A method and application of organic enhanced stabilization of hydroxyarsenic iron alum

Abstract

The present invention discloses a method and application for organic enhanced stabilization of arsenic in arsenic ferrocyanide, which belongs to the field of wastewater treatment technology. The method comprises the following steps: adding an organic solution containing carboxyl groups to arsenic (III)-containing wastewater, adding a sulfate solution of appropriate concentration, adjusting the pH to less than 3, and then slowly adding a solution containing trivalent iron salt, wherein Fe 3+ ∶As 3+ ∶SO4 2‑ The ratio of arsenic to ferrous iron is 1.5:1:0.25, and the pH value is kept constant during the injection process; the mixture is heated and stirred to a temperature of 25-65°C, reacted for a period of time, and after the reaction is completed, the precipitate is separated. The present invention accelerates the mineralization rate through the strong complexation between organic matter and trivalent iron, achieving a trivalent arsenic removal rate of over 95%. The resulting arsenic nitrite has low leaching toxicity, controlling the leaching toxicity to below 5 mg / L for the first time. The process is simple, and the residual arsenic concentration in wastewater is reduced by approximately 50%, with broad prospects for practical application.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and relates to a method for organic-intensified stabilization of hydroxyarsenosite and its application. Background Art

[0002] Arsenic exists primarily in the environment as inorganic arsenic oxides and methylated forms. Inorganic arsenic is far more toxic than organic arsenic, and trivalent arsenic is 25-60 times more toxic than pentavalent arsenic. Furthermore, As(III) is more soluble and mobile than As(V). At pH < 9.2, it primarily exists as non-ionic arsenite, making it more difficult to remove. Common methods that are effective for As(V) removal, such as chemical precipitation, adsorption, and ion exchange, are less effective for As(III).

[0003] Tushui hydroxyarsenic iron alum is the only iron-containing mineral discovered so far, derived from arsenite sulfate. Synthetic tushui hydroxyarsenic iron alum has yet to meet stability standards. Whether chemically synthesized or biosynthesized, leaching toxicity tests consistently show results exceeding 10 mg / L, exceeding the 5 mg / L limit stipulated in the "Hazardous Waste Leaching Toxicity Identification Standard." Therefore, tushui hydroxyarsenic iron alum's arsenic stabilization performance needs to be improved.

[0004] Chinese patent CN110451598A discloses a method for enhancing the removal of trivalent arsenic from acidic wastewater using humic acid. The method uses humic acid to enhance the stability of arsenic ferrocyanide. Although the arsenic removal rate after the reaction exceeds 90%, the arsenic leaching toxicity of the resulting arsenic ferrocyanide product exceeds 10 mg / L, failing to meet the "Standard for Identification of Leaching Toxicity of Hazardous Wastes" (GB 5085.3-2007). Therefore, further improving the arsenic removal rate and the stability of the resulting arsenic ferrocyanide product are key to achieving efficient treatment of arsenic-containing wastewater and simultaneously stabilizing the arsenic content. Summary of the Invention

[0005] The present invention addresses the shortcomings of existing technologies and proposes a method and application for organically enhanced stabilization of arsenic sulfate. This method significantly reduces the concentration of trivalent arsenic in wastewater after the reaction, improving the arsenic stabilization performance of the resulting arsenic sulfate product, achieving compliance with the "Standard for Identification of Hazardous Waste Leaching Toxicity" (GB 5085.3-2007). Furthermore, the present invention is simple and convenient, with readily available materials and strong practicality.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A method for enhancing the stabilization of arsenic oxide with organic matter comprises the following steps:

[0008] Add a carboxyl-containing organic solution to the arsenic (III) wastewater, and add a suitable concentration of sulfate solution to form a base solution, adjust the pH to <3, and then slowly add a trivalent iron salt solution, wherein Fe 3+ ∶As 3+ ∶SO4 2- The molar ratio of 1:1 is 1.5:1:0.25, and the pH value is kept constant during the injection process; heating and stirring to a temperature of 25-65°C for a period of time, and after the reaction is completed, separating and obtaining a precipitate;

[0009] Wherein, the organic matter containing a carboxyl group is glutamic acid or fulvic acid.

[0010] It should be noted that, during the formation of the base solution, the organic solution containing carboxyl groups and the sulfate solution can be added simultaneously, or the organic solution containing carboxyl groups or the sulfate solution can be added first; the mixing of the three only needs to be completed before adjusting the pH.

