Recovery of europium-activated red phosphor - based on lanthanide oxide or oxysulphide by two stage removal of sulphide phosphor etc.

摘要

Recovery of phosphor (I) is from an aq. suspension (II) also contg. binder (III) wetting agent (IV), antifoam (V), antifoam(V), sensitisers (VI) and sulphide phosphors (VII). In stage 1, (II) is mixed well with NaOH or KOH and H peroxide and then with a complex-forming acid (VIII to remove (III), (IV), (V) and (VI), then filtered and washed. The filter cake contg. (I) and (VII) is then suspended in water and mixed thoroughly with halogen (IX) in stage 2, filtered and washed. The filter cake then is pref. passivated at elevated temp., pref. at 900 degrees C for oxides and 300-500 esp. 450 degrees C for oxysulphides. Highly pure phosphor can be recovered.