Treatment of exhaust fluorescent lamps to recover yttrium: Experimental and process analyses

Journal Article · Thu Dec 15 00:00:00 EST 2011 · Waste Management

DOI:https://doi.org/10.1016/j.wasman.2011.07.004· OSTI ID:21578444

Ferella, Francesco ^[1]; Varelli, Ennio Fioravante ^[1]; Veglio, Francesco ^[1]

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1. University of L'Aquila, Department of Chemistry, Chemical Engineering and Materials - Ex-Optimes Loc., Campo di Pile, 67100 L'Aquila (Italy)

Highlights: > Recovery of yttrium from spent fluorescent lamps by sulphuric acid leaching. > The use of sulphuric acid allows to reduce calcium dissolutions. > Main contaminant of fluorescent powder are Si, Pb, Ca and Ba. > Hydrated yttrium oxalate, recovered by selective precipitation, is quite pure (>90%). > We have studied the whole process for the treatment of dangerous waste (plant capability). - Abstract: The paper deals with recovery of yttrium from fluorescent powder coming from dismantling of spent fluorescent tubes. Metals are leached by using different acids (nitric, hydrochloric and sulphuric) and ammonia in different leaching tests. These tests show that ammonia is not suitable to recover yttrium, whereas HNO{sub 3} produces toxic vapours. A full factorial design is carried out with HCl and H{sub 2}SO{sub 4} to evaluate the influence of operating factors. HCl and H{sub 2}SO{sub 4} leaching systems give similar results in terms of yttrium extraction yield, but the last one allows to reduce calcium extraction with subsequent advantage during recovery of yttrium compounds in the downstream. The greatest extraction of yttrium is obtained by 20% w/v S/L ratio, 4 N H{sub 2}SO{sub 4} concentration and 90 deg. C. Yttrium and calcium yields are nearly 85% and 5%, respectively. The analysis of variance shows that acid concentration alone and interaction between acid and pulp density have a significant positive effect on yttrium solubilization for both HCl and H{sub 2}SO{sub 4} medium. Two models are empirically developed to estimate yttrium and calcium concentration during leaching. Precipitation tests demonstrate that at least the stoichiometric amount of oxalic acid is necessary to recover yttrium efficiently and a pure yttrium oxalate n-hydrate can be produced (99% grade). The process is economically feasible if other components of the fluorescent lamps (glass, ferrous and non-ferrous scraps) are recovered after the equipment dismantling and valorized, besides the cost that is usually paid to recycling companies for collection, treatment or final disposal of such fluorescent powders.

• OSTI ID: 21578444
• Journal Information: Waste Management, Vol. 31, Issue 12; Other Information: DOI: 10.1016/j.wasman.2011.07.004; PII: S0956-053X(11)00309-6; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0956-053X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
AMMONIA
BARIUM
CALCIUM
EXTRACTION
FLUORESCENT LAMPS
GLASS
HYDRATES
HYDROCHLORIC ACID
LEACHING
LEAD
NITRIC ACID
OXALATES
OXALIC ACID
PRECIPITATION
RECYCLING
SILICON
SULFURIC ACID
VAPORS
YTTRIUM
YTTRIUM COMPOUNDS
ALKALINE EARTH METALS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CHLORINE COMPOUNDS
DICARBOXYLIC ACIDS
DISSOLUTION
ELEMENTS
FLUIDS
GASES
HALOGEN COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INORGANIC COMPOUNDS
LIGHT BULBS
METALS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
SEMIMETALS
SEPARATION PROCESSES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS