A corrugated plate photocatalytic reactor for degradation of waterborne organic contaminants

Abstract

A UV‐C/titanium dioxide (TiO2) plate coated photocatalytic reactor using a corrugated frame system was designed for water borne organic contaminant degradation. The anticipated advantages of using the corrugated layout include a larger photocatalytic surface area per unit volume and improved photocatalytic activity. The water distribution system was designed to assist effective interactions among the water pollutant, photocatalyst, and photons. The degradation of a methylene blue solution, as a model water contaminant, was carried out at room temperature (22 °C) at different concentrations and flowrates. With an 11 mg/L methylene blue solution, 70 % was degraded within the first 10 min using TiO2 coated corrugated plates, whereas under the same conditions the degradation rate was only 12 % for a corrugated reactor without a catalyst coating, and 4 % for a no‐plate reactor. The methylene blue degradation was described by the Langmuir‐Hinshelwood model, and the apparent photonic efficiency of the corrugated arrangement was found to be in the range of 1.53–2.83 % when half the initial concentration was degraded. The local area specific rate of energy absorption (LASREA) profile over the plates was determined from a model developed based on UV‐C light irradiation distribution and plate configuration. Light intensity measurements were carried out and were found to correlate with this model. A set of corrugated plate photocatalytic reactors with different geometries, but with the same coated area, were then analyzed and absorbed UV light intensities were integrated to determine the best geometry.

TiO2 based nanopowder coatings over stainless steel plates for UV‐C photocatalytic degradation of methylene blue

“…Figure shows the MB degradation rate constants obtained with different coatings, with the highest rate constant being 5.59 hours −1 . Due to different experimental conditions used by other researchers, MB degradation rates are difficult to compare; however, the value obtained in this work is higher than other reported rate constants for MB degradation with different coating and irradiation conditions: TiO 2 coated 16‐plate reactor: 4.55 hours −1 , for 250 mL of 11 mg/L MB under UV‐C (254 nm). A coating with optimized anatase/rutile ratio: 0.071 hour −1 , for 30 mL of 4 μM MB under UVA (365 nm). A TiO 2 transparent free‐standing coating: 0.046 minute −1 (2.76 hours −1 ), for 10 mL of 10 mg/mL MB under UVA (365 nm) black‐light tube. A TiO 2 coated spin disc reactor: 0.0003 second −1 (1.08 hours −1 ), for 550 mL of 8 mg/L MB under UV‐C (254 nm). A TiO 2 coated membrane: 0.0607 minute −1 (3.642 hours −1 ), for 4 mL of 20 μM MB under a sunlamp (UVA or UVB). …”

“…The coated rough surfaces may have micro geometry effects on energy absorption in the same way as a corrugated plate reactor described in previous work, in which a broader‐angled corrugated plate reactor absorbed more energy than a reactor with a sharper angle under the same irradiation condition of UV‐C light.…”

“…UV/photocatalyst based AOPs rely on photonic energy and a photocatalytic material, and the more energy the material absorbs, the more reactions may occur. Energy absorption also relies on reactor geometry and catalyst material properties . Due to the diffuse emission pattern of UV irradiation, light energy absorption will be also influenced by reactor geometries; it can be deduced that light energy absorption may be also influenced by surface morphology as excessive roughness of the coated surface may impede light energy absorption.…”

“…The TiO 2 coating method used was developed from previously reported work, in which 304 stainless steel plates were brushed with 25% (m 3 /m 3 ) diluted HCl concentrate (12 M), air‐dried, and oxidized in a muffled furnace for 2 hours. TiO 2 powder was suspended in 20% (m 3 /m 3 ) ethanol and brushed onto the oxidized steel plates, which were then annealed for 5 hours.…”

Issue Highlights

“…A 3D photonic energy absorption model was also developed based on the configuration of the reactor system, and light intensity measurements were found to correlate well with the model. Corrugated plate photocatalytic reactors with different geometries were then analyzed and absorbed UV light intensities integrated to determine the best geometry …”