Gas-Liquid-Solid interface enhanced photocatalytic reaction in a microfluidic reactor for water treatment

Abstract

This paper presents a novel triphase photocatalytic microreactor by generating periodic gas bubbles in running micro-flows, with the aim to control the Gas-Liquid-Solid interfaces stably, precisely and repeatedly, which can better understand interface kinetics contributing to photocatalytic reactions. The experimental results show that it achieves rapid water treatment with the degradation rate as high as 26.5 % s−1.The oxygen bubbles could promote photocatalytic reactions by adjusting volume ratio, and the degradation of methylene blue is improved by larger than 40 % as compared to nitrogen. The reaction rate constants under different volume ratios follow an exponential relationship and tend to saturate after 2:1 (gas:liquid). For oxygen bubbles, the reaction rate constant is k = 0.174 s-1, about 2.4 times of k0 (no bubbles). The space time yield is as high as 268.7 g l−1 day−1 and the photocatalysis space time yield is also estimated to 10-6 g l−1 day-1 W−1 due to large distance between light source and microreactor. The simulation results also demonstrate the effect of mass transfer, oxygen diffusion and self-refreshment and are approximately consistent with the experimental results.