Separation of carbon fibers in water using microbubbles generated by hydrogen bubble method

Carbon fibers (CF) are widely used for the reinforcement of plastics, and recycling them using water processes must meet environmental impact requirements. To recover CFs from water with reduced environmental risk, we developed a separation system that consisted of a 125-L cubic container with electrodes to generate microbubbles (MB) by hydrolysis. Microbubbles were adsorbed onto the CFs in the container, and after 30 min of electrolysis, the CFs floated to the surface because of the buoyancy of the adsorbed MBs. The recovery rate was dependent on the CF lengths and a surface treatment using sizing chemicals. Based on our mechanical model and calculating the difference between the MB buoyancy and CF gravity, the flotation efficiency was regulated by the CF length, bundle diameter, and MB adsorption ratio, which supported the experimental results. Using this technology, CFs and glass fibers can be separated in water from their mixtures, and the toxicological and environmental risks can be reduced.