| As the Information Age gains momentum, the amount of waste printed circuit boards is increasing rapidly in recent years. Waste printed circuit board is composed of many common metals, including copper, aluminum, zinc, iron and nickel, and certain amount of noble metals, including gold, silver, palladium, and platinum, which have a good recycling value because their content in waste circuit board is much higher than those in natural rocks or minerals. In the study of our project, which relates to the new methods of recycling platinum group metals in waste circuit boards, the methods for the determination of all metals in waste printed circuit board and the determination of platinum and palladium in noble metal smelting remainder of waste printed circuit board need to be established.The direct ICP-AES has been developed for determination of 14 metals in waste printed circuit board. Also, iodimetry is the assisting method for the determination of copper and flame atomic absorption spectrometry(FAAS) for the determination of gold and silver. After removing the organic part of waste circuit board by vacuum pyrolysis, ICP-AES was directly used to analyze 14 metals. The matrix was matched to calibration curve in order to remove the matrix interference for the direct determination. The analysis wavelength of each element was optimized. The lower detection limits were determinate. The relative standard deviations of the ICP-AES method were less than 3.7%. The recoveries were 91-107%. The relative standard deviations of FAAS for gold and silver were less than 3.5%, with recovery 95.8% for gold and 93.6% for silver.The method was established on the determination of platinum in lead samples by ICP-AES after separated and enriched by vacuum distillation. Under the condition of vacuum, platinum and lead can be separated at a high temperature because of their different vapor pressures. The enriched platinum was determined by ICP-AES after dissolved, and also lead was recovered in vacuum. Theoretic feasibility of the vacuum distillation method and the influence factors such as temperature, time and pressure have been studied in this paper. The results indicated that content of platinum in residue is higher than 99.01% under the condition of temperature of 1250 K, pressure of 30 Pa and time of 3 hours. The detection limit (3σ) was 0.0069mg/L with relative standard deviations of 1.7%. It was obtained a wide linear range of 0.023-20mg/L and the recovery is 99.8%～103.0%.The method was developed for the sequential determination of platinum and palladium by N,N'-Didodecyl Dithiooxamide(DDO) spectrophotometry after separated and enriched by vacuum distillation. Under the condition of vacuum, lead, zinc, platinum and palladium can be separated at a high temperature because of their different vapor pressures. The enriched platinum and palladium were determined sequentially by the DDO method, and also lead and zinc were recovered in vacuum. Theoretic feasibility of the vacuum distillation method was studied according to the feature of the sample and the experiment conditions were optimized. The results indicated that zinc and lead can be totally removed under the condition of 6 Pa of vacuity,900℃of temperature and 2 hours of distillation duration. The relative standard deviations of the method were less than 5%.The recoveries were 93.3%～113.3% for platinum and 99.2%～107.4% for palladium. |
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