Photodegradation of Ciprofloxacin and Ofloxacin Antibiotics and Their Photo-Metabolites with Sunlight

Research Article

Austin Chem Eng. 2019; 6(1): 1067.

Photodegradation of Ciprofloxacin and Ofloxacin Antibiotics and Their Photo-Metabolites with Sunlight

Koyuncuoglu P1* and Sponza DT2

1Department of Environmental Engineering, Pamukkale University, Turkey

2Department of Mechanical Engineering, Dokuz Eylul University, Turkey

*Corresponding author: Pelin Koyuncuoglu, Pamukkale University, Engineering Faculty, Environmental Engineering, Denizli, Turkey

Received: March 19, 2019; Accepted: May 02, 2019; Published: May 09, 2019


In this study, Nano Graphene Oxide Magnetite (Nano-GO/M) composite was prepared and characterized under laboratory conditions with FTIR and SEM analysis to investigate the metabolites of Ciprofloxacin (CIP) and Ofloxacin (OFL) antibiotics formed during photooxidation under sunlight. Two different metabolites of CIP and OFL namely desenthylenciprofloxacin (M1) and oxociprofloxacin (M3); and 9-Piperazino Ofloxacin (POF) and des-Methyl Ofloxacin (MOF) were in HPLC. For maximum removal efficiency (80%) of 1 mg/L initial CIP concentration, 250 min irradiation time were obtained as optimum time for photo-oxidation via sunlight irradiation at 80 W power in august at hours between 10.00 am and 17.00 pm (for 24 hours experiments, we keep going at these hours for 4.5 days). Best results were obtained at 1mg/L initial concentration of CIP, at original pH of CIP solutions (6.5) and at 2g/L Nano-GO/M concentration. For maximum OFL removal (82%) the optimum Nano-GO/M concentration was found to be 2g/L at 1mg/L OFL concentration, at pH 6.5, after 350 min irradiation time, at 35°C±5°C. Final concentrations of M1, M3, POF and MOF metabolites were found as 0.425, 0.125, 0.098 and 0.075 mg/L, respectively.

Keywords: Ciprofloxacin; Ofloxacin; Photo-oxidation; By-product; Sunlight


Antibiotics are commonly utilized for treatment and prevention of deadly infections in humans and animals [1]. Fluoroquinolones antibiotics (FQs) are one type of the most important synthetic antibiotics that are widely employed to treat infections [2]. Ciprofloxacin (CIP), Ofloxacin (OFL), Moxifloxacin (MOX), and Norfloxacin (NOR), are the antibacterial synthetic drugs, belonging to fluoroquinolones group [3]. They usually used to treat infections due to their potent antibacterial activity against gram-positive and gramnegative bacteria. Since the inefficient removal in the industrial and domestic wastewater treatment plants, FQs have been a frequently detected category of antibiotics in natural waters and wastewaters around the world, with concentrations ranging from ng/L to mg/L [4]. FQs in aquatic ecosystems could induce transcriptional changes in microbial communities, thus contributing to the development of resistant bacteria and genes [4]. FQs may also cause the physiological teratogenesis of plants/algae and be genotoxic/carcinogenic for organisms. Unfortunately, FQs are only weakly biodegradable [5]. As a consequence, the application of complementary processes able to efficiently eliminate antibiotics from water is urgently required [1]. So far, many different treatment technologies, such as adsorption [6- 8], biodegradation [9,10] and mainly chemical oxidation [2,11-15] have been applied in FQ removal. Among these approaches, chemical oxidation by means of a catalyst is a crucial subject for removal of complex compounds. Therefore, it is necessary to develop efficient catalyst for FQ removal.

Advanced Oxidation Processes (AOPs) are used to oxidize complex compounds in wastewater which are not degrading biologically. AOP benefit from the reactions of highly reactive hydroxyl radicals (•OH) that are produced in various ways, depending on the technique applied [16]. Nowadays, AOPs have been developed to remove FQs from wastewater [4,12,17,18]. Photocatalytic oxidation is a type of AOP. Serpone and Emiline [19], defined that photocatalysis, in its most simplistic description, is the acceleration of a photoreaction by action of a catalyst. Among the AOPs, heterogeneous photocatalysis has attracted attention as a promising technique for solving environmental problems especially in the degradation of organic pollutants in water treatment [20]. Furthermore, in photo driven AOPs, energy costs can be saved by using sunlight.

Graphene is Two-Dimensional (2D) sheets of carbon atoms arranged in a honeycombed network and gained much attention in last fifteen years. Owing to their chemical, physical, and mechanical properties, such as large special surface area, excellent electrical and thermal conductivity, high mechanical strength, flexibility, high surface to volume ratio and efficient wide range of light adsorption, graphene-based materials are popular in a broad range of applications [21,22]. Graphene Oxide (GO), originated from sheets of GO. There are a lot of oxygen-containing functional groups on GO nanosheets such as epoxy (C-O-C), Hydroxyl (OH) and Carboxyl (COOH) [23]. The oxygen containing groups on the GO nanosheets makes it easy to functionalize them. Iron oxide nanoparticles have received great interest in different applications due to their superior magnetic properties. Fe3O4, one of the iron oxides, has an inverse spinel structure where all the Fe2+ ions are located in the octahedral spaces and Fe3+ ions are located in the tetrahedral and octahedral spaces [24]. Being magnetic, abundant, biocompatible, and almost semiconductor, magnetite has received great attention in various fields especially in photocatalytic removal of organic pollutants [25]. Magnetic Fe3O4 has the advantage for the usage as support material of composite nano graphene oxide (Nano-GO/M) composite because it can be easily separated by an external magnetic field [26]. Iron oxide nanomaterials composited with GO as magnetic adsorbents were useful and do not need extra filtration or centrifugation.

