Gliding arc plasma treatment of levofloxacin using experimental design approach

The degradation of levofloxacin, a pharmaceutical pollutant model has been studied by gliding arc plasma (Glidarc). In this work, a full factorial design was applied to investigate the influence of the operating parameters and their interactions on the degradation yield. This experimental design demonstrates that the electrode-solution distance is the most influential factor followed by the concentration of levofloxacin and the applied voltage. Response surface methodology using Doehlert design was adopted to predict the optimal conditions of the plasma treatment. Results showed that for an applied voltage of 7.2 kV, an electrode-solution distance of 2.7 cm, and an initial concentration of 45.6 mg L-1, the degradation yield reached 52.81 +/- 1.19% after 90 min of plasma treatment, which corresponds to an energy yield of 40.1 mg kW(-1) h(-1). In addition, to develop a cost-effective system for the degradation of pharmaceutical pollutants, biodegradability of the plasma pretreated solutions was evaluated. Results showed that a readily biodegradable solution was obtained after only 30 min of plasma pretreatment. Hence, the feasibility and the efficiency of coupling plasma to biodegradation processes were confirmed. Moreover, coupling plasma to photocatalysis was carried out and results showed that 45 min of plasma treatment followed by 40 min of photocatalytic treatment achieved 100% degradation that neither the plasma process nor the photocatalysis process can reach alone.