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Resources 2014, 3 163 logical to send e-waste to smelters that accept copper/lead scrap. Currently, copper and lead smelters work as e-waste recyclers for the recovery of Pb, Cu and PMs. In these pyrometallurgical processes, e-waste/copper/lead scrap is fed into a furnace, whereby metals are collected in a molten bath and oxides form a slag phase. More details about the lead and copper smelting routes are explained in the next sections. 2.1.2.1. Lead Smelting Route Primary lead is produced from sulfide ores containing iron, zinc, copper, PMs, and other trace elements. The concentrated ore and e-waste is treated for the extraction of lead and PMs. The process consists of sintering (ores), reduction and refining stages. Sintering is carried out to reduce the sulfur contents of feed material that is composed of pyrite, lime rock, silica and high concentrated lead. The reduction process is conducted in blast furnaces with the help of coke where molten lead with about 85% purity is tapped from the bottom of the furnace. The plastics fraction of e-waste can partially replace coke as a reducing agent during the reduction stage, and the metals fraction ends up in the metal phase. In the refining stage, copper dross is skimmed off from the lead dross and is treated in a reverberatory furnace. The lead dross is processed by adding wood chips, fine coke and sulfur. The sulfur dross produced is separated and transferred to the reverberatory furnace. The heating of lead dross in the reverberatory furnace separates the lead bullion (rich in lead), matte (copper and other metals sulfides) and speiss (high in arsenic and antimony contents). Matte and speiss are treated in copper smelters for the extraction of copper and other associated metals [58]. In the last stage of e-waste processing via the lead smelting route, PMs and other elements are separated from the lead bullion. PMs are separated by the Parkes process, in which zinc forms an insoluble intermetallic compound with gold and silver. Other impurities including antimony, tin, arsenic, bismuth, and trance elements are also separated during the refining stage. Final products of refining stage include metallurgical grade lead (99.99%), PMs and other elements [58]. 2.1.2.2. Copper Smelting Route Primary and secondary copper smelting routes are adopted to recycle and extract PMs from e-waste. It is reported that copper smelting routes are more environmentally friendly compared to lead smelters that generate toxic fumes [36]. Copper smelting facilities near populations will minimize the cost of e-waste transportation and therefore the recycling economy will be improved. These advantages allow copper smelters to be installed near cities where e-waste is generated. In these processes, PMs are recovered via a conventional electrorefining process where they are segregated in slimes [59]. Commonly, copper smelting routes including matte and black copper are used for e-waste recycling. In the sulfur-based route (primary copper smelting), copper matte (40%) and blister copper (98.5%) are produced. Finally, blister copper is refined by fire refining to produce pure copper. In the black copper route (secondary copper smelting), crude copper is produced during a reduction process and is refined by oxidation in a converter. The black copper is an attractive route because it can receive high levels of impurities including Fe, Zn, Pb and Sn. These impurities are removed by oxidation as shown in Figure 3. The black copper smelting process consists of reduction and oxidation cycles. Impurities are mostly segregated into the vapor phase and are discharged in the off gas [36].PDF Image | Metal Extraction Processes for Electronic Waste
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