The Use of a Novel Graphitic Carbon Nitride/Cobalt Molybdate(G-C3n4/ComoO4) Nanocomposites for the Doxycycline Removal byPhotocatalytic Degradation in Pharmaceutical Industry Wastewatersand the Evaluation of Microtox (Aliivibrio Fischeri) and DaphniaMagna Acute Toxicity Assays

Abstract

In this study, a novel graphitic carbon nitride/cobalt molybdate (g-C3N4/CoMoO4) nanocomposites (NCs) as a photocatalys was examined during photocatalytic degradation process in the efficient removal of Doxycycline (DOX) from pharmaceutical industry wastewater plant, İzmir, Turkey. Different pH values (3.0, 4.0, 6.0, 7.0, 9.0 and 11.0), increasing DOX concentrations (5 mg/l, 15 mg/l, 30 mg/l and 45 mg/l), increasing g-C3N4/CoMoO4 NCs concentrations (1mg/l, 2 mg/l, 3 mg/l, 4 mg/l, 6 mg/l, 8 mg/l and 10 mg/l), different g-C3N4/CoMoO4 NCs mass ratios (5/5, 6/4, 7/3, 8/2, 9/1, 1/9, 2/8, 3/7 and 4/6), increasing recycle times (1., 2., 3., 4., 5., 6. and 7.) was operated during photocatalytic degradation process in the efficient removal of DOX in pharmaceutical industry wastewater. The characteristics of the synthesized nanoparticles (NPs) were assessed using X-Ray Difraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-Ray (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), and Diffuse reflectance UV-Vis spectra (DRS) analyses, respectively. The acute toxicity assays were operated with Microtox (Aliivibrio fischeri also called Vibriofischeri) and Daphnia magna acute toxicity tests. ANOVA statistical analysis was used for all experimental samples. The maximum 99% DOX removal efficiency was obtained during photocatalytic degradation process in pharmaceutical industry wastewater, at 150 W UV-vis light irradiation power, after 180 min photocatalytic degradation time, at pH=9.0 and at 25°C, respectively. The maximum 99% DOX removal was found with photocatalytic degradation process in pharmaceutical industry wastewater, at 30 mg/l DOX, at 150 W UV-vis light irradiation power, after 180 min, at pH=9.0 and at 25°C, respectively. The maximum 99% DOX removal was measured to 8 mg/l g-C3N4/CoMoO4 NCs with photocatalytic degradation process in pharmaceutical industry wastewater, at 30 mg/l DOX, at 150 W UV-vis light irradiation power, after 180 min, at pH=9.0 and at 25oC, respectively. The maximum 99% DOX removal was observed at 6/4wt g-C3N4/CoMoO4 NCs mass ratios at 30 mg/l DOX, at 150 W UV-vis light irradiation power, after 180 min, at pH=9.0 and at 25°C,respectively. The maximum 99% DOX removal was obtained in pharmaceutical industry wastewater during photocatalytic degradation process, after 1. recycle time, at 30 mg/l DOX, 8 mg/l g-C3N4/CoMoO4 NCs, at 6/4wt g-C3N4/CoMoO4 NCs mass ratio, after 180 min, at pH=9.0 and at 25°C, respectively.95.33% maximum Microtox (Aliivibrio fischeri) acute toxicity removal was found in DOX=30 mg/l after 180 min photocatalytic degradation time, and at 60°C, respectively. It was observed an inhibition effect of DOX=45 mg/l to Microtox with Vibrio fischeri after 180 min, and at 60°C. 91.27% maximum Daphnia magna acute toxicity removal was obtained in DOX=30 mg/l after 180 min and at 60°C, respectively. It was observed an inhibition effect of DOX=45 mg/l to Daphnia magna after 180 min, and at 60°C. DOX concentrations > 30 mg/l decreased the acute toxicity removals by hindering the photocatalytic degradation process. Similarly, a significant contribution of increasing DOX concentrations to acute toxicity removal at 60°C after 180 min, was not observed. It can be concluded that the toxicity originating from the DOX is not significant and the real acute toxicity throughout photocatalytic degradation process was attributed to the pharmaceutical industry wastewater, to their metabolites and to the photocatalytic degradation process byproducts. As a result, the a novel g-C3N4/CoMoO4 NCs photocatalyst during photocatalytic degradation process in pharmaceutical industry wastewater was stable in harsh environments such as acidic, alkaline, saline, and then was still effective process. When the amount of contaminant was increased, the a novel g-C3N4/CoMoO4 NCs photocatalys during photocatalytic degradation process performance was still considerable. The synthesis and optimization of g-C3N4/CoMoO4 heterostructure photocatalyst provides insights into the effects of preparation conditions on the material’s characteristics and performance, as well as the application of the effectively designed photocatalyst in the removal of antibiotics, which can potentially be deployed for purifying wastewater, especially pharmaceutical wastewater. Finally, the combination of a simple, easy operation preparation process, excellent performance and cost effective, makes this a novel g-C3N4/CoMoO4 NCs a promising option during photocatalytic degradation process in pharmaceutical industry wastewater treatment.