Both of them are higher than gold, but the output is only 1/20 of gold. It is a precious metal with good chemical stability, which is rarer and more valuable than gold, and has more value of maintaining and increasing value. Platinum ornaments are very popular in recent years, especially platinum inlaid ornaments are loved by people. Recovery of Gold from Gold-plated Cultural Relics Copper The Institute of Renewable Materials used oxidation roasting to recover gold from waste gold-plated cultural relics copper. The waste copper of gold-plated cultural relics is put into a special roasting furnace, oxidized and roasted at 800℃ for 30 minutes, and then taken out and put into water. The gold-plated layer is attached to the copper oxide scale and separated from the copper matrix. Then dissolving with dilute sulfuric acid, and separating and purifying the dissolved residue. The characteristic of this method is that there is no waste gas pollution in the roasting process. 300 kg of copper scrap was treated by this method, and gold 1.5 kg was recovered. Gold recovery rate >; 98%, the recovery rate of matrix copper >; 95%, by-product copper sulfate can be used as insecticide.
Recovery of gold from waste electronic components The I2-Nal-H2O system was adopted in Beijing Rare Metal Chemical Metallurgical Plant. The gold coating on waste parts was corroded, and gold was recovered by iron replacement or sodium sulfite reduction. Acidizing with sulfuric acid and oxidizing with potassium chlorate to regenerate iodine. The Institute of Material Recovery has developed a new process for extracting gold by electrolysis. Using thiourea and sodium sulfite as electrolyte, graphite as cathode plate, and gold-plated waste as anode, electro-gold removal was carried out. Through electrolysis, the gold on the plating layer is anodized to Au+, and then forms a complex cation Au[cs(NH2)]2+ with thiourea, and then is reduced to gold by sodium sulfite, which is deposited on the bottom of the plating solution, and the gold-containing precipitate is separated and purified to obtain pure gold powder. Matrix materials can recover nickel and cobalt. The recovery rate of gold in this process is 97~98%. Gold purity of products >; 99.95%。
[3] Recovering Gold and Palladium from Spent Catalyst Kunming Precious Metals Research Institute used hydrochloric acid and oxidant to leach for many times, so that gold and palladium entered the solution, zinc powder was replaced, hydrochloric acid and oxidant were dissolved, and oxalic acid was reduced to obtain pure gold powder; Palladium was purified from reduction mother liquor by conventional method. The purity of gold and palladium can reach 99.9%. The recovery rates were 97% and 96% respectively. China patent has been applied. [1] The Institute of Material Recovery, a new technology of electro-stripping silver, designed its own electro-stripping silver equipment, with graphite plate as cathode and stainless steel drum as anode, and there were many fine holes on the drum. Sodium citrate and sodium sulfite are electrolytes, and the silver-plated part enters from the head end of the drum and is sent out from the tail 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 for re-electroplating. The recovery rate of silver is 97-98% and the purity of silver powder is 99.9%.
[2] Recycling of waste silver-zinc batteries The waste silver-zinc batteries contain 52.55% silver and 42.7% zinc. Zinc is used as a negative electrode, and silver oxide is used as a positive electrode to coat the copper mesh skeleton. The materials are recovered by dipping zinc and copper in dilute sulfuric acid respectively, and the silver powder is directly melted into ingots. When copper is leached with dilute sulfuric acid, oxidant is added, zinc-containing solution is concentrated and crystallized to generate zinc sulfate, and copper-containing solution is concentrated and crystallized to generate copper sulfate. Zinc recovery rate >; The recovery rate of silver is 98%, and the purity of silver ingot is >: 99%.
[3] Recycling Silver from Waste Film Kunming Precious Metals Research Institute used dilute sulfuric acid solution to elute the silver-containing emulsion layer on color film, heated chlorine salt to precipitate silver halide, chlorinated and dried or washed with organic solvent to remove organic matter, suspended in alkaline medium, and reduced with sugar solid to obtain pure silver. The purity of silver is 99.9% and the direct yield is 98%. This law has been patented. The Institute of Material Recycling (formerly the Institute of Material Recycling of the Ministry of Internal Trade) used sodium thiosulfate solution to dissolve the silver halide on the waste film. During the dissolution process, an inhibitor was added to prevent the gelatin on the film from dissolving. The silver in the solution is recovered by electrolysis, and the substrate is recycled. Silver leaching rate >; The recovery rate is 98% and the purity of silver is 99.9%. This method has been applied to industrial production. [4] After exposure, development and fixing, about 70-80% of the silver in 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 been paid great attention to at home and abroad, and a lot of research work has been done. The recovery methods used include ion precipitation, electrolysis, metal replacement, drug reduction and ion exchange. The advantage of electrolysis is that the fixing solution after silver extraction can be returned for fixing. Large film studios in Chinese mainland use this method to recycle silver. [1] method for recovering platinum in nitric acid plant; ternary alloy catalyst net of platinum, palladium and rhodium is used in nitric acid production, and most of the precious metals consumed in production are deposited in oxidation furnace ash. Study on cooperation between Kunming Precious Metals Research Institute and Taiyuan Chemical Fertilizer Plant. 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 platinum, lead and rhodium is 83%, the total yield is 98%, and the product purity is 99.9%. The recycling process of old platinum net is simple. After dissolving, purifying, reducing, blending, stretching and weaving, the recovery rate of waste net is more than 99%.
