Summary of Key Points
Academician Xu Tongwen is a pioneer in the field of "ion membranes," and his membrane technology plays a crucial role in achieving carbon neutrality:
- Bipolar membranes are used to recycle waste materials and streamline industrial processes;
- Ultra-microporous membranes have broken through the bottlenecks in the industrialization of organic liquid flow batteries;
- Alkaline membrane electrolysis for hydrogen production avoids traditional drawbacks;
- These technologies can also transform traditional industrial processes such as organic acid production, reducing pollution and energy consumption.
Academician Xu believes that ultra-microporous ion membranes will be the core focus of future research, and advancements in AI and new applications (such as deep space exploration, rare earth separation) will drive the development of separation science.
1. Bipolar Membranes: The "Chemical Magic" of Turning Waste into Treasure
Bipolar membranes are special membranes that combine cation exchange and anion exchange layers. When energized, they can directly convert salt water into pure acids and bases without any impurities. This solves two major problems in traditional industries:
- Replacement of Traditional Acid-Base Additives: For example, adding alkali to the food industry introduces sodium ions, and adding acid introduces chloride ions, leading to the formation of residues that affect product quality. Bipolar membranes provide hydrogen ions/hydroxide ions directly, free from impurities.
- Waste Recycling + On-Line Regeneration: Waste liquids containing acids, bases, and salts can be converted into useful chemicals using bipolar membranes, reducing emissions. Salt can also be converted into acids and bases on-site—no need for the long-distance transportation of hazardous substances; simply add water and electricity to produce them, making it both safe and cost-effective.
The most remarkable application is the production of deuterated acids and bases using bipolar membranes. While traditional methods cost $1,500–3,000 per gram, Xu's team can produce 500 grams using just 500 milliliters of heavy water (about $4,000), significantly reducing costs. This technology can be used in the production of抗癌 drugs and OLED materials, addressing a critical bottleneck.
2. Organic Liquid Flow Batteries: Making Energy Storage More Environmentally Friendly and Cost-Effective
Liquid flow batteries are large-scale energy storage solutions. Traditional batteries use vanadium metals, which are expensive due to their mineral dependence. Xu's team has developed organic liquid flow batteries with active materials based on carbon, hydrogen, oxygen, and nitrogen. They have also developed ultra-microporous membranes that allow ions to move almost frictionlessly through the membrane, increasing current density from 100 milliamps per square centimeter to 500 milliamps—making organic liquid flow batteries more viable for industrial use. They are now collaborating with a company in Jiangsu and have reached a production capacity of 2 gigawatts, making them one of the largest companies in this field globally.
3. Alkaline Membrane Electrolysis for Hydrogen Production: The "Third Generation Revolution" in Hydrogen Energy
Green hydrogen is essential for carbon neutrality (produced by electrolyzing water using renewable energy). Previous technologies had drawbacks:
- Alkaline Water Electrolysis: The reaction is slow and cannot keep up with the variability of wind and solar power, resulting in low hydrogen purity.
- Proton Exchange Membrane Electrolysis: Requires precious metals like platinum and iridium, which are imported.
Academician Xu's alkaline membrane electrolysis technology overcomes these issues. Their membranes can produce hydrogen efficiently without the slow reaction times and purity issues associated with alkaline water, and they do not rely on expensive metals. Currently, their membranes have an annual production capacity of 100,000 square meters, but the electrochemical stacks are still under development, with the goal of achieving megawatt-scale production by 2027. This technology can convert wind and solar energy into hydrogen for storage, reducing reliance on coal-fired power.
4. Membrane Technology Transforming Traditional Industries: From High Pollution to Closed-Loop Green Processes
Take organic acid production as an example:
- In traditional fermentation processes, continuous addition of alkali is required to maintain pH levels, and the final products require treatment with lime and sulfuric acid, generating several tons of waste residues and wastewater.
With bipolar membranes:
- Sodium salts and acids enter the membrane, where hydrogen ions and acid anions combine to form organic acids, while hydroxide ions and sodium ions form sodium hydroxide.
- Sodium hydroxide can be directly reused in the fermentation process, creating a closed-loop system that reduces five steps in the production process, saving labor and equipment costs, and improving product quality.
This is the power of membrane technology: optimizing processes, reducing pollution, and lowering energy consumption to make traditional industries more environmentally friendly.
5. The Future Direction: Ultra-Microporous Membranes + AI
Academician Xu believes that ultra-microporous ion membranes (with pore sizes below 0.7 nanometers) will be the next breakthrough. Adding functional groups to traditional membranes can reduce stability, but ultra-microporous membranes allow for efficient ion transport without the need for many additional groups, resolving the trade-off between selectivity and stability.
Separation science will also evolve in the following directions:
- AI-Assisted Membrane Formation: High-speed cameras record the membrane formation process, and AI models analyze it to precisely control membrane thickness.
- New Applications: For example, using membranes to extract salts from seawater (separating calcium and magnesium ions while retaining sodium ions) or for rare earth separation (replacing multiple extraction steps to reduce acid-base pollution).
- New Types of Membranes: Ion-solubilizing membranes, which are inert materials that can adsorb media in acidic or alkaline environments, forming dynamic transport layers without the need for additional functional groups. These membranes can be "made on-site" to perform specific functions.
These technologies will further advance carbon neutrality, moving separation science from a need for separation to an energy-efficient state where separation is no longer necessary.
This interview demonstrates that membrane technology is not just a laboratory concept but a practical tool that can solve industrial challenges and drive green transformation. Academician Xu's research uses "membrane methods" to give traditional industries a "green heart."