A bio-inspired dynamic filter with unidirectional channels based on cross-linked cellulose loading palladium nanoparticles for catalytic reduction of 4-nitrophenol

Abstract

To remove the pollutants nitrophenol in wastewater, a bio-inspired dynamic filter (CE-Pd-EPI) with in-situ synthesized palladium nanoparticles (PdNPs) was prepared via chemical cross-linking and freeze casting. This bio-inspired filter has a hierarchical dual-porous structure with micron-scale unidirectional channels and nanoscale pores. This hierarchical porous structure facilitates rapid mass transfer of the liquid. Therefore, this filter can completely reduce 4-nitrophenol (4-NP, 2 mM) in 3 min. The rate constant (k) and turnover frequency (TOF) are 2.42 min−1 and 13.17 min−1, respectively, which are better than most reports so far. Moreover, this filter can also instantaneously catalyze the reduction of methylene blue (MB) to colorless. After five cycles, the conversion of 4-NP and MB by the filter still reaches 99.9%, demonstrating its excellent catalytic stability and reusability. In addition, in a continuous fluid catalytic system this filter has a low pressure (only 0.84 kPa) due to its bio-inspired unidirectional channel structure, which is extremely important for continuous industrial application. This bio-inspired dynamic filter has a guiding significance for the removal of organic pollutants in wastewater in industrial applications. Therefore, the bio-inspired dynamic filter described in this study has a great potential in the field of water treatment and environmental protection.