CN108191031A - A kind of no sulphur figure water hydroxyl sarmientite and its application in trivalent arsenic waste water is purified - Google Patents

Abstract

The present invention relates to a kind of no sulphur figure water hydroxyl sarmientite and its application in trivalent arsenic waste water is purified, wherein, the method for purification trivalent arsenic waste water includes：Trivalent arsenic waste water and trivalent ferrous solution are fed simultaneously, adjust the pH value of mixed solution to 1.41 2.45, stirring at normal temperature, precipitation and separation to obtain the final product, wherein drug used and reagent not containing sulfate radicals.The precipitation that this method obtains is i.e. without sulphur figure water hydroxyl sarmientite, chemical formula Fe₆(AsO₃)₄(HAsO₃)(OH)₄·4H₂O, crystal structure is identical with the crystal structure characteristic of figure water hydroxyl sarmientite, also belongs to a kind of mineral crystal structure, can be applied in the trivalent arsenic waste water of not containing sulfate radicals, forms precipitation and achievees the purpose that remove trivalent arsenic.

Description

A kind of sulfur-free hydroxyarsenite and its application in purifying trivalent arsenic wastewater

technical field

The invention relates to the technical field of environmental engineering, and more specifically relates to a sulfur-free hydroxyarsenite and its application in purifying trivalent arsenic wastewater.

Background technique

With the continuous development of my country's non-ferrous metal smelting industry, the discharge of wastewater containing trivalent arsenic is also increasing. However, arsenic and arsenic compounds are recognized as strong carcinogens, so it is necessary to strictly treat wastewater containing trivalent arsenic. be discharged afterwards.

In the prior art, precipitation method is generally used to remove trivalent arsenic. Publication number CN107010704A discloses a method for treating trivalent arsenic-containing wastewater, which reacts trivalent arsenic-containing wastewater, ferric iron solution and sulfate solution to form hydroxyarsenite crystals, thereby achieving the effect of removing trivalent arsenic , but this method needs to add two kinds of medicaments, the dosage is large, and there are many by-products. Publication No. CN106006754A discloses a method for synthesizing high-purity hydroxyarsenite by hydrothermal method, using ferric sulfate and trivalent arsenic to react at 100-130°C to generate hydroxyarsenite, which is mainly to obtain purity High figure water hydroxyarsenite is used for research, but it is not suitable for large-scale industrial treatment of wastewater containing trivalent arsenic.

Therefore, it is meaningful to develop a sulfur-free arsenite and apply it to the removal of trivalent arsenic, which can remove trivalent arsenic under the condition of mild reaction and no addition of sulfate.

Contents of the invention

Aiming at the deficiencies in the prior art, the invention provides a sulfur-free arsenite and its application in purifying trivalent arsenic wastewater. Without adding sulfate, only by reacting the trivalent arsenic-containing wastewater with the ferric iron solution, the sulfur-free arsenic ferrite crystals are precipitated, thereby removing the trivalent arsenic.

The technical scheme that the present invention adopts is as follows:

A method for purifying trivalent arsenic wastewater, comprising: feeding trivalent arsenic wastewater and ferric iron solution at the same time, adjusting the pH value of the mixed solution to 1.41-2.45, stirring at room temperature, and separating and precipitating. Neither contain sulfates.

In the above technical scheme, the medicines and reagents used do not contain sulfate radicals, and the waste water containing trivalent arsenic and the ferric iron solution are fed at the same time, fully contacted and mixed, and the pH value of the mixed solution is adjusted to 1.41-2.45. Stirring reaction to obtain precipitation (sulfur-free arsenite), thereby realizing the removal of trivalent arsenic. When the pH value is greater than 2.45, what is obtained is amorphous ferric hydroxide, and no sulfur-free arsenite precipitate is formed; when the pH value is less than 1.41, what is obtained is an amorphous solid phase. The technical solution has mild reaction conditions, can obtain crystal precipitates without adding additional sulfate radicals, thereby removing trivalent arsenic, is suitable for industrial application, and has low cost.

In the above technical solution, the pH value is preferably 1.56-2.08. Under these conditions, the yield and purity of the sulfur-free japonite can be improved.

In the above technical solution, the molar concentration of trivalent arsenic in the mixed solution is 0.015 mol/L-0.15 mol/L, preferably 0.15 mol/L. The higher the concentration, the more conducive to the formation of sulfur-free arsenite crystals.

