Estudo cinético da eletroxidação de Rifampicina usando DSA, platina e BDD como eletrodos

The occurrence of drug residues in sewage and natural waters has attracted the attention of researchers around the world. The indiscriminate use of certain medications and the drugs excreted, such as antibiotics, causes two environmental problems: one is the contamination of water resources and the other is that some microorganisms develop resistance to these drugs, causing genetic changes [1]. In the present study, we evaluate the catalytic efficiency of three electrodic materials: Ti/Ru0.3Ti0.7O2 and Ti/Pt anodes that are classified as active electrode, and Boron Doped Diamond (BDD), that is non active electrode [2], for treatment of an effluent contaminated with a model drug, Rifampicin. The studied effluent was a solution containing 0.2 g L-1 of rifampicin and Na2SO4 0.5 M to promote conductivity of solution. Electrolysis to each material were performed applying at constant current densities (30, 60, and 90 mA cm-2) and in two temperatures (30 and 60 °C). During the reaction, the concentration of the drug was monitored by absorption spectroscopy at 472 nm. The drug oxidation mechanism presents a first order kinetics. Plotting the relation ln (Abs0/abs) versus reaction time, is possible to notice two linear regions, at the start of the reaction (T <15 minutes), which has a higher drug concentration, and other in superior time where the rifampicin concentration is the lowest and there are presence of intermediate compounds. This result was observed for all electrodes. The rate constants of all electrodic materials for t<15 minutes and percentage of absorbance reduction after 3 hours of reaction are presented in Table 1. After reaction, the following order of efficiency can be observed: BDD> Pt> DSA. However, when we analyze the kinetic constant at the beginning of the reaction we have to reverse the order of effectiveness for higher current densities and temperature of 60 ° C, in which case the order is BDD > DSA > Pt. This result indicates that the concentration drug influences more significantly the oxidation of DSA and the intermediates formed can interfere with the reaction kinetics. However, in all conditions it is evident the higher efficiency of BDD in relation to other electrodic materials.