First, the gold recycling technology [1] from the gold relics of the cultural relics recycling gold materials recycling research institute using the oxidizing roasting method to recover the gold from waste gold relics. Scrapped gold cultural relics were placed in a special roaster, oxidized and calcined at 1000C for 30 minutes, removed into water, and affixed to the copper oxide scale on the copper oxide scale to separate from the copper matrix. Then dissolved with dilute sulfuric acid, dissolved slag to separate and purify gold. This method is characterized by non-polluting waste gas when roasting. In this method, 300 kilograms of waste cultural relics are treated and 1.5 kilograms of gold is recovered. The gold recovery rate is >98% and the matrix copper recovery rate is >95%. By-product copper sulfate can be used as an insecticide. [2] Recovery of waste gold from waste electronic components Beijing Idebarium Metals and Metallurgical Plant uses the I2-Nal-H2O system. Corrosion of the gold plating on the waste components, and the replacement of gold with iron or sodium sulfite reduction. Acidification with sulfuric acid, potassium chlorate oxidation iodine regeneration. The Institute of Materials Recycling and Utilization researched a new process for electrolytic gold withdrawing. Thiourea and sodium sulfite were used as the electrolyte, graphite was used as the cathode plate, and gold-plated scrap was used as the anode for electrolytic gold evacuation. After electrolysis, gold on the plated layer is anodized with Au+ and forms a complex cation Au[cs(NH2)]2+ with thiourea, which is then reduced to gold by sodium sulfite and settled at the bottom of the tank. The gold precipitate is separated and purified. Pure gold powder. Base material can recover nickel and cobalt. The recovery rate of this process gold is 97~98%. Product gold purity > 99.95%. [3] Recovery of Gold and Palladium from Waste Catalyst Kunming Institute of Precious Metals uses hydrochloric acid and oxidant for multiple leaching to allow gold and palladium to enter the solution, zinc powder replacement, hydrochloric acid and oxidant dissolution, and oxalic acid reduction to obtain pure gold powder; reducing mother liquor using conventional methods Purify palladium. The purity of gold and palladium can reach 99.9%. The recoveries were 97% and 96%, respectively. Has applied for a Chinese patent.
Second, the silver recycling technology [1] Electrolytic silverback new technology Materials recycling Institute designed its own electrolytic silver relief equipment, graphite plate as the cathode, stainless steel roller as the anode, there are many fine holes in the drum. Sodium citrate and sodium sulfite are the electrolytes. Silver plated parts enter from the first end of the drum and are sent out from the end of the drum. The silver on the surface of the plating enters the electrolyte, and the substrate of the plating is intact and can be used for re-plating. The silver recovery rate is 97-98%, and the purity of silver powder is 99.9%. [2] Waste Silver—Recycling of zinc batteries Waste silver zinc batteries contain 52.55% silver and 42.7% zinc. Zinc is a negative electrode, and silver oxide is a positive electrode coated on a copper mesh skeleton. The Research Institute for Recycling of Materials adopts dilute sulfuric acid for dipping zinc and copper respectively, and silver powder directly melts. When dilute sulfuric acid is immersed in copper, an oxidant is added, and the zinc-containing liquid is condensed and crystallized to produce zinc sulfate, and the copper-containing liquid is condensed and crystallized to produce copper sulfate. The zinc recovery rate was >98%, the silver recovery rate was 98%, and the silver ingot purity was >99%. [3] Recovering Silver from Waste Film Kunming Institute of Precious Metals uses a thin layer of sulfuric acid to elute a silver-containing emulsion layer on a color film, and a chlorine salt heats and precipitates the silver halide, chlorination or organic solvents to remove organic substances, and the alkaline medium uses sugar. The solid suspension was reduced to pure silver. Silver purity 99.9%, straight yield 98%. This law has applied for a patent. The Research Institute for Recycling of Materials (formerly the Ministry of Internal Trade Materials Recycling and Utilization Research Institute) used sodium thiosulfate solution to dissolve the silver halide on the waste film. The inhibitor was added during dissolution to prevent the dissolution of gelatin on the film. The solution was electrolyzed to recover silver. Film base recycling. The silver leaching rate was >99%, the recovery rate was 98%, and the silver purity was 99.9%. This method has been applied to industrial production. [4] After the silver sensitized material is recovered from the waste fixer after exposure, development, and fixing, about 70-80% of the silver on the black and white film enters the fixer, and almost all the silver of the color film enters the fixer. Silver is recovered from the waste fixer and highly valued at home and abroad. A large amount 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 electrolysis is that the fixer after silver extraction can be returned for fixing. Mainland larger movie studios use recycled silver from this method.