In the above technical solution, the molar concentration ratio of trivalent arsenic to ferric iron in the mixed solution is 0.3-1.5:1, preferably 1:1. Controlling the molar ratio of trivalent arsenic to ferric iron is to prevent excessive iron from forming iron hydroxide to take away arsenic in the form of adsorption.

In the above technical solution, the normal temperature is 15-30°C, preferably 25°C.

In the above technical solution, the time for the stirring reaction is 3 to 10 days, preferably 5 days.

The trivalent arsenic waste water and the ferric solution are reacted to form sulfur-free hydroxyarsenite precipitates, and the reaction temperature and time have an impact on the speed and purity of crystal formation. After comprehensive consideration, the temperature is preferably 25°C, and the reaction time is preferably 5 days.

In the above technical solution, preferably, the ferric iron is ferric nitrate, and the trivalent arsenic is sodium arsenite. Because nitrates including ferric nitrate are easily soluble in water, they can promote the reaction and have little effect on the formation of sulfur-free ferric arsenite crystals. In addition, the sulfur-free arsenite obtained in the present invention is the substance obtained by replacing the sulfate radical in the arsenite with arsenite ions, so using sodium arsenite is more conducive to the reaction.

The second object of the present invention is to provide a sulfur-free arsenite, which is the precipitate prepared in the above method for purifying trivalent arsenic wastewater.

The chemical formula of sulfur-free arsonite is Fe ₆ (AsO ₃ ) ₄ (HAsO ₃ )(OH) ₄ ·4H ₂ O, and its crystal structure is similar to that of arsonite Fe ₆ (AsO ₃ ) ₄ ( SO ₄ )(OH) ₄ ·4H ₂ O has the same crystal structure features.

The beneficial effect that the present invention has with respect to prior art:

The sulfur-free japonite Fe ₆ (AsO ₃ ) ₄ (HAsO ₃ )(OH) ₄ ·4H ₂ O provided by the invention is to replace the sulfuric acid in the crystalline structure of japonite with arsenous acid ions The substance behind the root can be prepared by stirring and reacting ferric and trivalent arsenic solutions at room temperature without adding sulfate radicals. The reaction conditions are mild and can be applied to trivalent arsenic waste water without sulfate Sulphurite, so as to realize the removal of trivalent arsenic, is of great significance for expanding the environmental application of Tushuijasite.

Description of drawings

Fig. 1 is the XRD comparison result figure of sulfur-free japonite and sulfur-containing jadosite in Example 1 of the present invention;

Fig. 2 is the infrared spectrum contrast result figure of non-sulfur arsonite and sulfur-containing arsonite in Example 1 of the present invention;

Fig. 3 is the comparison result figure of the Raman spectra of sulfur-free japonite and sulfur-containing jadosite and scorodite in Example 1 of the present invention;

Fig. 4 is the XRD result figure of the obtained sulfur-free hydroxyarsenite in the pH value of the reaction solution in the range of 1.27 to 2.45;

Fig. 5 is the microscopic morphology picture of the sulfur-free arsenite obtained by the reaction solution at different pH values;

Figure 6 is the arsenic and iron removal rate results when the pH value of the reaction solution is formed in the range of 1.27 to 2.45 without sulfur;

Fig. 7 is an XRD result diagram of the solid obtained when the molar concentration ratio of trivalent arsenic to ferric iron in the reaction solution is in the range of 0.3-15.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are only used to illustrate the present invention, and are not intended to limit the protection scope of the present invention.

Example 1

This embodiment provides a method for purifying trivalent arsenic wastewater, including: feeding and mixing wastewater containing sodium arsenite and ferric nitrate solution at the same time, and the molar concentrations of Fe(III) and As(III) in the mixed solution are respectively 0.15mol/L, 0.15mol/L, adjust the pH value of the mixed solution to 1.56, use magnetic stirring to react at 25°C for 5 days, and then separate the solid and liquid by suction filtration, and the drugs and reagents used do not contain sulfate .

As(III) and Fe(III) concentrations in the filtrate were detected to calculate the removal rate.

The resulting filter residue was washed three times with deionized water, and then dried at 80°C. The XRD result of the obtained solid sample is shown in FIG. 1 , the infrared spectrum is shown in FIG. 2 , and the Raman spectrum is shown in FIG. 3 .

Infrared spectrogram (Fig. 2) illustrates that this solid does not contain sulfate ion, and Raman spectrogram (Fig. 3) illustrates that this solid does not contain pentavalent arsenic but contains trivalent arsenic, and this implementation can be determined in conjunction with Fig. 1 to Fig. 3 In this example, a sulfur-free arsenite in which arsenite was substituted for sulfate was obtained, and it had the same crystal structure as that of sulfur-containing arsonite.

