A method for selective reduction removal and recovery of antimony from arsenic- and antimony-containing acidic wastewater

Abstract

This invention relates to a method for selectively reducing and removing and recovering antimony from acidic wastewater containing arsenic and antimony, comprising the following steps: adding a carboxylic acid compound to the acidic wastewater containing arsenic and antimony, mixing thoroughly, irradiating the mixture under ultraviolet light, and performing solid-liquid separation after ultraviolet irradiation to obtain metallic antimony and treated wastewater; wherein the molar ratio of antimony to carboxylic acid compound in the acidic wastewater containing arsenic and antimony is 1:(50-150). The principle of this invention is that ultraviolet light photolyzes the carboxylic acid compound to produce CO2. ·‑ Free radicals, CO2 ·‑ Free radicals can efficiently reduce Sb(III) and Sb(V) to metallic antimony (Sb(0)) both thermodynamically and kinetically, while their reaction with As(III) and As(V) is extremely slow and kinetically impossible. The residual concentration of antimony in the treated wastewater was as low as 25 μg / L, and the content of metallic antimony in the precipitate was as high as 99.9 wt%.

Description

Technical Field

[0001] This invention relates to the field of acidic wastewater treatment and resource recovery technology, specifically to a method for selectively reducing, removing, and recovering antimony from arsenic- and antimony-containing acidic wastewater. Background Technology

[0002] In many industrial sectors, particularly in non-ferrous metal smelting and ore mining, acidic wastewater containing high concentrations of arsenic and antimony is inevitably generated. Arsenic and antimony in this wastewater mainly exist in dissolved forms as As(III), As(V) and Sb(III), Sb(V), which are highly toxic and carcinogenic, and are listed as priority pollutants by the International Agency for Research on Cancer and many governments. Improper treatment of this type of wastewater and its discharge into the environment can pose a significant threat to the surrounding ecosystem and human health; therefore, effective treatment of arsenic- and antimony-containing acidic wastewater is urgently needed.

[0003] Traditional arsenic and antimony removal technologies in water treatment processes, such as adsorption, ion exchange, and membrane filtration, typically concentrate or enrich arsenic and antimony in wastewater. The arsenic and antimony are then transferred from the wastewater to waste residue and highly concentrated brine. These waste residues and brines, containing extremely high levels / concentrations of arsenic and antimony, are classified as hazardous waste, failing to completely eliminate their environmental risks. For example, CN110642324A discloses a method for removing antimony from wastewater using nascent secondary iron oxides as an adsorbent. However, due to the complex composition of the wastewater, the adsorption by the adsorbent is not selective; arsenic and antimony are adsorbed together, forming a mixed arsenic and antimony waste residue.

[0004] Antimony resources are extremely scarce. Based on the strategy of achieving harmlessness through resource recovery, selectively recovering antimony from acidic wastewater and recycling it as metallic antimony is a potential and feasible treatment strategy. This strategy can both prevent the formation of hazardous mixed waste residues and achieve the resource utilization of antimony.

[0005] Photochemical reduction is a green in-situ wastewater treatment technology. It has been proven that the reducing free radicals generated under ultraviolet irradiation possess hydrated electrons (e). aq - ), hydrogen radicals (H) · ), sulfite radicals (SO2) ·- ) and carbon dioxide free radicals (CO2 ·- These free radicals, such as e, have very low standard redox potentials. aq - H · and CO2 ·- The standard redox potentials of Sb are as low as -2.9V, -2.42V, and -1.9V, respectively, indicating strong reducing properties. Thermodynamically, Sb(V)(E) can be converted into Sb(V)(E) 0(Sb(V) / Sb(III))=0.363V), Sb(III)(E 0 (Sb(Ⅲ) / Sb(0))=0.204V) is reduced to metallic antimony (Sb(0)). Therefore, based on the thermodynamic and kinetic differences in the reduction processes of arsenic and antimony, a reducing active species system is constructed to reduce antimony to its elemental state without reducing arsenic, thereby achieving selective removal and recovery of antimony from acidic wastewater, which has significant environmental and economic benefits. Summary of the Invention

[0006] To address one or more technical problems existing in the prior art, this invention provides a method for the selective reduction removal and recovery of antimony from arsenic- and antimony-containing acidic wastewater, utilizing CO2 generated by ultraviolet photolysis of carboxylic acid compounds. ·- The high selectivity of free radical reduction of antimony enables the selective reduction and recovery of antimony from acidic wastewater containing arsenic and antimony.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for selectively reducing, removing, and recovering antimony from acidic wastewater containing arsenic and antimony, comprising the following steps: adding a carboxylic acid compound to the acidic wastewater containing arsenic and antimony, mixing evenly, irradiating the mixture under ultraviolet light, and performing solid-liquid separation after ultraviolet light irradiation to obtain metallic antimony and the treated wastewater, such as... Figure 1 As shown; wherein, the molar ratio of antimony to carboxylic acid compounds in the arsenic-antimony-containing acidic wastewater is 1:(50-150).

