Research Information System
SCIENCE OF THE TOTAL ENVIRONMENT, vol.912, no.2024, pp.1-22, 2023 (SCI-Expanded)
The decolorization
and TOC removal of solutions of Acid Brown 14 (AB14) diazo dye containing 50 mg
L-1 of total organic carbon (TOC) have been first studied in a continuous-flow
electrocoagulation (EC) reactor of 3 L capacity with Fe electrodes of ~ 110 cm2 area each. Total loss of color with poor TOC removal was found
in chloride, sulfate, and/or hydrogen carbonate matrices after 18 min of this
treatment. The best performance was found using 5 anodes and 4 cathodes of Fe
at 13.70 A and low liquid flow rate of 10 L h-1, in aerated 39.6 mM
NaCl medium at a pH range of 4.0-10.0. The effluent obtained from EC was
further treated by electro-Fenton (EF) using a 2.5 L pre-pilot flow plant,
which was equipped with a filter-press cell comprising a Pt anode and an
air-diffusion cathode for H2O2 electrogeneration.
Operating with 0.10-1.0 mM Fe2+ as catalyst at pH 3.0 and 50 mA cm-2,
a similar TOC removal of 68% was found as maximal in chloride and sulfate media
using the sequential EC-EF process. The EC-treated solutions were also treated by
photoelectro-Fenton (PEF) employing a photoreactor with a 125 W UVA lamp. The sequential
EC-PEF process yielded a much higher TOC reduction, close to 90% and 97% in chloride
and sulfate media, respectively, due to the rapid photolysis of the final
Fe(III)-carboxylate complexes. The formation of recalcitrant chloroderivatives
from generated active chlorine limited the mineralization in the chloride
matrix. For practical applications of this two-step technology, the high energy
consumption of the UVA lamp in PEF could be reduced by using free sunlight.