Kaolin-reinforced green polymeric membrane for sustainable desalination

Membrane distillation (MD) is a promising desalination technology due to its high salt rejection efficiency and adaptability to diverse feed solutions. However, its broader application remains constrained by temperature polarization (TP), primarily due to conductive heat loss. Maintaining high hydrophobicity in MD membranes is essential to prevent pore wetting and maintain thermal efficiency. However, the heavy reliance on fluorinated polymers and toxic solvents for membrane fabrication poses severe environmental risks. Consequently, developing non-fluorinated alternatives is crucial for advancing sustainable membrane technologies. In this study, we report the fabrication of a non-fluorinated, hydrophobic composite membrane with reduced thermal conductivity, aiming to mitigate TP and enhance MD performance. The membranes were synthesized via phase inversion, incorporating kaolin particles into a polymer matrix. Characterizations revealed a remarkable low thermal conductivity of 0.064 W/m·K, lower than most reported non-fluorinated polymer membranes for MD and approaches values seen in some aerogel-containing composites. MD experiments with concurrent real-time temperature monitoring were conducted to systematically evaluate both the desalination performance and TP effect. The optimal 10% kaolin-loaded membrane demonstrated a permeate flux of 19.7 kg m⁻² h⁻¹ and a salt rejection rate of 99.9%, outperforming the pristine membrane's flux of 11.8 kg m⁻² h⁻¹. This improvement is attributed to the superior heat-insulating properties of kaolin, which effectively mitigated TP by reducing conductive heat transfer. The optimized membrane demonstrated stable DCMD performance over 10 days with 10% NaCl feed, exhibiting only a 12% flux decline. In addition, techno-economic analysis revealed a levelized cost of water 3–5 times lower than conventional polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) membranes. By simultaneously eliminating toxic materials and cutting costs, this work demonstrates the profound viability of sustainable membrane technologies. © 2026 Elsevier B.V.