# Europium, Yttrium, and Indium Recovery from Electronic Wastes
## 3 Results and Discussion
### Indium Recovery from LCDs  
The elemental chemical composition was analyzed by a scanning electron microscopy (SEM) through an X-ray analyzer. Through this analysis, the presence of indium was verified on the LCD panel. From this analysis, a surface section of the LCD panel was considered and the results obtained from chemical composition are semiquantitative. Characterization carried out by X-ray diffraction (XRD) was impossible, since the diagram obtained shows that the LCD panel is an amorphous material, so a chemical analysis was carried out using X-ray fluorescence (FRX). The chemical characterization of the powder that was carried out by an X-ray fluorescence analysis is shown in Table 2.  
Figure 5: Process flow diagram for yttrium oxide recovery from CRT powder. From the results obtained by X-ray fluorescence, the presence of silicon is observed, because the panel is constituted by silicon dioxide (SiO\({}_{2}\)), calcium, strontium, and magnesium. These elements are part of the glass, since these they are fluxes that lower the panel melting point. In addition, 0.03% of indium was obtained, which corresponds to 300 mg/g of the panel. For the recovery of indium from the LCD screens, the screens were powdered up to a particle size of 274 \(\upmu\)m. The powder obtained was subjected to acid leaching in order to dissolve the indium. For this purpose, the concentration of the leaching agents, the leaching time, and the percentage of solids were varied, as shown in Figure 6.  
In Figure 5a, it is observed that there is not much difference as far as the use of the leaching agent is concerned. However, the use of H\({}_{2}\)SO\({}_{4}\) is preferable, since indium sulfate is easier to transform into indium oxide in later stages. Another aspect to keep in mind is that when the percentage of solids varies, the recovery of indium in solution does not fall below 90%. In Figure 6b, an indium recovery of 98% is observed at 8 h when H\({}_{2}\)SO\({}_{4}\) is used, while 8 h is required to recover 94% of the indium when HCl is used as a leaching agent. It was also determined that at the time of 2 h of leaching, the recovery of other elements such as iron and aluminum was 24% and 4%, respectively. If the leaching time is increased, the dissolution of these elements also increases, so it is recommended to not exceed the leaching time beyond 4 h.  
For the solvent extraction stage, di-(2-ethylhexyl) phosphoric acid (DEHPA) and tributyl phosphate (TBP) were used as extractants, whereas diesel and _n_-hexane were used as diluents. The pH in all of the assays was maintained at 1.7, and the contact time in all of the cases was 10 min. In Figure 7, the results obtained with both diluents are shown. \begin{table}
\begin{tabular}{c c} \hline
**Element** & **Composition (\%)** \\ \hline Si & 25.40 \\ Al & 7.55 \\ Ca & 4.70 \\ Sr & 3.70 \\ Mg & 0.90 \\ Cl & 0.10 \\ Sn & 0.09 \\ Fe & 0.08 \\ P & 0.05 \\ In & 0.03 \\ \hline \end{tabular}
\end{table} 
Table 2: Elemental chemical composition of the liquid crystal display (LCD) panel using X-ray fluorescence (FRX). Figure 6: (**a**) Influence of the percentage of solids in the recovery of indium with H\({}_{2}\)SO\({}_{4}\) and HCl; (**b**) Influence of the leaching time in the recovery of indium with H\({}_{2}\)SO\({}_{4}\) and HCl (20% of solids). At a pH value lower than 1.7, a preferred extraction of other metals such as Fe\({}^{2+}\) and Al\({}^{3+}\) is observed instead of Ir\({}^{3+}\) ions. On the other hand, the high content of H\({}^{+}\) ions present at this pH prevents the ln\({}^{3+}\) ion from being captured [30] and displaces the equilibrium to the left in the extraction reaction of indium, decreasing the extraction of it [31]. Therefore, a pH value of 1.7 was chosen, where a substantial increase in the extraction of indium is observed in the organic phase, reaching an average extraction of 99%. This phenomenon is due to the decrease in the concentration of H\({}^{+}\) ions, with the extraction of indium being favored according to [PERSON]'s principle.