(268c) On Demand Treatment of Wastewater Using 3D-Printed Membranes

Wastewater treatment is critical to the chemical industry. While conventional membranes have been utilized in oil-water separation for some time, demonstration of a 3D-printed membrane with well-controlled local structures, which renders it to have multi-selectivity, is still lacking to-date. Moreover, state-of-the-art wastewater treatments often involve multiple steps. Consequently, a more intensified process, which is enabled by a single multi-selective membrane, is highly desirable. In the current study, we present the first-of-its-kind demonstration of multicomponent and multiphase oil-water separation using 3D-printed membranes and an intensified process design. The driving force here is surface selectivity and topography rather than pressure. First, two-component oil-water separation with high efficiency, high flux, and excellent durability is achieved using 3D-printed polymethylmethacrylate (PMMA) membranes with zwitterionic hydrogel coating. The membranes are simultaneously hydrophilic/oleophobic and mechanically strong. Second, robust on-demand separations of immiscible liquid mixtures with high flux are enabled by a novel separation membrane with microscale repeating re-entrant structures. The re-entrant membrane is fabricated by two-photon polymerization (2PP) 3D-printing, and the re-entrant angle can be precisely manipulated to achieve on-demand separations. Third, novel supported ionic liquid membranes (SILM) have been developed to separate miscible liquid mixtures, which has been a key challenge in wastewater treatment using membranes. Ionic liquid (IL), which serves as the extraction solvent, is impregnated into PVDF membranes. The SILM is optimized with curvatures to have larger interfacial area and higher separation rate. Lastly, the successful separation of the three-component/two-phase liquid mixture (benzene/heptane/water) has been demonstrated with an integrated 3D-printed box. Efficient separation of water from benzene/heptane is achieved using the 3D-printed PMMA membranes with zwitterionic hydrogel coating at the bottom of the box, while the separation between benzene and heptane is achieved using the SILM on the sides of the box.