The pH value of the reaction solution is adjusted by nitric acid and sodium hydroxide. When the pH value is adjusted in the range of 1.27 to 2.45, the XRD result of the obtained solid is shown in Figure 4, and the obtained solid is amorphous in the solution with a pH value of 1.27. Solid phase, obtained in a solution with a pH value of 2.45 has both an amorphous solid phase and a small amount of sulfur-free arsenite, and in a solution with a pH of 1.41 to 2.08, all of which are sulfur-free. Its microscopic appearance is shown in Fig. 5.

In addition, the removal rates of arsenic and iron in the pH range of 1.27 to 2.45 are shown in Figure 6. The removal rate of ferric iron increases with the increase of pH, for example, the removal rate of ferric iron increases from 5.1% to 98.26% when the pH value increases from 1.27 to 2.45. The removal rate of trivalent arsenic is low when the pH value is less than 1.56. For example, when the pH value is 1.27-1.56, the removal rate of trivalent arsenic is about 40%. When the pH value is greater than 1.56, the removal rate of trivalent arsenic increases with the pH For example, when the pH value increases from 1.62 to 2.08 to 2.45, the removal rate of trivalent arsenic increases from 50.2% to 82% and then to 92%. Although the removal rates of trivalent arsenic and ferric iron are the highest at pH 2.45, the oxyarsonite formed under this condition contains a large amount of amorphous iron hydroxide, so it is not suitable as a sulfur-free Optimal conditions for the application of arsenic removal in Fig.

Adjust the ratio of trivalent arsenic and ferric iron in the initial reaction solution from 0.3 to 15 and control the pH value to 1.60. The obtained solid is detected by XRD (Figure 7) and confirmed that the ratio of trivalent arsenic and ferric iron is 0.3 to 1.5 Sulfur-free arsenite can be obtained, and when the ratio of trivalent arsenic to ferric iron is greater than 1.5, the obtained solids are all amorphous phases.

Control the ratio of trivalent arsenic and ferric iron to 1.0, pH value to 1.60, and adjust the concentration of trivalent arsenic in the initial reaction solution from 1.5×10 ^-3 mol/L to 1.5×10 ^-1 mol/L. When the concentration is lower than 1.5×10 ^-2 mol/L, no solid is produced, and when the concentration is higher than 1.5×10 ^-2 mol/L, sulfur-free oxyarsonite is obtained.

Finally, the above are only preferred implementations of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. A method for purifying trivalent arsenic wastewater, characterized in that it comprises: feeding trivalent arsenic wastewater and ferric iron solution simultaneously, adjusting the pH value of the mixed solution to 1.41-2.45, stirring at room temperature, and separating and precipitating to obtain , in which the drugs and reagents used do not contain sulfate. 2. A method for purifying trivalent arsenic wastewater according to claim 1, wherein the pH value is 1.56-2.08. 3. A method for purifying trivalent arsenic wastewater according to claim 1, characterized in that the molar concentration of trivalent arsenic in the mixed solution is 0.015mol/L to 0.15mol/L, preferably 0.15mol/L L. 4. A method for purifying trivalent arsenic wastewater according to claim 1, wherein the molar concentration ratio of trivalent arsenic to ferric iron in the mixed solution is 0.3 to 1.5:1, preferably 1: 1. 5. A method for purifying trivalent arsenic wastewater according to any one of claims 1-4, characterized in that the normal temperature is 15-30°C, preferably 25°C. 6. A method for purifying trivalent arsenic wastewater according to any one of claims 1-4, characterized in that the stirring time is 3-10 days, preferably 5 days. 7. A method for purifying trivalent arsenic wastewater according to any one of claims 1-4, characterized in that, the ferric iron is ferric nitrate, and the trivalent arsenic is sodium arsenite. 8. A sulfur-free arsenic arsenic, characterized in that, the sulfur-free arsenic arsenic is prepared in the method for purifying trivalent arsenic wastewater according to any one of claims 1 to 7 precipitation. 9. A sulfur-free hydroxyarsenite according to claim 8, characterized in that the chemical formula is Fe ₆ (AsO ₃ ) ₄ (HAsO ₃ )(OH) ₄ 4H ₂ O, and its crystal structure is the same as The crystal structures of Fe ₆ (AsO ₃ ) ₄ (SO ₄ )(OH) ₄ ·4H ₂ O in Fig.