Plant-derived coating enhances MXene's ability to clean drug-laden wastewater

Researchers at Khalifa University of Science and Technology have developed a new class of hybrid membranes that enhance the safety of hospital wastewater before it reaches treatment facilities. These membranes are constructed from sulfonated poly(ether sulfone) (SPES) and reinforced with Ti₃C₂Tₓ MXene, a two-dimensional material chemically modified with gallic acid. This modification addresses two major issues that have limited MXene's use in water-treatment membranes: its degradation in water and poor bonding with polymers.

MXenes, including Ti₃C₂Tₓ, are known for their large surface area, electrical conductivity, and adaptable surface chemistry. Ti₃C₂Tₓ MXene consists of titanium carbide layers with terminal groups that make it hydrophilic and negatively charged in water. These properties are beneficial for membrane applications, potentially enhancing water flow and selectivity. However, MXene's vulnerability to oxidation and poor compatibility with polymers have hindered its practical use.

The Khalifa University team overcame these challenges by functionalizing MXene with gallic acid, a plant-derived polyphenol. This functionalization protects the MXene from oxidative damage and improves its dispersion in the polymer matrix, leading to better bonding and performance. The resulting membrane, with an optimal 2% gMX loading, showed a 4.3-fold increase in pure-water flux compared to unmodified SPES membranes.

The gMX2 membrane not only demonstrated high water flux but also achieved over 95% rejection of dyes and pharmaceuticals in tests. This tight ultrafiltration capability allows it to effectively remove small organic molecules while maintaining high flux. In practical tests with hospital wastewater, the membrane showed improved antifouling performance and maintained a stable flux over 24 hours of operation.

The use of gallic acid, an inexpensive and abundant molecule, to stabilize MXene is significant for potential large-scale production. This advancement addresses key challenges in treating hospital effluents, which are major sources of pharmaceuticals in urban water systems. By enhancing MXene's stability and compatibility, the research team has advanced the material's applicability in real-world wastewater treatment scenarios.