In the production and use of gold or silver products, or gold or silver-containing products, a large amount of waste is generated and old products are used. The gold and silver grades of these waste materials are much higher than ore and the process is simple. It is also economically cost-effective and is therefore the second resource for extracting gold and silver.
The nature and shape of precious metal scrap vary widely, from solid to liquid; from metal plates to powder dust; some are close to pure metals, some are extremely low; some contain other metal impurities, some contain non- Metal impurities, sometimes mixed with some garbage, sundries, etc. Therefore, for professional recycling plants, waste collection must first be pretreated to become a high-quality material suitable for metallurgical processing, obtain high technical and economic indicators, and obtain high-quality metals.
In order to vigorously recycle precious metals from used raw materials, Johnson Marseille converted the gold refinery in Brinds, England, into a precious metal recycling plant specializing in waste materials in 1997. The plant is large, technologically advanced and capable. One of the recycling manufacturers dealing with various precious metal scraps, the waste disposal process is shown in Figure 1. The inside of the dotted line in the figure is the preprocessing and sampling process.
Figure 1 Johnson Marseille Chemical Company's flow chart for processing precious metal scrap
First, the pretreatment of waste materials
In the waste recycling plant, waste pretreatment includes the following processes.
(1) Weighing: The material is generally weighed in the future, for materials with high precious metal content, such as jewelry waste, utensils, enamel, profiles, etc. Accurate weighing is especially important. At present, the electronic scales are automatically weighed and accumulated at home and abroad.
(2) Primary selection: According to the appearance of the waste, the first selection is carried out by visual inspection, or by the grade of the waste. At the same time, remove debris, garbage and dust from the waste. Sorting is mainly done by hand.
(3) Classification: First, according to the type of precious metals contained, the materials are divided into gold-containing materials, silver-containing materials, other single precious metal materials and various precious metal materials. Or according to the characteristics of the material, it is further divided into magnetic materials, non-magnetic materials, low-grade materials, dust, garbage, liquid waste and various resin wastes, etc., so as to facilitate the recovery of sampling. However, some wastes have similar shapes, but their precious metal content may vary greatly. Therefore, the incoming materials should be carefully and carefully checked and classified. After sorting, mark the same material to avoid confusion.
Second, the sampling and analysis of waste
Pretreatment of the waste includes incineration, drying, grinding, sieving and mixing, followed by sampling. Sampling and composition analysis is a very important task for waste recycling plants. Sampling and analysis should be as representative as possible. Sampling, depending on the type, has different sampling methods. Table 1 shows the recycling business guide for gold-containing waste. Table 2 lists the gold content in various electronic industrial wastes. Table 3 lists the gold content in various alloys. The gold content in some gold-containing scraps is shown in Table 4. In addition, the gold content in various gold plating solutions is as follows: acidic gold plating solution 4 to 12 g/L, neutral gold plating liquid 4 g/L, and alkaline plating liquid 20 g/L. As well as gold-palladium catalyst is used in petrochemical 0.3% to 0.6%; platinum-based and palladium-based pulp slurry Waldo 85%. Thermocouples, platinum- iridium glass fiber leakage plates contain gold.
