Removal of pendimethalin from soil washing effluents using electrolytic and electro-irradiated technologies based on diamond anodes

Abstract

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 dm 3 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.

Environmental Applications of Boron‐Doped Diamond Electrodes: 2. Soil Remediation and Sensing Applications

“…The degradation and mineralization rate of the AO process using BDD anode can also be increased by combination with other processes such as electro‐Fenton, sonolysis or photolysis ,. Such approach allows for providing an additional source of .…”

“…OH and other oxidant species. The activation of sulfate radicals is also further improved, thus increasing the global effectiveness of the process …”

“…The degradation and mineralization rate of the AO process using BDD anode can also be increased by combination with other processes such as electro-Fenton, [40][41][42] sonolysis [43][44][45][46] or photolysis. [43,[45][46][47][48][49] Such approach allows for providing an additional source of * OH and other oxidant species. The activation of sulfate radicals is also further improved, thus increasing the global effectiveness of the process.…”

“…The activation of sulfate radicals is also further improved, thus increasing the global effectiveness of the process. [48] The global efficiency of the process does not only depend on energy consumption. The addition of electrolyte might be also an important operating cost.…”

Anodic oxidation for the remediation of soils polluted with perchloroethylene

“…SASW is generally an efficient way to clean soil. It has been studied exhaustively in our research group in previous works, [13][14][15][16][17] attaining good results in the depletion of target compounds both from the soil matrix and, later, from soil washing fluid (SWF) using anodic oxidation. Regarding the SASW process, special care should be taken with the selection of optimal washing fluid composition, volume, mixing rate, temperature and contact time.…”