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Research Contents

Our laboratory is divided into three research groups, Resource Circulation, Powders Simulation, Wastewater・Minerals Treatment.
Resource Circulation group is more divided three processing method, Electric, Physical, Chemical Click the button below to display the research content relevant to each group.
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    < Electric process >

     Focusing on the " electric pulse method," a highly selective and efficient physical separation technology, we aim to construct a new recycling production system by proposing a design and manufacturing process that facilitates disassembling.
     In order to find the optimised electric pulse conditions for the target, it is necessary to elucidate the separation mechanism and evaluate its applicability based on the specific separation mechanism. In addition, we evaluate and provide feedback on these technologies in terms of cost, environmental load, resource efficiency, and optimize them for social implementation.

    ■ Study on separation of active materials from cathode materials of lithium-ion batteries
     By 2030, demand for automotive lithium-ion batteries is expected to increase 10~20 times compared to that of 2020. Cathode materials of lithium-ion batteries (LiB) contain economically valuable metals such as Ni, Co, Mn, and Li, and the recovery of these metals is necessary in the process of resource recycling. We are conducting research to efficiently separate the active material from the current-collecting foil (Al foil), locatedat the boundary surface, by applying electric pulses to LiB cathode powders containing these valuable metals. Ultimately, we aim to establish an energy-saving and low-cost recycling loop by regenerating batteries in which the cathode active materials recovered by the electric pulse method are returned to the batteries.

    ■ Research and development of easily to disassemble structures and easily disassembled adhesives suitable for metal bonded bodies and multi-material separation
     In the automotive industry, there is an increasing need to design products that can be easily disassembled and recycled from a life cycle perspective. In this research, we are conducting research and development on easy to disassemble structures, using electric pulses to separate adhesive-bonded metal and multi-materials consisting of steel sheets and CFRP, which are used to reduce the weight of automobiles and aircraft, as well as easily disassembled adhesives with the addition of fillers. We are also conducting research and development of easy-dismantling adhesives by adding fillers.

    ■ Fundamental Study of Separation and Recovery of Carbon Fiber from CFRP Laminates
     CFRP (carbon fiber reinforced plastic) is increasingly used as a lightweight material in various industries such as automobiles, aircraft, and wind power generation. On the other hand, disposed CFRP is currently incinerated and landfilled, making the separation and recovery of carbon fiber from CFRP, as well as the reuse and recycling of carbon fiber, a pressing need in resource recycling. In this study, carbon fibers are separated and recovered from CFRP laminates using the electric pulse method, and the strength of the recovered carbon fibers is evaluated.

    ■ Investigation of selective recovery of silver from waste solar panel sheets after electric pulse pulverization.
     Silver is used in solar panels as a useful resource, and its separation and recovery in the recycling process is a challenge. In this research, we are studying the selective recovery of silver as particles by applying electric pulses to conductive silver paste wires in the cells of solar panels to cause a fine wire explosion of the silver paste wires. We are also conducting research on the recovery of silver from solar panel cells by collective pulverization using electrical pulses.

    < Physical process >

     The basis of recycling is a combination of "crushing and separation," "sorting," and "recovery". Crushing and separation are often caused by mechanical external methods and involve many physical phenomena. Therefore, there are many phenomena that have yet to be elucidated, and we are working to elucidate their mechanisms through the pulverization and separation of various objects. In addition to mechanical external stimuli, thermal processing is also used to take advantage of the characteristics of materials, and experimental verification and simulations are conducted to reproduce these phenomena.

    ■ Selectively removing lead by bromide volatilization
     In the recycling of plastics, those containing bromine cannot be mixed with recycled products due to the RoHS Directive that has been in effect since 2006, and most of them are disposed of by disposal or incineration. In this study, we are investigating the optimum conditions under which bromination volatilization occurs, with a view to effectively utilizing waste plastics containing bromine as a volatile bromination agent for metals.

    ■ Organization of a PV panel recycling process including the selectively recovery of copper, silver and tin
     The amount of used solar panels is expected to increase in the future, and a system to recycle large quantities of panels is needed. In this study, we examine the recovery of useful metals, including tin, which we have not focused on until now. At the same time, we aim to establish a new recycling flow that meets the needs of companies.