III. Recovery of platinum group metals [1] Recovery of platinum from nitric acid plant The catalytic alloys of platinum, palladium and rhodium are used in nitric acid production. Most of the precious metals that are consumed during production are deposited in the ash of the oxidizing furnace. Kunming Institute of Precious Metals and Taiyuan Chemical Fertilizer Co., Ltd., the process flow is as follows: furnace ash → iron trapping reduction smelting → oxidizing smelting → acid leaching → slag calcination → wet purification → platinum-palladium-tantalum ternary alloy powder. The yield of Pt, Pb and Rh is 83%, the total yield is 98%, and the product purity is 99.9%. The recovery technology of the old platinum nets is simple. The waste nets are dissolved, purified, and then reduced and then the ingredients are drawn and woven. The recovery rate is >99%. [2] The recovery of platinum in glass fiber industry Kunming Institute of Precious Metals proposes that Pt, Rh, and Au alloy waste be aqua resolved with aqua regia, and sodium nitrate be converted, hydrogen peroxide be reduced to separate gold, ion-exchange besides impurities, and hydrazine hydrate be recovered. Pure Pt, Rh. Platinum rhodium product purity 99%, recovery rate of 99%. The Institute for Recycling of Materials proposed a process for recovering platinum rhodium from waste firebricks and glass slag using a "dolomite-soda ash mixed sintering method." The waste refractory bricks were ball-milled, melted, crushed, sour-dissolved, filtered, and the filter residue was dissolved in aqua regia. The nitrates were removed and ion exchange was performed. The hydrazine hydrate was reduced to obtain the platinum-rhenium product. The total platinum rhodium yield is >99% and the product purity is 99.95%. The Institute has combined many years of production practices to propose a joint smelting and scraping method for recycling platinum crucibles in waste refractory bricks, reducing costs, shortening processes, and receiving better results. [3] Recovery of platinum and palladium from waste catalysts, dissolution of precious metals, Kunming Institute of Precious Metals and Shanghai Petrochemical Plant adopt high-temperature roasting, hydrochloric acid plus oxidation leaching, zinc powder replacement, hydrochloric acid and oxidant dissolution, solid ammonium chloride precipitation Platinum, calcined pure platinum, product purity of 99.9% platinum, the recovery rate of 97.8%. Has applied for a Chinese patent. Second, the Institute for the Recycling of Materials and the Ministry of Nuclear Industry cooperated with the “full-melt method†for leaching and ion exchange for the adsorption of platinum (or palladium). The platinum recovery rate was >98%. The yield of palladium is >97%. The product purity is >99.95%. Has applied for a Chinese patent and used it in several factories. Thirdly, the Research Institute of Materials Recycling and the Yangzi Petrochemical Company cooperated to study the recovery of palladium from spent palladium carbon catalysts. The spent catalyst was burned with carbon, leached with chlorination, complexed with ammonia, purified with acidification, and the final hydrated thorium was recovered to a purity of >99.95% sponge-palladium. A small amount of palladium in the slag solution was recovered by resin adsorption. Palladium recovery was >98%. Has applied for a Chinese patent. [4] Waste platinum and ruthenium catalyst recycling First, the Institute of Materials Recycling and the Changling refinery cooperation, the "all-solution" leaching, ion exchange adsorption platinum crucible, precipitant separation method platinum crucible. The platinum recovery rate is >98%, the indole yield is >93%, and the purity of the platinum and rhodium products is >99.95%. The tailing aluminum sulfate can be used as a catalyst carrier material. Second, Tsinghua University cooperates with Beijing Rare and Precious Metals Refinery. Platinum rhodium in the spent catalyst was recovered by extraction. The spent catalyst was dissolved with 40% sulfuric acid, the solution was extracted with 40% diisooctyl sulfoxide, the stripping solution was used to produce potassium citrate, the insoluble residue of sulfuric acid was burned to remove carbon, the acid-soluble leached platinum, and the solution of platinum solubilized by 40%. Iso-iso-octyl sulfoxide extracts platinum, and stripping liquid reduces platinum. The extraction rate of platinum is >99%, the stripping rate is >99%, the platinum yield is >97%, the purity of the product platinum is 99.9%, the extraction rate of rhenium is >99%, and the recognition rate is >99%. [5] Platinum-rhodium alloy separation and purification Kunming Institute of Precious Metals: Aluminum alloy for platinum-bismuth alloy "shredded, dilute hydrochloric acid leaching of aluminum, to obtain fine platinum rhodium powder, hydrochloric acid and oxidant dissolved, solution with trialkyl phosphine oxide extraction and separation of platinumé“‘ é“‘ 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å 离å é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ é“‘ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶ å…¶95% purity of platinum-rhodium products >99.95 [6] Purification from niobium-alloy scrap Ebara China Resources Recycling and Utilization Corporation East China Branch Co., Ltd. adopts oxygen combustion to separate strontium, lye absorbs niobium oxide, and sodium sulfide precipitates. Sulfur is crude, reoxidized, absorbed by hydrochloric acid solution, precipitated by ammonium chloride, and reduced by hydrogen to produce pure tantalum powder, and the recovery rate of tantalum is >98%.This method is suitable for the waste containing 3%~8% of tantalum.[7] Recycling of niobium in nib grinding wastes East China Branch proposed the recovery of pen tip grinding waste containing 0.4% to 1% of niobium by flotation, with sodium oleate as the flotation agent and 2# as the foaming agent and acidic medium. Concentrates containing more than 5% of lanthanum, tailings containing lanthanum <0.2%, thorium recovery> 90% [8] from spent catalyst slag Recovery of palladium and copper First, the Institute of Materials Recycling uses the Hcl-H2O2 two-stage countercurrent leaching, and the xanthate precipitation enrichment method for palladium and copper separation recovers copper from spent catalyst sludge containing Pd0.8% and Cu26.2%. Palladium recovery rate Pd> 98%, Cu> 95% [20] Second, Shenyang Institute of Mining and Metallurgy dilute Hcl immersion copper, iron replacement copper, leach slag oxidation roasting, leaching of rare earth water, zinc powder replacement, crude palladium It was purified by dipalladium dipalladium method, the purity of palladium was 99.99%, the recovery rate was >98%, and the copper yield was 92%.