A method for synthesizing zinc arsenide based on alkaline complex environment co-reduction

Abstract

This invention provides a method for the co-reduction synthesis of zinc arsenide in an alkaline composite environment. The method innovatively uses a strongly alkaline solution as the basic electrolyte and simultaneously dissolves zinc oxide (ZnO) and arsenic trisulfide (As₂S₃) as the zinc and arsenic sources, respectively, to form Zn(OH)₄. 2‑ and AsS3 3‑ / AsO3 3‑ A multi-ion coexistence system was developed. By introducing multifunctional composite additives into this system, the electrodeposition process was synergistically regulated. Specifically, the reduction process of Zn(II) in situ modified the cathode interface, reducing the double-layer thickness and enhancing the adsorption and electron transfer of arsenite ions on the cathode surface. Simultaneously, the coupled co-deposition of arsenic and zinc effectively squeezed out the adsorption sites of water molecules on the cathode surface and the electron ratio of the hydrogen evolution reaction, thereby significantly suppressing the hydrogen evolution side reaction and the generation of highly toxic arsine (AsH3) gas. Ultimately, a uniform and well-bonded zinc arsenide deposition layer was obtained on the cathode surface.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for the co-reduction synthesis of zinc arsenide based on an alkaline composite environment. Technical Background

[0002] Zinc arsenide, an important semiconductor material, typically requires high temperatures or highly toxic precursors, such as elemental arsenic and arsine, for its preparation, which presents challenges including high safety risks, high energy consumption, and complex processes. Electrochemical deposition, which can be performed at room temperature and pressure, is a promising alternative. However, electrodepositing zinc arsenide in aqueous solutions faces fundamental challenges. In acidic systems, arsenic primarily exists as arsenite (H3AsO3), which has a relatively positive reduction potential, but exhibits intense hydrogen evolution competition, resulting in low current efficiency. More seriously, the reduction process readily generates the highly toxic intermediate product—arsine gas (AsH3), posing extremely poor safety. In alkaline systems, arsenic primarily exists as the negatively charged arsenite ion (AsO3). 3- It exists in the form of a negatively charged cathode surface and generates a strong electrostatic repulsion, which leads to difficulties in mass transfer, high reduction overpotential, and extremely slow reaction kinetics, resulting in mass transfer and kinetic barriers.

[0003] Current technologies lack effective solutions that can simultaneously address the four major challenges of arsenic source introduction, interfacial repulsion, hydrogen evolution inhibition, and toxic gas generation. Therefore, developing a novel electrolyte system and deposition strategy is crucial. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for the safe and efficient electrodeposition of zinc arsenide in an aqueous solution system. This method achieves stable coexistence of arsenic and zinc ions, efficient modification of the cathode interface, strong suppression of hydrogen evolution reaction, and directional deposition of zinc arsenide by constructing a unique strongly alkaline composite electrolyte system and utilizing the multifunctional synergistic effect of additives. To achieve the above objectives, this invention adopts the following technical solution:

[0005] 1. Prepare a strong alkaline solution with deionized water to a pH value ≥ 12 (e.g., one or a mixture of 2-6 M NaOH, KOH, LiOH, or CsOH). Under stirring and heating (25-90°C), sequentially add calculated amounts of zinc oxide (ZnO) and arsenic trisulfide (As₂S₃) until fully dissolved, forming a solution containing Zn(OH)₄. 2- AsS3 3- AsO3 3- S2 2-A clear solution containing multiple ions can be obtained by adjusting the amounts of ZnOH and As2S3 added, thereby controlling the ion concentration in the system. The As(III) content is between 1 and 50 g / L, and the Zn(II):As(III) ratio is controlled at 1:1. The dissolution process occurs as follows: ZnO + H2O + 2OH- - → Zn(OH)4 2- As2S3 + 6OH - = Na3AsS3 + AsO3 3- + 3H2O.

