Photoelectrocatalytic degradation of tetracycline by a novel Gr /Ni-Sb-SnO2 photo-anode

• A novel graphite/Ni-Sb-SnO 2 photo-anode was used to degrade tetracycline. • Results confirmed that Gr/Ni-Sb-SnO 2 (1:5:95) is the best photo-anode • Rate constant of PEC is 1.56 times higher than for photocatalytic process alone • High TC removal of 83.7% was achieved at 4.6 mA/cm 2 , pH= 4.3, and 43mg/LTC. • Excellent degradation stability for Gr/Ni-Sb-SnO 2 (1:5:95) after five cycles The widespread use of pharmaceutical products in pharmaceutical therapies and agriculture has led to environmental pollution worldwide. In this work, a photoelectrocatalytic (PEC) process was applied for the degradation of a typical pharmaceutical product, tetracycline (TC), via a novel graphite (Gr)/Ni-Sb-SnO 2 photo-anode. The effect of nickel doping on the catalytic activity of the photo-anode was investigated with the help of XRD, SEM, AFM, and LSV techniques. The influence of several PEC parameters such as current density, pH, and initial concentration on the degradation of TC was studied and optimized using a response surface methodology (RSM). It was found that the Gr/Ni-Sb-SnO 2 (1:5:95) is the best photo-anode for TC degradation, and that increasing the nickel content above 1% has a negative effect on the Gr/Ni-Sb-SnO 2 efficiency. RSM was found to be effective in describing the mathematical model linking PEC variables with TC removal at a correlation coefficient of 98.89%. A significant interaction between the variables was observed in PEC, with the square term contributing 64.94% to the model, and current density was the most important factor affecting TC degradation. The optimal conditions were a current density of 4.6 mA/cm², pH of 4.36, an initial concentration of 43 mg/L, and a time of 150 min in which a TC removal rate of 83.7% was achieved corresponding to a COD removal of 62.3% at a total energy consumption of 64.46 kWh/m 3 . A significant synergistic effect of PEC was observed, with rate constant being 1.56 times higher than that obtained for the photocatalytic process alone. In addition, the Gr/Ni-Sb-SnO 2 (1:5:95) photo-anode exhibited excellent degradation stability after five cycles of degradation test. Hence, Gr/Ni-Sb-SnO 2 (1:5:95) may serve as a good photo-anode for the photoelectrochemical treatment of industrial wastewaters.