Resumen:
This work describes the treatment of soil polluted with the herbicide pendimethalin by
the combination of surfactant-aided soil-washing (SASW) and electrochemical advanced oxidation processes. Results show that it is possible to completely extract the herbicide
from soil using SDS (sodium dodecyl sulfate) solutions as soil washing fluid (SWF) and
ratios SWF/soil higher than 10 dm3 kg-1. Soil washing effluents obtained after the
application of the SASW consisted of a mixture of surfactant (high concentration) and
pesticide (low concentration) and their degradation by electrolysis, photo-assisted
electrolysis (photoelectrolysis) and sonoelectrolysis with diamond anodes has been
compared with that obtained by the application of single photolysis and sonolysis.
Opposite to photolysis and sonolysis, the different electrolytic techniques allow
decreasing the concentration of herbicide and surfactant in the effluents. Competition
between the surfactant and the herbicide oxidation is important and irradiation of highfrequency
ultrasound or UV light do not seem to outperform very importantly the results
obtained by single electrolysis in the effluents of the SASW obtained with low SDS/soil
ratios. Opposite, photoelectrolysis becomes the most efficient technology for the
treatment of SWF obtained at high SDS/soil ratios (those required for an efficient SASW).
Catalytic effect of the sulfate released during the degradation of SDS (in particular the
formation of sulfate radicals) can help to explain the differences observed. The removal
efficiency is higher during sonoelectrolysis, reaching a final removal of the pesticide after
8 hours of treatment of 86.22 %. Photoelectrolysis (57.59%) shows higher efficiencies
for the removal of SDS followed by sonoelectrolysis (52.64%) and, finally, electrolysis
(48.29%), after 8 hours of treatment.