Jun Sadaki

Separation of Rare Earth Fluorescent Powders by Two-Liquid Flotation using Organic Solvents

In this paper, we describe a method for separation of ultra-fine particles prior to recycling. The authors suggest a two-step process for separating a mixture of three different rare earth fluorescent powders (i.e., red, green, and blue). Each step of the process is a two-liquid flotation, which involves two organic solvents (i.e., a non-polar and a polar solvent, in order to create two different phases) and a surfactant to manipulate the wettability of the powders. In the first step, the green powder migrates toward a non-polar phase such as n-heptane and remains at the interface of two solvents. The remaining two components precipitate in the polar phase. In the second step, the blue powder migrates toward a non-polar phase and remains at the interface of two solvents, while the red powder precipitates in the polar phase. After testing various non-polar solvents, a selection was made, and the operational parameters (e.g., concentration of surfactant and solid) were varied in order to maximize the efficiency of the process. The grade and recovery of each separated fluorescent powder were both greater than 90%.

Life Cycle Assessment: A Tool for Evaluating and Comparing Different Treatment Options for Plastic Wastes from Old Television Sets

In the present work, energy recovery and mechanical recycling, two treatment options for plastic wastes from discarded television sets, have been assessed and compared in the context of the life cycle assessment methodology (LCA). The environmental impact of each option was assessed by calculating the depletion of abiotic resources (ADP) and the global warming potential (GWP). Then, the indicators were compared, and the option with the smaller environmental impact was selected. The main finding of this study was that mechanical recycling of plastics is a more attractive treatment option in environmental terms than incineration for energy recovery.

Concept of Seafloor Mineral Processing for Development of Seafloor Massive Sulfides

Seafloor Massive Sulfides (SMS), which were formed by deposition of precipitates from hydrothermal fluids vented from seafloor, is one of unconventional mineral resources beneath deep seafloors in the world. The authors have proposed the concept of seafloor mineral processing for development of SMS, where useful minerals included in SMS ores are separated on seafloor to be lifted while the remaining gangue is disposed on seafloor in appropriate ways. To apply column flotation, one of conventional methods in mineral processing, to seafloor mineral processing, the authors carried out simulating experiments of column flotation on deep seafloor using ores including copper, iron, lead and zinc as metallic elements. Prior to the experiments at high pressures, preparatory experiments at the atmospheric pressure were carried out to find out the optimum condition of the properties of pulp, a mixture of feed ore, water and chemical reagents. In flotation experiments at high pressures, formation and overflow of froth layer by bubbling were observed at 1MPa in both of pulps with pure water and artificial seawater. The analytical data showed that the concentration of metallic elements such as copper and zinc in the concentrates recovered from the experiments was higher than that in the feed ores while the concentration of silicon and calcium, which are assigned to gangue, in the concentrates was lower than that in the feed ores. These results suggest that column flotation can be applied to operation on seafloor.Copyright

Erasing Data and Recycling of Optical Disks

Optical disks, DVDs and CDs, are convenient recording media on which to safely store data for a long period of time. However, the complete data erasure from recorded media is also important for the security of the data. After erasure of data from optical disks, recycling the material is needed in order to recover the valuable components of the optical disks. Here, data erasure methods for optical disks are discussed in the view of material recycling. The main finding of the study is that the explosion of optical disks in water is a very suitable method for complete erasure of data on the disks as well as recycling of their materials.

Study on Seafloor Mineral Processing for Mining of Seafloor Massive Sulfides

Seafloor Massive Sulfides (SMSs), which were formed by deposition of precipitates from hydrothermal fluids vented from seafloor, has been expected as one of unconventional mineral resources on deep seafloors in the oceans. The authors have proposed the concept of seafloor mineral processing for SMS mining, where valuable minerals contained in SMS ores are separated on seafloor while gangue minerals are disposed on seafloor in appropriate ways. To confirm the applicability of column flotation, which is one of conventional mineral processing methods, to seafloor mineral processing, the authors carried out experiments simulating column flotation under the pressure conditions corresponding to the water depths down to 1000m in maximum using ore samples containing copper, iron, zinc and lead. In the experiments, formation of fine bubbles suitable to flotation and overflow of froth layer were observed at high pressures. The contents of copper and zinc in the concentrates recovered in the experiments at 1MPa were higher than those in the feed ores while the contents of silicon and calcium in the concentrates were lower than those in the feed ores. These results suggest that column flotation would be applicable to seafloor mineral processing.Copyright