[0006] 2. Subsequently, one or more additives such as sodium citrate, ammonium citrate, guar gum, selenium oxide, and sulfite are added to the liquid obtained in step 1, with the additive content ranging from 0.1 to 10 g / L. After the additives are introduced, they form complex ions with Zn(II) and As(III), adjusting the deposition potential and adsorption energy at the cathode interface. Simultaneously, the additives preferentially adsorb / deposit on the cathode surface and modify the electrochemical reaction interface, adjusting and changing the interfacial charge properties, compressing the electric double layer, and weakening the AsS32---. 3- AsO3 3- The electrostatic repulsion between the cathode and the cathode induces the deposition of zinc arsenide in the new city and inhibits the hydrogen evolution reaction, thus preventing the generation of highly hazardous hydrogen arsenide gas.

[0007] 3. Using pretreated low-carbon steel sheets, copper sheets, nickel sheets, titanium sheets, or other metal electrodes as cathodes, and inert electrodes (such as platinum-plated titanium mesh, Raney nickel, ruthenium-coated titanium anodes, etc.) as anodes, constant current electrolysis is performed at a temperature of 25-90°C under stirring conditions, with the cathode current density controlled at 5-500 mA / m. 2 After electrolysis for 1-10 hours, a grayish-black deposit is obtained on the cathode surface. This is removed through a multi-step cleaning process using deionized water and alcohol to obtain zinc arsenide. The cathode chemical reaction under alkaline conditions is: AsO3 3- +3e - +3H₂O=As+6OH - Zn(OH)4 2- +2e - =Zn+4OH - .

[0008] 4. The core mechanism of the reaction process is the reduction-dissolution process of Zn(II) and SO42-. 2- / S2O3 2-The reduction products dynamically modified the cathode interface, effectively compressing the Helmholtz double layer thickness and creating a channel for negatively charged arsenate ions to approach the cathode surface, greatly enhancing their adsorption and electron transfer processes. The co-deposition of arsenic and zinc competed for and crowded out the active sites and electrons on the cathode surface for water reduction (hydrogen evolution), fundamentally inhibiting the hydrogen evolution reaction (HER). Since HER is a key step in the formation of AsH3 (2As + 6H2O),... + + 6e - → 2AsH3↑ requires coupling with hydrogen evolution to provide H*), and after HER is inhibited, the generation pathway of highly toxic AsH3 is completely blocked.

[0009] Beneficial effects:

[0010] Compared with the prior art, the present invention has the following significant advantages:

[0011] 1. Use low-toxicity, low-cost As2S3 instead of As. 0 Or AsH3; the strongly alkaline environment completely inhibits the formation of AsH3, eliminating the safety hazard from the source.

[0012] 2. By employing a composite additive strategy, the mass transfer and kinetic challenges of arsenite ion reduction in alkaline systems were successfully addressed.

[0013] 3. By using interface engineering and site competition, the hydrogen evolution side reaction was significantly suppressed, allowing the current to be mainly used for arsenic-zinc co-deposition, resulting in a significant improvement in current efficiency.

[0014] 4. The strong alkaline environment, combined with the complexing agent, ensures the long-term stable coexistence of the various ionic components, making them less prone to decomposition and precipitation. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the zinc arsenide synthesis process of the present invention. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to embodiments.

[0017] Example 1:

[0018] Prepare a 3 M NaOH solution by taking 1 L of deionized water. Heat to 60°C, add 20 g of ZnO, and stir until completely dissolved to form Na₂Zn(OH)₄ and Zn(OH)₄. 2-The concentration was approximately 0.33 mol / L. Then, 81 g of As₂S₃ powder was added, and the mixture was stirred continuously for 2 hours until the solution turned into a dark brown clear liquid. The following were added sequentially: 15 g of sodium citrate (~0.05 M), 1 g of guar gum, 0.05 g of SeO₂ (~0.4 mmol / L), and 1 g of Na₂SO₃ (~8 mmol / L). The mixture was stirred until all additives were completely dissolved or dispersed. A 2 cm × 4 cm titanium sheet was used as the cathode, and a platinum-titanium mesh as the anode. The electrolyte temperature was maintained at 60°C, and the solution was magnetically stirred. A constant current was applied, with a cathode current density of 250 A / m. 2 The electrolysis time was 3 hours. During the electrolysis process, small bubbles (containing a small amount of hydrogen gas) were generated on the cathode surface. After the electrolysis was completed, a uniform, dense, and well-adhered gray-black deposition layer was formed on the cathode surface, and the cathode current efficiency was 94%. ICP-MS analysis showed that the Zn / As atomic ratio was approximately 1.5:1.

