The semiconductor industry in Taiwan relies heavily on water resources. However, fluoride-containing wastewater generated during manufacturing processes has long posed a major challenge due to the difficulty of treatment and reuse, making it a costly and burdensome issue for industry. Supported by the National Science and Technology Council (NSTC), the research team led by Distinguished Professor Chia-Hung Hou at the Graduate Institute of Environmental Engineering, National Taiwan University, has developed an innovative electrically driven separation and concentration technology based on Membrane Capacitive Deionization (MCDI). This breakthrough enables low-concentration fluoride wastewater, previously considered difficult to utilize, to be transformed into reusable resources, opening a new pathway for wastewater resource recovery and net-zero transition in the semiconductor sector.
Fluoride-containing wastewater is widely generated in semiconductor and electronics manufacturing. In particular, low-concentration fluoride wastewater has traditionally been treated through chemical precipitation, in which fluoride ions are converted into calcium fluoride sludge. This conventional approach not only limits opportunities for resource recovery, but also increases the burden of sludge transportation, downstream treatment, and associated carbon emissions. While high-concentration fluoride wastewater can already be converted into cryolite, a valuable material used in aluminum production and ceramic industries. However, practical and economically viable solutions for low-concentration fluoride wastewater have remained limited due to insufficient recovery efficiency.
To overcome this barrier and accelerate industrial implementation, the NTU research team collaborated with ReTech Environmental Solutions Co., Ltd., a company with extensive experience in semiconductor fluoride wastewater resource recovery. By integrating MCDI technology, the team developed a new concentration strategy for low-concentration fluoride wastewater. Driven by an electric field, the technology enables efficient ion migration and adsorption, allowing charged species in wastewater to be selectively removed and concentrated. Compared with conventional treatment processes, this approach offers several advantages, including chemical-free operation, no generation of chemical sludge, modular design, and strong potential for resource recovery. A laboratory-scale system with a treatment capacity of approximately 100 liters of fluoride-containing wastewater per day was successfully established. The system demonstrated the ability to concentrate low-concentration fluoride wastewater to levels suitable for cryolite production, and integrated system testing at an industrial site further confirmed its feasibility for practical resource recovery.
To further validate the scalability and on-site applicability of the technology, the team expanded the system and built a packaged capacitive fluoride concentration system capable of treating 1 ton of wastewater per day. This marks a significant step toward industrial deployment. The study also showed that material optimization plays a key role in improving sustainability: replacing conventional metal current collectors with graphite sheets significantly enhanced system stability and durability while also reducing carbon emissions. According to life cycle assessment results, the carbon footprint of recovering 1 mg of fluoride ion can be reduced from 0.098 kg CO₂-eq to 0.008 kg CO₂-eq, highlighting the substantial benefits of the technology in both carbon reduction and sustainable system design.
In addition, the team established the Net Zero WaterTech Hub at NTU’s Zhubei campus and, together with ReTech, launched a joint laboratory to serve as a platform for technology demonstration, collaboration, and industrial training. This initiative extends the team’s research achievements beyond the laboratory and into real industrial settings, linking technology validation, talent cultivation, and application promotion. Through this integrated effort, the team aims to accelerate the translation of innovative water treatment technologies into practical solutions that support circular economy development and low-carbon transformation in Taiwan’s semiconductor industry.
Media Contact：
Duan-Yi Wen
Associate Researcher
Department of Engineering and Technologies
National Science and Technology Council
Tel: +866(2)27377940
E-mail: dywen@nstc.gov.tw
