Separation and Recovery of Rare Earth Elements from Phosphor Sludge in Processing Plant of Waste Fluorescent Lamp by Pneumatic Classification and Sulfuric Acidic Leaching.

Abstract

The classification and acidic leaching behaviors of phosphor sludge have been examined to establish the recycling system of rare earth components contained in fluorescent lamp waste. At first, separation characteristic of rare earth components and calcium phosphate in phosphor sludge was investigated by pneumatic classification. After pneumatic classification of phosphor sludge, rare earth components were leached in various acidic solutions and sodium hydroxide solution. For recovery of soluble component in leaching solution, rare earth component was recovered by treatment processes such as hydroxide and oxalate precipitations. The experimental results obtained are summarized as follows:(1) In classification process, rare earth components in phosphor sludge were concentrated to 29.3 % from 13.3 %, and its yield was 32.9 %.(2) In leaching process, sulfuric acidic solution was more effective one as a leaching solvent of rare earth components than other solutions. Yttrium and europium in phosphor sludge were dissolved in sulfuric acidic solution of 1.5 kmol / m 3 concentration, and other rare earth elements were rarely dissolved in leaching solution. The leaching degree of yttrium and europium were respectively 92 % and 98 % in following optimum leaching conditions ; sulfuric acid concentration is 1.5 kmol / m 3 , leaching temperature 343 K, leaching time 3.6 ks and pulp concentration 30 kg / m 3 . (3) In recovery process, yttrium and europium could be recovered to above 99.1 % by means of hydroxide treatment and oxalate precipitation method.(4) Yttrium and europium from phosphor sludge contained in fluorescent lamp waste were recovered effectively by three processes of pneumatic classification, sulfuric acid leaching and oxalate precipitation methods. Their recovery was finally about 65 %, and its purity was 98.2 %. KEY WORDS : Fluorescent Lamp, Phosphor, Pneumatic Classification, Sulfuric Acid Leaching, Rare Earth Elements, Separation and Recovery

Floatability of rare earth phosphors from waste fluorescent lamps

“…Nowadays, they are considered to be potential urban mining resources for the recovery of rare earth metals through recycling. Gravity based processes such as the pneumatic separation (Takahashi et al, 2001) and the dense medium centrifugation of waste materials pre-treated with sodium oleate (NaOl) (Hirajima et al, 2005) as preliminary concentration operations before carrying out a complete chemical extraction of the rare earth metals. In view of the low efficiency of the first method as well as the high cost and negative environmental effects of the organic dense medium (di-iodomethane, CH 2 I 2 ) used in the second, an alternative method should be investigated.…”

Accomplishing simple, solubility-based separations of rare earth elements with complexes bearing size-sensitive molecular apertures

“…Of these, YOX has the highest intrinsic value because it contains 80 wt % of the total RE content of the phosphor waste and is composed exclusively of the two critical RE elements, Y and Eu. Recent developments in the recycling of phosphor materials have largely focused on the recovery of Eu and Y from YOX (11,(30)(31)(32)(33)(34)(35)(36)(37)(38) (29). Currently, however, only one industrially applied recycling process exists for lamp phosphor waste (29,39).…”

Separation of red (Y2O3:Eu3+), blue (BaMgAl10O17:Eu2+) and green (CeMgAl10O17:Tb3) rare earth phosphors by liquid/liquid extraction

“…Up to now, the collected phosphor complex can not be further separated and reused to make new lamps. At previous research work [5][6][7] , yttrium and europium elements could be recovered from waste phosphor sludge by means of leaching treatment and oxalate precipitation method after pneumatic classification. And then, rare earth powder of red phosphor (Y 2 O 3 :Eu 3+ ) was also reproduced by coprecipitation process [8] .…”