EDDS as complexing agent for enhancing solar advanced oxidation processes in natural water: Effect of iron species and different oxidants.

The main purpose of this pilot plant study was to compare degradation of five microcontaminants (MCs) (antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L) by solar photo-Fenton mediated by EDDS and solar/Fe:EDDS/S2 O8 2- . The effects of the Fe:EDDS ratio (1:1 and 1:2), initial iron species (Fe(II) or Fe(III) at 0.1 mM) and oxidizing agent (S2 O8 2- or H2 O2 at 0.25-1.5 mM) were evaluated. The higher the S2 O8 2- concentration, the faster MC degradation was, with S2 O8 2- consumption always below 0.6 mM and similar degradation rates with Fe(II) and Fe(III). Under the best conditions (Fe 0.1 mM, Fe:EDDS 1:1, S2 O8 2- 1 mM) antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L where 90% eliminated applying a solar energy of 2 kJ/L (13 min at 30 W/m2 solar radiation <400 nm). Therefore, S2 O8 2- promotes lower consumption of EDDS as Fe:EDDS 1:1 was better than Fe:EDDS 1:2. In photo-Fenton-like processes at circumneutral pH, EDDS with S2 O8 2- is an alternative to H2 O2 as an oxidizing agent.