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Knowledge Co-Creation - Profiles of researchers

Refining environmental purification technology through the engineering application of microscopic interface phenomena

Chiharu Tokoro
Associate Professor, Faculty of Science and Engineering, Waseda University

Changing from a desire to be a pianist to a career in science

My specialty is research for the separation and elimination of pollutants in the environmental field, as well as separation and collection of valuable metals during the recycling process. Although resource engineering is the base of my research, my motto is to refine technology through further scientific exploration of substance phenomena, as well as to be a leader in the discovery of important new technology which has yet to be practically applied.

Actually, I have enjoyed playing the piano ever since I was a small child. Until junior high school, I had seriously applied myself to becoming a professional musician. However, after entering high school, I began to consider different ways of leading my life. I always liked mathematics, chemistry and physics. I am a scientist who sometimes thinks that the act of reading piano sheet music and then performing is actually a science in itself! Upon entering university, I did not hesitate to major in science. I entered university immediately after the 1992 global summit had been held in Rio De Janeiro, Brazil. Environmental fields were experiencing a boom at that time. It was around that time that phrases such as "sustainability" and "global warming" began to be used.

At that time, I was looking through a lot of pamphlets from universities. The Department of Resource Engineering (currently the Department of Resources and Environmental Engineering)at the Waseda University School of Science and Engineering was the only institution that focused on the environment. The system in those days divided students into majors immediately after entering university, so I immediately decided to enter the Department of Resource Engineering. Even so, "environment" was a very vague theme for a high school student to grasp and I didn't have a clear image of what I would be studying.

After entering university and taking a variety of classes, I realized that "environment" is a single large concept. I also became familiar with the specific technical fields inside that concept. Although I sometimes felt a gap between reality and my own image, I ultimately became interested in the fields of environmental issues and environmental purification. I joined a laboratory in water environmental engineering headed by Professor Hiroshi Sasaki, who specialized in research for wastewater treatment.

The Department of Research Engineering had evolved from the Department of Mining. The department had a long history of research in technology known as mineral processing, which involves the handling of solids and metals. It had obtained unique know-how in that area. The Sasaki Laboratory conducted research of the analysis of solids, focusing on inorganic substances which are obtained after wastewater treatment. My area of expertise started with the graduate thesis which I wrote at the department. The Sasaki Laboratory emphasized actual experiments and I spent every day with a beaker in one hand, doing experiments.

Upon entering graduate school, I stopped doing experiments for a while. Instead, I used computer simulation to optimize processes, create control models and construct systems. This was the approach that I used while conducting research during the Master's and Doctoral programs. Learning this approach is of great use to me now. In my research, I use both actual experiments and simulations. Specifically, I extract laws from the complicated phenomena of actual substances and then create models. I then use the models in simulations which envision a variety of cases. Such models and simulations are powerful tools for in-depth research which incorporates both engineering and science, as well as for the refinement of practical adaptation.

Repeatedly performing wastewater treatment experiments while precisely managing the process

Developing an interest in the interface of solids and liquids

Wastewater treatment using solid-liquid interface properties

Environmental technology is actually a "down-to-basics" field which focuses on onsite application and usefulness. For example, in the field of treatment for wastewater and polluted water, there is so much emphasis on cleaning the water that large amounts of chemical solution are used for purification. The final result is a large amount of sludge which is difficult to dispose of--in reality, this kind of rough treatment is still being performed.

Today is known as the age of environmentalism. As such, it is necessary to spread technology which uses increasingly efficient methods with small environmental load in order to finely separate hazardous substances and useful substances. I am currently focusing on a wastewater treatment technology called solid-liquid interface. This technique hasn't been given much consideration until now. It is an interface in the substance field which involves changing substances into solids or liquids, or even mixing solids and liquids in some cases. I am particularly interested in a method which focuses on the microscopic behavior of complex systems which occur within that process. The properties of being an interface fulfill a catalytic role. Also, interfaces are electrically charged. This causes certain ions to be condensed, thus resulting in a variety of special phenomena which differ from the conventions of normal physics and chemistry.

For example, even if large amounts of chemical solution aren't injected as normal, I discovered that it is possible to efficiently precipitate hazardous substances by using a method in which small amounts are gradually injected over a long period of time. Although this violates the common sense of chemical equilibrium theory, this phenomenon occurs in solid-liquid interface. Application of this method leads to reduced costs and reduced environmental load by greatly decreasing the amount of sludge. For me, the most interesting part of research is discovering and utilizing principles which violate common sense.