[0008] The beneficial effects of this invention are: the method for selectively reducing and removing and recovering antimony from acidic wastewater containing arsenic and antimony utilizes CO2 generated by ultraviolet photolysis of carboxylic acid compounds. ·- The highly selective reduction of antimony by free radicals enables the reduction and recovery of antimony from acidic wastewater containing arsenic and antimony. The specific principle is that CO2... ·- Free radicals can efficiently reduce Sb(III) and Sb(V) both thermodynamically and kinetically; although CO2 ·- Free radicals can thermodynamically reduce As(III) and As(V), but the reaction rate between them and As(III) and As(V) is extremely slow, making the reaction kinetically impossible. Based on this difference, a highly efficient and selective removal and recovery of antimony from arsenic- and antimony-containing acidic wastewater has been achieved. This invention can efficiently and selectively reduce and remove antimony from acidic wastewater, reducing the residual concentration of antimony in the wastewater to as low as 25 μg / L. Figure 2 And obtained high-purity metallic antimony (>99.9wt%) products. Figure 3 and Figure 4 It has the advantages of being quick and simple to operate and having strong selectivity for antimony reduction.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, the arsenic- and antimony-containing acidic wastewater includes one or more types of acidic wastewater generated during the smelting, mining, and beneficiation of non-ferrous metals.

[0011] Furthermore, the concentrations of arsenic and antimony in the acidic wastewater containing arsenic and antimony are 0.1 mg / L to 200.5 mg / L, respectively. The concentrations of arsenic and antimony in the acidic wastewater containing arsenic and antimony can be selected as 0.1 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, 50 mg / L, 60 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 140 mg / L, 150 mg / L, 160 mg / L, 180 mg / L, and 200 mg / L, respectively.

[0012] Furthermore, the carboxylic acid compounds include one or more mixtures of organic compounds containing carboxyl groups or carboxylate ions.

[0013] Furthermore, the carboxylic acid compounds include one or a mixture of two or more of tartaric acid, lactic acid, citric acid, potassium oxalate, ethylenediaminetetraacetic acid, ethyl trifluoroacetate, trimellitic acid, oxalic acid, terephthalic acid, and pyromellitic tetracarboxylic acid.

[0014] Furthermore, the ultraviolet light includes single-wavelength, multi-wavelength, or continuous ultraviolet light with an effective wavelength in the range of 190–900 nm, and the selectable wavelengths are 190 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, and 900 nm.

[0015] The beneficial effect of adopting the above-mentioned further scheme is that it stimulates carboxylic acid compounds to decompose into CO2. ·- Free radicals.

[0016] Furthermore, the irradiation time of the ultraviolet light is 1 hour to 2.5 hours.

[0017] Furthermore, the carboxylic acid compound is directly added to the acidic wastewater containing arsenic and antimony, or the carboxylic acid compound is prepared into a concentrated solution and added to the acidic wastewater containing arsenic and antimony.

[0018] Furthermore, after adding carboxylic acid compounds to the acidic wastewater containing arsenic and antimony, the mixture is thoroughly mixed by shaking, stirring, or agitation.

[0019] Furthermore, the solid-liquid separation includes one or more combinations of centrifugation, pressure filtration, and membrane filtration. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to the present invention;

[0021] Figure 2 The residual concentrations of arsenic and antimony in the wastewater after treatment in Example 3;

[0022] Figure 3 The X-ray diffraction (XRD) pattern of the precipitate was obtained in Example 3;

[0023] Figure 4 The energy dispersive X-ray spectrum (EDS) of the precipitate was obtained in Example 3. Detailed Implementation

[0024] The technical solutions in the embodiments of this invention will be described in detail and completely. It is worth noting that the mentioned embodiments are only a part of the many examples of this invention, and not all of them. Based on the embodiments given in this invention, those skilled in the art can deduce all other possible implementation methods without creative effort, and these derived embodiments are also considered to be within the protection scope of this invention.

[0025] Example 1

[0026] Potassium oxalate solid was added to acidic wastewater containing arsenic (1.5 mg / L) and antimony (10.2 mg / L), achieving a molar ratio of antimony to potassium oxalate of 1:50. The mixture was stirred uniformly using a magnetic stirrer. A 1000W high-pressure mercury lamp (emitting light in the 190–900 nm wavelength range) was used for irradiation. After 10 minutes, precipitates formed. Irradiation continued for 1 hour, followed by filtration through a 0.45 μM filter membrane to separate the precipitates from the treated wastewater. During this process, the concentrations of arsenic and antimony ions in the treated wastewater were measured using atomic fluorescence spectrometry (AFS). The results showed that the arsenic concentration remained essentially unchanged, while the antimony concentration gradually decreased, reaching below 50 μg / L at the end of the reaction. XRD analysis indicated that the precipitate was metallic antimony, and EDS analysis revealed a metallic antimony content of 99.97 wt%.

