Separation and concentration of indium from a liquid crystal display via homogeneous liquid–liquid extraction

Separation and concentration of indium from a liquid crystal display (LCD) was conducted using homogeneous liquid–liquid extraction (HoLLE) in order to completely recycle the LCD. First, using 2.40 M hydrochloric acid, 1.52 mg of indium was leached from the LCD of a mobile phone while keeping the amount of leached foreign metals, such as iron and aluminum, as low as possible. The ability to recycle the LCD glass is also expected because arsenic and antimony, which are used as antifoamers for the glass, were separated in the leaching residue. Next, on the basis of the metal leaching results for a mobile phone LCD, HoLLE with Zonyl FSA (CF3(CF2)nCH2CH2SCH2CH2COOH, n = 6–8, Du Pont Co.) was conducted via the formation of metal-1,10-phenanthroline chelates on a solution formulated to simulate the leachate from a mobile phone LCD. Using this technique, more than 96.7% of the indium was extracted from the simulated leaching solution into the sedimented liquid phase. After phase separation, the volume ratio (Va/Vs) of the aqueous phase (Va) and the sedimented liquid phase (Vs) was 438 (46 ml → 0.105 ml). In addition, the sedimented liquid phase was dropped on a filter and evaluated using X-ray fluorescence analysis. After determination of the elements concentrated into the sedimented liquid phase, the mass concentration of indium in the sedimented liquid phase was estimated to be 10.4 wt%. This result indicated that the mass concentration ratio was 405 because the mass concentration of indium in the mobile phone LCD was 0.0257 wt% on the basis of being determined by heating and leaching with aqua regia.