阅读说明：本技术 一种利用砷酸钠化学还原制备单质砷的方法 (Method for preparing simple substance arsenic by chemical reduction of sodium arsenate ) 是由 钟祥华 衷水平 刘文元 陈素余 吴晓林 于 2020-05-19 设计创作，主要内容包括：本发明公开了一种利用砷酸钠化学还原制备单质砷的方法,以铜冶炼厂闪速炉烟尘中性浸出-磁选-碱浸后,碱浸液冷冻制得高纯砷酸钠晶体为原料,添加水合肼作为还原剂,盐酸为pH调节剂,在一定的温度下反应一定时间,过滤,干燥即得单质砷。本发明适用于铜冶炼高砷烟尘的开路提砷,可以实现烟尘中有价元素的富集和回收；化合物砷还原成单质砷,毒性降低的,单质砷容易保存且产品附加值提高。其工艺流程清晰高效、资源利用率高,且经济实用、安全环保,具有良好的工业前景和社会效益。(The invention discloses a method for preparing simple substance arsenic by chemical reduction of sodium arsenate, which comprises the steps of performing neutral leaching-magnetic separation-alkaline leaching on flue gas of a flash furnace of a copper smelting plant, freezing the alkaline leaching solution to obtain high-purity sodium arsenate crystals as a raw material, adding hydrazine hydrate as a reducing agent and hydrochloric acid as a pH regulator, reacting for a certain time at a certain temperature, filtering and drying to obtain the simple substance arsenic. The invention is suitable for the open-circuit arsenic extraction of the high-arsenic smoke dust in copper smelting, and can realize the enrichment and recovery of valuable elements in the smoke dust; the compound arsenic is reduced into simple substance arsenic, the toxicity is reduced, the simple substance arsenic is easy to store, and the added value of the product is improved. The process flow is clear and efficient, the resource utilization rate is high, and the method is economical, practical, safe and environment-friendly and has good industrial prospect and social benefit.)

1. A method for preparing simple substance arsenic by chemical reduction of sodium arsenate is characterized in that: taking high-purity sodium arsenate crystals as a raw material, adding hydrazine hydrate as a reducing agent, and hydrochloric acid as a pH regulator, carrying out chemical reduction reaction, filtering, and drying to obtain simple substance arsenic.

2. The method for preparing elemental arsenic by chemical reduction of sodium arsenate according to claim 1, wherein: the high-purity sodium arsenate crystal is prepared by carrying out alkaline leaching on copper smelting smoke and then freezing, and the preparation concentration is 60 g/L-100 g/L.

3. The method for preparing elemental arsenic by chemical reduction of sodium arsenate according to claim 1, wherein: the reducing agent is hydrazine hydrate diluted by 5-20 times.

4. The method for preparing elemental arsenic by chemical reduction of sodium arsenate according to claim 1, wherein: the reducing agent used was hydrazine hydrate added with different excess factors, said factors being between 1 and 3.

5. The method for preparing elemental arsenic by chemical reduction of sodium arsenate according to claim 1, wherein: hydrochloric acid is used for adjusting the pH value to 6-10.

6. The method for preparing elemental arsenic by chemical reduction of sodium arsenate according to claim 1, wherein: the temperature of the chemical reduction reaction is 30-90 ℃.

7. The method for preparing elemental arsenic by chemical reduction of sodium arsenate according to claim 1, wherein: the time of the chemical reduction reaction is 1 h-4 h.

8. The method for preparing elemental arsenic by chemical reduction of sodium arsenate according to claim 1, wherein: the obtained simple substance arsenic is in a crystal cluster and a plum blossom shape, and the average grain diameter of crystal grains is 8 mu m.

Technical Field

The invention belongs to the field of preparing simple substance arsenic by chemical reduction, and particularly relates to a method for preparing simple substance arsenic by chemical reduction of sodium arsenate.

Background

Arsenic, also known as arsenic, has three allotropes of arsenic ash, arsenic yellow and arsenic black, which are relatively stable and are customarily called "metallic arsenic", which has a hexagonal crystal structure and luster, and is the most stable form. In nature, arsenic is mainly composed of arsenopyrite (FeAsS) and arsenopyrite (FeAsS)₂) Copper-sulfur-arsenic ore (Cu)₃AsS₃) Realgar (As)₂S₃) Hen yellow (As)₂S₃) And the like. The arsenic is mostly prepared from the by-products of smelting non-ferrous metals such as copper, lead, gold and the like, and is mostly produced in the form of arsenic compounds, such as arsenic trioxide, arsenic acid, arsenate, arsenic sulfide and the like. Arsenic is harmful, but arsenic is also beneficial, plays an important role in national economic production process, and is mainly used for manufacturing non-ferrous metal alloys and semiconductor material gallium arsenide. It is worth noting that there is an increasing trend in the demand for metallic arsenic, and in particular the demand for high purity arsenic is a significant trend. The price of high-purity arsenic is hundreds of times higher than that of commercial arsenic, the application of high-purity arsenic is increasingly widespread with the development of high technology, and the demand for the high-purity arsenic is undoubtedly increased with the widespread application of mobile phones, multimedia technology and optical fiber communication.

