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標題: | 以分散反萃取支撐液膜萃取廢液晶顯示器之銦 Extraction of Indium from Waste Liquid Crystal Display by Supported Liquid Membrane with Strip Dispersion |
作者: | Wei-Nien Hsia 夏瑋念 |
指導教授: | 駱尚廉 |
關鍵字: | 廢棄液晶顯示器,銦回收,超聲波,分散式反萃取,支撐式液膜, Waste LCD,Indium recovery,Ultrasonic wave,Supported liquid membrane,Strip dispersion, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 金屬銦在地球上的含量稀少且提煉較困難,被定義為稀有金屬,其中全世界超過八成銦的使用,都是被製造成透明導電材料氧化銦錫膜(Indium Tin Oxide, ITO),並大量地應用在液晶顯示器(Liquid Crystal Display, LCD)當中,由於經濟的成長與人口不斷地增加,再加上電子設備的壽命都不長,大約只有3-5年,因此產生了大量的電子廢棄物,對於資源的需求卻不斷增加,如何從廢棄液晶面板中回收銦以避免資源之耗盡是目前需要解決之課題。
本研究先利用人工方式撕除偏光膜,將其剪裁成3cm×3cm大小,液晶面板之兩片玻璃基板於剪裁時會分開,再利用丙酮萃取其內層之液晶,避免對後續回收金屬銦造成影響。經此前處理後,銦之回收分為兩階段,先利用硫酸並輔以超聲波加強其回收效率,接續則利用分散式反萃取支撐式液膜進行濃縮純化程序。 在酸溶階段,利用硫酸將金屬銦從固相氧化銦錫膜中轉移至液相內,根據金屬銦之回收效率,並加以考量藥劑使用量及耗能大小,權衡後可得最佳之參數分別為:硫酸0.75M、超聲波功率300W、固液比1:2及反應時間1小時,溶液過濾後再以ICP-OES測定之,此階段金屬銦之回收率為97.05%、濃度為152.95ppm、純度為94.16%。 第二階段則利用分散反萃取支撐式液膜同時進行萃取與反萃取程序,對酸液內之銦離子進行濃縮及純化,將第一階段酸溶結束之溶液作為進料相共1500ml並以0.3L/min之流量通入支撐式液膜之管端,有機相使用萃取劑D2EHPA溶於稀釋劑Isopar-L內並添加10%之修飾劑十二醇以避免第三相生成共500ml,反萃取相為30ml之鹽酸,將有機相與反萃取相混合均勻後以0.3L/mins之流量通入支撐式液膜之殼端,總反應時間為30分鐘,每間隔5分 鐘採取進料相溶液一次,並收集實驗完成後之反萃取溶液,利用ICP-OES測定,則可得到進料相中銦離子濃度減少之速率和最終反萃取溶液內之銦離子濃度,並藉此結果選擇最佳參數為使用D2EHPA濃度20%;進料相之pH值調整為3以及反萃取劑濃度2N,在這些條件下銦的濃度可從進料相之152.95ppm濃縮純化至5457.02ppm,雖然金屬銦的回收率降低為73.36%,但純度提高為99.99%。 本研究之結果顯示,利用硫酸輔以超聲波之程序來回收廢棄液晶面板內稀有金屬銦之效果非常好,使得酸溶後溶液內銦離子之比例非常高,以利後續濃縮純化等步驟,整體銦回收的效率優異,最終之產物是含銦之鹽酸溶液,濃度以及純度皆很高,分別為5457.02ppm與99.99%,對後續進行之電解精鍊、置換等等還原回收程序皆有很大的幫助。 Indium is a rare metal because of its scarcity on the earth and difficulty to refine. Almost over 80% of indium is used for the production of Indium Tin Oxide (ITO) film that is a transparent and conductive material. ITO is widely used in the manufacture of Liquid Crystal Display (LCD) as a functional material. Due to population growth and rapid economic development, most electrical equipment lifetimes are quite short (usually only 3-5 years), resulting in a large amount of electronic waste. Therefore, it is of great importance to recover indium from waste LCD to avoid resource depletion. The pretreatment in this study was to peel the polarizing film manually. The LCD was cut into small pieces with 3 cm×3 cm, and then two glass substrates would break apart. Liquid crystal is a composite material contained different kinds of organics. The acetone was used to dissolve liquid crystal in order to avoid the difficulties for indium recovery and the harm to environment and people. After pretreatment, the indium recovery process can be divided into two stages. The first stage was sulfuric acid leaching with the assistance of ultrasonic waves, to enhance the recovery efficiency of indium from waste LCD. Secondly, supported liquid membrane with strip dispersion was used to concentrate and purify the solution. In the acid leaching process, sulfuric acid was used to dissolve indium from solid phase to aqueous phase. The best operation condition can be determined according to the indium recovery rate, chemicals dosage and energy consumption. From experimental results, the best parameters were sulfuric acid of 0.75 M, the ultrasonic wave power of 300 W, the processing time of 60 min and the solid-to-liquid ratio (S/L) of 1:2. After the leaching process, the indium concentration was measured by using ICP-OES. The recovery rate of indium was 97.05%, the concentration of indium was 152.95 ppm and the indium purity was 94.16%. Extraction and stripping processes can be carried out simultaneously by using the supported liquid membrane technology to concentrate and purify the indium. In this stage, 1500 ml of leachate obtained from leaching process was pumped into the tube side of the supported liquid membrane with the volumetric flow rate of 0.3 L/min as feed solution. Organic solution, which contained D2EHPA as extractant, 10% of 1-dodecanol as modifier and isopar-L as diluent, was totally 500 ml. Stripping solution was 30 ml of hydrochloric acid. The mixture of organic solution and stripping solution was pumped into the shell side of supported liquid membrane with the volumetric flow rate of 0.3 L/min. The total retention time was 30 min. The indium concentration of feed solution was measured every 5 min, and the stripping solution was collected after the process. The best operation condition can be determined according to indium recovery efficiency and the indium concentration in stripping solution. The result indicated that the best parameters were feed solution pH of 3, hydrochloric acid of 2 N and D2EHPA of 20%. Although in this stage, the recovery rate of indium was reduced to 73.36%, the concentration and the purity of indium increased to 5457.02 ppm and 99.99%, respectively. This study showed that the indium solution with high purity can be obtained by sulfuric acid leaching with the assistance of ultrasonic waves and supported liquid membrane processes. The purity and concentration of indium in the final product (hydrochloric acid solution) were as high as 99.99% and 5457.02 ppm, respectively. These recovery processes are beneficial to folllow-up electrolytic refining or replacement process to get pure indium metal. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/69537 |
DOI: | 10.6342/NTU201801171 |
全文授權: | 有償授權 |
顯示於系所單位: | 環境工程學研究所 |
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