Catalytic Membrane Reactor Immobilized with Alloy Nanoparticle-Loaded Protein Fibrils for Continuous Reduction of 4-Nitrophenol

A catalytic membrane reactor, which contains a membrane matrix and a catalytic film of alloy nanoparticle-loaded β-lactoglobulin fibrils (NPs@β-LGF), was developed for the continuous-flow reduction of 4-nitrophenol (4-NP). The Cu–Ag and Cu–Ag–Au alloy NPs were synthesized using β-LGF as a scaffold and stabilizing agent. In this process, the Cu nanoclusters were formed in the initial stage and were able to promote the synthesis of Ag0, which acts as a reducing agent for the rapid formation of Au0. Furthermore, a catalytic membrane reactor was constructed by depositing the NPs@β-LGFs on a membrane matrix. The catalytic activity of the Cu–Ag–Au alloy NPs was higher than that of the Cu–Ag alloy NPs, using the reduction of 4-NP to 4-AP as a model reaction. The observed rate constant in the continuous-flow system is also higher than that in the batch system. In addition, these catalytic membrane reactors had good operating stability and antibacterial activity.