    ■ Research of grinding of two components slag
     Particle size reduction and milling rates for single samples have been extensively studied. However, in industrial applications , multi-component samples are milled. In this study, we conduct milling tests on bi-component slag to clarify under which conditions (sample proportions and milling conditions) the selective milling of only one of the components occurs. We also aim to reproduce such phenomena by DEM simulation.

    ■ Fundamental Study on the Separation of Contaminated Particles for Promotion of Plastic Circulation
     It is known that impurities such as glass in the material pellets used during PET bottle molding can cause bursting. In order to realize bottle-to-bottle recycling, we are constructing advanced removal technology for impurities contained in used PET bottle flakes. In addition to aiming to remove minute amounts of impurities, we aim to promote plastic recycling by clarifying the causes of contamination.

    < Chemical process >

     Of the three basic recycling processes, "crushing and separation," "sorting," and "recovery," chemical treatment is often used for "recovery”. By accurately understanding chemical reactions and their mechanisms, we can improve conventional treatment methods and propose new processes, aiming to build low-cost, high-efficiency processes that can be applied to many resources.

    ■ Investigation of methods to recover valuable metals from all-solid-state lithium-ion batteries
     Lithium-ion batteries, for which demand is expected to increase rapidly with the spread of EVs, contain rare metals, and recycling of these metals is required to realize a recycling-oriented society. In this study, we are investigating metal recovery processes through roasting and acid solution processes for next-generation lithium-ion batteries that use solid electrolytes.

    ■ Study of the effect of fluorine on metal leaching from cathode active materials
     In the field of lithium-ion battery recycling, using an underwater electric pulse is a promising method for the separation of cathode active material from aluminum foil. This method has low environmental impact and can effectively release cathode active material in a short time. However, fluorine and other precious metals may also be eluted into the solution during discharge. Therefore, to investigate the source of fluorine and its effect on metal extraction, we are conducting leaching experiments using different fluorine concentrations and detailed surface observations of used LiBs.

     Powders are known to exhibit very peculiar behavior, as they are sometimes described as the “fourth state” after gases, liquids, and solids. Because of this, it is difficult to evaluate and measure their behavior by experimental methods, and the mechanisms of even simple unit operations have not been fully elucidated. Against this background, large scale operating conditions are currently determined based on empirical rules, and optimization often requires enormous costs.
     We are utilizing DEM (Discrete Element Method) simulation, a type of powder simulation, to elucidate the mechanisms of various powder processes such as milling, separation, mixing, and granulation, to optimize each process.

    ■ Evaluation of Grindability of Media Stirred Mill by DEM Simulation
     Although media stirred mills are used for fine grinding in various industrial fields, the milling mechanism has not been clarified. Therefore, the optimal mill geometry and operating conditions are determined empirically, which is a costly process. Therefore, we are using DEM to elucidate the milling mechanism and determine the optimum operating conditions, which are difficult to do experimentally.

    ■ Development of a new coarse-grained model for adhesion in DEM simulations
     DEM is a very computationally demanding method and requires additional ingenuity for large-scale analysis. Although coarse-grained models can significantly reduce the computational load, the applicability of the models is still limited. In this study, we are working to establish a new coarse-grained model that additionally takes into account adhesion forces, which are an important factor in the powder production process.

    ■ Evaluation of Grindability of Disk Mill by DEM-CFD Simulation Introducing Fracture Model
     Disk mills are used for fine grinding in a variety of industries, but the detailed grinding mechanism has not been clarified. Therefore, it is expensive to determine the optimum equipment geometry and operating conditions only by experiments. Therefore, we are using CFD (Computational Fluid Dynamics) simulations coupled with DEM, and directly simulating particle breakdown using a breakdown model to elucidate the grinding mechanism and determine optimal operating conditions, which are difficult to do experimentally.