[0011] Preferably, the mass ratio of fulvic acid to arsenic (III) is 1-5:750, preferably 2:750;

[0012] Preferably, the mass ratio of glutamic acid to arsenic (III) is 1-5:750, preferably 3:750.

[0013] In the above technical solution, the added trivalent iron is ferric nitrate nonahydrate solution.

[0014] In the above technical solution, the heating reaction temperature is 25-65°C, preferably 55°C.

[0015] In the above technical solution, the reaction time is 6-72h, preferably 12h-24h, and more preferably 12h.

[0016] In the above technical solution, the reaction pH is adjusted to 2-2.8, preferably 2.4.

[0017] In the above technical solution, the stirring rate in the reaction solution is 300-700 rpm, preferably 500 rpm.

[0018] In the above technical solution, the rate of injecting the trivalent iron salt solution is 1000-2500 l / min, preferably 1500 l / min.

[0019] In the above technical solution, the Fe 3+ ∶As 3+ ∶SO4 2- The molar ratio is 1.5:1:0.25.

[0020] Principle of the present invention:

[0021] Natural organic matter, especially carboxyl-containing organic matter, has a strong complexing effect with trivalent iron. In the early stage of the reaction, with the addition of trivalent iron, a binary complex of trivalent iron-organic matter is rapidly formed in the solution. At the same time, it reacts with sulfate ions in the solution to generate a precursor, sulfate iron-containing mineral. This mineral has a high affinity for trivalent arsenic, further accelerating the aggregation of arsenic, causing the mineralization points in the reaction system to reach local supersaturation, and then forming stable hydroxoarsenic iron alum crystals in a short period of time, achieving the effect of enhanced removal of trivalent arsenic and high efficiency and stability.

[0022] The present invention also provides the application of the above-mentioned method for enhancing the stabilization of hydroxoarsenic iron alum with organic matter in arsenic-containing wastewater.

[0023] Beneficial effects of the present invention:

[0024] 1. After treatment with the present invention, the concentration of trivalent arsenic in the solution is significantly lower than that without the addition of organic matter, and the arsenic removal rate reaches over 95%. Among them, the residual concentration of trivalent arsenic in the solution with the addition of fulvic acid is reduced by 41.49% compared with that without the addition of organic matter, and the residual concentration of trivalent arsenic in the solution with the addition of glutamic acid is reduced by 49.87% compared with that without the addition of trivalent arsenic. The leaching toxicity of the obtained product, hydroxyarsenic ferroalite, is 10.45 mg / L when no organic matter is added. The leaching toxicity of the product, hydroxyarsenic ferroalite, obtained after the addition of fulvic acid is 5.14 mg / L, which is 50.81% lower than that without the addition of organic matter. The leaching toxicity of the product, hydroxyarsenic ferroalite, obtained after the addition of glutamic acid is 4.95 mg / L, which is 52.63% lower than that without the addition of organic matter. Compared with other patents, this is the first time that the standard of less than 5 mg / L in the "Identification Standard for Leaching Toxicity of Hazardous Wastes" (GB5085.3-2007) has been met, greatly improving the stability of the obtained mineral.

[0025] 2. The natural organic matter used in the present invention is cheap and easily available, the reaction process is mild and controllable, the experimental operation is simple, and the application scope is broad. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 The enhanced removal rate of As(III) in acidic wastewater at different fulvic acid concentrations in Example 1 and the leaching toxicity of arsenic in hydroxyarsenic iron alum are shown in FIG.

[0028] Figure 2The enhanced removal rate of As(III) in acidic wastewater at different glutamate concentrations in Example 1 and the leaching toxicity of arsenic in hydroxyarsenopyrite obtained are shown.

[0029] Figure 3 This is a comparison chart of the XRD of the precipitated product obtained by enhanced removal of As(III) from acidic wastewater by fulvic acid at different reaction temperatures in Example 2 and the standard card.

[0030] Figure 4 This is a comparison chart of the XRD of the precipitated product obtained by enhanced removal of As(III) from acidic wastewater by glutamic acid at different reaction temperatures in Example 2 and the standard card.

[0031] Figure 5 The removal rate of As(III) in acidic wastewater enhanced by fulvic acid at different reaction temperatures in Example 2 and the leaching toxicity of arsenic in hydroxyarsenic iron alum obtained are shown.

[0032] Figure 6 The removal rate of As(III) in acidic wastewater enhanced by glutamate at different reaction temperatures in Example 2 and the leaching toxicity of arsenic in hydroxyarsenopyrite obtained are shown.