[2] Recovery of Platinum in Glass Fiber Industry Kunming Precious Metals Research Institute proposed that pure platinum and rhodium can be obtained by hydrolyzing alloy wastes of platinum, rhodium and gold with aqua regia to convert nitrate into sodium salt, then reducing and separating gold with hydrogen peroxide, removing impurities with ion exchange and reducing with hydrazine hydrate. The purity of platinum and rhodium products is 99% and the recovery rate is 99%. The Institute of Material Recycling proposed the process of recovering platinum and rhodium from waste refractory bricks and glass slag by "dolomite-soda mixed sintering method". Ball milling, melting, water crushing, acid dissolving and filtering the waste refractory bricks, dissolving the filter residue with aqua regia, removing nitrate and carrying out ion exchange; Hydrazine hydrate is reduced to obtain platinum and rhodium products. The total yield of platinum and rhodium is >: 99%, and the purity of the product is 99.95%. Combined with many years' production practice, the institute put forward a method combining separation and metallurgy to recover platinum and rhodium from waste refractory bricks, which reduced the cost, shortened the process and achieved good results.
[3] One of the methods to recover platinum and palladium from waste catalyst is to dissolve precious metals. Kunming Institute of Precious Metals and Shanghai Petrochemical Complex adopt high-temperature roasting, hydrochloric acid plus oxidation leaching, zinc powder replacement, hydrochloric acid plus oxidant dissolution, solid ammonium chloride precipitation of platinum, and calcination to obtain pure platinum. The purity of platinum product is 99.9% and the recovery rate is 97.8%. China patent has been applied. Secondly, the Institute of Material Recovery cooperated with the Fifth Research Institute of the Ministry of Nuclear Industry, and adopted the "all-melting method" to leach and adsorb platinum (or palladium) through ion exchange. The recovery rate of platinum was >: 98%. The yield of palladium is > 97%, and the product purity is >; 99。 95%。 China patent has been applied for use in many factories. Thirdly, the Institute of Material Recycling cooperated with Yangzi Petrochemical Company to study the recovery of palladium from waste palladium-carbon catalyst. The spent catalyst was purified by charcoal burning, chlorination leaching, ammonia complexation, acidification and other steps, and finally the purity was obtained by hydrazine hydrate reduction. The recovery rate of palladium is more than 98%. China patent has been applied.
[4] The waste Pt-Re catalyst 1 species was recovered, and the Institute of Material Regeneration cooperated with Changling Refinery to separate Pt-Re by "full solution" leaching, Pt-Re ion exchange adsorption and precipitant. Platinum recovery rate >; 98%, rhenium yield >; The purity of platinum and rhenium products is >: 99.95%, and the tail liquid aluminum sulfate can be used as raw material for producing catalyst carrier. Second, Tsinghua University cooperates with Beijing Rare and Precious Metals Refinery. Recovery of platinum and rhenium from spent catalyst by extraction. Dissolve waste catalyst with 40% sulfuric acid, extract rhenium in solution with 40% diisooctyl sulfoxide, produce potassium rhenate with stripping solution, remove carbon from sulfuric acid insoluble residue through combustion, leach platinum with acid, extract platinum with 40% diisooctyl sulfoxide in leaching solution, and reduce and precipitate platinum with stripping solution. Extraction rate of platinum >: 99%, stripping rate >; 99%, the direct yield of platinum >; The purity of product platinum is 99.9%; The extraction rate of rhenium is over 99%, and the negative recognition rate is over 99%.
[5] Separation and purification of Pt-Rh alloy Kunming Precious Metals Research Institute proposed that Pt-Rh alloy was crushed with aluminum alloy, aluminum was leached with dilute hydrochloric acid to obtain Pt-Rh fine powder, which was dissolved with hydrochloric acid and oxidant, and the solution was extracted with trialkyl phosphine oxide to separate Pt-Rh, and rhodium was purified by ion exchange. The purity of rhodium is 99.99%, and the recovery rate of rhodium is 92~94%. China patent has been applied. Secondly, Chengdu 208 Factory imported a set of platinum and rhodium separation equipment from Japan. The platinum yield was 98.5%, the rhodium yield was 95%, and the purity of platinum and rhodium products was >: 99.95.
[6] Purification of Osmium from Iridium Alloy Waste; East China Branch of China Material Recovery Corporation used oxygen to separate Osmium and Iridium, alkali solution absorbed osmium oxide, sodium sulfide precipitation, desulfurization to obtain crude osmium, reoxidation, hydrochloric acid solution absorption, ammonium chloride precipitation, hydrogen reduction to prepare pure osmium powder, and the recovery rate of osmium. 98%。 This method is suitable for waste containing 3%~8% osmium.
[7] Recovering ruthenium from nib grinding waste East China Branch proposed to recover nib grinding waste with ruthenium content of 0.4%~ 1% by flotation. Sodium oleate as flotation agent, 2# oil as foaming agent and acid medium. The obtained concentrate contains more than 5% ruthenium, and the tailings contain ruthenium; 90%。
[8] Recovering one of palladium and copper from waste catalyst residue. In the Institute of Material Regeneration, two-stage countercurrent leaching with Hcl-H2O2 was used to separate palladium and copper, and the copper and palladium were recovered from the waste catalyst residue containing 0.8% PD and 26.2% Cu. The recovery rate of Pd & gt98% and copper & gt95%[20]. Secondly, Shenyang Institute of Mining and Metallurgy used dilute Hcl to leach copper, iron to replace copper, leaching residue was oxidized and roasted, dilute aqua regia was leached, zinc powder was replaced, and crude palladium was purified by palladium dichloride complexation method, and the purity of palladium was 99.99%. The recovery rate is over 98%, and the copper yield is 92%.