Table 1 Main gold-containing waste recycling business guide
Material type | Source | Pretreatment | Sampling method |
Polished sand | Silver work | dry | Mechanical mixing and sampling (bulk) Manual groove reducer (small batch) |
Ingot - silver, gold | Primary and secondary producers | Drill or saw into standard strips or smelting, deposition sampling | |
Gold scrap | Processing jewelry | Ibid. | |
Foundry waste - gold, silver | Processing jewellery and silver work | Melt into a sample block, drilled, crushed Cuttings, smelting, sediment sampling | |
Waste coins, coinage waste - gold, silver | Currency billet processor and mint | Melt, cast sample block, drill, crush Cuttings, smelting, sediment sampling | |
Concentrate-mining | Mining Company | dry | Mechanical mixing and sampling |
å©åŸš-platinum group metal | Laboratory, electronics and glass industries | Smelting, sediment sampling | |
Dental gold alloy | Processing dentistry and laboratory | Ibid. | |
Gold and silver alloy | Primary and secondary producers | Casting sample blocks, drilling and crushing cuttings | |
Drill cuttings - silver | Precious metal industry users Processing jewellery and silver work | Magnetic separation | Melt, cast sample blocks, drill, crush drill cuttings or smelting, grinding, sorting, separating, sediment sampling |
Debris | Precious metal industry users Precious metal smelter | Grinding and screening | Mechanical mixing and sampling (bulk), optional (small batch), smelting, drilling and sieving of metal particles |
Medal waste - gold, silver | Mint, billet processing | Smelting, sediment sampling | |
Milling chips - silver, gold, platinum group metals | Precious metal industry users Processing jewellery and silver work | Magnetic separation | Burning sample blocks, drilling and crushing drill cuttings, depositing samples or sawing, casting sample blocks and sawing samples |
Metal scrap of platinum group metals | Industrial users, processed jewelry | Drill or saw into a standard strip | |
Ceramic industry waste | Ceramic industry | Incineration, grinding, screening | Mechanical mixing and sampling (bulk) hand selection (small batch) |
Residue - gold, silver | Intermediate product collector, refiner | Dry and incinerate and sieve | Ibid. |
Residue - Platinum Group - High and Low Grade | Industrial users, semi-finished product collectors | Ibid. | Ibid. |
Electric contact waste - platinum group | Electric contact processor and user | Grinding and screening | Dissolve the sample block and saw it |
Electronic waste | electronics industry | Burning, grinding, screening | Various methods for special materials |
Slag - from smelting | Processing jewellery and silver work Precious metal smelter | Grinding and screening | Mechanical mixing and sampling (large batch), hand-selected (small batch) smelting, drilling and sieving out metal particles |
Laboratory utensils - platinum group | Laboratory, electronics industry | Ibid. | |
Lcmcl strips - gold, silver | Processing jewelry | Casting sample blocks, drilling, crushing drill cuttings | |
Slag, slag-silver and gold | Precious metal smelters, jewelry processing and silver work | Grinding and screening | Mechanical mixing and sampling (bulk) hand selection (small batch) |
Mud - silver and gold | Photographic, electroplating, semi-finished producers and refiners | Drying, grinding and sieving | Ibid. |
Chips - metal materials - gold, silver, platinum | Industrial users, processed jewellery and silver workers | Magnetic separation | Cast sample blocks, drill, crush drill cuttings or smelt. Drilling, sampling |
Cleaning materials - jewelry grinding | Processing jewellery and silver work | Incineration, grinding, screening | Mechanical mixing and sampling (large batch), hand selection (small batch) |
Car shavings - gold, silver, platinum group metals | Industrial users, processed jewellery and silver workers | Magnetic separation | Casting sample blocks, drilling, crushing Cuttings or smelting. Grinding, screening |
Note: The guide is taken from Lu Yiyuan, Bin Wanda, Precious Metallurgy, Central South University of Technology Press, P452~456, 1990.
Table 2 Gold content in various electronic components
Scrap name | Model specification | Use | Unit | ω(Au)/g |
