Recovery of gold from gold-posted cultural relics
The Material Recycling Research Institute uses the oxidation roasting method to recover gold from the waste gold-posted cultural relic copper. The waste gold-plated cultural relic copper is put into a special roasting furnace, and it is oxidized and roasted at a constant temperature of 1000C for 30 minutes. It is taken out and put into water. The gold-plated layer is attached to the copper oxide flakes and separated from the copper matrix. Then use dilute sulfuric acid to dissolve, and dissolve the residue to separate and purify gold. This method features no pollution waste gas during roasting. Use this method to process 300 kilograms of waste cultural relics of copper and recover 1.5 kilograms of gold. The gold recovery rate is>98%, and the matrix copper recovery rate is>95%. The by-product copper sulfate can be used as an insecticide.
 Recovery of gold from waste electronic components
Dissolve the gold plating on the waste components, replace it with iron or reduce it with sodium sulfite to recover the gold. It is acidified with sulfuric acid and oxidized by potassium chlorate to regenerate iodine.
The Material Recycling Research Institute has developed a new process for electrolytic gold withdrawal. Use thiourea and sodium sulfite as electrolyte, graphite as cathode plate, and gold-plated waste as anode for electrolytic gold withdrawal. Through electrolysis, the gold on the coating is anodicized to Au+ and then forms complex cation Au[cs(NH2)]2+ with thiourea, which is then reduced to gold by sodium sulfite, which is deposited on the bottom of the tank, and the gold-containing precipitate is separated and purified. Pure gold powder. The base material can be recycled nickel and cobalt. The gold recovery rate of this process is 97~98%. Product gold purity>99.95%.
 Recovery of gold and palladium from spent catalyst
The Kunming Institute of Precious Metals uses hydrochloric acid and an oxidant for multiple leaching, so that gold and palladium enter the solution, zinc powder is replaced, hydrochloric acid is added to the oxidant to dissolve, and oxalic acid is reduced to obtain pure gold powder; the mother liquor is reduced to purify palladium by conventional methods. The purity of gold and palladium can reach 99.9%. The recovery rates were 97% and 96%, respectively. Has applied for a Chinese patent.
Silver recycling technology
 New electrolytic silver withdrawal process
The Material Recycling Institute designed its own electrolytic silver removal equipment, using graphite plates as cathodes, stainless steel drums as anodes, and there are many fine holes on the drums. Sodium citrate and sodium sulfite are electrolytes, and the silver-plated parts enter from the head end of the drum and are sent out from the end of the drum. The silver on the surface of the plated part enters the electrolyte, and the substrate of the plated part is intact and can be returned to electroplating again. The recovery rate of silver is 97-98%, and the purity of silver powder is 99.9%.
 Recycling of waste silver-zinc batteries
Waste silver-zinc batteries contain 52.55% silver and 42.7% zinc. Zinc is the negative electrode, and silver oxide is the positive electrode, coated on the copper mesh framework. The Material Recycling Research Institute uses dilute sulfuric acid to dip zinc and copper respectively, and directly melt the ingot with silver powder. Oxidant is added during copper leaching with dilute sulfuric acid, zinc-containing liquid is concentrated and crystallized to produce zinc sulfate, and copper-containing liquid is concentrated and crystallized to produce copper sulfate. Zinc recovery rate>98%, silver recovery rate 98%, silver ingot purity>99%.
 Recovery of silver from waste film
The Kunming Institute of Precious Metals uses dilute sulfuric acid to elute the silver-containing emulsion layer on the color film, the chloride salt is heated to precipitate the silver halide, the chlorinated calcination or organic solvent is washed to remove the organic matter, and the alkaline medium is suspended and reduced with sugar solids to obtain pure silver. The purity of silver is 99.9%, and the direct yield is 98%. This law has been patented.
The Material Recycling Research Institute (formerly the Material Recycling Research Institute of the Ministry of Internal Trade) uses sodium thiosulfate solution to dissolve the silver halide on the waste film. In the dissolution process, an inhibitor is added to prevent the dissolution of the gelatin on the film. The dissolving solution is electrolyzed to recover the silver. Film base recycling. The silver leaching rate is>99%, the recovery rate is 98%, and the silver purity is 99.9%. This method has been applied to industrial production.
 Recovery of silver from waste fixing solution
After the photosensitive material is exposed, developed, and fixed, about 70-80% of the silver on the black and white film enters the fixing solution, and almost all the silver in the color film enters the fixing solution. The recovery of silver from waste fixing solution has received great attention at home and abroad, and a lot of research work has been carried out. The recovery methods used are ion precipitation, electrolysis, metal replacement, drug reduction, and ion exchange. The advantage of the electrolysis method is that the fixing solution after silver extraction can be returned for fixing. Larger film studios in mainland China all use this method of recycled silver.
Platinum Group Metal Recovery Technology
 Methods of recovering platinum in nitric acid plants
The platinum, palladium, and rhodium ternary alloy catalyst mesh used in the production of nitric acid, and most of the precious metals consumed in the production are deposited in the ash of the oxidation furnace. The Kunming Institute of Precious Metals and Taiyuan Fertilizer Plant cooperated in research. The process flow is as follows: furnace ash → iron capture reduction smelting → oxidation smelting → acid leaching → slag calcination → wet purification → platinum, palladium and rhodium ternary alloy powder. The direct yield of Pt, Pb, and Rh is 83%, the total yield is 98%, and the product purity is 99.9%. The recycling process of the old platinum mesh is simple. After the waste mesh is dissolved, purified, and reduced, it is then mixed into the wire-drawing mesh, and the recovery rate is>99%.
