Enhanced management and antifouling performance of a novel NiFe-LDH@MnO2/PVDF hybrid membrane for efficient oily wastewater treatment.

Layered double hydroxides (LDHs) have gained significant recognition for their facile synthesis and super-hydrophilic two-dimensional (2D) structure to fabricate antifouling membranes for oily wastewater separation. However, conventional PVDF membranes, due to their hydrophobic nature and inert matrix, often exhibit insufficient permeance and compatibility. In this study, a novel NiFe-LDH@MnO2/PVDF membrane was synthesized using ultrasonic, redox, and microwave-hydrothermal processes. This innovative approach cultivated grass-like NiFe-LDH@MnO2 nanoparticles within an inert PVDF matrix, promoting the growth of highly hydrophilic composites. The presence of NiFe-LDH@MnO2 resulted in pronounced enhancements in surface morphology, interfacial wettability, and oil rejection for the fabricated membrane. The optimal NiFe-LDH@MnO2/PVDF-2 membrane exhibited an extremely high pure water flux (1364 L m-2•h-1), and increased oil rejection (from 81.2% to 93.5%) without sacrificing water permeation compared to the original PVDF membrane. Additionally, the NiFe-LDH@MnO2/PVDF membrane demonstrated remarkable antifouling properties, evident by an exceptional fouling resistance ratio of 96.8% following slight water rinsing. Mechanistic insights into the enhanced antifouling performance were elucidated through a comparative "semi-immersion" investigation. The facile synthesis method, coupled with the improved membrane performance, highlights the potential application prospects of this hybrid membrane in emulsified oily wastewater treatment and environmental remediation.

Multi-functional MnO2-doped Fe3O4 nanoparticles as an artificial enzyme for the colorimetric detection of bacteria.

The authors describe a rapid enzyme-free colorimetric assay for food- and water-borne pathogens by using the multi-functional MnO2-doped magnetic ferrite nanoparticles (MCDs-MnO2 NPs). These nanoparticles not only can recognize, absorb, and separate the analyte from the matrix efficiently but also can directly catalyze the oxidation of TMB into a blue colored product without H2O2. In the presence of target, the nanoparticles preferentially bind to the target surface and the interaction between nanoparticles and TMB can be blocked, providing turn-off sensing of bacteria. By combining the superior capture efficiency of magnetic beads with the high catalytic activity of the enzyme mimic, the turn-off colorimetric assay can detect the gram-positive bacterium and the gram-negative bacterium by the naked eye at a low detection limit (102 cfu mL-1) with a wide line arrange from 10 to 106 cfu mL-1. With the advantage of simplicity, sensitivity, and specificity, this proposed approach showed promise in rapid instrumental and on-site visual detection of bacteria for determination of water contamination. Graphical abstract.