Recycling of florescent phosphor powder Y2O3:Eu by leaching experiments
Due to the advancing development of new technologies and consumer goods the future demand for raw materials will rise significantly. The finite primary raw materials will not be able to meet the demand quickly enough or the prices for the extraction will rise enormously. In consequence, a recycling of process waste and end of life products will be in future an essential step in order to meet the demand. Y2O3:Eu fluorescent phosphor was identified as the main composition in phosphor waste fractions and was chemical leached and bioleached with A. ferrooxidans. A selective leaching towards Y in bioleaching batches was observed and already after four days 100 % could be leached. The bioleaching with the bacteria showed no significant differences in comparison to the abiotic control without microorganism. Initial Fe3+ in the medium was identified as the driving force and lower extraction efficiencies of the biotic batches were attributed to a biosorption process and to high pH-values. This work showed that the extraction of yttrium out of waste products with high Y2O3:Eu content by chemical leaching with Fe-addition under mild conditions offers a good perspective to support the material demand of Y in the future growing market. In comparison to bioleaching of other fluorescent phosphors and waste fractions leaching efficiencies up to 100% were achieved and it was identified that the microorganisms can positively influence the leaching effect. Furthermore, it became obvious that the leaching behavior of microorganisms was highly dependent on the sample material. As relevant parameters mainly the structural composition of the phosphor was identified.