indium extraction from lcd screens
INDIUM EXTRACTION FROM LCD SCREENS A.P. GABRIEL*, B.B. GIORDANI*, A.KASPER*. AND H.M. VEIT* * PPGE3M – Materials Engineering Department, Federal University of Rio Grande do Sul – UFRGS. Av. Bento Gonçalves, 9500, Setor IV, Prédio 43426, CEP: 91501-970, Porto Alegre, Brazil.
SUMMARY: 1. INTRODUCTION. 2. MATERIALS AND METHODS. 2.1 Manual Disassembly. 2.2 Comminution of the screens. 2.3 Chemical Characterization. 2.4 Leaching. 3. RESULTS AND DISCUSSIONS. 3.1 Disassembling the monitors 3.2 Comminution of the screens. 3.3 Characterization. 3.4 Leaching. 4. CONCLUSIONS. AKNOWLEDGEMENTS. REFERENCES.
1. INTRODUCTION The electrical and electronic equipment (EEE) sector is one of the fastest growing in the world. The rapid and constant innovation makes EEE obsolete in a short time. When they become obsolete or stop to working, these products are now considered as waste electrical and electronic products (WEEE). The main WEEE are products such as TVs, computers, cell phones and home appliances. The recycling of these WEEE involves a wide range of techniques and processes, aiming at the recovery of the different materials, especially metals. Television and computer monitors, for example, have a complex structure, consisting mainly of glass, polymers, various metals and printed circuit boards, which add value to these materials. In addition to these materials, these wastes may contain precious metals such as gold and silver, and also indium, which could be recovered for their potential value. Since its invention, liquid crystal displays (LCDs) (Figure 1) have become one of the main types of screens used in televisions, computers and cell phones. These equipments have a short life cycle and interesting amount of valuable materials. The LCDs have in their composition materials such as polymers, metals and ceramics (glass), which makes it difficult to recycle. Among the metals present, it is possible to find the indium (In), a rare and very versatile metal, used in LCDs in the form of an indium tin oxide (ITO). ITO is composed of a higher fraction of indium oxide (90%) and a smaller fraction of tin oxide (10%). ITO is a transparent and conductive material and is important in the manufacture of thin-film transistors (TFT), used in liquid crystal displays. Thus, this study aimed to extract indium from LCD screens leaching with hydrochloric acid.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 1: Image of an LCD screen 2. MATERIALS AND METHODS 2.1 Manual Disassembly Initially, LCD monitors from different brands and year of manufacture were collected. After, the monitors were weighed and manually disassembled to segregate the components. The monitors were separated, basically, into four parts: liquid crystal screen, polymer sheets, polymer shell and printed circuit boards. In this work only the screens were used. 2.2 Comminution of the screens The screens were milled for 6 hours in a alumina ball mill brand Servitech model CT-242. 2.3 Chemical Characterization The X-Ray Fluorescence analysis (Thermo Niton XL3t portable analyzer) was used to verify the presence of the indium element in the powder obtained by grinding. 2.4 Leaching Samples of the powder obtained from the milled screens were separated for carrying out the leaching tests. For each test, a specific amounts of materials were used as shown in Table 1. Table 1: Leaching tests parameters with hydrochloric acid. Concentration Leaching Time Temperature 1M
4 hours
4M
4 hours
6M
4 hours
28°C 60°C 28°C 60°C 28°C 60°C
Amount of Material 0.5g e 5g 0.5g e 5g 0.5g e 5g 0.5g e 5g 0.5g e 5g 0.5g e 5g
Volume 50ml 50ml 50ml 50ml 50ml 50ml
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3 RESULTS AND DISCUSSION 3.1 Manual Disassembling The monitors were basically separated into four parts: liquid crystal screen, polymer sheets, polymeric shell and printed circuit boards, as shown in Figure 2. In table 2 it is possible to verify the total weight of two monitors and the weight of the screens.
Figure 2: LCD monitors disassembled: (a) screen (b) polymer sheets (c) polymer shell (d) printed circuit board. Table 2: Mass of samples collected. Brand Year of Manufacture A 2005 B 2006
Total Weight 4.3kg 4.0kg
Screen Weight 0.46kg 0.37kg
3.2 Comminution of the screens Figure 3 shows the ball mill with the screens comminuted. In Figure 4, it is possible to see the material obtained after 6 hours of milling.
Figure 3: Material inside the ball mill container.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 4: Material obtained after milled 3.3 Chemical Characterization In Table 3, the main components obtained by the FRX test, in powder after comminution, are described. The main elements found are part of the usual formulation for glass production, but in addition, indium and tin were also detected. It is possible to see that the values of indium and tin detected in the FRX assay are very low, indicating that their amount in the screens is very small. Table 3: Components found in FRX Component SiO2 Al2O3 CaO As2O3 SrO K2O SnO2 InO2
Sample 68.58 % 12.93 % 7.36 % 1.45 % 1.13 % 0.41 % 0.04 % 0.02 %
3.4 Leaching The results of the leaching tests are presented in Table 4. Table 4: Results obtained in the leaching test with HCl to samples with 6 hours of milling. Concentration Temperature Result 5g (mg/kg) Result 0,5g (mg/kg) 28°C 192.8 212 1M 60°C 199.5 275 28°C 186.7 296 4M 60°C 217.1 259 28°C 203.4 227 6M 60°C 192.9 299
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
It was verified that with 5g of material, the results did not show significant differences when comparing temperature and concentration. It is possible to notice that the molarity of the acid has little influences on the results. However, with 0.5g, it was possible to obtain a better results, for both low and high concentrations. With 4M, at room temperature, was possible extract 296mg of In/kg.
