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The aim of the research was to investigate the removal of metronidazole from aqueous solutions by Fe/charcoal micro-electrolysis fluidized bed reactor. The effective variables influencing the metronidazole removal including the initial pH of the solution, the initial concentration of metronidazole, contact time, aeration rate and Fe/charcoal ratio were studied. The amount of secondary iron ions pollution in the reactor effluent was investigated by a flame atomic absorption device. Degradation reaction kinetics were studied. The removal efficiency of metronidazole in the actual hospital wastewater sample was investigated under optimal conditions of the reactor. The stability and performance of the reactor was investigated through 4 consecutive cycles. Data analysis was performed by SPSS-16. The maximum removal efficiencies were obtained in optimal conditions including pH: 7, the contact time of 70 min, aeration rate of 6 L/min, charcoal/Fe ratio 1:1 and initial concentration of metronidazole of 10 mg/L as 90 and 78 percent for synthetic solutions and actual wastewater respectively. No secondary pollution of iron ions was detected. In the study of linear kinetic models, the degradation process followed pseudo -first kinetic order. The Fe/charcoal micro-electrolysis system is well-suited for efficient removal of antibiotics from aqueous solutions and applies to industrial scale. [ABSTRACT FROM AUTHOR]

In this study, the effects of some operational factors, such as pH value, nano-ZnO loading, UV-A irradiation time, and power of radiation on the degradation efficiency of metronidazole (MNZ) in aqueous solution were discussed through photocatalytic experiments using nano-ZnO as the photocatalyst. Results show that removal of metronidazole (MNZ) and COD has a direct correlation with power of UV-A lamp and irradiation time. MNZ solution (80 mg L-1) was rapidly removed by the irradiation of UV lamp OSRAM 125 W high pressure within 180 min. In nano-ZnO/UV photocatalysis reactor, irradiation time and power of UV lamp have a great effect on metronidazole degradation. Statistical analysis (One-way ANOVA) has shown that the pH (in acedic and basic condition) and variation of nano-ZnO concentration has no significant effects on MNZ removal, COD, and BOD5/COD ratio. But the maximum degradation of MNZ occurred at pH 10 and 1.5 gL-1 nano-ZnO. Maximum degradation of MNZ and COD was 96.55 and 95.42%, respectively. In addition, biodegrad-ability improved from ~0 to 0.091 within 180 min. [ABSTRACT FROM AUTHOR]

The increasing use of pharmaceuticals and the ongoing release of drug residues into the environment have resulted in significant threats to environmental sustainability and water safety. In this sense, developing a robust and easy-recovered magnetic nanocomposite with eminent photocatalytic activity is very imperative for detoxifying pharmaceutical compounds. Herein, a systematic study was conducted to investigate the photocatalytic ozonation for eliminating metronidazole (MET) from aqueous media utilizing the CuFe 2 O 4 /SiO 2 /ZnO heterojunction under simulated sunlight irradiation. The composite material was fabricated by a facile hydrothermal method and diagnosed by multiple advanced analytical techniques. Modelling and optimization of MET decontamination by adopting the central composite design (CCD) revealed that 90 % of MET decontamination can be achieved within 120 min of operating time at the optimized circumstance (photocatalyst dose: 1.17 g/L, MET dose: 33.20 mg/L, ozone concentration: 3.99 mg/min and pH: 8.99). In an attempt to scrutinize the practical application of the CuFe 2 O 4 /SiO 2 /ZnO/xenon/O 3 system, roughly 56.18% TOC and 73% COD were removed under the optimized operational circumstances during 120 min of degradation time. According to the radical quenching experiments, hydroxyl radicals (HO•) were the major oxidative species responsible for the elimination of MET. The MET degradation rate maintained at 83% after seven consecutive runs, manifesting the efficiency of CuFe 2 O 4 /SiO 2 /ZnO material in the MET removal. Ultimately, the photocatalytic ozonation mechanism over the CuFe 2 O 4 /SiO 2 /ZnO heterojunction of the fabricated nanocomposites was rationally proposed for MET elimination. In extension, the results drawn in this work indicate that integrating photocatalyst and ozonation processes by the CuFe 2 O 4 /SiO 2 /ZnO material can be applied as an efficient and promising method to eliminate tenacious and non-biodegradable contaminants from aqueous environments. [Display omitted] • An ozonation-integrated photocatalysis was developed for MET decomposition. • CuFe 2 O 4 /SiO 2 /ZnO revealed excellent reusability and high practical implementation. • Superior decomposition of approximately 90% of MET was achieved in 120 min. • HO.• was the dominant radical for the photocatalytic-ozonation degradation of MET. [ABSTRACT FROM AUTHOR]