Boosting membrane distillation lifespan: Superhydrophobic micro-nano surface construction and concentrate concentration management

Membrane distillation (MD) is a critical technique for achieving near-zero discharge of hypersaline wastewater. However, it often faces challenges due to frequent mineral scale accumulation on the membrane surface and within its pores, particularly during the later stages of concentration, which compromises the membrane's lifespan and sustainability. This study explores the effects of implementing scaling control using micro–nano structured superhydrophobic nanofibrous membranes for concentrating reverse osmosis seawater concentrate and simultaneously aims to identify the membrane concentrating critical point (MCCP), a vital threshold that precedes irreversible scaling, to enhance sustainable desalination. Our findings show that the micro-nanostructures on the superhydrophobic membrane surface significantly reduce salt nucleation on the membrane surface and within the membrane pores, effectively extended the membrane MCCP for stable membrane flux, water recovery and reusability. Moreover, the membrane service life can be substantially extended by halting the concentration process before salt crystals embed into the membrane pores. This research highlights the critical role of these two control factors in augmenting membrane service life, offering valuable theoretical and practical insights for MD applications in hypersaline wastewater treatment.