Development of intensified flat-plate packed-bed solar reactors for heterogeneous photocatalysis

• Published in: Environmental science and pollution research international Vol. 28; no. 19; pp. 24023 - 24033
• Main Authors: Ramos, Bruno, Carneiro, João Gabriel M., Nagamati, Leandro Issamu, Teixeira, Antonio Carlos S. C.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2021; Springer Nature B.V
• Subjects: Acetaminophen; Advanced Oxidation/Reduction Technologies: An Perspective from Iberoamerican Countries; Aquatic Pollution; Aqueous solutions; Atmospheric Protection/Air Quality Control/Air Pollution; Beads; Carbon dioxide; Carbon dioxide emissions; Catalysts; Deactivation; Design specifications; Diameters; Drinking water; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Irradiation; Mass transfer; Microfluidics; Photocatalysis; Rate constants; Reactor design; Reactors; Renewable energy; Slurries; Slurry reactors; Sol-gel processes; Steel structures; Substrates; Three dimensional printing; Ultraviolet radiation; Void fraction; Waste Water Technology; Water Management; Water Pollution Control; Zinc oxide; Microfluidic reactors; Catalyst immobilisation; Photocatalysis; Packed-bed reactor; Process intensification; Fixed bed; 3D printing
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-020-11806-9

Solar-driven photocatalysis is a promising water-cleaning and energy-producing technology that addresses some of the most urgent engineering problems of the twenty-first century: universal access to potable water, use of renewable energy, and mitigation of CO 2 emissions. In this work, we aim at improving the efficiency of solar-driven photocatalysis by studying a novel reactor design based on microfluidic principles using 3D-printable geometries. The printed reactors had a dimensional accuracy of 97%, at a cost of less than $1 per piece. They were packed with 1.0-mm glass and steel beads coated with ZnO synthesised by a sol-gel routine, resulting in a bed with 46.6% void fraction (reaction volume of ca. 840 μL and equivalent flow diameter of 580 μm) and a specific surface area of 3200 m 2  m −3 . Photocatalytic experiments, under sunlight-level UV-A irradiation, showed that reactors packed with steel supports had apparent reaction rates ca. 75% higher than those packed with glass supports for the degradation of an aqueous solution of acetaminophen; however, they were strongly deactivated after the first use suggesting poor fixation. Glass supports showed no measurable deactivation after three consecutive uses. The apparent first-order reaction rate constants were between 1.9 and 9.5 × 10 −4  s −1 , ca. ten times faster than observed for conventional slurry reactors. The mass transfer was shown to be efficient (Sh > 7.7) despite the catalyst being immobilised onto fixed substrates. Finally, the proposed reactor design has the merit of a straightforward scaling out by sizing the irradiation window according to design specifications, as exemplified in the paper.