Crude Silver Research Articles

Recovery of Crude Silver and Valuable Metals from Tin Anode Slime

Recovery of Crude Silver and Valuable Metals from Tin Anode Slime

Vacuum evaporation and condensation thermodynamics and evaporation kinetics of pure silver

A comprehensive analysis of the characteristics of vacuum evaporation and condensation of pure silver is crucial for advancing vacuum separation and purification technology for crude silver. This study analyzes the vacuum evaporation and condensation thermodynamics and evaporation kinetics of pure silver. The results reveal a substantial increase in the saturated vapor pressure and theoretical maximum evaporation rate of pure silver with increasing temperature. When the temperature is in the range of 1373 ∼ 1773 K and the pressure is in the range of 0.1 ∼ 10 Pa, the average molecular free path is between 0.514 ∼ 66.415 cm. Moreover, the mean molecular free path of silver increases with increasing temperature and decreasing pressure. Besides, the silver triple point occurs at a temperature of 1234.78 K and a pressure of 0.343 Pa. The average evaporation rate of pure silver demonstrates a linear relationship with temperature, and the relationship with pressure conforms to the Logistic model. Notably, the vacuum evaporation of pure silver is a first-order reaction. Furthermore, in this study, the kinetic equation of vacuum evaporation of pure silver is established. In the temperature range of 1473–1673 K, the gas phase mass transfer is the rate-controlling step rather than the mass transfer in the gas phase boundary layer. As the temperature increases, the rate-controlling step gradually changes into gas relative flow mass transfer and gas-liquid interface evaporation mass transfer.

Vacuum thermal decomposition behavior of Ag2Te

Silver and tellurium are crucial valuable metallic elements in anode slimes. During pyrometallurgical processing, tellurium exists in the alloy as the stable compound Ag2Te. The current process of separating tellurium from silver-tellurium compounds in crude silver by oxidizing tellurium into slag leads to undesirable loss of silver, low recovery rates of tellurium, and considerable slag. An environmentally friendly and efficient vacuum thermal decomposition process of Ag2Te was proposed, and the effects of temperature, pressure, and holding time on the decomposition of Ag2Te were investigated. The Experimental temperature was thermodynamically calculated to be in the range of 1473–1673 K and pressure in the range of 1–100 Pa. As the temperature increases, especially above 1573 K, the silver volatiles increase significantly, and silver and tellurium vapors react strongly to form stable silver-tellurium compounds. Investigating the volatilization and condensation mechanisms of silver and tellurium highlights the importance of inhibiting silver volatilization to achieve efficient separation of silver and tellurium. Volatiles containing 98.85% tellurium mainly as tellurium monomer, and a remained melt consisting of 95.56% silver primarily as silver monomer were produced at 1523 K, 50 Pa, and an 8-h holding time.

Clean and efficient recovery of silver from silver-tin alloys by vacuum evaporation-multistage condensation

The recycling of waste lead-free solder and the tin refining process generates large quantities of silver-tin alloys, which have a very high potential for recovery but for which there is no clean and efficient means of recovery. This study examined the saturation vapour pressure, separation coefficients, prediction of the T-x(y) phase diagram of the silver-tin alloys, and condensation rate to explore the feasibility of using vacuum evaporation-multistage condensation as a method for separating silver-tin alloys. The results suggest that in the process of vacuum evaporation, both silver and tin will evaporate, and the evaporability of silver is slightly greater than that of tin. In the process of multistage condensation, tin condenses before silver. Furthermore, the vacuum evaporation-multistage condensation method was experimentally validated. The results suggest that the TF consists of crude silver, with a silver content of 98.17 wt% and a silver distribution rate of 43.60%. The MP consists of a silver-tin alloy with 7.87 wt% silver content and exhibits a silver distribution rate of 53.06%. The RE is crude tin containing 0.27 wt% of silver content and a silver distribution rate of 5.14%. The separation rate of Ag is 96.64%. This study provides a clean and efficient method that is instructive for the recovery of Ag-Sn alloys.

Investigation on the occurrence state and distribution behavior of elements in the separation and purification of crude silver by vacuum volatilization - Fractional condensation

In this paper, an innovative idea of vacuum separation and purification of crude silver is proposed, and theoretical calculations and kilogram-scale experimental studies are carried out. The theoretical calculation results show that the order of saturated vapor pressure and theoretical maximum volatilization rate of each element in crude silver is Se > Te > Sb > Bi > Pb > Ag > Cu > Au. In the temperature range of 1373–1773 K, the separation coefficient and vapor-liquid equilibrium composition of Ag-Au and Ag-Cu alloys were calculated. The experimental results show that the crude silver is mainly composed of Ag-Au and Ag-Cu-Se-Te phases. Under the optimal experimental conditions, the total volatilization rate of crude silver after primary vacuum separation and purification was 90.36%, and the distribution rates of gold and silver in the residue were 98.26% and 1.10%, respectively. The secondary vacuum separation and purification of the first and second order condenser volatile from the primary vacuum separation and purification were carried out, and gold was enriched 149 and 128 times in the residue, respectively, and the main phases of the volatiles were Ag, Ag2Se and Ag2Te, of residue were Au-Sb phase, Au-Cu phase and Au-Ag-Cu phase.

