Intensification of photocatalytic degradation of organic dyes and phenol by scale-up and numbering-up of meso- and microfluidic TiO₂ reactors for wastewater treatment

A new experimental set-up permitting scale-up and serial internal numbering-up of meso- and micro photocatalytic systems, respectively, was developed to compare their photodegradation efficiency, by using of a commercially avaliable TiO₂ (P25), against Rhodamine B (RB) and Methylene Blue (MB) under UV irradiation in water. A circular photocatalytic unit constituted of TiO₂ embedded into PDMS was the basic unit of the meso and microchemical reactors. Different volumetric capacity, from 10 μL to 1000 μL, and different flow rates (0.05–1.0 mL min⁻¹) were evaluated to understand the best approach to design a more efficient fixed bed photoreactor for photocatalytic degradation. The multi-photocatalytic microreactor system with the best performace, built-up by plugging six modular microreactor plates (M6), was tested for photooxidition of phenol under UV irradiation, as well. P25 catalyst showed different photodegradation efficiency depending on the photocatalytic meso- and microreactor design and flow parameters. The photocatalytic efficiency for the meso- and microdevices was evaluated by figure-of-merit electrical energy per order (E_EO) and apparent quantum yield. The numbered-up M6 system had a lower electrical energy consumption compared with others. The microfluidic device M6 was able to achieve 97% of photodegradation of MB and RB (1.2 10⁻⁵ mol L⁻¹) in 1 h compared to 96% conversion of the best mesoreactor in 16 h, while reached a total mineralization of phenol (1.2 10⁻⁴ mol L⁻¹) to CO₂ and H₂O in 6 h.