The simple substance arsenic has two preparation methods of a fire method and a wet method. Wherein the pyrogenic process preparation method has vacuum steam-forming-taking, pyrogenic carbon reduction, oxygen reduction and the like; the wet method is prepared by electrodeposition, metal extraction and reduction, and the like. As arsenic is a volatile element, the pyrogenic process can pollute the atmosphere and can cause harm to the environment and the health of people; the operation temperature for preparing the simple substance arsenic by the wet method is low, the arsenic is not volatilized basically, and the safety coefficient is high compared with the arsenic prepared by the pyrogenic method. Therefore, the process of recovering and preparing arsenic by the whole wet method has been regarded by people since the seventies of the last century. The preparation of simple substance arsenic by an electrodeposition method in wet preparation is easy to generate toxic gas (arsine), and the electrolytic potential needs to be strictly controlled to avoid the generation. Metal reduction extraction is simpler than electrodeposition, using reducing agents such as stannous chloride, oxalic acid, sodium hypophosphite, etc. to displace arsenic from aqueous solutions containing arsenic salts. Although the method needs to consume certain reagents and is high in cost, the method is still an important method.

The arsenic content in the smoke dust of the flash furnace of the smelting plant is high, the arsenic element is enriched through the process flows of neutral leaching, magnetic separation, alkaline leaching and the like, and the high-purity sodium arsenate crystal is prepared by freezing. The sodium arsenate as the arsenic-containing compound has strong toxicity and is not easy to store, and if the sodium arsenate is used as the raw material, simple substance arsenic which has relatively weak toxicity and is easy to store is prepared and directly sold, so that the additional value can be greatly improved.

According to the production plan of a smelting plant, more than 3000 tons of metallic arsenic are required to be treated every year, the arsenic is treated as dangerous waste, and the annual treatment cost is more than 8000 ten thousand yuan. If the metal arsenic in the high-arsenic material can be extracted and sold by a certain method, the material is harmless, not only can the enterprise benefit be increased, the environmental pollution be reduced, but also the vicious circulation of the arsenic in a smelting system is avoided, the problems that the arsenic of a subsequent anode plate exceeds the standard, an electrolytic cleaning liquid workshop runs in an overload mode, the arsenic is difficult to treat harmlessly and the like are solved, the arsenic treatment cost of a subsequent workshop section is effectively reduced, and the research has important practical significance.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for preparing simple substance arsenic by chemical reduction of sodium arsenate, which realizes the enrichment and recovery of valuable elements in smoke dust; the compound arsenic is reduced into simple substance arsenic, the toxicity is reduced, the simple substance arsenic is easy to store, and the added value of the product is improved. The method has the advantages of high resource utilization rate, simple process flow, high efficiency and environmental protection.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for preparing simple substance arsenic by chemical reduction of sodium arsenate comprises the steps of performing neutral leaching-magnetic separation-alkaline leaching on flue gas of a flash furnace in a copper smelting plant, freezing the alkaline leaching solution to obtain high-purity sodium arsenate crystals as a raw material, adding hydrazine hydrate as a reducing agent and hydrochloric acid as a pH regulator, reacting for a certain time at a certain temperature, filtering, and drying to obtain the simple substance arsenic.

Wherein the content of the first and second substances,

concentration of sodium arsenate solution: 60 g/L-100 g/L;

dilution multiple of hydrazine hydrate: 5-20 parts of;

excess hydrazine hydrate coefficient: 1-3;

adjusting the pH value with hydrochloric acid: 6-10;

reaction temperature: 30-90 ℃;

reaction time: 1 h to 4 h

The obtained simple substance arsenic is in a crystal cluster and a plum blossom shape, and the average grain diameter of crystal grains is 8 mu m.

When sulfuric acid, which is one of the additional products of copper smelteries, is selected as a pH regulator, elemental arsenic cannot be prepared, while when hydrochloric acid is used as the pH regulator, elemental arsenic is prepared, and chloride ions in the hydrochloric acid may have an activating effect on arsenate ions.

The invention has the following remarkable advantages:

(1) the invention provides a new idea for recycling valuable elements in copper smelting smoke dust, and realizes the full utilization and sustainable development of resources;

(2) the invention provides a new method for reducing harmful element arsenic in copper smelting smoke dust, has simple process and less medicament consumption,

effectively reduces the circulating accumulation of arsenic in a copper smelting system and improves the economic and environmental protection benefits of enterprises.

(3) The invention provides a new way for preparing the simple substance arsenic, and the simple substance arsenic has certain research and application values in high-end products such as non-ferrous metal alloy, semiconductor material gallium arsenide and the like.

Drawings

FIG. 1 is a flow chart of the process steps for preparing elemental arsenic by chemical reduction of sodium arsenate in example 1;

FIG. 2 is a spectrum of the energy spectrum analysis of example 1 for preparing elemental arsenic by chemical reduction of sodium arsenate;

FIG. 3 is a secondary electron diagram of the chemical reduction of sodium arsenate to elemental arsenic in example 1.

Detailed Description

In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.