Se estudian las eficiencias cuánticas de mineralización para la degradación foto-Fenton del herbicida comercial 2,4-D Amina empleando un reactor de laboratorio. Para todos los ensayos la concentración inicial del contaminante es de 30 ppm expresado en términos de la sal de dimetil amina del ácido 2,4 diclorofenoxiacético (TOC equivalente 13.5 ppm). A partir de los resultados experimentales y los cálculos de la velocidad promedio de absorción de fotones, se computaron las eficiencias cuánticas de mineralización aparente y absoluta. Para 30 min de reacción (T=25ºC), se alcanzaron valores máximos de eficiencias cuánticas de mineralización aparente y absoluta de 0.378 y 0.590 mol/Einstein, respectivamente. Para ensayos realizados empleando el reactor solar escala planta piloto, la mineralización completa del contaminante es alcanzada luego de 180 min (R=50). Además, para condiciones similares de operación solares se obtuvo una reducción 43 % mayor de TOC en la degradación del principio activo respecto al herbicida comercial.A study of the quantum efficiency of the photo-Fenton mineralization of a commercial herbicide 2,4-D amine in a laboratory reactor is presented. All the experimental runs were performed with an initial concentration of contaminant of 30 ppm expressed in terms of the dimethyl amine salt of 2,4-dichlorophenoxyacetic acid (equivalent to 13.5 ppm TOC). A set of experimental runs were performed to study the effects of the operating parameters on the Total Organic Carbon (TOC) conversion as a function of time. Different values of the hydrogen peroxide and ferric iron initial concentrations, and reaction temperatures were studied. From the experimental results and the average photon absorption calculations for the photo-Fenton treatment of this commercial herbicide, apparent and absolute quantum efficiencies of mineralization were defined and computed. For 25 °C and a reaction time equal to 30 min, maximum apparent and absolute quantum efficiencies of mineralization equal to 0.378 and 0.590 mol/Einstein, respectively, were obtained. Results of the commercial herbicide degradation using a solar reactor at pilot plant scale are also presented. The complete mineralization of pollutants is achieved after 180 min of reaction (R = 50). In addition, for similar solar operating conditions, a 43% greater TOC reduction was achieved for the degradation of the active principle with respect to the commercial herbicide.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES)