- 學位論文
利用微波裂解回收廢印刷電路板之貴金屬
Precious Metals Recovery from Waste Printed Circuit Board Using Microwave Pyrolysis
摘要
近年來，隨著手機市場的蓬勃發展，汰舊換新的速度過快，導致手機中的印刷電路板廢棄問題日益嚴重，稀有金屬的需求量亦不斷增加。手機中的印刷電路板其成分複雜，含有超過50種金屬組成，其中包含貴金屬金、鈀以及銀等，其他金屬如銅、鈣以及錫等亦佔大多數。然而在處理廢棄印刷電路板時，處理流程中常會發生空氣中粉層污染、廢水污染以及掩埋造成之土壤污染。因此，目前許多研究開始針對如何有效回收印刷電路板中之稀有金屬並降低環境造成污染的方向處理。 本研究旨在提供設備成本低廉、低環境衝擊，且能夠有效的回收金屬資源的處理技術。因此，實驗之設計為利用微波誘發裂解之處理程序加入濕式冶金法，以較低的能耗，有效的將廢棄印刷電路板層與層之間分離，減少傳統機械破碎法中粉塵散逸以及質量損失的問題，並增加後續使用溼式冶金法時，貴金屬金之回收效率。在溼式冶金法中找出回收率高且低污染之溶劑含金水溶液，以利最終回收程序的進行。貴金屬金之回收流程包含四個階段，分別為微波裂解、酸浸法、萃取與氧化沉澱。 在微波裂解程序中以350 W 在400℃下進行反應40分鐘，將廢棄印刷電路板中層與層間完全分離；在酸浸階段中，以2 M硫酸加過氧化氫有效回收高達95 %的銅離子，以降低後續對貴金屬金所造成的屏蔽效應；酸浸法以0.1 M硫代硫酸銨、0.01 M硫酸銅以及0.2 M氨水將貴金屬金完全從印刷電路板中溶出，達到高回收率的目的；最後步驟以添加萃取劑以及添加氧化劑之方式，分別對金離子進行回收。結果顯示萃取劑對於硫代硫酸銨溶液中之金離子無萃取效果，而利用氧化劑則可以成功將金離子以固體方式沉澱回收。 本研究之成果顯示利用微波裂解輔以濕式冶金法，對於貴金屬金之回收流程，具有相當好的效果。在酸浸法中可以完全將貴金屬金從電路板中去除，並以氧化劑使貴金屬金以固體沉澱。在低成本、低污染以及高效益的流程中，未來有機會可以應用於實際工廠中，對於環境具有良好的幫助。 關鍵詞：微波裂解、貴金屬金回收、廢棄印刷電路板
並列摘要
In recent years, a rapid increase in mobile phone market led to growing demand of precious metals such as gold and palladium. Printed circuit boards of mobile phones are made of up to 50 different elements such as gold, silver, platinum, palladium, and other precious metals. Although recycling precious metals from waste printed circuit boards (WPCBs) is promising, inappropriate handing may cause pollution to air, water, and soil. Current trends in recycling WPCBs including mechanical process, pyrometallurgy and hydrometallurgy; however, they have problems about recovery rate, energy consumption and environment pollution. Therefore, the hydrometallurgy combined with thermal pyrolysis to recover precious metals of WPCBs has attracted such attentions. The aim of this study is to find out a technique for metals recovery from WPCBs, which has high efficiency, low energy consumption, and low environmental pollution. The main component of the printed circuit board is glass fiber, which is composed of carbon material. Carbon is a good microwave absorber, and its heating rate can reach 9.98 to 21℃per seconds under microwave irradiation. Thus, microwaves can enhance the pyrolysis of WPCBs. Microwave-enhanced pyrolysis (MEP) was used as a pretreatment to separate the inner layers of WPCBs, and to enhance metal recovery efficiency. Meanwhile, thermogravimetric analysis (TGA) was used to determine the maximum weight loss of WPCBs, as a reference for controlling the power of microwave-enhanced pyrolysis. According to the experiment, the maximum weight loss of WPBCs occurred at 400℃, which was achieved by MEP at 350 W to complete pyrolysis in 40 minutes. Sulfuric acid and Thiosulfate were used to leach the pyrolysis WPCBs for copper and gold recovery. The best recovery from copper is using 2 M sulfate with hydrogen peroxide up to 95% or more. The high recovery rates of gold are using by 0.1 M thiosulphate, 0.015 M CuSO4 and 0.2 M NH3. At the extraction part, extraction gold from thiosulphate is not sufficiently effective. Finally, the leachate of gold was reduced by oxidant as H2O2. The combination of microwave pyrolysis and hydrometallurgical can reduce energy consumption and decrease environmental pollution. This study is an environmentally friendly technique for the recover precious metals from WPCBs. Key Words: Microwave-Enhanced Pyrolysis; Precious Metal Recovery; Waste Printed Circuit Boards
參考文獻
延伸閱讀
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