An universal approach of catalyst immobilization inside hydrophobic PFA tubing under well dispersed manner for continuous-flow applications

Abstract

Grafting of catalysts inside the hydrophobic surface tubing, for high throughput continuous-flow applications, is rather challenging. In the present work, we report an indirect and universal approach for catalysts immobilization inside the hydrophobic surface of perfluoroalkoxy alkane (PFA) tubing. Pristine Fe3O4 or catalysts grafted Fe3O4 magnetic nanoparticles (MNPs) (Fe3O4@Catalyst) was immobilized into the PFA tubing pre-crammed between the two ring magnets faced opposite poles. Reinforcement magnetic flux of two magnets grasp the MNPs enough tightened with well dispersed conditions. In particular, two devices were prepared by immobilizing two different catalysts: silver (Ag) grafted Fe3O4 MNPs (Fe3O4@PDA-Ag) and pyromellitic acid (PA) grafted Fe3O4 (Fe3O4@PA). The efficacy of approach was investigated in terms of green chemistry i.e., Ag-catalyzed continuous-flow instantaneous reduction of pollutants 4-nitrophenol (4-NP) and methylene blue (MB), and adsorption of Congo red (CR) dye using Fe3O4@PA adsorbent. Under continuous-flow manner, Fe3O4@PDA-Ag showed very high catalytic performance and produced 98 % reduction of 4-NP to 4-aminophenol in 118 s of residence time with 400 μL min−1 flow rate. And Fe3O4@PA exhibited higher adsorption of CR dye as compared to corresponding conventional shaking process. The adsorption capacity of Fe3O4 and Fe3O4@PA adsorbents towards CR dye was compared and estimated that the qe value was 419 and 748 mg g−1 in 94 s of residence time, respectively. Furthermore, the adsorbents, Fe3O4 and Fe3O4@PA, were regenerated in-line by infusing dilute ammonia solution followed by water. Therefore, it is practical that the magnetic support provide tight and well dispersed environment to the Fe3O4@Catalyst which facilitates the contact of catalysts with reactant, resulted high throughput continuous-flow applications. © 2022 Elsevier B.V.