Photocatalytic degradation of aniline by solar/TiO2 system in the presence of the electron acceptors Na2S2O8 and H2O2

Abstract

Aniline aqueous solution degradation by solar/TiO2 system in combination with electron acceptors such as Na2S2O8 and/or H2O2 was studied. The effects of TiO2 initial concentration, dose of persulfate and hydrogen peroxide, and pH were evaluated. The solar/TiO2/Na2S2O8 process was found to be more efficient than the solar/TiO2/H2O2 process. Under optimal conditions, the percentage of removal of solution TOC was 91.5% in approximately t30W = 30 min (reaction time = 60 min). The addition of persulfate, until to an optimum value, to the solar/TiO2 system inhibited the electron/hole pair recombination, increasing the availability of holes and SO4− and consequently HO radicals·H2O2 also inhibited the electron/hole recombination and generated HO radicals although an excess reduced the degradation efficiency. The roles played by reactive intermediate species, such as SO4−, HO, O2− and holes in both solar/TiO2/Na2S2O8 and solar/TiO2/H2O2 processes were determined using appropriated quenchers. SO4− radicals and holes were found to be the main responsible species in the solar/TiO2/Na2S2O8 system.