High-Strength Aramid Nanofiber/Sodium Alginate Composite Membranes for Efficient Osmotic Energy Conversion

Osmotic energy harvesting from salinity gradients represents a promising and sustainable pathway for renewable energy generation. While reverse electrodialysis (RED) is a viable technology for extracting this energy, conventional ion-selective membranes often suffer from inadequate surface charge density and limited mechanical strength, severely hindering their large-scale application. Herein, we fabricated a mechanically robust aramid nanofibers (ANFs)/sodium alginate (SA) composite membrane. This design synergistically integrates the abundant ionic groups of SA with the robust mechanical framework of ANFs, resulting in simultaneous enhancements in structural stability and charge transport properties. The composite membrane achieves a tensile strength of 131.76 MPa, representing a 52.92% improvement over pure ANFs membranes. Benefiting from its balanced ion selectivity and mechanical integrity, the membrane yields a power density of 13.10 W/m2 under a 50-fold salinity gradient, which increases to 49.65 W/m2 under a 500-fold salinity gradient. Furthermore, under simulated alkaline wastewater conditions (pH 11), the membrane maintains a power output of 15.53 W/m2, confirming its potential for simultaneous wastewater treatment and energy recovery. These findings demonstrate that integrating nanofibers with biopolymers is an effective strategy for constructing durable, high-performance ion-selective membranes for sustainable osmotic energy utilization.