title: Materials recovery from waste liquid crystal displays: A focus on indium.
abstract: In the present work the recovery of indium and of the polarizing film from waste liquid crystal displays was experimentally investigated in the laboratory. First of all, the polarizing film was removed by employing a number of different techniques, including thermal and chemical treatments. Leaching of indium was then performed with HCl 6N, which allowed solubilisation of approximately 90% In (i.e. 260 mg In per kg of glass) at room temperature, without shredding. Indium recovery from the aqueous phase was then investigated through solvent extraction with polyethylene glycol (PEG)-based aqueous biphasic systems. Indium extraction tests through the PEG-ammonium sulphate-water system were conducted as a function of PEG concentration, salt concentration and molecular weight of PEG, using 1,10 phenanthroline as a ligand. The experimental results demonstrated that indium partitioning between the bottom (salt-rich) and the top (PEG-rich) phase is quite independent on the composition of the system, since 80-95% indium is extracted in the bottom phase and 5-20% in the top phase; it was also found that when PEG concentration is increased, the ratio between the bottom and the upper phase volumes decreases, resulting in an increase of indium concentration in the bottom phase (at [PEG]=25% w/w, indium concentration in the bottom phase is ∼30% higher than the initial concentration before the extraction).
authors.affiliation: ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Via Anguillarese 301, 00123 Rome, Italy. Electronic address: danilo.fontana@enea.it.
authors.forename: Danilo
authors.initials: D
authors.lastname: Fontana
authors.affiliation: Politecnico di Milano, Department of Civil and Environmental Engineering, Piazza Leonardo da Vinci 32, 20133 Milan, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Forte
authors.affiliation: ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Via Anguillarese 301, 00123 Rome, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: De Carolis
authors.affiliation: Politecnico di Milano, Department of Civil and Environmental Engineering, Piazza Leonardo da Vinci 32, 20133 Milan, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Grosso
mesh_terms: D059029:Electronic Waste / Q000032:analysis*; D007204:Indium / Q000737:chemistry*; D050866:Liquid Crystals / Q000032:analysis*; D059027:Recycling / Q000379:methods*; D018505:Waste Management / Q000379:methods*
chemical_list: D007204:Indium
keywords: ABSs; Hydrometallurgy; Indium; Waste LCDs