<i>In Situ</i> Growth and Regeneration of Photocatalyst: A Continuous High-Throughput Microphotoreactor

A process for high-throughput and continuous long-term photocatalytic operations using a microphotoreactor (MPR) is introduced. This is the first process of its kind that uses an MPR for long-term operations without dismantling it for catalyst regeneration and that can be directly installed in industry. We used a well-known and versatile photocatalyst, ZnO, for this process since the catalyst growth, properties, and mechanism of photocatalytic activity are well-studied and documented. ZnO nanorods grow <i>in situ</i> after assembling the reactor by flowing precursors using the seed-mediated hydrothermal growth method. We demonstrate that our process and hence the developed MPR is facile, robust, and reproducible using two model systems to validate photocatalytic activity: (1) degradation of an organic dye and (2) degradation of antibiotics and their combinations. These compounds are abundant in the Indian ecosystem due to textile industries and the rampant use of antibiotics. We show that the ZnO nanorods grown <i>in situ</i> were able to degrade ∼94% and 99% of the dye and ∼95% and 81% of the antibiotic at neutral and alkaline pH, respectively, under UV light irradiation. We also illustrate the stability and long-term usability (after installation) of our MPR by performing an <i>in situ</i> deactivation and regeneration of the photocatalyst and hence its possible applicability in hospitals and textile industries.