DD246551A1 - METHOD FOR RECOVERING RARE CONNECTIONS FROM FLUORESCENT LAMPS - Google Patents

Abstract

The invention relates to the separation of phosphors from unusable fluorescent lamps and the recovery of rare earth compounds from such phosphor waste. The inventive method includes the crushing of the glass body of the lamps, the separation of the resulting phosphor powder and glass powder by sieving, associated with the washing of the coarse glass pieces with water, and the dissolution of the phosphors with hydrochloric or nitric acid, the rare earths from the filtered solutions are purified by precipitation as hydroxides and subsequently as oxalates of impurities on other metal compounds.

Description

Field of application of the invention

The invention relates to the separation of phosphors from unusable or incorrectly produced fluorescent lamps and the recovery of rare earth compounds from such phosphor waste.

Characteristic of the known technical solutions

For the production of fluorescent lamps, especially energy-saving low-pressure mercury vapor. Discharge lamps with light corresponding to the spectrum of normal daylight used mixtures of red, green and blue phosphors (tri-band phosphors) contain compounds of individual rare earth elements as host lattices or activators.

Important phosphors for fluorescent lamps are z. B. Mg (PO ₃ I ₂ (host lattice): Ce ³⁺ (activator ion), Y ₂ O ₃ : Eu ²⁺ , SrAl ₂ O ₄ : Eu ²⁺ , YVO ₄ : Eu ²⁺ , Sr ₃ (PO ₄ ) ₂ : Eu ²⁺ , Sr ₂ P ₂ O ₇ : Eu ²⁺ , Sr ₅ (PO ₄ I ₃ Cl

Three-band phosphors of the following composition are described: Y ₂ O ₃ : Eu:> (red phosphor, emission peak 611 nm)

060.67 TBC ₃₃ MgAl ₁₁ O-Ig (green phosphor, emission peak 545 nm)

Bao, 86Euo, ₁₄ Mg ₂ Al ₁₆ 0 ₂ 7 (blue luminescent substance, emission peak 450 nm)

Because of the relatively high prices of the individual pure rare earth oxides, in particular of europium, terbium and yttrium oxides, the recovery of rare earth compounds from unusable fluorescent lamps or corresponding phosphor waste is of economic interest.

Depending on the particular composition of the red, green and blue luminescent substances used, at least europium, yttrium, cerium and terbium compounds as well as certain amounts of aluminum and alkaline earth compounds are to be expected in the phosphor waste. For the separation of the phosphor layers from fluorescent lamps, the treatment of the crushed glass body of the lamps in water is described with ultrasound, the phosphor mixtures are then separated by sedimentation and filtration of water (DD 224323 A 1,1985).

For the recovery of rare earth compounds from 'fluorescent mixtures, which are recovered from fluorescent lamps, no special processes are described. However, a number of methods are known for the recovery of rare earth compounds from phosphor waste, which are obtained in the processing of unusable or incorrectly produced color picture tubes. Since phosphors for cathode ray tubes / color picture tubes usually contain larger amounts of sulfides of zinc or cadmium and rare earth oxides and thus have a substantially different material composition than phosphors for fluorescent lamps, known methods are not easy to transfer to the processing of phosphor waste from fluorescent lamps ,

For phosphor waste from color picture tubes, the removal of the impurities from binders, pigments and green and blue luminescent substances by treatment with water, alkalis, complexing agents, oxidizing agents and acids is practiced, with the proportion of red phosphor remaining undissolved. In addition, the complete dissolution of the phosphor waste in acids and the subsequent separation of the rare earths by adsorption on cation exchangers or by precipitation as oxalates is known. A disadvantage of all processes which relate expressly to the processing of the phosphor waste from color picture tubes, is that there is no sufficient separation of the rare earths from the other components of the waste is achieved or the separation is complicated and expensive.

Object of the invention

The aim of the invention is to propose a simple process for the recovery of rare earth compounds from fluorescent lamps, which on the one hand involves the separation of the phosphor layers from the lamps and on the other hand the recovery of rare earth compounds from the phosphor waste.

Explanation of the essence of the invention

It has been found that by chopping the glass body of the fluorescent lamps in spiked roller crushers, jaw crushers, Hammmer mills or other suitable devices to pieces <10 mm. Screening of the glass breakage over sieves with mesh sizes 0.2 mm. Washing the Siebrückstandes with water, separation of the sieve passage from the water by sedimentation or filtration, a mixture of glass powder and phosphor mixture is obtained, which is treated to dissolve the proportion of phosphor mixtures with hydrochloric acid or nitric acid. After dilution of the digestion mass with water, the undissolved glass particles are separated and precipitated from the resulting solution, the rare earths for the separation of divalent metals, in particular Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ with ammonia in ammoniacal solution as hydroxides ,

The rare earth hydroxides are filtered off, washed with water and redissolved in hydrochloric or nitric acid. From the acidic solution, the rare earths are precipitated as oxalates with oxalic acid to remove Al ³⁺ . After filtering, washing with water and drying, the rare earth oxalates are converted to other rare earth compounds, e.g. B. burned to rare earth oxides, and fed to the separation into individual rare earth compounds.

The inventive method can be carried out with little effort and easily accessible raw materials and excipients. The method according to the invention is explained in more detail in the following exemplary embodiment:

example

Of 20 SW double-tube lamps, 012mm, I = 120mm, the sockets with the contact pins and plastic parts were removed; the glass bodies were tamped in a steel mortar so that the fragments were smaller than 10 mm. The glass breakage was screened and passed through a 0.2 mm mesh screen to obtain 12.3 g of phosphor glass powder mixture and 837 g glass pieces. The pieces of glass on the sieve were washed out by pouring 500 ml of water. From the resulting aqueous suspension 0.6 g of phosphor glass powder mixture were separated by filtration. The combined phosphor glass powder mixtures were stirred with 100 ml of 36% hydrochloric acid at 90 ° C. for 3 hours. The digestion mass was then diluted with 200 ml of water and separated from undissolved portions by filtration through a glass suction filter. The solution was brought to pH = 9 by addition of ammonia water and then heated briefly to boiling. The precipitate of rare earth hydroxide with aluminum impurities was filtered off, washed with water and rinsed with 10 ml of 36% hydrochloric acid + 50 ml of water from the filter. The resulting rare earth chloride solution was diluted to 250 ml with water, blunted with ammonia-water until pH = 2 and mixed with cold saturated oxalic acid solution until the precipitation of the rare earth oxalates was complete. The solution was heated to 60 ^° C. for 1 hour. The precipitate of Seltenerdoxalaten was filtered, washed with water, dried and calcined at 900 ⁰ C. There were obtained 3.45 g of a rare earth oxide mixture containing 88.0% Y ₂ O ₃ , 5.1% Eu ₂ O ₃ , 2.3% Tb ₄ O ₇ and 4.6% CeO ₂ , which was free from other impurities.

Claims (2)

Invention claim: 1. A process for the recovery of rare earth compounds from fluorescent lamps, characterized by coarsely crushing the glass body, separation of phosphor powder and galspulver by sieving and washing with water from coarse glass pieces, dissolving the phosphors with hydrochloric or nitric acid, precipitation of the rare earths from the filtered solutions with Ammonia as hydroxide, dissolution of the hydroxides in hydrochloric or nitric acid and precipitation of the rare earths as oxalates from acidic solution. 2. The method according to claim 1, characterized in that the size reduction takes place on pieces <10mm and phosphor powder and glass dust are separated on screens with mesh size 0.2 mm.