 Recycling of platinum in glass fiber industry
The Kunming Institute of Precious Metals proposed that the Pt, Rh, and Au alloy wastes should be deeply decomposed with aqua regia, the nitrate is converted to sodium salt, the hydrogen peroxide is reduced to separate the gold, the ion exchange is used to remove impurities, and the hydrazine hydrate is reduced to obtain pure Pt and Rh. The purity of platinum and rhodium products is 99%, and the recovery rate is 99%.
The Research Institute of Material Recycling has proposed a process for recovering platinum and rhodium from waste refractory bricks and glass slag by using the 'dolomite-soda ash mixed sintering method'. The waste refractory bricks are ball milled, melted, crushed in water, acid dissolved, filtered, and the filter residue is dissolved in aqua regia to remove nitrate and ion exchange; hydrazine hydrate is reduced to obtain platinum rhodium products. The total yield of platinum and rhodium is>99%, and the purity of the product is 99.95%. The institute combined with many years of production practice to propose a combined process of beneficiation and smelting to recover platinum and rhodium in waste refractory bricks, which reduces costs, shortens the process, and achieves better results.
 Recovery of platinum and palladium from spent catalyst
First, the method of dissolving precious metals, Kunming Institute of Precious Metals and Shanghai Petrochemical General Plant use high-temperature roasting, hydrochloric acid and oxidation leaching, zinc powder replacement, hydrochloric acid and oxidant dissolution, solid ammonium chloride immersion platinum, calcined to obtain pure platinum, product platinum purity 99.9%, the recovery rate is 97.8%. Has applied for a Chinese patent. Second, the Material Recycling Research Institute cooperated with the No. 5 Institute of the Ministry of Nuclear Industry to adopt the 'full melting method' leaching, ion exchange adsorption of platinum (or palladium), and the platinum recovery rate was>98%. The yield of palladium>97%. The purity of the products are all>99.95%. It has applied for a Chinese patent and used it in several factories. Third, the Material Recycling Research Institute and Yangzi Petrochemical Company cooperated to study the recovery of palladium from waste palladium-carbon catalysts. The spent catalyst is purified by carbon burning, chlorination leaching, ammonia complexation, acidification, and finally hydrazine hydrate reduction to obtain sponge palladium with a purity of>99.95%. A small amount of palladium in the waste liquid such as complexing residue is recovered by resin adsorption. Palladium recovery rate>98%. Has applied for a Chinese patent.
 Recovery of waste platinum and rhenium catalysts
First, the Material Recycling and Utilization Research Institute cooperated with Changling Refinery to adopt the method of 'full solution' leaching, ion exchange adsorption of platinum rhenium, and precipitation agent separation of platinum rhenium. Platinum recovery rate>98%, rhenium yield>93%, platinum-rhenium product purity>99.95%, tail liquid aluminum sulfate can be used as a raw material for the production of catalyst carriers. Second, Tsinghua University cooperates with Beijing Rare and Precious Metals Refinery. The platinum rhenium in the spent catalyst is recovered by the extraction method. The spent catalyst is dissolved with 40% sulfuric acid, the rhenium is extracted with 40% diisooctyl sulfoxide in the dissolving solution, the stripping solution is used to produce potassium rhenate, the sulfuric acid insoluble residue is burnt to remove carbon, the platinum is leached by acid, and the platinum leaching solution is subjected to 40% Diisooctyl sulfoxide extracts platinum, and the stripping solution reduces the platinum deposit. Platinum extraction rate>99%, back extraction rate>99%, platinum direct yield>97%, product platinum purity 99.9%; rhenium extraction rate>99%, counter-recognition rate>99%.
 Separation and purification of platinum and rhodium alloys
The Kunming Institute of Precious Metals proposed: the platinum-rhodium alloy is crushed with aluminum alloy, and the aluminum is leached with dilute hydrochloric acid to obtain fine platinum-rhodium powder, which is dissolved in hydrochloric acid and an oxidizing agent. The solution is extracted and separated with trialkyl phosphine oxide to separate platinum and rhodium, and rhodium is purified by ion exchange. The purity is 99.99%, and the recovery rate of rhodium is 92~94%. It has applied for a Chinese patent. Second, the Chengdu 208 plant introduced a set of platinum and rhodium separation equipment from Japan. The platinum yield is 98.5%, the rhodium yield is 95%, and the purity of platinum and rhodium products is equal.>99.95.
 Purification of osmium from osmium-iridium alloy waste
The East China Branch of the former China Material Recycling Corporation used oxygen combustion to separate osmium and iridium, lye absorbs osmium oxide, precipitates sodium sulfide, removes sulfur to obtain crude osmium, reoxidizes, absorbs hydrochloric acid, ammonium chloride precipitates, and reduces hydrogen. Take pure osmium powder, the recovery rate of osmium>98%. This method is suitable for waste materials containing 3%-8% osmium.
 Recovery of ruthenium from nib grinding waste
The flotation method is proposed to recover the nib grinding waste with 0.4% to 1% ruthenium. Sodium oleate is a flotation agent, 2# oil is a foaming agent, acidic medium. The obtained concentrate contains more than 5% ruthenium, the tailing contains less than 0.2% ruthenium, and the recovery rate of ruthenium is more than 90%.
 Recovery of palladium and copper from spent catalyst residue
First, the material recycling research institute uses Hcl-H2O2 two-stage countercurrent leaching, xanthate precipitation enrichment palladium and copper separation method to recover copper and palladium from waste catalyst sludge containing 0.8% Pd and 26.2% Cu. The recovery rate is Pd>98%, Cu>95%. Second, the Shenyang Institute of Mining and Metallurgy uses dilute Hcl copper leaching, iron replacement copper, oxidation roasting of the leaching residue, dilute aqua regia leaching, zinc powder replacement, crude palladium dichlorodiamine complex palladium purification method, palladium purity 99.99%. The recovery rate is>98%, and the copper yield is 92%.