Degradation of gestodene (GES)-17α-ethinylestradiol (EE2) mixture by electrochemical oxidation

Evidence of the negative effects of several pharmaceutical molecules, such as hormones and steroids, on the environment can be observed throughout the world. This paper presents the results of the anodic oxidation of the mixture of gestodene steroid hormones and 17 α-ethinylestradiol present in aqueous medium. The tests were conducted in an undivided cell containing a working volume of 50 mL, using a Na₂SO₄ solution as support electrolyte and boron-doped diamond electrodes. The experiments were adjusted to the structure of a 3³ factorial design. The evaluated factors were: support electrolyte concentration (0.02, 0.05, and 0.10 M), pH of the reaction media (2, 3, and 4), and current density (16, 32, and 48 mA cm^-2). Under the optimum conditions (0.02 M Na₂SO₄, pH 4, and current density of 32 mA cm^-2), the degradation of at least 93% of the initial concentration of gestodene and 17α-ethinylestradiol was reached in a reaction time of 5 and 10 min, respectively. The complete degradation of both molecules required 15 min of reaction. Under these conditions, the degradation profile of the pharmaceutical mixture as each one of the active ingredients, followed a pseudo-first order kinetic behavior (k_mix = 0.0321, k_GES = 0.4206, and k_EE2 = 0.3209 min^-1).