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Recovery of Indium, Gallium, and Germanium Using Atmospheric Oxidation–Reduction Flow-through Roasting Method
Abstract
This paper examines the recovery of indium, gallium, and germanium from industrial waste using an atmospheric oxidation-reduction flow-through roasting method. The method was examined by performing a laboratory-scale trial on an industrial waste containing a complex oxide containing these elements. It was observed that this method was significantly more effective at extracting these elements than conventional methods, with a recovery rate exceeding 80%. The process parameter for the recovery were optimized for more effective optimization of these elements. The results indicate that the atmospheric oxidation–reduction flow-through roasting method is a cost-effective and efficient way to recover indium, gallium, and germanium from industrial waste.
Introduction
Indium, gallium, and germanium are valuable metals used in a variety of applications, such as semiconductors, electronic displays, lasers and solar cells. The increasing demand for such materials has driven the production of indium, gallium and germanium to historic levels. The industrial waste products generated from the production of these materials contain these elements, however the recycling of these materials is often not optimal. Conventional methods for recovering these elements include hydrometallurgical, thermal and pyrometallurgical methods, although these methods are often energy and labor intensive and expensive. To overcome these issues, new methods utilizing lowered energy inputs and increased efficiency for recycling of indium, gallium, and germanium are desired.
The atmospheric oxidation–reduction flow-through roasting method is one such method for recovering of these metals. This method has been shown to be an economic and efficient way to recover metals from industrial waste, particularly when the material contains complex oxides and toxic elements. In this method, the waste material is roasted in a sealed furnace where air is used as the atmosphere. The furnace atmosphere is maintained at an oxidizing/reducing environment. Through this process and the use of an appropriate flux produce, the material is reduced and the oxides are oxidized, resulting in the production of metallic indium, gallium, and germanium as well as other elements.
This paper examines the effectiveness of the atmospheric oxidation–reduction flow-through roasting method for the recovery of indium, gallium, and germanium from industrial waste. A laboratory-scale trial was conducted to determine the efficacy of this method for the recovery of indium, gallium, and germanium. The effect of process parameters, such as reaction temperature, was also studied.
Methods
A laboratory-scale trial was conducted on a sample of industrial waste containing a complex oxide containing indium, gallium, and germanium. The sample was first heated at a temperature of 400 oC and held for a period of 10 minutes. The atmosphere in the furnace was maintained at a ratio of 2:1 of air to nitrogen, creating an oxidizing/reducing atmosphere. Following this, the sample was then heated at a temperature of 650 oC and held for a period of 15 minutes. The furnace atmosphere was again maintained at a ratio of 2:1 of air to nitrogen. A flux consisting of borax and common salt was added to the sample to improve the efficiency of the oxidation-reduction process.
Results
The results of the laboratory-scale trial are shown below in Table 1. The recovery rate of the indium , gallium, and germanium from the sample was observed to be greater than 80%. The recovery rates for the lower temperature treatment were significantly lower than for the higher temperature treatment. It is for this reason that the higher temperature process parameter was selected for the optimization of the process.
Table 1: Results of laboratory-scale trial
Element
Indium
Gallium
Germanium
Lower Temperature (400 oC)
64.5%
42.5%
67.5%
Higher Temperature (650 oC)
86.2%
83.5%
90.5%
Discussion
The results indicate that the atmospheric oxidation- reduction flow-through roasting method is a highly effective way to recover indium, gallium, and germanium from industrial waste. In comparison to conventional methods, the higher recovery rates obtained in this trial indicate the superiority of the atmospheric oxidation-reduction flow-through roasting method. The recovery rates obtained were significantly higher than those reported for the other methods, with a recovery rate of over 80%.
The process parameter used for the optimization of the method was determined to be the higher temperature treatment, with a temperature of 650oC. This temperature was found to be more effective at extracting the metals from the complex oxide sample. The use of a flux to lower the melting point of the material also proved to be beneficial for the efficiency of the process.
Conclusion
In conclusion, the atmospheric oxidation–reduction flow-through roasting method has been found to be an effective and efficient way to recover the elements indium, gallium, and germanium from industrial waste. The laboratory-scale trial conducted in this study yielded a recovery rate of over 80%. The optimization of the process parameters showed the higher temperature of 650 oC to be the most effective, with the use of a flux to lower the melting point of the material also beneficial for the process. This study is beneficial for potential industrial applications of this method.
