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 / m3 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 / m3, leaching temperature 343 K, leaching time 3.6 ks and pulp concentration 30 kg / m3.
(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 %.
