filter, wash, and dry to obtain a light red powder, which is the target product.

Example 3

Prepare 1 liter of 50 g/L arsenic-containing solution according to the above method, and adjust the pH of the solution to 2 with concentrated sulfuric acid. Weigh 397.62 grams of ferrous chloride tetrahydrate according to the molar ratio of iron to arsenic of 3, add it into the solution and keep the solution stirring. Air was bubbled through the solution at a flow rate of 5 liters/minute. The solution was heated to 70 degrees Celsius, kept stirring and reacting with oxygen for 12 hours. After the solution was cooled, it was filtered, the precipitate was washed with deionized water, and dried to obtain a light green powder solid. And the arsenic content in the solution after the reaction was tested by direct reading plasma spectrometer (ICP), and the arsenic deposition rate was calculated to be 99.5%. Soak the obtained solid powder in a sodium hydroxide solution with a pH of 14 for 2 hours, filter, wash, and dry to obtain a red powder, which is the target product.

The above products have been subjected to toxicity leaching tests in accordance with the provisions of "Solid Waste Leaching Toxic Leaching Method Horizontal Oscillating Method HJ 557-2010", and the results show that the concentration of arsenic in the leach solution is lower than 5 mg/L, which is a safe solid waste and a safe way to fix arsenic. Material.

Claims (10)

1. A method for utilizing an arsenic-containing solution to prepare iron arsenate/goethite materials with a core-shell structure to realize arsenic fixation, characterized in that: after the pH of the arsenic-containing solution is adjusted to acidity, in the arsenic-containing solution Adding ferrous salt and introducing oxygen-containing gas, stirring and reacting under heating conditions, obtains ferric arsenate precipitate; the ferric arsenate precipitate is immersed in alkaline solution to react, and the product is obtained. 2. The method for preparing ferric arsenate/goethite materials with a core-shell structure by using an arsenic-containing solution according to claim 1, wherein the arsenic-containing solution is the arsenic-containing solution produced by the metallurgical industry Wastewater, or arsenic-containing leachate from arsenic-containing fumes and/or slag. 3. The method according to claim 1 or 2 for preparing iron arsenate/goethite materials with a core-shell structure to fix arsenic by using an arsenic-containing solution, wherein the arsenic content in the arsenic-containing aqueous solution is 5 ~50 g/L. 4 . The method for preparing iron arsenate/goethite materials with a core-shell structure by using an arsenic-containing solution according to claim 1 to achieve arsenic fixation, characterized in that: the pH of the arsenic-containing solution is adjusted to 1-3. 5. The method for preparing ferric arsenate/goethite materials with a core-shell structure by using an arsenic-containing solution according to claim 1 to achieve arsenic fixation, characterized in that: the addition of the ferrous salt in the arsenic-containing solution The amount is 1.2 to 5 times the molar amount of arsenic in the arsenic-containing solution. 6. The method for preparing iron arsenate/goethite materials with a core-shell structure by utilizing an arsenic-containing solution according to claim 1 or 5 to realize the method for arsenic fixation, characterized in that: the ferrous salt is ferrous sulfate, At least one of ferrous chloride and ferrous nitrate. 7. The method for arsenic fixation by using an arsenic-containing solution to prepare iron arsenate/goethite materials with a core-shell structure according to claim 1, characterized in that: the flow rate of the oxygen-containing gas is 0.1-5 liters / per minute; the oxygen-containing gas is oxygen and/or air. 8. According to claim 1, 2, 4, 5 or 7, the method for preparing iron arsenate/goethite materials with a core-shell structure to fix arsenic by using arsenic-containing solution to fix arsenic is characterized in that: Add ferrous salt and oxygen-containing gas into the arsenic-containing solution, heat to 70-95°C, and stir for 6-12 hours. 9 . The method for preparing iron arsenate/goethite materials with a core-shell structure by using an arsenic-containing solution according to claim 1 to achieve arsenic fixation, characterized in that the pH of the alkaline solution is 10-14. 10. The method for preparing iron arsenate/goethite materials with a core-shell structure by using an arsenic-containing solution according to claim 1 to achieve arsenic fixation, characterized in that: the iron arsenate precipitate is immersed in an alkaline solution for reaction The time is from 1 to 24 hours.