UV-Assisted Regeneration of TiO2-Modified Activated Carbons for Gas-Phase Methyl Ethyl Ketone Removal: Effects of Carbon Support and Reactor Configuration

Activated-carbon adsorption is widely used to remove volatile organic compounds (VOCs) from air, but adsorbent saturation limits its long-term sustainability. This study investigates gas-phase methyl ethyl ketone (MEK) adsorption and UV-assisted regeneration of TiO2-modified carbon adsorbents. Three commercial carbons were initially screened, and Black Pearls 2000 was selected for comparison of mechanical mixtures with TiO2 and composites prepared by depositing TiO2 onto the carbon support. The effects of calcination procedure, irradiation time, adsorbate loading, and reactor configuration were evaluated. Tested materials were also characterized by nitrogen physisorption (BET), Scanning and Transmission electron microscopy (SEM, TEM), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). MEK uptake was measured in a laboratory-scale continuous-flow system using micro-gas chromatography. Depositing 5 wt.% TiO2 largely preserved the initial MEK uptake of Black Pearls and yielded higher regeneration efficiencies than mechanical mixing. Capacity recovery reached approximately 90% after 3 h of UV irradiation and approached 94% with longer exposure. Under the investigated conditions, UV-assisted regeneration outperformed thermal treatments, which achieved approximately 70% recovery at 250 °C. Repeated regeneration after complete saturation led to progressively declining performance, whereas partial-loading operation maintained 94% of the initial partial-loading uptake over seven cycles. Among the configurations allowing in situ regeneration, the flat prototype achieved higher normalised MEK uptake during the 2 h adsorption steps, while the cylindrical prototype retained substantially higher absolute MEK uptake per unit mass. These results highlight the need to optimise material preparation, regeneration conditions, and reactor geometry jointly, considering both cyclic stability and absolute adsorption performance.