Aplicação do processo de peroxidação eletroquímica na degradação de ciprofloxacina e identificação de subprodutos

Abstract

Emerging contaminants are compounds, coming mainly form the industry, that have been detected in the environment and can cause adverse effects in the heath of living beings and the environment. Among these compounds, pharmaceuticals can be highlighted, due to its wide use, complex molecular structure and low biodegradability, hindering their treatment by conventional processes. Within this context, this research investigated the degradation of the antibiotic Ciprofloxacin (CIP) by the advanced process Electrochemical Peroxidation (EP). For that, different conditions were applied in an electrochemical cell (EC) composed of 304 stainless steel electrodes (AI 304) and O2 injection, being investigated the operational parameters: H2O2 concentration (25 - 1000 mg L-1), electric current density (ECD) (19,71 – 164,26 A m-2), Fe2+ concentration (0,5 and 2,0 mg L-1), initial pH (2,5 – 9,0) and electrolysis times (5 – 90 min). The response variables obtained by the application of the process were total organic carbon (TOC) and CIP (mg L-1), as well as the monitoring of the control variables solution pH and residual H2O2. The optimal condition of the EP process attained removal of TOC (43%) and CIP (88%) in 30 minutes of electrolysis when the following experimental conditions were applied: H2O2 concentration (100 mg L-1), ECD (32,85 A m -2) and initial pH 3,0. With the best experimental conditions, the presence of metal ions coming from the dissolution of the electrodes was assessed and bioassays with Lactuca sativa were performed in order to investigate the toxic effects of the treated and untreated CIP solutions, in terms of median lethal concentration (LC50), absolute germination (AG) and germination index (GI). The byproducts were identified using gas chromatography coupled to mass spectrometry (CG-MS) and contributed in the assessment of the relation of the emergence of compounds during the process with the possible toxic effects caused by the oxidation of the CIP molecule. Low levels of toxicity were observed in electrolysis times lower than 45 minutes. The byproducts and a lower dissolution of the electrodes material in lower electrolysis times may be related to the low toxicity levels, demonstrating that the EP process became more efficient and environmentally safe when applied in optimal conditions up to 30 minutes electrolysis time. Thus, the EP process was efficient in the degradation of the CIP molecules, and could be used as a complementary treatment, contributing in the reduction of the adverse effects caused by the inappropriate discharge of pharmaceutical in the environment.