Recycling of Used Toner Carrier for Electro-Photographic Printing by Hydrothermal Treatment

To achieve the recycling of the used toner carrier particles, which are ferrite sintered particles coated with polymer film, the hydrothermal treatment of the used toner carrier powder in pure water or H2O2 aqueous solution was investigated. The polymer films coated on the ferrite core particles could be mostly removed by the sonication after the hydrothermal treatment in pure water. However, the polymer resin was not completely decomposed by the hydrothermal treatment in pure water, and large amount of pure water (liquid/solid ratio is more than 50 cm3/g) was required for decreasing the carbon content (<0.1 mass%) sufficiently. On the other hand, the polymer films could be completely removed by the hydrothermal treatment in 5.4 mass% H2O2 aqueous solution without sonication. In this case, H2O2 will effectively work as oxidizer for the polymer resin during the hydrothermal treatment. The recovered ferrite core particles obtained by the present hydrothermal treatment exhibited the same magnetic and/or electric properties as the virgin ferrite core particles. Therefore, it is found that the present hydrothermal treatment in the presence of H2O2 oxidizer (5.4 mass%) can be one of efficient recycling processes for toner carrier particles for the electrophotographic machine.