Gradient Porous Structured MnO2-Nonwoven Composite: A Binder-Free Polymeric Air Filter for Effective Room-Temperature Formaldehyde Removal.

Recently, MnO2-coated polymeric filters have shown promising performance in room-temperature formaldehyde abatement. However, a commonly known concern of MnO2/polymer composites is either MnO2 crystal encapsulation or weak adhesion. This work reports a low-cost high-throughput and green strategy to produce binder-free MnO2-nonwoven composite air filters. The production approach is energy saving and environmentally friendly, which combines MnO2 crystal coating on bicomponent polyolefin spunbond nonwovens and subsequent heat immobilizing of crystals, followed by the removal of weakly bonded MnO2. The binder-free MnO2-nonwoven composites show firm catalyst-fiber adhesion, a gradient porous structure, and excellent formaldehyde removal capability (94.5% ± 0.4%) at room temperature, and the reaction rate constant is 0.040 min-1. In contrast to the MnO2-nonwoven composites containing organic binders, the HCHO removal of binder-free filters increased by over 4%. This study proposes an alternative solution in producing catalyst/fabric composite filters for formaldehyde removal.