Table Speech


“Environmental Preservation Month” Meeting
“Water Purification by Using Carbon Fibers – Water Environment Management through Carbon and Natural Forces”

May 20, 2009

Mr. Akira Kojima

Mr. Akira Kojima
Special Appointment Professor, Gunma National College of Technology,
Department of Chemistry and Materials Science

The theme of my speech today is water environment management technology by utilizing the natural forces of carbon and water, and how carbon fibers can purify water.
Since our planet is dependant upon water, concerns about water pollution are as important as global warming from CO2 emissions for out future.
Carbon fiber is widely known to be “strong, light and uninflammable.” I found out by chance an additional amazing feature that it is very friendly to living creatures.
The carbon fiber we actually use is an aggregation of 12,000 fibers with the thickness of one-tenth of human hair. Looking through an electron microscope, it is a straight thread without any pores.
15 years ago, I accidentally dropped a carbon fiber into a ditch. When I quickly picked it up, two sticky leaves were sticking to it. I wondered why. We found out the “stickiness” was a bio-film, formed by microbes which stuck to it in an instant.  Carbon fiber is “strong (as strong as irons), stiff (hard to bend), light (one-fifth of iron), uninflammable and thin (one-tenth of human hair).” In addition to these characteristics, it has an excellent water purification function. Now they are contributing for the environment management by purifying water and promoting inhabitation of fish at around 250 locations throughout Japan.
Experiments were conducted by using carbon fiber fabric woven at Nishijin in Kyoto, and fibers woven into a centipede shape at Kiryu in Gunma, both of these places are well-known for weaving. Let me show you some of the experiment results.
We took water from Izu Marsh in Miyagi Prefecture, the second dirtiest lake in Japan. A 5-meter-carbon fiber was soaked in the water, stirred and left for 3 hours. Water became evidently clearer as dirt in the water gathered and stuck to the fiber.
Carbon fibers proved to be effective in removing the sludge as deep as one meter in a pond in Hamamatsu City. We placed carbon fibers in the water and left them. After 4 months, changes were observed and water transparency improved dramatically as microbes in the pond clung to the fibers and purified the water. Underwater cameras showed clear water in which fish swam around freely.
Lake Haruna in Gunma Prefecture is famous for smelt fishing on ice during winter time. One winter, about a dozen years ago, not a single fish was caught. We were requested by the local community to experiment on water purification. We placed carbon fibers covering only 0.5% of the lake of 4-kilomenter-perimeter, thus created artificial algae at the depth of 5 meters. Monitoring cameras clearly recorded the development of planktons gathering naturally, followed by carps and crucian carps as they feed on the planktons. Pond smelts usually spawn on algae, but they preferred the thin thread of carbon fibers to lay their eggs. Nylon or polyester didn’t work. Baby fish hatched safely and swam around freely in the lake.
We confirmed the inhabitation of smelts by setting a stationary net into the spot where we placed carbon fibers. No smelts were found only 30 meters away from this spot. Ever since the algae bed was formed in Lake Haruna, smelts bite as soon as you throw in the line. We have done no maintenance work over the past 10 years, and yet the good condition remains the same.
Also in Suruga Bay, we created a forest of fiber carbons at a depth of 10 meters, which turned into virtually an artificial marine farm. All the experiment results show that carbon fiber resuscitates natural forces.
“Blue-green algae” often grow in ponds, marshes and lakes, caused by phosphor. We have also experimented on the phosphor-removal technology, by throwing in carbon fibers glued to metal iron plate. The chemical bond between ferric ion and phosphoric acid resulted in the formation of water-insoluble iron phosphate. We used metal wire net for this experiment, which was rusted red in just a few hours while phosphor in the water disappeared. This technology will surely prevent the growth of blue-green algae.
Water purification by carbon fiber is a so-called “local production for local consumption” type of technology that utilizes organisms in the locality. Microbes in Tokyo are used for Tokyo. Microbes eat the dirt in water and change into gas. This technology fully utilizes natural forces. No energy is required. It is a “low-tech” technology.
The technology for fish breeding also makes use of natural forces, as it collects planktons that live in the location, attracts fish and eventually makes them lay eggs through natural forces.
Carbon fibers under water attract many microbes and turn the spot into an arena for microbial activity. Sludge is the largest factor that triggers water pollution, but it can be decomposed into gas by microbes. I am convinced that water purification technology can be improved furthermore when we utilize the power of “carbon and microbes.”