Photocatalytic solar discoloration of Reactive Red 84 employing titanium dioxide modified with iron

Abstract

In this investigation, TiO₂ and Fe/TiO₂ (0, 0.15, 0.25, 0.40 iron mass%) were compared as photocatalysts to determine its best efficiency with respect to decoloration time and mineralization measured as total organic carbon (TOC) of a textile dye, Reactive Red 84 (water solution at 50 mg/L). The catalysts were synthesized using the sol-gel method under specific conditions (450°C 2h, using titanium terbutoxide, TBT). Doping with ferric nitrate was carried out. At lab scale (first stage), the TiO₂ and Fe/TiO₂ and the controls were exposed to visible light lamps adding 1 mL/L H₂O₂ (8.6 mmol/L) and 1 g/L of each catalyst. The iron doped catalysts were activated using visible light lamps. The results obtained indicated that the best catalyst was Fe-0.25 iron mass% doped TiO₂ (TSGF-0.25, technique sol-gel Fe). Decoloration time was 120 minutes of reaction and mineralization reached approximately 50% measured as TOC after 240 minutes. At pilot scale (second stage) using a CPC (Compound Parabolic Collector) solar reactor, the best catalyst (TSGF-0.25) decolorized 100% requiring 3.87 kJ/L of accumulated energy (Q_UV) and degraded 77% of the initial dissolved dye measured as TOC. Visible light proved to be suitable when using iron-doped materials.