BDD-persulfate-based anodic oxidation process for progestin degradation: Optimization of conditions, eco-compatibility tests, and cost evaluation

Abstract

Considering the increasing presence of the hormones levonorgestrel (LNG) and gestodene (GES) in wastewater, the limited effectiveness of conventional treatment methods, and the demand for advanced complementary processes, our study aimed to optimize an anodic oxidation treatment with a focus on low specific energy consumption (SEC) and costs. An electrochemical system coupled to a boron-doped diamond anode (BDD) was continuously used to treat synthetic and real pharmaceutical wastewater from contraceptive production. The central design composite and response surface methodology were the tools employed for optimization. The lowest SEC was obtained as a response to the main process variables: current density, initial pH, and the concentration of the support electrolyte ([Na2S2O8]). The optimal condition ([Na2S2O8]0 = 0.07 mol L−1; [LNG]0,RPW = 1.02±0.05 mg L−1 and [GES]0,RPW = 1.05±0.05 mg L−1; j = 37.5 mA cm−2; pH = 6.75) was established considering an SEC ≤ 3.6 ± 0.8 kWh g−1 and progestins removal ≥70%, which was the experimental condition used to evaluate acute toxicity to Daphnia similis and the effect on estrogenic activity removal using the YES assay. Notably, our study evaluated, for the first time, a comparative investigation that highlights the substantial effect of support electrolytes over the eco-compatibility assessment of the anodic oxidation process investigated. The adaptability of the operation indicates the prospective suitability for the implementation of the process in wastewater treatment facilities in the pharmaceutical industry.