[0027] Example 2

[0028] Solid trimellitic acid was added to acidic wastewater containing arsenic (200.5 mg / L) and antimony (100.2 mg / L), achieving a molar ratio of antimony to trimellitic acid of 1:150. The mixture was then stirred uniformly using a mechanical stirrer. A 1000W high-pressure mercury lamp (190–900 nm wavelength range) was used for 10 minutes of irradiation, after which particle precipitation was observed. After 1 hour of continuous irradiation, the precipitate was separated from the treated wastewater by filtration through a 0.45 μM filter. During this process, the concentrations of arsenic and antimony ions in the treated wastewater were measured using atomic fluorescence spectrometry (AFS). The results showed that the arsenic concentration remained essentially unchanged, while the antimony concentration gradually decreased, reaching below 30 μg / L at the end of the reaction. XRD analysis indicated that the precipitate was metallic antimony, and EDS analysis revealed a metallic antimony content of 99.91 wt%.

[0029] Example 3

[0030] Oxalic acid solution was added to acidic wastewater containing arsenic and antimony at concentrations of 23.5 mg / L and 14.2 mg / L, respectively, to achieve a molar ratio of antimony to oxalic acid of 1:140. Uniform stirring was achieved using a magnetic stirrer. A 32W low-pressure mercury lamp with a wavelength of 253.7 nm was used. Particle precipitate formation was observed after 15 minutes of irradiation. After 2.5 hours of continuous irradiation, centrifugation was performed to separate the precipitate particles from the treated wastewater. During this process, the concentrations of arsenic and antimony ions in the treated wastewater were measured using atomic fluorescence spectrometry (AFS). It was found that the arsenic concentration remained essentially unchanged during the reaction, while the antimony concentration gradually decreased, reaching below 25 μg / L at the end of the 2.5-hour reaction. XRD analysis showed that the diffraction peaks of the obtained precipitate were consistent with those of Sb(O) (PDF#35-0732). Figure 3 The results indicate that the precipitate is mainly composed of Sb(0), and EDS analysis revealed that the Sb(0) content in the precipitate was 99.98 wt%. Figure 4 ).

[0031] Example 4

[0032] A terephthalic acid solution was added to acidic wastewater containing arsenic (17.6 mg / L) and antimony (10.4 mg / L), achieving a molar ratio of antimony to terephthalic acid of 1:80. The mixture was then stirred thoroughly. A 500W medium-pressure mercury lamp (emitting light with a wavelength of 225–450 nm) was used for 10 minutes to observe particle precipitation. After 1.5 hours of continuous irradiation, the precipitate was separated from the treated wastewater by filtration through a 0.45 μM filter. During this process, the concentrations of arsenic and antimony ions in the treated wastewater were measured using atomic fluorescence spectrometry (AFS). The arsenic concentration remained essentially unchanged, while the antimony concentration gradually decreased, reaching below 20 μg / L at the end of the reaction. XRD analysis showed that the precipitate was metallic antimony, and EDS analysis revealed a metallic antimony content of 99.93 wt%.

[0033] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0034] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for selectively reducing and removing and recovering antimony from arsenic- and antimony-containing acidic wastewater, characterized in that, Includes the following steps: A carboxylic acid compound is added to acidic wastewater containing arsenic and antimony, and after mixing evenly, the mixture is irradiated under ultraviolet light. After ultraviolet light irradiation, solid-liquid separation is performed to obtain metallic antimony and treated wastewater; wherein, the molar ratio of antimony to carboxylic acid compound in the acidic wastewater containing arsenic and antimony is 1:(50-150). The carboxylic acid compounds include one or more of tartaric acid, lactic acid, citric acid, potassium oxalate, ethylenediaminetetraacetic acid, ethyl trifluoroacetate, trimellitic acid, oxalic acid, terephthalic acid, and pyromellitic tetracarboxylic acid; the CO2 generated by the photolysis of the carboxylic acid compounds using ultraviolet light... •- The high selectivity of free radical reduction of antimony enables the reduction and recovery of antimony in acidic wastewater containing arsenic and antimony.

2. The method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to claim 1, characterized in that, The arsenic- and antimony-containing acidic wastewater includes one or more types of acidic wastewater generated during the smelting, mining, and beneficiation of non-ferrous metals.

3. The method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to claim 1, characterized in that, The concentrations of arsenic and antimony in the acidic wastewater containing arsenic and antimony range from 0.1 mg / L to 200.5 mg / L.

4. The method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to claim 1, characterized in that, The ultraviolet light includes single-wavelength, multi-wavelength, or continuous-wavelength ultraviolet light with an effective wavelength in the range of 190–900 nm.

5. The method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to claim 1, characterized in that, The irradiation time of the ultraviolet light is 1h to 2.5h.

6. The method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to claim 1, characterized in that, The carboxylic acid compounds are added directly to acidic wastewater containing arsenic and antimony, or the carboxylic acid compounds are prepared into a concentrated solution and added to acidic wastewater containing arsenic and antimony.

7. The method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to claim 1, characterized in that, After adding carboxylic acid compounds to acidic wastewater containing arsenic and antimony, the mixture is thoroughly mixed by shaking, stirring, or agitation.

8. The method for selectively reducing and recovering antimony from arsenic- and antimony-containing acidic wastewater according to claim 1, characterized in that, The solid-liquid separation includes one or more of centrifugation, pressure filtration, and membrane filtration.

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