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CN-121988748-A - Method for preparing pure silver powder through short-flow environment-friendly emission reduction

CN121988748ACN 121988748 ACN121988748 ACN 121988748ACN-121988748-A

Abstract

The invention discloses a method for preparing pure silver powder by short-process environment-friendly emission reduction, which belongs to the technical field of material metallurgy and comprises the core steps of firstly adding disodium ethylenediamine tetraacetate as a selective complexing agent into an electrolyte containing silver nitrate and impurity ions such as copper, nickel, bismuth and the like, and forming a stable water-soluble complex with the impurity ions, so that the apparent reduction potential of the impurity metal ions is negatively shifted by at least 200mV, and the activity and reduction potential of the impurity ions in the solution are reduced. Secondly, controlling the potential for reduction, dropwise adding ascorbic acid, glucose and a reducing agent, and stopping the reaction when the potential is reduced to the end point of a silver ion reduction platform. Since the impurity ions are effectively "masked" and controlled by the silver reduction window, the selectivity of the reduction reaction tends to silver ions, thereby directly obtaining pure silver powder having extremely low impurity content. The method has the advantages of short process flow, low cost, less three wastes discharge, no need of complex intermediate purification steps, and is particularly suitable for direct production of silver metallurgy enterprises.

Inventors

  • ZHANG WENQIANG
  • WANG YUNFEI
  • ZHU QIANG
  • LI DECHANG
  • YE LONGGANG
  • LIAO ZHOU
  • CAO HUAN
  • DAI WENKAI
  • LIU YONG
  • LIAO WEI
  • ZHAO YONGJIANG

Assignees

  • 水口山有色金属有限责任公司

Dates

Publication Date
20260508
Application Date
20260311

Claims (10)

  1. 1. The method for preparing the pure silver powder by short-process environment-friendly emission reduction is characterized by comprising the following steps of: s1, preparing a raw material liquid, namely obtaining silver nitrate electrolyte containing silver nitrate and one or more impurity metal ions of copper, nickel and bismuth at least containing copper ions; S2, selective potential shift pretreatment, namely adding ethylenediamine tetraacetic acid disodium salt serving as a selective masking agent into the electrolyte, stirring to enable the disodium ethylenediamine tetraacetic acid disodium salt to be fully dissolved and carry out complexation reaction with impurity metal ions to form a stable water-soluble complex, so that the apparent reduction potential of the impurity metal ions is negatively shifted by at least 100 mV; s3, under the stirring condition, adding a reducing agent into the solution processed in the step S2, monitoring the oxidation-reduction potential of the solution in real time, and immediately stopping the reaction when the potential drops to the end point of the silver ion reduction platform; s4, after the reaction is finished, carrying out solid-liquid separation on a reaction system, and washing and drying the obtained solid product in sequence to obtain the pure silver powder.
  2. 2. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein in the step S1, the concentration of Ag + in the silver nitrate electrolyte is 3-100g/L, and the pH value of the electrolyte is 0.3-6.0.
  3. 3. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein in the step S2, the addition amount of the disodium ethylenediamine tetraacetate is 0.5 to 4.5 times of the total molar amount of metal ions of copper, nickel and bismuth impurities in the electrolyte.
  4. 4. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein in the step S2, the stirring time of the complexing reaction is 5-60 minutes, the temperature of the reaction solution in the complexing reaction process is controlled to be 20-50 ℃, and the stirring speed is 200-800r/min.
  5. 5. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein in the step S3, the reducing agent is one of ascorbic acid and glucose or a compound reducing agent formed by compounding the ascorbic acid and the glucose according to any proportion.
  6. 6. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein in the step S3, the end point of the silver ion reduction platform is that the standard potential of silver of the electrolyte is reduced to +0.4V Ag/AgCl.
  7. 7. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein in the step S3, the reaction temperature of the controlled reduction is controlled to be 30-70 ℃, and the stirring rate in the reduction reaction process is 300-1000r/min.
  8. 8. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 5, wherein in the step S3, the reducing agent is firstly prepared into an aqueous solution, then the aqueous solution is added into the reaction system, the concentration of the aqueous solution of the reducing agent is 10-60g/L, the aqueous solution of the reducing agent is added in a dropwise or slowly inflow mode, and the adding rate is controlled to be 0.5-6 mL/liter of aqueous solution of the reducing agent/liter of silver nitrate electrolyte/min.
  9. 9. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein in the step S4, the solid-liquid separation is performed by adopting a filtering or centrifuging mode; The washing is to sequentially wash the solid product for a plurality of times by using deionized water and absolute ethyl alcohol until the washing liquid is neutral; The drying is vacuum drying or drying under inert gas atmosphere, the drying temperature is 40-80 ℃, and the drying time is 2-8h.
  10. 10. The method for preparing pure silver powder by short-process environment-friendly emission reduction according to claim 1, wherein the purity of the pure silver powder prepared by the method is more than or equal to 99.9wt%, wherein the content of single components of copper, nickel and bismuth impurities is less than or equal to 0.005wt%, the silver powder is submicron particles, the average particle size is 0.3-1.0 μm, and the crystal structure is a pure face-centered cubic structure.

