In this work, the remediation of wastewater polluted with 2,4-D via conductive-diamond electrochemical oxidation using solar energy as a direct electrical power source has been investigated. The changes in operating conditions during the solar test are clearly related to the day-night cycle, with a maximum solar irradiation intensity of 450 W m(-2) at noon and an average daily charge supplied of 22.5 A h m(-2) d(-1). A solar irradiation intensity greater than 100W m(-2) is necessary to produce current, and values over 200 A m(-2) are required for efficient solar-powered processes. Despite fluctuations in the intensity supplied to the electrochemical cell, electrolysis with diamond electrodes can attain complete depletion of 2,4-D and its mineralization, although the changing operating conditions applied during the electrolysis powered by solar energy favor the accumulation of many intermediates. In contrast, only very low concentrations of two intermediates were detected during electrolysis powered galvano-statically with a power supply at 3.0 A, indicating that the intensity highly influences the oxidation rate involved in the electrolysis. (C) 2015 Elsevier B.V. All rights reserved.