臺灣博碩士論文加值系統

資源的回收、精煉及再利用是當今全世界各先進國家積極投入的重點研究項目，同時更是人類永續發展的重要指標。本研究主要是針對廢日光燈管的螢光粉進行氧化釔的回收及精煉提純。利用硫酸－亞臨界水萃取可獲得釔以及其他存在於廢螢光粉中的元素，再將萃取液進行元素分析可進一步計算出濾出效率。
亞臨界水萃取實驗是在一套小型反應設備中進行，主要包括一個可更換鐵弗龍內襯之不鏽鋼批次反應器、磁石攪拌子、以熱電耦偵測並控制加熱之裝置、電子式調壓閥、逆止閥及連接至氮氣瓶的不鏽鋼管。利用這組設備，可探討酸液濃度、萃取溫度、萃取時間與萃出效率之間的關係。釔元素回收於萃取液之後，接著進行一系列的純化試驗。利用氫氧化鈉調整萃取液pH值至2與3之間，此時部分金屬離子會產生沈澱。過濾去除固體後再加入硫化鈉，除了釔、鈣、銪、鎂以外的金屬離子皆會形成難溶的硫化物固體沈澱。過濾去除固體之濾液進行電解程序能將三價銪離子還原成二價亞銪離子，再添加硫酸氨使產生硫酸鈣及硫酸亞銪沈澱。過濾去除固體後於濾液中加入草酸會生成草酸釔及草酸鎂沈澱。再將草酸釔及草酸鎂進行熱處理，在氮氣氛圍中提高溫度至草酸鎂的沸點溫度(365.1 ℃)以上使其汽化，隨後通入空氣並持續升溫至600 ℃停留兩小時，就能獲得最終產物氧化釔。經過這一系列方法的處理，釔的純度可達到99.9 wt.%以上

Recycling, refining and reuse are currently important research topics for the advanced countries. It is an essential indicator for sustainable development of the earth. In this project, yttrium element will be retrieved from waste fluorescent powder coming from dismantling of spent fluorescent tube. Yttrium and the other excrescent elements will be leached by subcritical water extraction. The leaching efficiency will be estimated. Furthermore, the results will be compared with those from conventional extraction.
The subcritical water extraction will be carried out by a bench-scale device, which contains a teflon chamber inside of the stainless steel batch reactor, magnetic stirrer, thermocouple-controlled heating system, digital pressure regulator valve, check valve and stainless steel pipe connecting nitrogen gas. The effects of acid concentration, extraction temperature and extraction time will be studied on leaching efficiency of yttrium. After the recycling of yttrium, the refining test will proceed with a series of experiments. First, the pH value of the extraction solution will be adjusted with sodium hydroxide and the precipitates will be filtered. The sodium sulfide will be then added into the solution and the solid metal sulfide will be formed and removed. In order to reduce Eu3+ into Eu2+, the electrolysis experiment will be carried out by passing the current into the solution with a platinum meshes as the electrode. Ammonium slufate will be then put into the solution. Solid europium (II) sulfate and calcium sulfate will be formed and filtered. Oxalic acid will be then put into solution and the precipitates of yttrium oxalate and magnesium oxalate will be formed. Finally, the both oxalates will be calcined. Magnesium oxalate will be gasified above its boiling point 365.1 ℃, and yttrium oxalate will become yttrium oxide at 600 ℃calcination for 2 hours.
The results indicate that the acid amount used in the subcritical water process is more less than the process with the operation temperature below 100 ℃. As the pH value is between 2.5 and 3.0, the addition of oxalate acid into the etching solution can obtain the yttrium oxalate, and the yttrium recovery and purity can reach 80% and 95%, respectively. The recrystallization of yttrium nitrate processes under suppersaturation can increase the pruification of yttrium. On the other hand, thermal treatment, including reduction of oxide and then vaporization in vaccum, can efficiently remove europium oxide, zinc oxide and indium oxide away from yttrium oxide.

誌謝..............................................ⅰ
中文摘要..........................................ⅱ
英文摘要........................................ iii
目錄............................................. v
表目錄......................................... vii
圖目錄.......................................... ix
第一章 緒論......................................1
1-1 概論......................................1
1-2 用途.......................................8
1-3 稀土元素回收................................9
1-4 稀土元素化合物..............................12
1-5 稀土元素氫氧化物..........................14
1-6 稀土元素草酸鹽...............................17
1-7 介紹銪.....................................24
第二章 研究方法..................................29
2-1 精煉......................................30
2-2 研究步驟...................................33
2-2-1 硫酸-亞臨界水萃取釔....................33
2-2-2 調整溶液pH值進行部份雜質沈澱............34
2-2-3 選擇性沈澱－形成硫化物.................35
2-2-4 電解還原銪離子........................37
2-2-5 選擇性沈澱－形成硫酸鹽.................37
2-2-6 草酸沈澱及煅燒........................38
2-2-7 元素分析.............................38
第三章 結果與討論.................................40
3-1 硫酸－亞臨界水萃取...........................40
3-2 釔精.......................................47
第四章 結論........................................56
參考文獻...........................................57

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