Potential Recovery of Silver (Ag) from X-ray Fixer Waste by Alkaline Treatment

The study aims to establish a chemical method of silver recovery from x-ray processing fixer waste by alkaline treatment using sodium hydroxide (NaOH). The samples used in the study were collected from selected hospitals and radiology centers in Cagayan de Oro City, Philippines. The NaOH precipitation method was employed by varying the amount of NaOH from 8.00 g to 15.00 g per 600 mL of the fixer waste sample. The recovered crude silver for the two sampling periods ranged from 0.88 g to 2.46 g. The method resulted to optimum recovery at pH 9. The One Way ANOVA indicates that there are significant differences on the amount of silver recovered when varying the amount of NaOH in “sampling A”. The Tukey Test further reveals that there exists an evident rise in the recovered silver using 10.00 g to 15.00 g of NaOH. In “sampling B” the amount of silver recovered does not significantly differ when varying the amount of NaOH used on average basis. The raw data, however, also revealed a significant rise in the amount of silver recovered using 10.00 g to 15.00 g of NaOH where pH was approximately 9.

Recovery of Tellurium From Sodium Carbonate Slag

Abstract This study is devoted to tellurium recovery from sodium carbonate slag, formed in the fire refining process of crude silver. The slag was modified by silica additions and then reduced by carbon oxide. The degree of the slag modification was defined by the parameter kw: where:ni- the mole numbers of silica, sodium carbonate and sodium oxide. The compositions of the investigated slag determined by the parameter kw and the mole fraction of the tellurium oxide (xTeO2 ) are given in the following Table. The reduction of tellurium was very fast for all the investigated slags, which was manifested by an almost complete conversion of CO into CO2. Unfortunately, at the same time, a side reaction took place, and as a results sodium telluride was formed, which reported to the slag: (Na2O)slag + Te(g) + CO = (Na2Te)slag + CO2 The tellurium content in the reduced slag decreases as the parameter kw increases, and only the slag with the kw equal unity was suitable for the tellurium recovery in form of dusts, containing more than 76 wt-% tellurium.

High hydrostatic pressure inactivation kinetics of the endogenous lipoxygenase in crude silver carp (Hypophthalmichthys molitrix) extract

SummaryInactivation kinetics of endogenous lipoxygenase in crude silver carp (Hypophthalmichthys molitrix) extract was studied for thermal (50–80 °C, ambient pressure) and high hydrostatic pressure combined with heat treatment (300–700 MPa at 50–80 °C) process conditions. Lipoxygenase (LOX) inactivation followed first‐order kinetics at all pressure–temperature combinations used. Moreover, LOX inactivation rates became less pressure dependent with increasing pressure at all temperatures studied and also showed less temperature dependence of the enzyme inactivation rate at various high pressure levels tested. It is evident that inactivation kinetics is complex affected by both pressure and temperature. Therefore, response surface methodology (RSM) was attempted to investigate combined temperature–pressure processing conditions on LOX inactivation kinetics in crude silver carp extract samples. In conclusion, the LOX inactivation rate constant was modelled as a function of both temperature and pressure conditions by a quadratic polynomial equation as follows: .

非鉄金属製錬プロセスと操業 竹原製煉所における貴金属製錬

In the precious metals processing line, raw slimes including metals and silver are first decopperized and deselenized, and then converted to noble lead in the melting and settling furnace. Thereafter, it is turned into a crude silver anode by cupellation with the residual lead from the lead refining process. This crude silver is refined by electrolysis to produce electrolytic silver. Electrolytic gold is produced from the crude gold obtained from the sediments of silver electrolysis and part of it is used to produce high purity gold for electronic industry. Aside from these metals, selenium, tellurium, platinum and palladium are recovered.Recently, We have some improvement in these processes.

