Novel Bubble Column Design Constructed for Catalytic Ozonation – Effectiveness Assessment by Hydrodynamics and Kinetic Regime Determination

This article introduces an innovative design for a bubble column tailored for catalytic ozonation. A semi-batch reactor was employed with strategically positioned baffles to accommodate catalysts throughout the column. These baffles, constructed with a specially designed mesh-type material, not only served as catalyst supports but also provided an additional active surface for efficient mass transfer on both macro and micro scales. This groundbreaking approach has advanced heterogeneous catalysis by utilizing a multi-structured scaffold enriched with chemically active species. The dual role of the baffles was envisioned to enhance the physical absorption of ozone gas into the liquid and catalytic action in the production of reactive oxygen species (ROS) through ozone decomposition. However, it is crucial to note that any alteration in the column's geometry can influence the mass transfer resistance. The primary objective of this study was to assess the efficiency of the newly constructed bubble column by determining hydrodynamic parameters. For the column without mesh, the volumetric mass transfer coefficient (kLa) ranged between 0.007 and 0.009 1/s. Upon the incorporation of the mesh, kLa increased to values between 0.007 and 0.01 1/s. Simultaneously, the overall interphase surface rose from 42.16 ± 6.2 1/m to 53.29 ± 7.9 1/m, and the film mass transfer coefficient (kL) improved from (1.68 ± 0.1) × 10−4 to (2.13 ± 0.2) × 10−4 m/s after the mesh installation. This novel column design was specifically engineered for the treatment of textile wastewater. Dye degradation experiments demonstrated a higher rate of color removal when the mesh was inserted, surpassing traditional ozonation methods. Furthermore, the Hatta number increased from 3 to 5 with mesh usage, and the enhancement factor (E) shifted from 2.6 to 4. These enhanced Hatta values and improvement factors suggest that the new column construction successfully transitioned the operating regime from moderate to high speed.