Breakthrough in Salinity Gradient Energy Conversion

A team of researchers from the School of Civil and Environmental Engineering has developed a novel multilayered composite membrane that enables effective energy conversion at the interface between seawater and wastewater treatment plant (WWTP) effluent. The breakthrough has the potential to harness substantial untapped energy from the natural phenomenon of ion permeation at the seawater-freshwater interface. According to the study, the membrane's design and preparation strategy have enabled high energy conversion under a salinity gradient, with an output power density of up to 6.1 W m-2.

Key Takeaways:

• The research team designed a multilayered composite membrane by integrating CNTC-MOF intermediate layers with charge-gradient sulfonated poly (ether ether ketone) (SPEEK) for effective energy conversion at the seawater-WWTP effluent interface.
• Density functional theory (DFT) calculations demonstrated that the incorporation of an organic-inorganic layer into the pristine membrane established a hydrogen bond network, improving water retention and enhancing cation transport.
• The synthesized composite membrane showed excellent long-term stability and high energy conversion under a salinity gradient, with an output power density of up to 6.1 W m-2.
• Additionally, the membrane enabled thermal-osmotic synergy, achieving an output of up to 10.2 W m-2 through low-grade heat integration.
• The research concluded that the developed membrane holds promise for waste energy utilization and has the potential to compensate for the technical application limitations caused by insufficient freshwater resources.
• The study was supported by the Shenzhen Science and Technology Funding Project and has been peer-reviewed.

Statistics:

• The output power density of the developed membrane reached as high as 6.1 W m-2 at a 50-fold KCl salinity gradient.
• Thermal-osmotic synergy enabled an output of up to 10.2 W m-2 through low-grade heat integration (triangle T = 30 K).
• The salinity conversion in real environments (seawater/WWTP effluent gradient) reached a maximum output power density of approximately 3.0 W m-2.
• The membrane showed excellent long-term stability, allowing for sustained energy conversion over an extended period.

Sources:

• "Designing Hydrogen Bond Network Inside Thermal-driven Multilayered Membrane for Sustainably Effective Energy Conversion From Seawater and Wwtp Effluent," Advanced Functional Materials, 2025.
• Shenzhen Science and Technology Funding Project.
• School of Civil and Environmental Engineering, Harbin Institute of Technology Shenzhen.
• Research authors: Feiyun Sun, Qi Wang, Haojie Zeng, Bin Zhong, Zhirui Chen, Baiyang Ji, Dingyu Xing, and Jiajia Yuan.