Description

Method for preparing pure silver powder through short-flow environment-friendly emission reduction Technical Field The invention belongs to the technical field of material metallurgy, and particularly relates to a method for preparing pure silver powder by short-process environment-friendly emission reduction. Background Silver is used as a rare noble metal, and is widely applied to the fields of electronic information, chemical catalysis, biological medicine, high-end jewelry, new energy materials and the like by virtue of excellent electrical conductivity, thermal conductivity, ductility and chemical stability, and particularly, high-end application scenes such as electronic slurry, precise electroplating and the like, strict requirements are put on the purity, granularity and morphology of silver powder, and the market demand of high-purity silver powder is continuously increased. Along with the development of noble metal metallurgy industry, high-purity silver powder is efficiently prepared from silver metallurgy electrolyte, so that high-value utilization of silver resources is realized, and the method becomes one of the core directions of industry research and production. The current mainstream technology for preparing high-purity silver powder industrially is a three-step method, which comprises the steps of separating and purifying silver ions from ore leaching solution or silver metallurgy mixed electrolyte by complex means such as chemical precipitation, solvent extraction, ion exchange or electrolytic refining to obtain high-purity silver nitrate electrolyte, then carrying out electrodeposition by taking the purified silver nitrate electrolyte as a raw material to obtain metallic silver, then dissolving the metallic silver with nitric acid to prepare silver nitrate solution again, and finally carrying out liquid phase reduction on the silver nitrate solution by adopting reducing agents such as hydrazine hydrate, sodium borohydride and the like to obtain silver powder products. The silver powder production process has the technical defects that the final purity of silver powder can be ensured through multi-step purification, the process flow is long, a plurality of industrial links of smelting, chemical industry and materials are involved, the operation steps are complicated, the production period is long, the production efficiency is low, the silver is subjected to repeated form conversion of ion state, simple substance state, ion state, simple substance state in the production process, the loss of noble metal silver is inevitably caused, the recovery rate of silver resources is reduced, a large amount of chemical agents such as electrolytic reagent, nitric acid and reducing agent are consumed in the process, meanwhile, the investment of special equipment such as electrolytic refining, dissolution reaction and reduction preparation is large, the equipment operation energy consumption and maintenance cost are high, the comprehensive cost of silver powder production is high, the fourth step that the large amount of use of the chemical agents can generate a large amount of three wastes such as waste liquid, heavy metal waste residue, the subsequent treatment difficulty is high, the cost is high, and secondary environment pollution is easily caused, and the development requirements of current green metallurgy and environmental protection and emission reduction are contrary. In order to solve the problems of long flow and high cost of the traditional three-step method, researches and attempts are made in recent years to directly prepare silver powder from impurity-containing silver electrolyte by liquid phase reduction, and the steps of intermediate electrodeposition, nitric acid dissolution and the like are omitted. However, the conventional liquid phase reduction method always fails to break through the core technical bottleneck that the silver electrolyte generally contains Cu 2+、Pb2+、Bi3+、Ni2+ and other impurity metal ions, the reduction potential of the impurity ions is similar to that of silver ions, the conventional reduction process cannot realize selective inhibition of the impurity ions, the co-reduction reaction of the impurity ions and the silver ions is extremely easy to occur in the reduction process, the impurity simple substances can be separated out along with silver powder and enter the product, the purity of the silver powder is greatly reduced, the purity of the product is difficult to reach the high-purity standard of 99.9% in most cases, and the use requirements of high-end fields such as electrons, medicines and the like cannot be met. If the impurity co-reduction is to be avoided, complex pre-purification treatment is still needed to be carried out on the silver-impurity-containing electrolyte, and finally the problems of complicated flow and high cost are not eliminated, and the technical advantages of direct reduction cannot be realized. In summary, in the silver powder produ