Experimental and computational investigation of cold atmospheric plasma/visible-light/N-TiO2 in treatment of synthetic and real wastewaters

Abstract

Cold atmospheric plasma and visible-light photocatalysis (CAPVP) is considered as an effective advanced oxidation process. Experimental and computational investigation of CAPVP application for treatment of synthetic and industrial wastewaters was conducted for the first time in this work. N-TiO₂ as a visible-light photocatalyst was synthesized and characterized. The CAPVP reactor was developed and its performance in synthetic (cefixime) and real wastewater (Eshtehard Industrial Zone, Iran) was investigated. The effect of catalyst dosage, discharge voltage, inlet gas, visible-light power, and electrode distance from water surface was investigated on the cefixime degradation efficiency. The combined CAPVP with catalyst dosage = 1 g L⁻¹, air flow rate = 5 L min^-1 under visible-light power of 36 W with discharge voltage = 35 kV and the electrode-water surface distance of 5 mm caused about 95 % cefixime degradation after 20 min. A three-layered feed forward back propagation artificial neural network was developed for analysis of different variables influence on the CAPVP process. Findings showed that the catalyst dosage and discharge voltage had the highest effect on the degradation among the investigated variables. Also, the comparative experiments showed that the efficiency of the CAPVP was higher than that of one stage photocatalysis and plasma processes and showed a synergistic coefficient of 3.06. Furthermore, the CAPVP was used to treat the effluent of the real industrial wastewater and the effect of the catalyst dosage and discharge voltage was investigated on treatment efficiency. The results indicated that the combined process for 240 min reduced the COD of the effluent of Eshtehard Industrial Zone up to 95 %.