[0033] Figure 7 The figure shows the removal rate of As(III) in acidic wastewater enhanced by fulvic acid at different reaction times in Example 3 and the leaching toxicity of arsenic in hydroxyarsenic iron alum obtained.

[0034] Figure 8 The figure shows the removal rate of As(III) in acidic wastewater enhanced by glutamate at different reaction times in Example 4 and the leaching toxicity of arsenic in hydroxyarsenopyrite obtained.

[0035] Figure 9 The residual concentration of As(III) in the acidic wastewater was removed by adding fulvic acid or glutamic acid after 72 hours of reaction in Comparative Example 1 and Example 2.

[0036] Figure 10 The product obtained by comparing Example 1 and Examples 3 and 4 for removing As(III) from acidic wastewater after 12 h of reaction is whether fulvic acid or glutamic acid is added. The leaching toxicity of arsenic in hydroxyarsenosite is shown. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] Example 1

[0039] This example compares the effects of different organic matter concentrations on the removal of As(III) from acidic wastewater. The specific process is as follows:

[0040] A 0.1 mol / L As(III) solution (30 mg / L) and a 0.025 mol / L Na2SO4 solution (30 ml) were mixed to form a base solution. Fulvic acid or glutamic acid solutions (0 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, or 50 mg / L) were then added. The pH was adjusted to 2.4 with dilute nitric acid or sodium hydroxide. A 0.15 mol / L Fe(III) solution (30 ml) was then added to the base solution using a peristaltic pump at a rate of 1500 μl / min, maintaining a constant pH. The stirring speed during the reaction was 500 rpm. The reaction was incubated at 25°C for three days. After the reaction, the supernatant was collected for arsenic concentration analysis. The supernatant was then vacuum filtered through a 0.22 μm filter and dried at 60°C. The solid sample was then tested for arsenic leaching toxicity.

[0041] Example 2

[0042] This example compares the effects of different reaction temperatures on the removal of As(III) from acidic wastewater by organic matter. The specific process is as follows:

[0043] A 0.1 mol / L As(III) solution (30 mg / L) and a 0.025 mol / L Na2SO4 solution (30 ml) were mixed to form a base solution. 30 ml of either a 20 mg / L fulvic acid solution or a 30 mg / L glutamic acid solution were added. The pH was adjusted to 2.4 with dilute nitric acid or sodium hydroxide. A 0.15 mol / L Fe(III) solution (30 ml) was then added to the base solution at a rate of 1500 μl / min using a peristaltic pump, maintaining a constant pH. The stirring speed during the reaction was 500 rpm. After the addition of the samples, the reaction was carried out at 25°C, 35°C, 45°C, 55°C, and 65°C for three days. After the reaction, the supernatant was collected for arsenic concentration analysis. The supernatant was then vacuum filtered through a 0.22 μm filter and dried at 60°C. The solid sample was then tested for arsenic leaching toxicity.

[0044] Example 3

[0045] This example compares the effects of different reaction times on the removal of As(III) from acidic wastewater using fulvic acid. The specific process is as follows:

[0046] A 0.1 mol / L As(III) solution (30 mg / L) and a 0.025 mol / L Na2SO4 solution (30 ml) were mixed to form a base solution. A 20 mg / L fulvic acid solution (30 ml) was then added. The pH was adjusted to 2.4 with dilute nitric acid or sodium hydroxide. A 0.15 mol / L Fe(III) solution (30 ml) was then added to the base solution using a peristaltic pump at a rate of 1500 μl / min, maintaining a constant pH. The stirring speed during the reaction was 500 rpm. After the addition of the sample, the reaction was incubated at 55°C for 6, 12, 24, 48, or 72 hours. The supernatant was collected for arsenic concentration analysis, vacuum filtered through a 0.22 μm filter, and dried at 60°C. The solid sample was then tested for arsenic leaching toxicity.

[0047] Example 4

[0048] A 0.1 mol / L As(III) solution (30 mg / L) and a 0.025 mol / L Na2SO4 solution (30 ml) were mixed to form a base solution. 30 ml of a 30 mg / L glutamic acid solution was then added. The pH was adjusted to 2.4 with dilute nitric acid or sodium hydroxide. 0.15 mol / L Fe(III) (30 ml) was then added to the base solution using a peristaltic pump at a rate of 1500 μl / min, maintaining a constant pH. The stirring speed during the reaction was 500 rpm. After the addition of the sample, the reaction was incubated at 55°C for 6, 12, 24, 48, or 72 hours. The supernatant was collected for arsenic concentration analysis, vacuum filtered through a 0.22 μm filter, and dried at 60°C. The solid sample was then tested for arsenic leaching toxicity.

