A Trimode Self-Cleaning Composite Membrane with an Eco-friendly Substrate for Energy-Saving Wastewater Recycling

A separation membrane with low or clean energy costs is urgently required for energy-saving and long-term service since electric energy generated from burning non-renewable resources will gradually cause a burden to the environment. At present, the conventional membrane being used in one mode is critical for a variety of scenarios in real life, which suffers from a trade-off effect, short service life, being difficult to recycle after damage. Herein, we report a trimode purification membrane composed of an eco-friendly polycaprolactone (PCL) substrate and functional graphene dioxide/polyaniline (GO/PANI) particles. Due to the photothermal transfer and photocatalytic properties of GO/PANI blend, the composite membrane can absorb 97.44% solar energy to handle natural seawater or mixed wastewater, which achieves a high evaporation rate of 1.47 kg m⁻² h⁻¹ in solar-driven evaporation mode. For the photocatalytic adsorption–degradation mode, 93.22% of organic dyes can be adsorbed and degraded after 12 h irradiation under 1 kW m⁻². Moreover, electric-driven cross-flow filtration mode as a supplement also shows effective rejection over 99% for organic dyes with a high flux over 40 L m⁻² h⁻¹ bar⁻¹. The combination of solar-driven evaporation, photocatalytic adsorption–degradation, and electric-driven cross-flow filtration demonstrates a prospective and sustainable strategy to generating clean water from sewages.

Graphical Abstract

A trimode self-cleaning composite membrane of bio-degradable substrate PCL and functional particles GO/PANI were successfully fabricated, which can purify natural seawater or mixed wastewater stably in solar-driven evaporation mode, handle organic dyes by reduction–oxidation chemical transformation in photothermal adsorption–degradation mode, and be applied in cross-flow filtration mode driven by electric as a supplement for rainy, cloudy days, or at night.