Comparison of Photocatalytic Membrane Reactor Types for the Degradation of an Organic Molecule by TiO2-Coated PES Membrane

Chhabilal Regmi,Agnes Schulze,Jonathan Cawettiere Espíndola,Andrea Iris Schäfer,Shabnam Lotfi,Kristina Fischer

doi:10.3390/catal10070725

Abstract

Photocatalytic membrane reactors with different configurations (design, flow modes and light sources) have been widely applied for pollutant removal. A thorough understanding of the contribution of reactor design to performance is required to be able to compare photocatalytic materials. Reactors with different flow designs are implemented for process efficiency comparisons. Several figures-of-merit, namely adapted space-time yield (STY) and photocatalytic space-time yield (PSTY), specific energy consumption (SEC) and degradation rate constants, were used to assess the performance of batch, flow-along and flow-through reactors. A fair comparison of reactor performance, considering throughput together with energy efficiency and photocatalytic activity, was only possible with the modified PSTY. When comparing the three reactors at the example of methylene blue (MB) degradation under LED irradiation, flow-through proved to be the most efficient design. PSTY1/PSTY2 values were approximately 10 times higher than both the batch and flow-along processes. The highest activity of such a reactor is attributed to its unique flow design which allowed the reaction to take place not only on the outer surface of the membrane but also within its pores. The enhancement of the mass transfer when flowing in a narrow space (220 nm in flow-through) contributes to an additional MB removal.

Highlights

The continuous contamination of water bodies by effluents from wastewater treatment plants (WWTPs), hospitals, municipal sewage systems, industries, run-off water from agricultural land and other sources poses a great threat to both human and aquatic health [1,2]
The Thermogravimetric Analysis (TGA) measurement was performed to quantify the amount of TiO2 nanoparticles deposited per surface area on the membrane for the best comparison of the reactor designs
The performances of three different reactors operated at different light intensities, sources and flow modes were compared using the figures-of-merit space-time yield (STY), photocatalytic space-time yield (PSTY), specific energy consumption (SEC) and degradation rate constant

Summary

Introduction

The continuous contamination of water bodies by effluents from wastewater treatment plants (WWTPs), hospitals, municipal sewage systems, industries, run-off water from agricultural land and other sources poses a great threat to both human and aquatic health [1,2]. Heterogeneous photocatalysis, TiO2 , has been widely used in micropollutant removal in water due to its good performance to light irradiation, relatively high activity, non-toxicity and cost-effective synthesis process. It can exist in three crystalline forms, namely anatase, rutile and brookite. Anatase has been reported to exhibit higher photocatalytic efficiency [3,4,5]. The membrane separation process [6,7] has emerged as a promising technique for applications such as water treatment. A combining of membrane separation and the photocatalytic mechanism

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