[0049] Comparative Example 1

[0050] A base solution of 30 mg / L of 0.1 mol / L As(III) solution, 30 ml of 0.025 mol / L Na2SO4, and 30 ml of pure water was mixed. The pH was adjusted to 2.4 with dilute nitric acid or sodium hydroxide. A peristaltic pump was used to add 30 ml of 0.15 mol / L Fe(III) to the base solution at a rate of 1500 μl / min, maintaining a constant pH of 2.4. The stirring speed during the reaction was 500 rpm. After the addition of the sample, the reaction was incubated at 55°C for 6, 12, 24, 48, and 72 hours. After the reaction, the supernatant was collected for arsenic concentration analysis. The supernatant was then vacuum filtered through a 0.22 μm filter and dried at 60°C. The solid sample was then tested for arsenic leaching toxicity.

[0051] Figure 1The enhanced removal rate of As(III) from acidic wastewater at fulvic acid concentrations of 0-50 mg / L in Example 1 and the leaching toxicity of the obtained product (Figure 1) are shown. As can be seen from the figure, the arsenic removal rate remains at approximately 95% with changes in fulvic acid concentration, showing no significant change. Regarding leaching toxicity, the lowest leaching toxicity is 16.14 mg / L at a fulvic acid concentration of 20 mg / L. Therefore, it can be concluded that a 20 mg / L fulvic acid concentration is most conducive to the stability of the obtained product (Figure 1).

[0052] Figure 2 The enhanced removal rate of As(III) from acidic wastewater at glutamate concentrations of 0-50 mg / L in Example 1 and the leaching toxicity of the obtained product (Figure 1) are shown. As shown in the figure, the arsenic removal rate remains at approximately 95% with changes in glutamate concentration, showing no significant change. Regarding leaching toxicity, the lowest leaching toxicity is 18.45 mg / L at a glutamate concentration of 30 mg / L. Therefore, it can be concluded that a glutamate concentration of 30 mg / L is most conducive to obtaining the stability of the product (Figure 1).

[0053] Figure 3 Figure 2 shows the removal efficiency of As(III) from acidic wastewater enhanced by fulvic acid at different reaction temperatures and the leaching toxicity of the obtained product, hydroxyarsenosite. As shown in the figure, as the reaction temperature increases, the arsenic removal efficiency reaches its highest at 55°C, reaching 98.77%. Regarding leaching toxicity, the lowest leaching toxicity is 8.16 mg / L at a reaction temperature of 55°C. Therefore, a reaction temperature of 55°C is most conducive to arsenic removal or obtaining a stable product under the action of fulvic acid.

[0054] Figure 4 Figure 2 shows the removal efficiency of As(III) from acidic wastewater enhanced by glutamate at different reaction temperatures and the leaching toxicity of the obtained product, hydroxyarsenosite. As shown in the figure, as the reaction temperature increases, the arsenic removal efficiency reaches its highest point at 55°C, reaching 98.95%. Regarding leaching toxicity, the lowest leaching toxicity is 10.36 mg / L at a reaction temperature of 55°C. Therefore, a reaction temperature of 55°C is most conducive to arsenic removal and obtaining a stable product under the action of glutamate.

[0055] Figure 5, 6 is a comparison chart of the XRD and standard cards of the precipitated product obtained in the process of enhanced removal of As(III) in acidic wastewater by fulvic acid or glutamic acid at different reaction times in Examples 3 and 4. As can be seen from the figure, compared with the standard card of Figure Hydroxy Arsenic Iron Aluminum of PDF#44-1468, the characteristic peaks of Figure Hydroxy Arsenic Iron Aluminum appeared at 9° and 27°, regardless of the action of fulvic acid or glutamic acid, indicating that Figure Hydroxy Arsenic Iron Aluminum is the only phase of the synthetic product. According to the XRD diagram, the characteristic peak intensity of the (020) crystal plane corresponding to 9° will be enhanced within 24h-48h regardless of the action of fulvic acid or glutamic acid. Comparison Figure 7 ,8 It can be seen that the enhancement of the characteristic peak intensity of the (020) crystal plane of hydroxyarsenopyrite is not conducive to the stability of arsenic.

