Mineralization of aniline using hydroxyl/sulfate radical-based technology in a waterfall reactor

- UV/H2O2 with persulfate in a waterfall reactor degraded 100% of aniline in 20 min.
- 49% of mineralization was achieved in 90 min at pH = 4 and 250 ppm of persulfate.
- The synergism between UV/H2O2 and the combined UV/H2O2/PS process was 10.1%.
- Phenol was the main intermediate formed by UV/H2O2/PS proces.
- Sulfate radicals increases aniline degradation rate and mineralization extent.

The aim of this work is to study the applicability of a UV/H2O2 process intensified with persulfate (PS) as a source of SO4− radicals to efficiently mineralize a synthetic effluent containing aniline in a glass reactor arranged in a cascade configuration. pH conditions were studied and the concentration of PS was optimized. The synergism for aniline mineralization between the UV/H2O2 process and the combined UV/H2O2/PS process was quantified in 10.1%.Aniline degradation reached 100% under the UV/H2O2/PS process after 20 min. Its mineralization is favored under acidic conditions and with the presence of persulfate (optimal conditions: 49% in 90 min; pH = 4; [PS] = 250 ppm). On the contrary, the worst conditions were found at pH = 11, since hydrogen peroxide decomposes and carbonates were formed increasing the scavenging effect.The different mechanisms involved (formulated from intermediates identified by mass spectrometry) confirm these results. Aniline was found to follow a degradation pathway where phenol is the main intermediate. The presence of sulfate radicals increases phenol degradation rate leading to a higher mineralization extent. Benzoquinone was identified as the main aromatic oxidation product of phenol, whereas succinic, 4-oxo-pentanoic, fumaric and oxalic acids were detected as aliphatic oxidation products for both UV/H2O2 and UV/H2O2/PS oxidation processes.

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