锗 Ordinary diode Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Silicon rectifier component Thyristor rectifier Thyristor rectifier Thyristor rectifier Thyristor rectifier Thyristor rectifier Thyristor rectifier Thyristor rectifier Thyristor rectifier Silicon rectifier diode Silicon rectifier diode Silicon steady voltage diode Silicon double-base diode Silicon double-base diode Silicon double-base diode Silicon high frequency small power transistor Frequency low power Silicon high frequency power High frequency transistor cap High frequency transistor cap Low frequency and high power Low frequency and high power Low frequency and high power High frequency transistor transistor holder High frequency transistor transistor holder High frequency and low power High frequency small power switch Reed relay Silicon single NAND gate Black and white video tape recorder Transistor three-tone record player Mercury vapor analyzer Trace oxygen analyzer | 2AP1～30 2CZ1A～11 2CZ1A 2CZ5A 2CZ20A 2CZl00A 2CZ200A 2CZ300A 2CZ500A 2CZ600A 2CZ700A 2CZ800A 2CZl000A 2CZl200A 2CZl500A 3CT5A 2CZ20A 2CT50A 2CT200A 2CT5A 2CZl0A 2CZ20A 2CZ50A 2CP6A-6K, 10-2, 41-60 2CP1A-2, 21-29, 31-33 2CW21A-S22A -W1-59-20 BT32-33 BT31 BT31-35 3DG 3DG4.6, 8.3DK 2 3DG401-410, 3DK 4 Figure non-30 Figure non-32 3DD50.75 3DD300 3DD150G 4 F 6 B 1 P 6 3AG-1-50 3AG-1-50 AJAg 5TZ14.2, 72 CDLS-1 SD-1 UGY SXE1 type | Gold wire lead Gold antimony films Kim Min Kim Min Kim Min Gold film Gold film Gold film Gold film Gold film Gold film Gold film Gold film Gold film Gold film Gold bismuth , gold boron palladium Gold bismuth, gold boron palladium Gold bismuth, gold boron palladium Steamed gold, gold boron palladium Gold film Gold film Gold film Gold film Gold film Gold film Gold film Steamed gold, gold wire lead Steamed gold, gold wire lead Gold wire, gold enamel Gold plated, gold wire, steamed gold Gold plating, steaming gold hot pressing Gold plating, steaming gold hot pressing Electroless gold plating Electroless gold plating Steamed gold, gold plated, gold wire Steamed gold, gold plated, gold wire Steamed gold, gold plated, gold wire Electroless gold plating Electroless gold plating Gold and silver alloy Gold and silver alloy Gold plated piece Electroplating gold Gold silk platinum Gold nickel contact Gold piece gold wire Gold piece gold wire | Ten thousand support Million Million Million only only only only only only only only only only Ten thousand Ten thousand Ten thousand only only only only Ten thousand Ten thousand Ten thousand Ten thousand Ten thousand Ten thousand Ten thousand Ten thousand Ten thousand 10,000 only 51 Ten thousand Ten thousand Million Million Million support support Million Million Million 4 station station station station | 2 0.04 43.847 128.75 397.68 0.35 0.4 0.5 0.64 0.7 0.78 0.8 1.0 1.5 2.2 93.76 401.71 919.789 838 0.02 0.03 0.04 0.17 23.47 48.5 48.5 6.27 4 3.8 10.5 52 10 13 400 800 1.400 10.24 20.48 0.5 0.5 60 60.2 1.85 0.1 1.5 15 |
Note: The data in this table are taken from Lu Yiyuan, Bin Wanda, Precious Metallurgy, Central South University of Technology Press, P457~459, 1990.
Table 3 Main components of various alloys
Gold alloy name | Brand | chemical composition/% |
Copper alloy of gold and silver Gold, silver alloy of gadolinium Gold, silver and copper alloy Gold, silver and copper manganese alloy Gold, silver, copper and manganese alloy Gold, silver, copper, manganese and nickel alloy Gold nickel copper alloy Gold nickel chrome Gold nickel chrome Gold nickel chrome Gold nickel chrome Gold nickel chrome Gold nickel chrome tantalum alloy Gold nickel chrome tantalum alloy Au-Pd alloy, iron-aluminum | AuAgCu35-5 AuAeCuGd35-5-0.5 AuAgCuGd35-10-0.5 AuAgCuMn33.5-3-3 AuAgCuMnGd33.5-3-2.5-2 AuAgCuMnNi33.5-3-2.5-2 AuNiCu7.5-1.5 AuNiCr5-1 AuNiCr5-1.25 AuNiCr6-2 AuNiCr3.5-2.5 AuNiCr7-0.6 AuNiCrGd7-0.5-0.4 AuNiCrRh7-0.6-0.4 AuPdFeA138-8.5-1 | Au60, Ag35, Cu5 Au59.5, Ag35, Cu5, Gd0.5 Au54.5, Ag35, Cu10, Gd0.5 Au61.5, Ag33.5, Cu3, Mn3 Au59, Ag33.5, Cu3, Mn2.5, Gd2 Au59, Ag33.5, Cu3, Mn2.5, Ni2 Au91, Ni7.5, Cu1.5 Au94, Ni5, Cr1 Au93.75, Ni5, Cr1.25 Au92, Ni6, Cr2 Au94, Ni3.5, Cr2.5 Au92.4, Ni7, Cr0.6 Au92.1, Ni7, Cr0.5, Gd0.4 Au92, Ni7, Cr0.6, Rh0.4 Au52.5, Pd38, Fe8.5, Al1 |
Note: The data in this table are taken from Lu Yiyuan, Bin Wanda, Precious Metallurgy, Central South University of Technology Press, P459, 1990.
Table 4 Gold content in some gold-containing wastes
Scrap name | ω(Au)/% |
Copper plated Gold plated triode Gold plated flat Double tube Gold-containing resin Gold-plated circuit board Gold plated wire Golden mud Gold plated wall panel Tin-antimony alloy containing gold Wang Shui non-slag | 0.18~3.84 0.03 to 0.3 0.2 to 2.68 0.22 2.93~15.6 0.08~0.14 3.13~7.80 32.59 1.43 79.71 1.0 to 2.0 |
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