リサイクリング・プロセスと操業 細倉金属鉱業（株）における鉛製錬

The Hosokura Metal and Mining Co., Ltd. produces electrolytic lead (99.99% purity) and bismuth, antimony trioxide, crude silver etc. from recycled lead-acid batteries and various types of lead-bearing industrial intermediates. Mining and smelting of lead, zinc and silver bearing ores from the original Hosokura Mine began over 1,200 years ago, but was terminated with the closure of the mine in 1987 and, since then, the production of recycled lead and the treatment of mine wastewater have been continued. The current company was reorganized in March, 2006. Although the capacity for monthly lead production based on a blast-furnace operation followed by electro-refining is around 2,000 t /month, a serious shortage of recycled batteries triggered technology development to accept lead dross and lead residue etc.also as low grade raw material in the summer of 2005. Another main operation of this company is the treatment of mine wastewater, 15 t /min on average, from the closed mine and the effluents from lead plants to meet the water quality standard against toxic elements including lead. Overcoming the lead-leakage problem at this plant in May, 2002, the thoroughly renewed and strengthened water-treating system with a big deep bed filtration facility at the final stage enables us to contribute to the environment improvement of this area and rebuild the tight, friendly correlation with the surroundings. Both the plants are operating under the company policies of environmental conservation, compliance and community involvement.

銅電解スライム塩素浸出残渣から回収した塩化銀中の不純物元素の化学的形態および選択的溶解除去

A new hydrometallurgical process has been developed of silver recovery from chlorine leaching residue of anode slime in copper electro-refining, which includes the leaching of residue with aqueous Na2SO3 solution of pH=10.5 for 1h and at 25°C, followed by recovery of crude silver chloride at pH=1.0 with addition of 70% aqueous H2SO4 solution to the leaching solution and its purification with scrubbing by using various aqueous solutions of 6 kmol m-3 HCl and 30wt% H2O2, or 0.1 kmol m-3 EDTA at the temperatures ranging from 50 to 70°C. In this process, lead, selenium and tellurium are representative impurities in the crude silver chloride. Based on some chemical condition, it is speculated that the crude silver chloride contains mainly silver selenide and silver telluride as impurities. Scrubbing the silver chloride with HCl-H2O2 aqueous solution was effective to eliminate these impurities from the silver chloride. On the other hand, it is difficult to eliminate lead with the scrubbing, indicating that lead is incorporated in the silver chloride crystal. However, EDTA solution was effective for the elimination of lead to the level of less than 10 ppm.

精銅工場における貴金属製錬（住友金属鉱山（株））

Niihama Copper Refinery of Sumitomo Metal Mining Co., Ltd. has been producing mainly electrolytic copper and precious metals since 1919.The production of gold has been quadrupled during the latest decade because of increasing copper concentrate smelting at Toyo smelter and starting treatment of high gold ores. The ores come from Sumitomo's Hishikari Gold Mines and contain about 80 grams gold per ton.Copper anode slimes produced from Niihama Refinery and Toyo Refinery are decopperized with sulphuric acid, deselenized by roasting and smelted by use of an electric furnace to concentrate precious elements. Lead refinery slimes produced at Harima ISP Refining Works are also charged to the furnace.The bunions from the electric furnace are treated and refined in a cupel after antimony and lead removal. The resulted crude silver is casted into silver anodes.In order to cope with increasing slime production, a new method, chloridizing furnace for lead removal has been adopted and a new cupel has been introduced.The treatment process for silver anode slimes has been improved to obtain up-grade quality of gold anodes. The productivity of gold electrolytic processes are advanced by use of the anodes.

Solvation of ions. Some applications. IV A novel process for the recovery of pure silver from impure silver chloride

Silver chloride is exceptionally soluble in dimethylsulfoxide saturated with calcium chloride at 25°C. Solutions containing up to 196 gl −1 silver as Ca(AgCl 2) 2 have been prepared. If 30–40% by volume of water is added to such solutions, then pure silver chloride is precipitated almost quantitatively. The silver chloride can be easily converted to pure (99.99%) silver metal either by melting at 1100°C with excess sodium carbonate as flux, or by reducing with hydrogen at 300–400°C, or by reducing an aqueous suspension with zinc dust. The water added to the DMSO solution can be recovered by distillation and both it and the CaCl 2-DMSO bottoms are recycled for further leaching. This leads to a fast and cheap process for obtaining silver from crude silver chloride, or from materials containing silver in a form that can be converted to silver chloride. Applications to an anode slimes leach residue, a silver halide teaching laboratory residue, and the silver chloride cake from a gold refinery are demonstrated.

Determination of selenium and tellurium in silver chloride and uranium oxide

Methods are described for the determination of selenium and tellurium in crude silver chloride produced as a by-product of the refining of gold, and in high-purity uranium oxide. Selenium and tellurium are separated from one another as well as from the numerous other substances in the sample before they are extracted into organic solvents and determined spectrophotometrically. For the determination of selenium 3,3'-diaminobenzidine is used and for tellurium, sym-diphenylthiourea. A minimum of 2 ppm of each element may be determined in silver chloride and 0.3 ppm in uranium oxide. Statistical data are given to show the precision and accuracy of the methods.

Determination of bismuth and lead in crude silver by a.c. polarography.

Determination of bismuth and lead in crude silver by a.c. polarography.