Photocatalytic degradation of aniline using an autonomous rotating drum reactor with both solar and UV-C artificial radiation.

The aim of this work was to evaluate the performance of a novel self-autonomous reactor technology (capable of working with solar irradiation and artificial UV light) for water treatment using aniline as model compound. This new reactor design overcomes the problems of the external mass transfer effect and the accessibility to photons occurring in traditional reaction systems. The UV-light source is located inside the rotating quartz drums (where TiO2 is immobilized), allowing light to easily reach the water and the TiO2 surface. Several processes (UV, H2O2, Solar, TiO2, Solar/TiO2, Solar/TiO2/H2O2 and UV/Solar/H2O2/TiO2) were tested. The synergy between Solar/H2O2 and Solar/TiO2 processes was quantified to be 40.3% using the pseudo-first-order degradation rate. The apparent photonic efficiency, ζ, was also determined for evaluating light utilization. For the Solar/TiO2/H2O2 process, the efficiency was found to be practically constant (0.638-0.681%) when the film thickness is in the range of 1.67-3.87 μm. However, the efficiency increases up to 2.67% when artificial UV light was used in combination, confirming the efficient design of this installation. Thus, if needed, lamps can be switched on during cloudy days to improve the degradation rate of aniline and its mineralization. Under the optimal conditions selected for the Solar/TiO2/H2O2 process ([H2O2] = 250 mg/L; pH = 4, [TiO2] = 0.65-1.25 mg/cm2), 89.6% of aniline is degraded in 120 min. If the lamps are switched on, aniline is completely degraded in 10 min, reaching 85% of mineralization in 120 min. TiO2 was re-used during 5 reaction cycles without apparent loss in activity (<2%). Quantification of hydroxyl radicals and dissolved oxygen allows a chemical-based explanation of the process. Finally, the UV/Solar/TiO2/H2O2 process was found to have lower operation costs than other systems described in literature (0.67 €/m3).