CN1170008C

CN1170008C - Method for removing bismuth and antiomny from silver electrolyte

Info

Publication number: CN1170008C
Application number: CNB00126155XA
Authority: CN
Inventors: 吴根喜; 陈达平; 邢晓峰; 郝保平; 李建华
Original assignee: QIANKUN GOLD AND SILVER REFINING CO Ltd INNER MONGOLIA
Current assignee: QIANKUN GOLD AND SILVER REFINING CO Ltd INNER MONGOLIA
Priority date: 2000-08-23
Filing date: 2000-08-23
Publication date: 2004-10-06
Anticipated expiration: 2020-08-23
Also published as: CN1339619A

Abstract

The present invention relates to a method of removing bismuth and antimony from a silver electrolyte in the refining process of silver electrolysis. The method uses the characteristic that nitrates of the bismuth and the antimony can be hydrolyzed under the condition of low acidity, a proper amount of silver oxide and ammonia water are added to the silver electrolyte step by step and precipitated bismuth and antimony can be recovered through filtration. The sliver electrolyte can be used again after being regulated by nitric acid and silver nitrate. The method has the advantages of simple operation, short purification time, reuse of the electrolyte and little loss of noble metal.

Description

Method for removing bismuth and antimony from silver electrolyte

The invention relates to a method for removing bismuth and antimony from silver electrolyte, which is a difficult problem in the process of silver electrolytic refining to remove bismuth (Bi) and antimony (Sb) in the electrolyte. The current common method is to scrap the electrolyte or concentrate, crystallize, melt and redissolve the electrolyte. The methods cannot fundamentally solve the problem of repeated use of the purified silver electrolyte, and have the defects of high energy consumption, complex equipment, long purification period, high noble metal loss and the like of the treatment method.

The invention aims to provide a method for removing bismuth and antimony from a silver electrolyte, which utilizes the hydrolysis characteristic of nitrate of bismuth and antimony in a low-acidity environment to carry out hydrolysis precipitation on the nitrate of bismuth and antimony so as to achieve the aim of removing bismuth and antimony.

The purpose of the invention is realized by the following measures:

slowly adding silver oxide (Ag) into silver electrolyte₂O) until the pH value of the silver electrolyte is 2-3, and slowly adding 5-10% ammonia (NH)₄OH) until the PH value of the silver electrolyte is 5-6. The chemical reaction formula of adding silver oxide into the electrolyte is as follows:

ammonia water is a weak base solution which can be used for continuously increasing the pH value of electrolysis to ensure that Bi and Sb reach hydrolysis precipitation, and the chemical reaction formula is as follows:

at this time, most of Bi, Sb, Fe and a part of Pb in the electrolyte are precipitated at the bottom of the electrolyte in the form of basic nitrate or hydroxide. Standing for 7-9 hours. Mixing the supernatantFiltering, wherein the impurities Bi, Sb, Fe and the like in the supernatant are reduced to 10^-3(g/L) is less than the order of magnitude, nitric acid and nitric acid are usedThe silver is adjusted to 3-9 g/L and 100-120g/L and then returned to the electrolytic bath for use.

Adding hydrochloric acid (HCL) with the concentration of 5% into the filtered precipitation slag, stirring and filtering, recovering bismuth (Bi) and antimony (Sb) from the filtrate, washing the precipitated silver chloride (AgCL), adding the hydrochloric acid (HCL) and stirring, adding iron (Fe) when the pH value of the silver chloride (AgCL) is 2-3, and stirring to obtain the crude silver powder.

The invention has the following functions and advantages:

the process can be carried out step by step, so that the accumulation of a large amount of impurities in the electrolyte is avoided, the electrolyte even reaches the scrapping degree, a small amount of silver is contained in filter residues in the purification process, and the silver is separated from other impurities by using a proper amount of hydrochloric acid. The process can be carried out partially or completely in practical application, which plays an important role in producing qualified electrolytic silver I. The agent used in the purification process does not have any side effect on the subsequent electrolysis. Nor do they accumulate in large amounts due to multiple purifications, which gradually decompose and run away over time. The method has the outstanding advantages that the electrolyte can be recycled, and the method has the unique advantages of simple operation, short purification time, low precious metal loss, strong practicability and the like.

The following example is given:

the attached drawing is a process flow chart,

as shown in the process flow chart, silver oxide (Ag) is slowly added into the silver electrolyte₂O) until the PH of the silver electrolyte was measured to be 2, and then ammonia (NH) was slowly added at a concentration of 5%₄OH) until the PH of the silver electrolyte is measured to be 5. The reaction formula of adding silver oxide into the electrolyte is as follows:

at this time, most of Bi, Sb, Fe and a part of Pb in the electrolyte are precipitated at the bottom of the electrolyte in the form of basic nitrate or hydroxide. And standing for 8 hours. Filtering the supernatant, wherein the impurities Bi, Sb, Fe and the like in the supernatant are all reduced to 10^-3The acid content is adjusted to 9g/L and the silver content is adjusted to 120g/L by nitric acid and silver nitrate, and the acid content and the silver content are returned to the electrolytic bath for use.

Adding hydrochloric acid (HCL) with the concentration of 5% into the filtered precipitation slag, stirring and filtering, recovering bismuth (Bi) and antimony (Sb) from the filtrate, washing the precipitated silver chloride (AgCL), adding the hydrochloric acid (HCL) and stirring, adding iron (Fe) when the pH value of the silver chloride (AgCL) is 3, and stirring to obtain the crude silver powder.

Claims

1. A process for removing Bi and Sb from the silver electrolyte features that the silver oxide (Ag) is slowly added to the silver electrolyte₂O) until the pH value of the silver electrolyte is 2-3, and slowly adding 5-10% ammonia (NH)₄OH) until the PH value of the silver electrolyte is measured to be 5-6, standing for 7-9 hours, filtering out precipitation slag, adjusting the supernatant into regenerated silver electrolyte with the acid content of 3-9 g/L and the silver content of 100-120g/L by using nitric acid and silver nitrate, sending the regenerated silver electrolyte back to the silver electrolytic tank for use again, adding hydrochloric acid (HCL) with the concentration of 5% into the filtered precipitation slag, stirring and filtering, recovering bismuth (Bi) and antimony (Sb) from the filtrate, washing the precipitated silver chloride (AgCL), adding hydrochloric acid (HCL) into the filtrate, stirring, adding iron (Fe) into the silver chloride (AgCL) when the PH value of the silver chloride (AgCL) is 2-3, and stirring to obtain the crude silver powder.