Abstract :
[en] As various electrical and electronic equipment pieces are frequently replaced due to technological development or changes, the recycling of the generating in huge amount e-wastes is of outstanding importance. The research in this field is inevitable in the spotlight of creating the circular economy. The recycling strategy is generally aiming at the recovery of materials like plastics and metals, as well as of valuable, even critical elements and compounds along with the satisfactory treatment of toxic ones. For this sake the mechanical treatment is combined with the chemical/bio/thermal techniques.
Due to the numerous elements used for their manufacturing, LCD (Liquid Crystal Displays) display panels provide a wide range of valuable and critical, but also toxic elements. Thus, instead of disposal of waste LCD panels, the recovery of such elements can not only prevent possible environmental hazards but endorse the utilisation of secondary raw materials.
It was proved that the mechanical pre-treatment is an important step, first of all, to recycle materials like plastics and common metals. Furthermore, the chemical mass transfer is governed by the concentration gradient, the area exposed and the retention time. Nevertheless, the presence of the “alien” components in the mass transfer can dramatically decrease the concentration gradient, the contact surface, as well as the diffusion rate. And finally, the lower the material flow to be submitted for the chemical processing, the lower the specific reagents requirement and, therefore the costs of the process (Bokányi, 2014).
Thus, the mechanical removal of LCD polarizing film seems to be highly advisable; however is not easy, needs 200-250 °C high temperature as well. At the same time, the ITO (Indium-Tin-Oxide) surface layer at favourable conditions can be exposed for the diffusion even without removing polarizing foil.
Therefore, one experimental series of our current research was focused on the comparison of acidic leaching of the stripped and ground LCD panel with and without the polarizing film. Another experimental series was devoted to the effect of fineness on the leachability of indium, tin and other elements. Thereafter, ground LCD was produced with different fineness in Retsch ZM 200 centrifugal mill. Based on the data obtained, important conclusions were drawn
