Upcycling Eggshell Waste into Hydroxyapatite Nanofillers for High-Performance Membranes in Water Desalination and Energy Harvesting

Advancing sustainable water and energy technologies requires multifunctional materials that simultaneously deliver superior performance and environmental value. Here, we demonstrate how hydroxyapatite (HAp) nanofillers, derived from upcycled eggshell waste, can push the performance limits of polymeric membranes beyond conventional benchmarks. Incorporation of HAp into electrospun poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) produced nanofibrous membranes with enhanced porosity, optimized pore size distribution, enhanced surface roughness, higher thermal stability, and improved dielectric properties. These enhancements arise because HAp disrupted polymer chain packing to increase porosity, created nanoscale roughness for antiwetting stability, and improved thermal resistance under membrane distillation operating conditions. As a result, the optimized membranes achieved record water-gap membrane distillation performance (flux of 36.58 kg m⁻² h⁻¹, 99.98% salt rejection under humic acid-saline feeds), exceeding the flux of commercial PVDF membranes. Additionally, the membranes were demonstrated as effective materials for triboelectric nanogenerators with an open-circuit voltage up to 125 V for real-time biomechanical motion sensing. By positioning eggshell-derived HAp not merely as a filler but as a performance-driving component, this work demonstrates how waste valorization can redefine the performance envelope of both desalination membranes and energy-harvesting devices, establishing a circular strategy for addressing water, energy, and sustainability challenges. Integrating sustainable filler synthesis, advanced water purification, and energy-harvesting functionalities, this work establishes a novel pathway toward next-generation multifunctional membranes for environmental remediation and human−machine interfacing.