利用廢面板玻璃製備奈米孔洞材料應用於水中重金屬去除及硼回收之研究

Sustainable valorization of mesoporous material from display panel waste glass for removal of heavy metals and recovery of boron

蔡正國(Cheng-Kuo Tsai)

指導教授 ： 董瑞安

國立清華大學/原子科學院/生醫工程與環境科學系/博士(2019年)

摘要

隨著地球資源不斷消耗面臨短缺之問題，為達永續環境之目的，藉循環經濟的理念，進行廢棄物的有效資源再利用，以製成各式產品為一重要課題。國內為液晶顯示器(TFT-LCD)主要生產國，佔全球生產量30%以上，TFT-LCD 廣泛應用於電子產品如手機、電視、平板電腦、車用顯示器等，然而這些電子產品仍有壽命之廢棄與製程過程中產生廢料之問題，未來將會有大量廢棄TFT-LCD面板玻璃待處理。TFT-LCD面板主要成分為含有高量氧化矽與氧化鋁等金屬氧化物的玻璃材料，藉此開發高值化低成本技術，以回收面板玻璃材料轉換製備奈米多孔性材料，將應用於水體水質淨化與回收再利用，達到「搖籃到搖籃」的環境永續目標。
本研究利用田口實驗設計法以L18直交表找出最佳化製程參數，研究顯示熔融溫度(1000 ℃)、廢面板玻璃與碳酸鈉重量比(1:2)、鹽酸濃度(0.1N)、酸洗時間 ( 4小時)、乾燥溫度與時間(110 ℃與12小時) 為最佳製程條件。利用BET 等溫氮氣吸附分析發現廢面板玻璃經由碳酸鈉活化結構形成相分離改質後比表面積高達175 (m2/g)，並搭配穿透式電子顯微鏡剖面影像鑑定平均孔洞大小為12 nm，為一中孔性矽酸鋁奈米材料；此材料具有電荷吸引性與高比表面積等特性功能，在酸性pH 3.5環境下對重金屬銅、鋅、鎳、鋇等有高吸附能力分別為64.5、34.0、23.1及105 mg/g；此外，進一步以放量填充管柱進行工業電鍍廢水中鎳重金屬去除試驗，結果顯示吸附能力達18.7 mg/g相當於實驗值，顯示此中孔性奈米材料在工業上為一高效率多孔性吸附劑。
此中孔性矽酸鋁奈米材料利用其對鋇具有高吸附能力特性，將此材料應用在過氧化流體化結晶(COP-FBC)技術作為結晶載體，能有效從高濃度硼廢水進行回收硼，研究結果顯示中孔性矽酸鋁奈米材料具有高結晶效率達93.4 % 形成硼化鋇氧化物(barium borate)，利用掃描式電子顯微鏡發現此載體具有特殊結晶路徑 (1) 此材料表面吸附二價鋇離子形成高結晶親和性、(2)富硼相氫氧化物離子與材料表面二價鋇離結合形成針狀結晶、(3)結晶經由材料孔隙往內層成長、(4)當材料已結晶成長飽和時，會自主架橋繼續長晶形程多層晶殼，達到高結晶特性。最後此結晶材料產物利用高溫X光繞射鑑定可知在600℃具相轉化形成硼化鋇材料，可作為光學玻璃原料再使用。本研究結果顯示利用廢棄面板玻璃可製備獲得新穎中孔性矽酸鋁奈米材料，且確實能有效應用於處理工業廢水中重金屬汙染去除及從高濃度硼廢水回收硼，以利達到永續環境之目標。

關鍵字

廢面板玻璃、 ； 田口實驗設計 ； 流體化結晶床 ； 吸附劑 ； 中孔性奈米材料

並列摘要

The recycling of the huge amount of thin film transistor liquid crystal display (TFT-LCD) glass wastes has become one of the worldwide environmental issues. Herein, a novel and cost-effective synthesis method for the fabrication of mesoporous aluminosilicate composite from the TFT-LCD waste has been developed to serve as the environmentally benign adsorbent for the removal of metal ions including Cu2+, Zn2+ and Ni2+, and as the carrier for recovery boron in terms of chemical –oxo precipitation fluidized bed crystallization (COP-FBC).
In this study, optimum parameters for fabrication of mesoporous aluminosilicate nanomaterial from TFT-LCD waste glass was been developed by using Taguchi experimental design technique. It is noteworthy that the parameters including melting temperature, added alkaline agent ratio, acid concentration, leaching time, calcinate temperature and time were optimized at 1000℃, 2 time agents, 0.1 N HCl, 4 hours, 110℃ and 12 hours, respectively. After melting procedure at 1000 C in the presence of Na2CO3 for phase separation, the mesoporous structure of aluminosilicate which had a surface area of 175 m2 g-1 and an average particle size of 12 nm was created. The surface functional groups of tailored mesoporous aluminosilicate nanocomposite (M-ANC) material were negatively charged .The adsorption capacity for Cu2+, Zn2+ ,Ni2+ and Ba2+ were 64.5, 34.0, 23.1 and 105mg g-1, respectively, at pH 3.5. Moreover, the environmental applicability of mesoporous aluminosilicate material is evaluated by column experiment in the presence of real electroplating wastewater. M-ANC can effectively remove Ni2+ in the electroplating wastewater with the adsorption capacity of 18.7 mg g-1.
On the other hand, the negatively charged surface and mesoporous structure of aluminosilicate material enhance the adsorption of Ba2+ onto surface, which is conducive to the enhancement of recovery of boron species. Moreover, the crystallization ratio of boron by mesoporous aluminosilicate material can be up to 93.4%. The cross-sectional SEM images and high-temperature X-ray diffraction (HT-XRD) results confirm the boron recovery mechanism in which the negatively charged functional group as well as the meso-porosity of mesoporous aluminosilicate material triggers the rapid formation of need-shaped precipitates of barium peroxoborate. The peroxoborate was converted to barium borate after calcination at 600 °C. Results obtained in this study clearly demonstrate the possibility of fabricating environmentally benign mesoporous aluminosilicate adsorbents from TFT-LCD waste to toward metal ion removal and sustainably recover and crystallize boron species from water and wastewater in COP-FBC.

並列關鍵字

TFT-LCD panel waste ； Taguchi experimental design ； Chemical –oxo precipitation fluidized bed crystallization (COP-FBC) ； Adsorbents ； Mesoporous material

參考文獻

References

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