4 CONCLUSIONS Through the preliminary results already obtained, it was possible to verify that the LCD monitors are extremely heterogeneous in relation to the materials present. After manual disassembly, it was noted that the monitors have ,especially, polymers, printed circuit boards and the screen, that represent, in average, 10% of total weight of a monitor. The analysis by FRX showed that the glass used in the LCD screen contains usual components of the glasses, besides the presence of the indium, in the form of ITO layer. In the leaching tests, the better conditions obtained, were with hydrochloric acid 4M, room temperature and 6M, 60ºC, with 296 and 299 mg In/kg, respectively.
AKNOWLEDGEMENTS The authors thanks CAPES and CNPq for financial supports.
REFERENCES Chou, W.L. and Huang, Y.H. (2009). Electrochemical removal of indium ions from aqueous solution using iron electrodes. Journal of Hazardous Materials 172, 46–53. Gabriel A.P., Grochau I.H., Santana R.M.C. and Veit H.M. (2013). Reciclagem de Carcaças de Monitores: Propriedades Mecânicas e Morfológicas. Polímeros, vol. 23, n. 6, p. 823-831. Gramatyka P., Nowosielski R. And Sakiewicz P. (2007). Recycling of waste electrical and electronic equipment. Journal of Achievements in Materials and Manufacturing Engineering Vol. 20 Issues 1-2. Li, R., Yuan, T., Fan, W., Zhou, L., Wu, H. and Li, J. (2014). Removal of tin and extraction of indium from acid : dissolved solution of waste indium : tin targets. J. Cent. South Univ. 21, 1741e1746. Schaik A.V. and Reuter M.A. (2010). Dynamic modelling of E-waste recycling system performance based on product design. Minerals Engineering 23, 192–210. Wang X., Lu X., and Zhang S. (2013). Study on the waste liquid crystal display treatment: Focus on the resource Recovery. Journal of Hazardous Materials 244– 245; 342– 347. Yang J., Retegan T. and Ekberg C. (2013) Indium recovery from discarded LCD panel glass by solvent extraction. Hydrometallurgy 137; 68–77.
SUMMARY: 1. INTRODUCTION. 2. MATERIALS AND METHODS. 2.1 Manual Disassembly. 2.2 Comminution of the screens. 2.3 Chemical Characterization. 2.4 Leaching. 3. RESULTS AND DISCUSSIONS. 3.1 Disassembling the monitors 3.2 Comminution of the screens. 3.3 Characterization. 3.4 Leaching. 4. CONCLUSIONS. AKNOWLEDGEMENTS. REFERENCES.
1. INTRODUCTION The electrical and electronic equipment (EEE) sector is one of the fastest growing in the world. The rapid and constant innovation makes EEE obsolete in a short time. When they become obsolete or stop to working, these products are now considered as waste electrical and electronic products (WEEE). The main WEEE are products such as TVs, computers, cell phones and home appliances. The recycling of these WEEE involves a wide range of techniques and processes, aiming at the recovery of the different materials, especially metals. Television and computer monitors, for example, have a complex structure, consisting mainly of glass, polymers, various metals and printed circuit boards, which add value to these materials. In addition to these materials, these wastes may contain precious metals such as gold and silver, and also indium, which could be recovered for their potential value. Since its invention, liquid crystal displays (LCDs) (Figure 1) have become one of the main types of screens used in televisions, computers and cell phones. These equipments have a short life cycle and interesting amount of valuable materials. The LCDs have in their composition materials such as polymers, metals and ceramics (glass), which makes it difficult to recycle. Among the metals present, it is possible to find the indium (In), a rare and very versatile metal, used in LCDs in the form of an indium tin oxide (ITO). ITO is composed of a higher fraction of indium oxide (90%) and a smaller fraction of tin oxide (10%). ITO is a transparent and conductive material and is important in the manufacture of thin-film transistors (TFT), used in liquid crystal displays. Thus, this study aimed to extract indium from LCD screens leaching with hydrochloric acid.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 1: Image of an LCD screen 2. MATERIALS AND METHODS 2.1 Manual Disassembly Initially, LCD monitors from different brands and year of manufacture were collected. After, the monitors were weighed and manually disassembled to segregate the components. The monitors were separated, basically, into four parts: liquid crystal screen, polymer sheets, polymer shell and printed circuit boards. In this work only the screens were used. 2.2 Comminution of the screens The screens were milled for 6 hours in a alumina ball mill brand Servitech model CT-242. 2.3 Chemical Characterization The X-Ray Fluorescence analysis (Thermo Niton XL3t portable analyzer) was used to verify the presence of the indium element in the powder obtained by grinding. 2.4 Leaching Samples of the powder obtained from the milled screens were separated for carrying out the leaching tests. For each test, a specific amounts of materials were used as shown in Table 1. Table 1: Leaching tests parameters with hydrochloric acid. Concentration Leaching Time Temperature 1M
4 hours
4M
4 hours
6M
4 hours
28°C 60°C 28°C 60°C 28°C 60°C
Amount of Material 0.5g e 5g 0.5g e 5g 0.5g e 5g 0.5g e 5g 0.5g e 5g 0.5g e 5g
Volume 50ml 50ml 50ml 50ml 50ml 50ml
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3 RESULTS AND DISCUSSION 3.1 Manual Disassembling The monitors were basically separated into four parts: liquid crystal screen, polymer sheets, polymeric shell and printed circuit boards, as shown in Figure 2. In table 2 it is possible to verify the total weight of two monitors and the weight of the screens.