    ■ Optimization study of wet particle conveying process by DEM simulation
     Wet particles are often very difficult to control in particle processing due to adhesion and agglomeration caused by liquid cross-linking forces. Therefore, we are working on the optimization of conveying conditions by analyzing the conveying behavior of wet particles and elucidating the mechanism using DEM.
     The Wastewater Group is developing technologies to recover valuable metals in mine and industrial wastewater by chemical and physicochemical treatment, proposing removal processes for hazardous substances, and elucidating removal mechanisms. The group is working hard every day in a well-equipped research environment, using not only solution analysis of wastewater but also advanced solid analysis equipment for the precipitated particles after treatment. Using chemical equilibrium calculation software, we have developed our own wastewater treatment model to optimize the process.
     We are trying to conduct not only basic research but also research with a view to versatility and industrialization. We also tackle problems that are not currently apparent, and conduct research that envisions environmental problems in the near future. We have many points of contact with society and are always conscious of our social responsibility as a research institutione.

    ■ Development of Ni Recovery Process from Acidic Liquid Waste Containing Nickel (Ni) Using Sulfide Method
     Recently, many organic chemical reaction processes using Ni as a metal catalyst have been developed. Since the effluent contains high concentrations of Ni after the reaction, it is expected that Ni can be recovered and reused as a new Ni resource. In this study, we focus on the precipitation method using Ni sulfide, which has low solubility, and conduct an experimental study to establish a reaction process that can achieve high yield while suppressing the generation of hydrogen sulfide.

    ■ Evaluation of Hg stability on pyrite surface for stable treatment of mercury (Hg)-containing wastes
     Pyrite is being considered for use as an Hg insolubilizer because of its high affinity for Hg, which must be strictly controlled in the environment. However, the stability of adsorbed Hg is not well known, and there are concerns about long-term risks such as Hg re-leaching in final disposal sites. In this study, the stability of adsorbed Hg on pyrite surfaces under various chemical conditions is investigated to provide a basis for the stable disposal of Hg-containing wastes.

    ■ Removal of zinc (Zn) from mine wastewater by formation of silicate minerals
     In the treatment of mine wastewater containing Zn, Zn forms hydroxides in the high alkaline range, requiring a post-neutralization treatment, which increases the cost of chemicals. Therefore, Zn removal technology in the neutral range is required, and previous studies have shown that adsorption and coprecipitation removal using aluminum hydroxide and manganese dioxide are effective. However, even with these technologies, Zn removal may not be sufficient for mine wastewater, which has a high environmental impact. Therefore, this study focuses on the use of silicate minerals to develop a new Zn removal technology using silicate mineral formation.

    ■ Unraveling the characteristics of pyrite/chalcopyrite flotation separation in high Ca/Mg-contained water and novel method development for upgrading separation efficiency
     Considering the lower economic value and higher abundance of pyrite in most copper ores, the separation efficiency among pyrite and copper-contained minerals caused extensive concern. We try to integrate the utilization of the High Ca/Mg contained process water or seawater as an alternative in flotation systems to facilitate the separation efficiency between unwanted pyrite and valuable chalcopyrite. A series of novel methods are being developed to upgrade their separation efficiency via selective reduction of the undesirable Cu-activation and the Ca/Mg depression effect.

    ■ Elucidation of oxyanions removal using carboxylic acid–modified layered double hydroxides (LDHs)
     Layered double hydroxides (LDHs) have received great attention due to their ability to remove several harmful cations and anions from contaminated water. Recent studies have shown LDHs functionalized with organic materials exhibit higher sorption affinity for oxyanions. Herein, we developed modified LDHs with carboxylic acid for enhancing the removal of oxyanions from contaminated water. The detailed removal mechanism for oxyanions is elucidated using several microscopic tools.

    ■ Study on the autocatalytic oxidation of manganese from superacid condition and application in Fe-Mn separation
     The superacid wastewater obtained after pickling contains a high concentration of Fe3+ and Mn2+, which must be properly recovered for metal recycling. Through a series of neutralization and oxidation operations, we found that Mn precipitation as MnO2 can be achieved even under super acidic conditions. Based on this knowledge, we are trying to develop the separation process via precipitating Mn while leaving soluble Fe in wastewater.