Development of Novel Separation Technique of Phosphors Used in Fluorescent Lamps: Preliminary Studies

摘要

In our work we studied the possibility of developing a microflotation technique to separate end of life phosphors (fluorescent lamp material) to recycle them. Flotation is classically used in the mine industry in large scale annually hundred of kilotons of ores are separated from the waste this way Nowadays microflotation started widespread in environmental industry and especially in paper industry as a step of waste treatment. The classical flotation technique uses the differences in surface (wetting) properties of particles to separate them. The particles are suspended in aqueous solutions and then foam is formed. Given particles can attach to the foam bubbles and hence travel out from the vessel. Other particles do not attach to or detach from the bubbles and remain in the vessel. The particle - bubble attachment is driven by colloid and hydrodinamie forces. As the particle size goes down to the micron range like in case phosphors for fluorescent lighting applications - the extent of inertial and gravitational forces drop, so the surface and hydrodynamic forces get prevailing. However, under specific conditions the size of the particles may be modified by selective particle - particle aggregation / stabilization that can be controlled by controlling the composition of the solution from which the flotation is done. In this way one can reach the desired selectivity. [1-3] To achieve this goal we need to have a thorough understanding in how the particle -particle and particle - bubble interaction can be modified by altering the suspension pH, surfactant type and concentration.