Multilayer polyelectrolyte and palladium nanoparticle decorated porous materials as fixed-bed reactors for efficient reduction of 4-NP

In this study, a continuous flow catalytic reactor based on three-dimensional porous sponge bed with the uniform distribution of catalyst to treat 4-NP wastewater efficiently. The porous sponge is used as a support to construct polyelectrolyte multilayers by loading dopamine. And the multilayer polyelectrolyte is closely bound to dopamine to form polyelectrolyte film, and the nanocatalysts are synthesized by electrostatic adsorption of precursors. The reactor realizes the uniform and stable distribution of the catalyst in the three-dimensional porous sponge, and the reactant transfers from bulk solution to catalyst surface by the way of convection and diffusion, which enhances mass transfer and further improves the reaction efficiency. Under the operating conditions of a catalytic bed as small as 3 cm, a 4-NP concentration up to 4.5 mM, and a flow rate of 300 μL min −1 , the conversion rate remained above 96 % for up to 200 h, indicating that the reactor has good catalytic efficiency. The results showed that this continuous flow catalytic system structure has excellent performance in wastewater treatment.