Optimization of Indium Recovery and Separation from LCD Waste by Solvent Extraction with Bis(2-ethylhexyl) Phosphate (D2EHPA)

Jiaxu Yang,Christian Ekberg,Teodora Retegan

doi:10.1155/2014/186768

Jiaxu Yang, Christian Ekberg + Show 1 more

Open Access

https://doi.org/10.1155/2014/186768

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Abstract

Indium tin oxide (ITO) is currently the choice of electrode material in liquid crystal displays (LCDs). D2EHPA is known to be an extractant that can be used to selectively recover indium from 1 M sulfuric acid. In order to optimize the extraction and separation of indium from LCD waste, the effects of pH, temperature, time, and extractant concentration on the distribution ratios of In(III) and the major impurities such as Al(III), Cu(II), Fe(III), and Zn(II) were investigated. Metal concentrations in the aqueous feed were based on the concentrations found in the leach liquor of LCD panel glass at 0.1 g/mL S/L ratio. This study showed that extraction of indium could be increased at <293 K and stripping of indium could be increased at >293 K. Furthermore, by increasing D2EHPA concentration from 0.1 M to 0.25 M, extraction of indium could be increased from 70% to >95%.

Highlights

Indium is a rare metal with an average concentration of 0.05 ppm in the Earth’s crust [1]
Other work [8, 9] studied the recovery of indium from waste Indium tin oxide (ITO) by leaching in sulfuric acid, followed by solvent extraction using D2EHPA diluted in kerosene as the organic phase
Solvent extraction equilibriums of metals found in zinc refinery residues (In3+, Ga3+) with D2EHPA and two similar extractants have been investigated by Nakamura et al [10]

Summary

Introduction

Indium is a rare metal with an average concentration of 0.05 ppm in the Earth’s crust [1]. There has been a greater interest in the recovery of indium from various secondary sources, such as production waste from ITO etching processes and from discarded LCDs. A previous literature study [3] reviewed many organic molecules and showed that both solvating and acidic organophosphate extractants can separate indium from other metal ions dissolved in various acidic aqueous media. Other work [8, 9] studied the recovery of indium from waste ITO by leaching in sulfuric acid, followed by solvent extraction using D2EHPA diluted in kerosene as the organic phase. A recycling process which recovers indium from waste LCD glass was proposed

Theory

Experiments

Results and Discussion

M H2SO4

Conclusion

D: Distribution ratio