The anodic oxidation of tetracycline was performed in an up-flow reactor, operating in batch mode with recirculation, using as anode a boron-doped diamond electrode. The influence on the degradation rate of solution initial pH (2 to 12), applied current intensity (25 to 300 A m(-2)) and type of electrolyte (sodium sulphate or sodium chloride) were investigated. For the assays run at equal current density, with sodium sulphate as electrolyte, the solution's initial pH of 2 presented the highest absorbance and chemical oxygen demand removals. Regarding the influence of current density, for equal charge passed, the organic load removal rate decreased with the increase in applied current. When sodium sulphate was used as an electrolyte, high-performance liquid chromatography (HPLC) results have shown an almost complete removal of tetracycline after a 2-h assay. HPLC results have also shown the presence of oxamic acid as one of the intermediates of tetracycline anodic oxidation. The complete removal of tetracycline was much faster in the presence of chloride ions that promoted the complete degradation of this antibiotic in 30 min. However, in the presence of chloride ions, the tetracycline mineralization is slower, as observed by the lower organic carbon removal rate when compared to that of the tetracycline degradation in the presence of sulphate.
Abstract. Antibiotics named tetracycline (TC) are the most popular group of pharmaceutical compounds used in therapeutic purpose in human and veterinary medicine and in aquaculture, due to their characteristics as broad spectrum antibiotic. The tetracyclines are a group of natural and semisynthetic products that are bacteriostatic agents with activity against a wide variety of organisms, but of limited use today because of acquired resistance. Even at low concentrations, tetracycline and its metabolites may have a negative influence on the environment. Tetracycline is weakly metabolized or absorbed into the body, some of the ingested antibiotic being eliminated through urine and feces directly into the environment as most of the primarily unchanged form or secondary compounds. Nowadays tetracycline residues can be detected in surface water that was discharged from municipal wastewater treatment plants and agricultural drained. In this study, the degradation of tetracycline and the influence of experimental parameters (initial pH, initial concentration, different flow velocity (mL/s), solution temperature ( o C), current intensity (mA)) on electrochemical degradation with BDD electrode were evaluated. The following parameters were analyzed for the samples collected during the electrochemical assays in electrochemical cell with stirrier and BDD/stainless steel electrodes: Chemical oxygen demand (COD), total organic carbon, nitrogen (total Kjeldhal, organic and inorganic), HPLC and UV-Visible absorption spectrophotometry.
This paper presents a study on mineralization of the triphenyl-methan dye, Crystal Violet (CV) in aqueous medium at pH 3.0, by environmentally friendly electrochemical methods such as Electro-Fenton (EF) processes using boron-doped diamond (BDD) anode, in terms of effects of the experimental parameters on the mineralization degree. Experimental data obtained on EF method allow identifying the main factors influencing the rate of mineralization process: the nature of the anode (Pt / BDD), temperature, pH, current intensity, initial concentration of CV, dose of Fe 2 + and Cu 2 + ions. The maximum of the degree of mineralization achieved was 97.14%, under the condition that we may consider the best: BDD anode, pH = 3.0, I = 300 mA, T = 308 K, the initial concentration of CV = 100 ppm, iron dose 1.0 mM and 0.25 mM dose of copper.
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