Mechanochemical degradation of 2,4-D adsorbed on synthetic birnessite

Mechanochemical degradation of 2,4-D (2,4-dichlorophenoxyacetic acid) adsor bed on synthetic birnessite (delta-MnO2 was investigated using heat conduct ion calorimetry. The overall transformation kinetics of 2,4-D on birnessite after light grinding were approximately first-order, with an apparent acti vation energy of approximately 37 kJ mol(-1) for the range of temperatures 10-50 degrees C. The two decomposition products detected under mechanochemi cal degradation and incubation were 2,4-dichlorophenol and CO2, but no cons umption of gaseous oxygen was detected. A positive correlation was found be tween Mn(II) produced and CO2 evolved, suggesting that the decomposition of 2,4-dichlorophenol involves the oxide substrate as a source of oxygen and yields Mn(II). (C) 2000 Elsevier Science B.V. All rights reserved.