[0056] Figure 7 Figure 8 shows the removal rate of As(III) from acidic wastewater using fulvic acid or fulvic acid-enhanced As(III) removal at different reaction times in Examples 3 and 4, and the leaching toxicity of the obtained product, arsenic ferrocyanide. As shown in the figure, when the reaction time is greater than 12 hours, the arsenic removal rate reaches over 95%. In contrast, a 95% removal rate requires three days to achieve this in the previous patent. This is because the binary complex formed by organic matter and trivalent iron increases the local supersaturation and accelerates the formation of arsenic ferrocyanide. Therefore, under the action of heating and organic matter, the reaction time can be greatly reduced. In terms of leaching toxicity, the leaching toxicity of arsenic ferrocyanide synthesized under the action of fulvic acid is as low as 5.14 mg / L at a reaction time of 12 hours, while the leaching toxicity of arsenic ferrocyanide synthesized under the action of glutamic acid is as low as 4.95 mg / L at a reaction time of 12 hours, meeting the standard of less than 5 mg / L in the "Standard for Identification of Leaching Toxicity of Hazardous Wastes" (GB 5085.3-2007) for the first time. When the reaction time increases, the leaching toxicity increases significantly because the remaining organic matter and low pH in the solution slowly release the iron in the synthetic product and also cause the desorption of arsenic.

[0057] Figure 9 The residual concentration of As(III) in acidic wastewater removed by Example 2 and Comparative Example 1 with or without the addition of organic matter is shown. When no organic matter is added, the arsenic concentration after the reaction is completed is 156 mg / L. When 20 mg / L of fulvic acid is added, the residual arsenic concentration after the reaction is completed is 91.6 mg / L. When 30 mg / L of acid and glutamic acid are added, the residual arsenic concentration after the reaction is completed is 78.5 mg / L. Under the action of organic matter, the arsenic concentration after the reaction decreases by 41.28% and 49.68%, respectively, greatly improving the arsenic removal rate.

[0058] Figure 10The 12-hour leaching toxicity of the products obtained in Example 2 and Comparative Example 1, with and without the addition of organic matter, for the removal of As(III) from acidic wastewater. Without the addition of organic matter, the leaching toxicity of the product obtained after the reaction was 18.42 mg / L. With the addition of 20 mg / L of fulvic acid, the leaching toxicity was 5.14 mg / L. With the addition of 30 mg / L of glutamic acid, the leaching toxicity was 4.95 mg / L. The addition of organic matter reduced the leaching toxicity by 72.10% and 73.13%, respectively, significantly improving the stability of the mineral.

[0059] Combined with the above results, it can be seen that the optimal conditions for using organic matter to enhance the treatment of As(III) in acidic wastewater are a fulvic acid concentration of 20 mg / L or a glutamic acid concentration of 30 mg / L, a reaction time of 12 h, a reaction temperature of 55 ° C, and a pH of 2.4.

[0060] The above embodiments are merely descriptions of specific implementation methods of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and changes based on the existing technology. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for enhancing the stabilization of arsenic oxide with organic matter, characterized in that: The following steps are involved: Add a carboxyl-containing organic solution to the arsenic (III) wastewater, and add a sulfate solution to form a base solution, adjust the pH to <3, and then inject a solution containing trivalent iron salt, where Fe 3+ ∶As 3+ ∶SO4 2- The molar ratio of 1:1 is 1.5:1:0.25, and the pH value is kept constant during the injection process; the mixture is heated to 25-65°C with stirring, and the reaction is completed, and the precipitate is separated; The organic matter containing a carboxyl group is glutamic acid; the mass ratio of glutamic acid to arsenic (III) is 1-5:750; and the reaction time is 6h-72h.

2. The method according to claim 1, characterized in that The mass ratio of glutamate to arsenic (III) is 3:

750.

3. The method according to claim 1, characterized in that The trivalent iron salt is one of ferric sulfate, ferric chloride and ferric nitrate nonahydrate.

4. The method according to claim 3, characterized in that The trivalent iron salt is ferric nitrate nonahydrate.

5. The method according to claim 1, characterized in that The reaction temperature was 55°C.

6. The method according to claim 1, characterized in that The reaction time is 12h.

7. The method according to claim 1, characterized in that The reaction pH is 2-2.

8.

8. The method according to claim 7, characterized in that The reaction pH was 2.

4.

9. The method according to any one of claims 1 to 8, characterized in that During the reaction, the injection rate of the ferric salt solution was 500-2500 μl / min, and the stirring rate was 300-700 rpm.

10. The method according to claim 9, characterized in that The injection rate was 1500 μl / min and the stirring rate was 500 rpm.

11. Use of the method for enhancing the stabilization of hydroxoarsenic iron alum by organic matter according to any one of claims 1 to 10 in the treatment of arsenic-containing wastewater.

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