[0019] Example 2:

[0020] Keeping the electrolysis parameters and temperature unchanged from Example 1, a basic electrolyte without additives was prepared, and other conditions were the same as in Example 1. The results showed that the deposited layer became uneven, the hydrogen evolution was significantly increased, a distinct garlic odor (characteristic odor of AsH3) was observed, and the cathode current efficiency was only 56%. This comparative experiment demonstrates the crucial role of additive-based electrolyte composition design in improving deposited layer quality and suppressing side reactions.

[0021] Example 3:

[0022] Electrolytes with different As(III) contents were prepared, including five groups with As(III) contents of 5, 10, 20, 30, and 40 g / L, with other conditions the same as in Example 1. The results showed that at low As(III) concentrations (<10 g / L), due to the lack of reducing active components in the electrolyte, the hydrogen evolution reaction dominated, thus inducing the production of toxic AsH3. With increasing As(III) and Zn(II) ion concentrations in the electrolyte, the number of bubbles on the cathode surface significantly decreased, and no garlic odor was produced. Electrolysis for 3 hours at a As(III) content of 40 g / L resulted in an AsH3 content of less than 0.019 Nm in the exhaust gas. 3 / t As This study confirms that multi-ion coupling competitive cathode adsorption and reaction sites can effectively block the formation pathway of highly toxic AsH3.

[0023] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing zinc arsenide based on nanoparticle-induced synthesis, characterized in that, Includes the following steps: S1. Prepare a strong alkaline solution with deionized water to a pH value ≥ 12. Under stirring and heating conditions of 25-90°C, add calculated amounts of zinc oxide (ZnO) and arsenic trisulfide (As2S3) sequentially until fully dissolved, forming a solution containing Zn(OH)4. 2- AsS3 3- AsO3 3- S2 2- A clear solution containing multiple ions; S2. Then, add an additive with a content of 0.1~10 g / L to the liquid obtained in step S1; S3. Using pretreated low-carbon steel sheets, copper sheets, nickel sheets, titanium sheets, etc., as cathodes and inert electrodes as anodes, constant current electrolysis is carried out at a temperature of 25-90°C under stirring conditions, with the cathode current density controlled at 5-500 mA / m. 2 After electrolysis for 1 to 10 hours, a gray-black deposit is obtained on the cathode surface. After cleaning with deionized water and alcohol, zinc arsenide product is obtained.

2. The method according to claim 1, characterized in that, The strong alkaline solution mentioned in step S1 is one or a mixture of 2-6 M NaOH, KOH, LiOH, and CsOH.

3. The method according to claim 1, characterized in that, The ion concentration in the clarified solution described in step S1 is controlled by adjusting the amount of ZnOH and As2S3 added, wherein the content of As(III) is 1~50 g / L, and the ratio of Zn(II) to As(III) is controlled at 1:

1.

4. The method according to claim 1, characterized in that, The chemical reaction that occurs during the dissolution process in step S1 is as follows: ZnO + H2O + 2OH - → Zn(OH)4 2- ; As2S3 + 6OH - = Na3AsS3 + AsO3 3- + 3H2O。 5. The method according to claim 1, characterized in that, The additive mentioned in step S2 is one or more of sodium citrate, ammonium citrate, guar gum, selenium oxide, and sulfite.

6. The method according to claim 1, characterized in that, In step S3, the inert electrode is one of platinum-plated titanium mesh, Raney nickel, or ruthenium-coated titanium anode.

7. The method according to claim 1, characterized in that, In step S3, the cathode chemical reaction is: AsO3 3- +3e - +3H₂O=As+6OH - Zn(OH)4 2- +2e - =Zn+4OH - .

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