In-situ triboelectric nanogenerator for energy self-cycling electrochemical systems in wastewater treatment

Abstract

Enhancing energy efficiency in wastewater treatment is essential for achieving carbon neutrality in the water sector. However, the potential and feasibility to recover in-situ mechanical energy from the complex and multidirectional fluid dynamics of aeration-induced flows remains underexplored. Here we present a self-sustaining treatment system that couples a coronal triboelectric nanogenerator (C-TENG) with membrane capacitive deionisation (MCDI) for energy self-cycling contaminant removal. The tailored C-TENG could harvest low-frequency water wave energy in aeration tanks to directly power the MCDI unit for the treatment of real wastewater. Both simulations and experimental validation were conducted to optimise the system configuration, obtaining sufficient energy recovery from a single 18 cm-diameter C-TENG unit and allowing the subsequent MCDI to effectively remove phosphorus (95 %) and a range of metal ions (70 %-80 % for Fe³⁺, Ni²⁺, Cu²⁺, Cr³⁺, Cd²⁺, and Pb²⁺) from real secondary effluent. Moreover, integrating 75 % energy recovery efficiency through self-regeneration reduced MCDI energy consumption to 0.26 kWh/m³, enabling low-energy ion removal and electric energy storage in the C-TENG//MCDI system, while supporting further treatment. This innovation introduces a scalable and sustainable approach that couples fluidic energy harvesting with electrochemical treatment, offering a viable route to upgrade existing wastewater infrastructure.