Yoon et al. [27] studied arsenic removal using Fe3O4– graphene oxide composite (M-GO) and Fe3O4- reduced graphene oxide composite (M-rGO). The M-GO was obtained more effective to adsorb both As(III) and As(V) than M-rGO, because the more functional groups existing on the M-GO. The adsorption capacity of M-GO and M- rGO for As(III) and As(V) were 85mg/g (MGO for As(III)), 38mg/g (M-GO for As(V)), 57mg/g (M-rGO for As(III)), and 12mg/g (M- rGO for As(V)). Kinetic results indicated that the adsorption process could be defined by the pseudo-secondorder kinetic model under the selected arsenic concentration range (1mg/L, 0.3mg/L and 0.15mg/L), and the adsorption isotherm was fitted well to Freundlich model. Dong et al. [26], recently reported a study about removal of two pollutants namely Levofloxacin (LEV) and Lead (Pb) by using GO. 10mL GO suspension (40mg/L) was used as the adsorbent. 10mL of LEV or Pb solutions of seven different concentrations (LEV: 1, 2, 5, 10, 20, 30, and 40 mg/L; and Pb: 1, 2, 5, 10, 20, 40, and 60 mg/L) were used for sorption experiments for 24 h retention time at 25°C. GO showed strong affinity for LEV and Pb in aqueous solutions with Langmuir maximum adsorption capacities of 256.6 and 227.2 mg/g, respectively. Liu et al. [28], reported the use of graphene as an adsorbent for removal of Methylene Blue (MB) from its aqueous solution. The dye uptake capacity increased from 153.5mg/g to 204.08mg/g with the rise in temperature from 293 K to 333 K while the maximum dye removal (~ 99.68%) was observed at pH 10.0. Adsorption equilibrium data fitted well to the Langmuir isotherm model than the Freundlich model. Tayyebi et al [29], studied the removal of Sr2+ and Co2+ ions (50mg/L initial concentration) by using magnetic GO (M-GO). 20mg of adsorbent was added to vessels which contained 100mL of Co2+ or Sr2+ solution at pH 6.5. M-GO is saturated at the loading of 0.28 and 0.56 meq/g of Sr2+ and Co2+ ions, respectively. Adsorption isotherms of Sr2+ and Co2+ ions, which were fitted by Langmuir monolayer model.

The objective of this study was i) to synthesize a novel nano particle, ii) to obtain the optimum operational conditions for maximum removal yields of CIP and OFL iii) and to evaluate the formation of by-products of CIP (M1 and M3) and OFL (POF and MOF) during photocatalytic decomposition under sunlight with Nano-GO/M.

Material and Methods

Quartz glass reactors for the photocatalytic treatment under sunlight

In sunlight studies, quartz glass reactors coated with teflon were used for photocatalytic experiments. Experiments were carried out at different retention times of the day (30,120,250,350 min and 24h) and different initial concentration of CIP and OFL and the reactors were placed at an angle of 90 degrees to the sun at hours 08.00-17.00. The pH of the reaction mixture was adjusted from 4 to 6.5 and 10 using 1 mol/L of H2SO4 and NaOH solutions. The effects of 0.5g/L,2g/ L,3.5g/L,5g/L and 10g/L Nano-GO/M composite concentrations on the removals of CIP and OFL with constant sunlight time (250 min for CIP removal, 350 min for OFL removal were chosen due to preliminary studies results) at original pH of CIP and OFL solution (pH=6.5) under sunlight irradiation with a power of 80 W at outdoor temperature (35°C ± 5°C).

Synthesis of nano-GO/M composite under laboratory conditions

GO was synthesized using modified Hummer’s method that involved both oxidation and exfoliation of graphene. In a typical synthesis, 5 g purchased graphene was dispersed in 120ml H2SO4 by adding 2.5 g of NaNO3 in glass flasks coated by teflon on a magnetic stirrer for 30min placed in a water bath at a temperature of 18°C by the procedure given by Nengsheng et al. [30]. After stirring the mixture mentioned above at a rpm of 5000; 15 g of KMnO4 was added gradually, and continued to stir the last mixture overnight, continuously at 18°C. Then, 150ml H2O was slowly added and continued to mix a day at 98°C. Finally, 50mL of 30% H2O2 was added to the final mixture. The mixture was washed with 5% HCl and deionized water for several times and then, centrifuged and dried under vacuum for purification the GO which was obtained in a solid phase. The Fe3O4 nano particles were dispersed in 25mL water and added to 50mL GO aqueous solution. This mixture contained 1 mg Fe+3 /1mL GO and it was stirred at 60°C through 1h. The nanocomposite was collected by using a magnet from the outside of the glass reactor and washed with water three times [30].

Analytical methods

HPLC equipment specifications: A HPLC Degasser (Agilent 1100), a HPLC Pump (Agilent 1100), a HPLC Auto-Sampler (Agilent 1100), a HPLC Column Oven (Agilent 1100) and a HPLC Diode- Array-Detector (DAD) (Agilent 1100) were used. Figure 1,2 shows the molecular structure of CIP and OFL and their metabolites, respectively.