Degradation of the herbicide 2,4-DP by anodic oxidation, electro-Fenton and photoelectro-Fenton using platinum and boron-doped diamond anodes.
This paper reports the degradation of 2,4-DP (2-(2,4-dichlorophenoxy)-propionic acid) solutions of pH 3.0 by environmentally friendly electrochemical methods such as anodic oxidation, electro-Fenton and photoelectro-Fenton with a Pt or boron-doped diamond (BDD) anode. In the two latter techniques an O(2)-diffusion cathode was used and 1.0mM Fe(2+) was added to the solution to give hydroxyl radical (*OH) from Fenton's reaction between Fe(2+) and H(2)O(2) generated at the cathode. All treatments with BDD are viable to decontaminate acidic wastewaters containing 2,4-DP since they give complete mineralization, with loss of chloride ion, at high current due to the great production of oxidant *OH at the BDD surface favoring the destruction of final carboxylic acids. *OH formed from Fenton's reaction destroys more rapidly aromatic products, making the electro-Fenton and photoelectro-Fenton processes much more efficient than anodic oxidation. UVA light in photoelectro-Fenton with BDD has little effect on the degradation rate of pollutants. The comparative procedures with Pt lead to slower decontamination because of the lower oxidizing power of this anode. The effect of current on the degradation rate and efficiency of all methods is studied. The 2,4-DP decay always follows a pseudo-first-order kinetics. Chlorohydroquinone, chloro-p-benzoquinone and maleic, fumaric, malic, lactic, pyruvic, acetic, formic and oxalic acids are detected as products by chromatographic techniques. A general sequence accounting for by the reaction of all these intermediates with the different oxidizing agents is proposed.
Brillas
Enric
E
Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain. brillas@ub.edu
Baños
Miguel Angel
MA
Skoumal
Marcel
M
Cabot
Pere Lluís
PL
Garrido
José Antonio
JA
Rodríguez
Rosa María
RM
D015084:2,4-Dichlorophenoxyacetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006540:Herbicides / Q000737:chemistry*; D006861:Hydrogen Peroxide; D007501:Iron; D010084:Oxidation-Reduction
C045076:Fenton's reagent; D006540:Herbicides; D015084:2,4-Dichlorophenoxyacetic Acid; D006861:Hydrogen Peroxide; D007501:Iron; C010571:dichlorprop