Effluents containing pesticides are the cause of great concern because these compounds exhibit toxicity, environmental persistence and most are recalcitrant. Among the organic compounds used to combat pests highlight the organophosphate insecticides, which have lower toxicity when compared to organochlorine compounds. Two organophosphate insecticides have been widely used in Brazil, they are: methyl parathion (MP) and chlorpyrifos (CP). Among the methods of wastewater treatment, it emphasizes the electrochemical data with the use of boron-doped diamond electrode, which shows high efficiency in removing organic compounds with low adsorption capacity processes. This study proposes a method of treatment for wastewater containing MP and CP (separately) using electrodes of boron-doped diamond (BDD) with different doping levels (15,000 to 30,000 ppm B/C ratio, designated by BDD15 and BDD30, respectively) in acid medium. The electrodes were characterized using morphological and electrochemical techniques, such as Scanning Electron Microscopy, Digital Optical Microscopy, Raman Spectroscopy, X-Ray Diffraction, Cyclic Voltammetry and Scanning Electrochemical Microscopy. The efficiency of the degradation process was monitored by analytical techniques such as UV-Vis spectroscopy, High Performance Liquid Chromatography (HPLC) using spectroscopic detectors in the UV region and diode array detector (DAD) and the total organic carbon analyzer (COT). The process efficiency is related to the doping level of the BDD electrode and the compounds. The SEM images showed smooth growth of the film on the substrate titanium and the Raman spectra confirm the growth of carbon with sp3 bond (diamond) bonds and the incorporation of boron atoms. Analyses of X-Ray Diffraction showed the crystallinity of the BDD. Electrochemical characterizations showed the wide potential range of both electrodes and the electronic transfer system Fe(CN)63-/4- showed greater reversibility with more doped electrode. The same result was obtained with the SECM technique. MP insecticide assays showed that the most doped electrode was more effective in decreasing the concentration (maximum 86%) and removal of organic matter (maximum 72%) with lower electric consumption. Regarding the insecticide CP removal, no significant difference was observed in the pesticide removal and mineralization of organic matter using two BDD electrodes. However, the kinetics of removal was faster when the BDD30 electrode was used. Thus, it can be stated that highly doped electrodes are efficient in the organic matter removal, but the increase the efficiency of doping should be associated with the compound to be degraded. (AU) |
