Electrodegradation of tetracycline on BDD anode

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 tetracycline initial concentration and recirculation flow rate were investigated. Assays were performed at constant current density, 300 A m−2, using as electrolyte a sodium sulfate aqueous solution, 5 g L−1. At the experimental conditions tested, HPLC results have shown an almost complete removal of tetracycline after 2 h assay. The removals of the organic load, measured as chemical oxygen demand (COD) and total organic carbon (TOC), increased with tetracycline initial concentration and recirculation flow rate. At the highest recirculation flow rate tested, 100 L h−1, with an initial tetracycline concentration of 150 mg L−1, after 4 h assay, the removals of COD, TOC and absorbance (measured at 276.5 and 360.0 nm) were 93%, 87%, 99% and 100%, respectively. Regarding the total Kjeldahl nitrogen elimination, it takes place mainly via transformation of organic nitrogen into ammonium, nitrate and nitrite. The total nitrogen removal increased with initial tetracycline concentration and showed also a tendency to increase with recirculation flow rate.

► High degree of mineralization can be achieved in the electrooxidation of tetracycline at a BDD anode.
► During the anodic oxidation of tetracycline organic nitrogen is mainly converted to ammonium, nitrate and nitrite.
► Average mass transfer coefficients increase with recirculation flow rate.