Application of powder simulation

Environmental research deals with wastewater, emissions gas, waste products and other complex systems as they exist in the real world. Such research has produced powder processing, which is one of the oldest industrial technologies. Powder processing seeks to separate useful particles and hazardous particles from a variety of particles which are mixed in gases or solids. Although powder processing is old, it is a very deep technological field in which much is still unknown.

In the first place, the environmental field deals with a broad range of themes. There probably aren't many other people who want to focus on solid-liquid interface or microscopic particles. Environmental projects are advancing rapidly around the world. Therefore, I will not be satisfied with current conditions. I believe that it is important to develop technology which is one or two steps more advanced and to contribute to the application/spreading of such technology.

Gaining new ideas from social change

Recently, I am researching technology for efficiently stripping mounted parts from the printed circuit boards of computers. The goal of this technology is to condense rare metal during the recycling process for information appliances. Conventionally, circuit boards have been recycled by grinding them to bits while parts are still mounted. Afterwards, gold and silver which are economically feasible to recycle are extracted. This method diffuses rare metal to a very low concentration, thus making condensation extremely difficult. Condensation would become much easier if it were possible to separately process parts which contain large amounts of rare metal.

A vast amount of waste is disposed of, making it economically unrealistic to remove each part by hand. Mechanization is necessary. Therefore, I am researching technology for efficiently stripping certain parts through methods such as swirling the circuit boards through the air and having them collide with a wall. In other words, I rotate the circuit boards in a drum which is like a fully-automatic washing machines--no, I'm just joking, of course I use a more sophisticated device than that! For example, I want to separate parts from the board by using simple force such as dropping something onto the floor or through impact such as striking. I refer to this as "autogenous grinding." In the case of ore, it breaks cleanly at the border of layers with different properties. By applying softer force, it is possible to perform separation without complete pulverization. My idea is to use this property in order to efficiently strip away parts according to differences in the connection strength.

Of course, since I am conducting my research at academia, I continue a cycle of experimentation and theorization. Specifically, I create models of the mechanization for stripping parts, use the models in simulations and then make further improvements to machines. Furthermore, I am now creating a database containing the connection strength for each part, as well as valid removal methods. I have created a variety of test circuit boards and implemented trial-and-error experimentation, but it is a difficult task. There is also a movement to establish recycling laws in the future for small home appliances, cellular phones and smartphones. This compels me to be a pioneer of new technology.

Additionally, I am also involved in research to convert CO2 into ethanol by applying the fenton method, which is a well-known technique in wastewater treatment. The fenton method is capable of decomposition even organic materials which are difficult to decompose. In the method, an active substance known as a radical is emitted and a powerful oxidation reaction occurs. Normally, technology to generate ethanol from CO2 uses forceful methods which conduct hydrogen reduction at high temperatures. However, the fenton method makes it possible to generate ethanol under normal atmospheric conditions. This is very strange and interesting. Currently, only a very small amount can be generated, but it is a theme which I intend to review further in order to increase efficiency. It is a field which no one else has attempted and I embrace the challenge of developing environmentally-friendly energy.

During the next 20 or 30 years, there will be even more significant changes in the world's energy supply-demand balance. There will also be further changes in environmentally-conscious thinking and technology. I predict that there will be many great paradigm shifts in which our values change completely. When conducting research in this field, it is necessary to constantly pay attention to major trends in the world. It is also necessary to stay abreast of economics and legislation. I actively visit and tour recycling sites both in Japan and overseas. I also value the opportunity to have discussions with individuals from industry and government. Of course, I conduct a great deal of research through an industry-academia alliance. People who are averse to focusing on areas outside of their specialty would have trouble conducting research in the environmental field. For me, a great appeal of environmental research is gaining new research ideas from within social change.

Using an electron microscope for detailed observation of elements within a solid

Chiharu Tokoro
Associate Professor, Faculty of Science and Engineering, Waseda University

In 1998, graduated from the Department of Resource Engineering at the School of Science and Engineering, Waseda University. In 2000, completed the Master's Program in Geosystems Engineering at the Graduate School of Engineering, the University of Tokyo. In 2003, completed the Doctoral Program. Holds a PhD in engineering. In 2004, appointed as a Research Assistant at the School of Science and Engineering, Waseda University. In 2007, appointed as a Full-Time Instructor at the Faculty of Science and Engineering, Waseda University. Assumed her current position in 2009. Areas of expertise include resource environmental engineering and powder engineering.