Method for synergistically converting and decomposing calcium-arsenic precipitate through ultrasonic waves

Abstract

The invention relates to a method for synergistically converting and decomposing a calcium-arsenic precipitate through ultrasonic waves. The method for synergistically converting and decomposing the calcium-arsenic precipitate through the ultrasonic waves comprises the following steps that (1), the calcium-arsenic precipitate and water are mixed according to a liquid-solid ratio of (2 to 10) to 1 for size mixing, carbon dioxide gas is introduced at a leaching temperature of 25-90 DEG C, a cavitation generation device is introduced, the calcium-arsenic precipitate is reacted with an aqueous solution of carbon dioxide, and mixed slurry is obtained; (2), liquid-solid separation is carried out on the mixed slurry to obtain calcium carbonate and an arsenic-containing solution; and (3), evaporative crystallization-carbon thermal reduction is carried out on the arsenic-containing solution to obtain metal arsenic. According to the method for synergistically converting and decomposing the calcium-arsenic precipitate through the ultrasonic waves, the calcium-arsenic precipitate (calcium arsenate, calcium arsenite or a mixture of the calcium arsenate and the calcium arsenite) can be quickly converted and decomposed, so that calcium carbonate with low arsenic content is obtained from the calcium-arsenic precipitate under the action of an ultrasonic cavitation effect, the conversion rate of the calcium-arsenic precipitate is effectively improved, the content of arsenic in the calcium carbonate is further reduced, and finally, the purposes of reducing the hazardous waste disposal cost of the arsenic of enterprises and performing harmless disposal are achieved.

Description

technical field [0001] The invention belongs to the technical fields of metallurgy and environmental protection, and in particular relates to a method for ultrasonic synergistic conversion and decomposition of calcium-arsenic precipitates. Background technique [0002] Arsenic is a toxic element that mainly exists in the form of sulfide and is associated with minerals formed by other metals such as lead, zinc, copper, etc. It will produce a large amount of sulfide in the process of non-ferrous metal smelting and sulfuric acid industrial flue gas acid production process Arsenic slag and high (low) arsenic wastewater. The arsenic in these arsenic sulfide residues and arsenic-containing wastewater must be removed with stable compounds. Therefore, the removal and harmless disposal of arsenic in the field of non-ferrous metal smelting has always been a research hotspot. [0003] The current patents on the disposal of arsenic-containing waste liquid and the decomposition method o...

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Problems solved by technology

[0004] From the previous patents and the research status at home and abroad, it can be seen that most arsenic fixation technologies adopt lime precipitation method (atmospheric pressure method, hydrothermal method), and other methods include scorodite method and vitrification method; these technologies are all There are certain defects: (1) The lime precipitation method is a commonly used treatment method for arsenic sulfide slag and arsenic-containing wastewater. This method uses lime to precipitate arsenic in the solution, and then produces arsenic-containing intermediate products-calcium arsenate or arsenous acid Calcium; the main component of calcium arsenate is a mixture of calcium hydroxide and calcium arsenate. The calcium salt of arsenic has a high solubility and is not stable in chemical properties. Pay high environmental protection tax per ton; therefore, due to environmental protection and economic considerations, it is imminent to realize the economical, environmental protection, safe and harmless disposal of calcium arsenate slag

(2) The scorodite method is to oxidize the arsenic precipitate in the iron-containing solution through normal pressure or pressurized hydrothermal reaction to form scorodite crystals and solidify them. Since there are many types of scorodite crystal forms, a stable crystal form is formed. Scorodite has harsh conditions (usually it can be formed under pressurized hydrothermal conditions with a temperature above 160°C), so there are usually some easily soluble scorodite, which has high disposal costs, unstable sediments, and harsh conditions. (3) Although the vitrification method realizes the harmlessness of arsenic by solidifying arsenic through high-temperature transformation, because arsenic is extremely volatile, the process control needs to prevent the secondary volatilization of arsenic from polluting the environment, and usually requires heating Melt calcium arsenate solids and other slags (Si, Fe, Na, etc.) at 1200°C and then solidify, so there are problems such as high energy consumption costs, poor economic efficiency, and secondary pollution of arsenic

[0005] To sum up, the lime precipitation method is often used in the current arsenic removal and harmless disposal technology, and the scorodite method and vitrification method essentially solidify unstable calcium arsenate or calcium arsenite, and have not realized their Recycling

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