稀土金屬如釔(Y)和銪(Eu)為兩種廣泛應用在電子產品中不可或缺的金屬，常作為螢幕顯示器中的螢光材料。隨著電子產品設計日新月異、其生命週期短縮，近年來電子廢棄物數量不斷持續增加。因此，有效地將稀土金屬從電子廢棄物中回收與再利用極具經濟價值。本實驗研究目的為利用次臨界水萃取程序回收廢棄陰極射線管中螢光粉的稀土金屬釔與銪，並探討酸種類、酸濃度以及萃取溫度對其回收之影響。定性結果顯示，廢棄陰極射線螢光粉成分複雜，除了稀土金屬釔及銪之外尚有重金屬鋅與鉛。實驗結果顯示，使用鹽酸、硫酸與硝酸進行萃取，以硫酸萃取金屬釔及銪的萃取效率最好，同時重金屬雜質鋅與鉛的萃取含量低。當萃取溫度控制在100oC，且硫酸濃度從0.1提升到0.75 M，金屬釔與銪的萃取效率亦有效提升。除此之外，硫酸濃度在0.75 M、萃取溫度從100oC提升至150oC時，金屬釔與銪的萃取效率分別從27.13%及28.60%大幅提升至100%。另一方面，本研究採用連續萃取的方式探討次臨界水萃取後固態螢光粉殘留物中重金屬(鋅與鉛)的型態變化，並評估其在環境中的釋放行為。連續萃取實驗結果顯示，經過次臨界流體萃取可有效的將鋅與鉛轉換成穩定、低流動性的型態。

Rare earth metals such as yttrium (Y) and europium (Eu) are widely applied in electronic products, especially as an essential constituent in the phosphor. With the life cycle of electronic products becomes shorter, the amount of electronic waste (e-waste) increases continuously in recent years. Therefore, recycling and reuse of rare earth metals from the e-waste is critical for sustainable development. The current study investigated Y and Eu recovery from waste cathode ray tube (CRT) phosphor by subcritical water extraction (SWE). Effects of acid type, acid concentration and extraction temperature were examined. Experimental results indicated that extraction efficiency of Y and Eu was the best using sulfuric acid (H2SO4) while that of heavy metal was the lowest compared to hydrochloric acid (HCl) and nitric acid (HNO3). Both Y and Eu extraction efficiency increased as H2SO4 concentration increased from 0.1 M to 0.75 M. It is noted that Y and Eu extraction efficiency could reach 100% from 27.13% and 28.60%, respectively, when temperature increased from 100oC to 150oC at 0.75 M of H2SO4. On the other hand, sequential extraction was conducted to assess speciation of heavy metals, such as Zn and Pb in waste CRT phosphor residue after SWE. The sequential extraction results revealed that SWE process transformed heavy metals to a more stable state.

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