Figure 2: LCD monitors disassembled: (a) screen (b) polymer sheets (c) polymer shell (d) printed circuit board. Table 2: Mass of samples collected. Brand Year of Manufacture A 2005 B 2006
Total Weight 4.3kg 4.0kg
Screen Weight 0.46kg 0.37kg
3.2 Comminution of the screens Figure 3 shows the ball mill with the screens comminuted. In Figure 4, it is possible to see the material obtained after 6 hours of milling.
Figure 3: Material inside the ball mill container.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 4: Material obtained after milled 3.3 Chemical Characterization In Table 3, the main components obtained by the FRX test, in powder after comminution, are described. The main elements found are part of the usual formulation for glass production, but in addition, indium and tin were also detected. It is possible to see that the values of indium and tin detected in the FRX assay are very low, indicating that their amount in the screens is very small. Table 3: Components found in FRX Component SiO2 Al2O3 CaO As2O3 SrO K2O SnO2 InO2
Sample 68.58 % 12.93 % 7.36 % 1.45 % 1.13 % 0.41 % 0.04 % 0.02 %
3.4 Leaching The results of the leaching tests are presented in Table 4. Table 4: Results obtained in the leaching test with HCl to samples with 6 hours of milling. Concentration Temperature Result 5g (mg/kg) Result 0,5g (mg/kg) 28°C 192.8 212 1M 60°C 199.5 275 28°C 186.7 296 4M 60°C 217.1 259 28°C 203.4 227 6M 60°C 192.9 299
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
It was verified that with 5g of material, the results did not show significant differences when comparing temperature and concentration. It is possible to notice that the molarity of the acid has little influences on the results. However, with 0.5g, it was possible to obtain a better results, for both low and high concentrations. With 4M, at room temperature, was possible extract 296mg of In/kg.
4 CONCLUSIONS Through the preliminary results already obtained, it was possible to verify that the LCD monitors are extremely heterogeneous in relation to the materials present. After manual disassembly, it was noted that the monitors have ,especially, polymers, printed circuit boards and the screen, that represent, in average, 10% of total weight of a monitor. The analysis by FRX showed that the glass used in the LCD screen contains usual components of the glasses, besides the presence of the indium, in the form of ITO layer. In the leaching tests, the better conditions obtained, were with hydrochloric acid 4M, room temperature and 6M, 60ºC, with 296 and 299 mg In/kg, respectively.
AKNOWLEDGEMENTS The authors thanks CAPES and CNPq for financial supports.
REFERENCES Chou, W.L. and Huang, Y.H. (2009). Electrochemical removal of indium ions from aqueous solution using iron electrodes. Journal of Hazardous Materials 172, 46–53. Gabriel A.P., Grochau I.H., Santana R.M.C. and Veit H.M. (2013). Reciclagem de Carcaças de Monitores: Propriedades Mecânicas e Morfológicas. Polímeros, vol. 23, n. 6, p. 823-831. Gramatyka P., Nowosielski R. And Sakiewicz P. (2007). Recycling of waste electrical and electronic equipment. Journal of Achievements in Materials and Manufacturing Engineering Vol. 20 Issues 1-2. Li, R., Yuan, T., Fan, W., Zhou, L., Wu, H. and Li, J. (2014). Removal of tin and extraction of indium from acid : dissolved solution of waste indium : tin targets. J. Cent. South Univ. 21, 1741e1746. Schaik A.V. and Reuter M.A. (2010). Dynamic modelling of E-waste recycling system performance based on product design. Minerals Engineering 23, 192–210. Wang X., Lu X., and Zhang S. (2013). Study on the waste liquid crystal display treatment: Focus on the resource Recovery. Journal of Hazardous Materials 244– 245; 342– 347. Yang J., Retegan T. and Ekberg C. (2013) Indium recovery from discarded LCD panel glass by solvent extraction. Hydrometallurgy 137; 68–77.
