The next step in E-waste recycling is recovery. The three main technologies used in recovery are: (i) Pyrometallurgy (ii) Hydrometallurgy and (iii) Electrometallurgy. Pyrometallurgy has been a traditional technology for recovery of precious metals from waste electronic equipment. The technology uses high temperatures that include smelting and roasting to chemically convert the feed materials and separate metals and impurities into different phases so valuable metals can be recovered. Pyrometallurgy involves heating in a blast furnace at temperatures above 1500°C to convert waste to a form that can be refined. The oxide waste is heated with a reducing agent, such as carbon in the form of coke or coal; the oxygen of the metal combines with the carbon and is removed in carbon dioxide gas. The waste material in E-waste (non-metallic parts) is called gangue; it is removed by means of a substance called a flux which, when heated, combines with it to form a molten mass called slag. Being lighter than the metal, the slag floats on it and can be skimmed or drawn off. Examples of technical hardware are submerged lance smelters, converters, rotary furnaces, electric arc furnaces etc (Cui & Zhang, 2008; UNEP, 2007). Hydrometallurgy, sometimes called leaching, involves the selective dissolution of metals from their waste. Hydrometallurgical processing techniques use strong acidic or caustic watery solutions to selectively dissolve and precipitate metals. Metal is recovered by electrolysis of the solution. If metal obtained from waste still contains impurities, special refining processes
The next step in E-waste recycling is recovery. The three main technologies used in recovery are: (i) Pyrometallurgy (ii) Hydrometallurgy and (iii) Electrometallurgy. Pyrometallurgy has been a traditional technology for recovery of precious metals from waste electronic equipment. The technology uses high temperatures that include smelting and roasting to chemically convert the feed materials and separate metals and impurities into different phases so valuable metals can be recovered. Pyrometallurgy involves heating in a blast furnace at temperatures above 1500°C to convert waste to a form that can be refined. The oxide waste is heated with a reducing agent, such as carbon in the form of coke or coal; the oxygen of the metal combines with the carbon and is removed in carbon dioxide gas. The waste material in E-waste (non-metallic parts) is called gangue; it is removed by means of a substance called a flux which, when heated, combines with it to form a molten mass called slag. Being lighter than the metal, the slag floats on it and can be skimmed or drawn off. Examples of technical hardware are submerged lance smelters, converters, rotary furnaces, electric arc furnaces etc (Cui & Zhang, 2008; UNEP, 2007). Hydrometallurgy, sometimes called leaching, involves the selective dissolution of metals from their waste. Hydrometallurgical processing techniques use strong acidic or caustic watery solutions to selectively dissolve and precipitate metals. Metal is recovered by electrolysis of the solution. If metal obtained from waste still contains impurities, special refining processes
7._Complete_Thesis.docx