Treatment of simulated decontamination wastewater in nuclear power plants by membrane distillation using Janus membrane

Abstract

In the daily operation of nuclear power plants, large amounts of low-level radioactive decontamination wastewater are generated for the cleaning and washing purposes. Compared to traditional methods such as evaporation and chemical precipitation, which are energy-intensive and prone to generating large-volume secondary pollutants, membrane distillation (MD) demonstrates advantages through waste heat utilization and reduction in concentrate volume. In this study, a Janus membrane was fabricated by dual-layer coating on polytetrafluoroethylene (PTFE) hollow fiber membranes incorporating a poly-dopamine/polyethyleneimine intermediate layer and a polyvinyl alcohol/tannic acid hydrogel top layer. The Janus membrane demonstrated exceptional anti-wetting stability, delaying membrane wetting onset by at least 30-fold compared to commercial PTFE membranes, while achieving >99.97 % rejection of nuclides (Sr²⁺, Cs⁺, Co²⁺). Long-term VMD experiments confirmed stable performance (8 L·m⁻²·h⁻¹ flux) over 60 h with periodic cleaning, showcasing its potential for sustainable low-level radioactive wastewater treatment. The underlying mechanism of the anti-wetting properties of the Janus membrane was then elucidated by comprehensive analysis of membrane physicochemical properties as well as the simulation study using molecular dynamics and density functional theory calculation. This work advances membrane design for nuclear wastewater management by synergistically integrating anti-wetting properties and nuclide recovery capabilities.