Mehmet KOBYA

Article | 2021 | Chemosphere286 ( 2 )

Herein, ZnCr layered double hydroxide (ZnCr LDH), and its nanocomposites with GO and rGO were synthesized using the co-precipitation method. The samples were characterized using XRD, FT-IR, SEM, TEM, BET, and XPS techniques. The sonophotocatalytic activity of the ZnCr LDH, ZnCr LDH/GO, and ZnCr LDH/rGO was investigated via the degradation of rifampicin (RIF) in the ultrasonic bath under visible light irradiation. The synergy index of more than 1 determined for ZnCr LDH/rGO indicated the positive interaction of sonocatalysis and photocatalysis resulted by hybridizing the LDH nanosheets with rGO. The maximum sonophotocatalytic degrada . . .tion efficiency of 87.3?as achieved in the presence of ZnCr LDH/rGO nanocomposite with the concentration of 1.5 g L-1 for degradation of RIF with an initial concentration of 15 mg L-1 within 60 min sonication under visible light irradiation. The addition of different scavengers indicated that hydroxyl radicals, superoxide anion radicals, and the generated holes played a dominant role in the degradation of the pollutant molecules. A possible degradation mechanism was suggested based on the intermediates. The antibacterial tests confirmed the higher antibacterial activity of ZnCr LDH/GO compared with ZnCr LDH and ZnCr LDH/rGO against Grampositive Staphylococcus aureus More less

Mehmet KOBYA

Article | 2023 | Chemosphere314

Landfill leachate treatment involved with the membrane bioreactor (MBR) combined with membrane treatment via nanofiltration (NF) and/or reverse osmosis (RO) is widely used in Turkey. This treatment produces landfill leachate membrane concentrates (LLMCs) with an undesirably high concentration of contaminants. In the study, two different nanofiltration concentrates of leachate were coagulated. Coagulant dosages from 0.10 to 5.0 g of Me3/L (Me3: Al3 or Fe3), and the pH values ranged from 4.0 to 8.0 and 3.0-9.0 for Al-based and Fe-based coagulants, respectively. The most efficient pH values were 5.0 and 4.0 for Al3 and Fe3, respectivel . . .y. These pH values are lower than those known to be effective in coagulants. The reason for this is the presence of humic substances in the wastewater. The cost of Fe2(SO4)3.xH2O was the lowest than other coagulants at the end of the cost analyses obtained from Istanbul region landfill leachate NF concentrate (NFCL-1) and Kocaeli region landfill leachate NF concentrate (NFCL-2). Under optimum conditions, the costs for NFCL-1 and NFCL-2 were calculated as 0.55 and 0.46 /removed kg COD, respectively More less

Mehmet KOBYA

Article | 2021 | Chemosphere268

Herein, the main aim is to study the influence of the materials

Ertan ORUC

Article | 2017 | Chemosphere166

We investigated changes in nuclear factor kappa B (NFkB) activity, antioxidant responses and histopathological effects in the liver, gill and kidney tissues of rainbow trout exposed to nickel chloride (Ni). Two different concentrations (1 mg/L and 2 mg/L) were administrated to fish for 21 days. Tissues were taken from all fish for NFkB activity, histopathological examination and determination of superoxide dismutase (SOD), catalase (CAT) enzyme activity and of lipid peroxidation (LPO), and glutathione (GSH) levels. The findings of this study indicated that Ni exposure led to a significant increase in LPO indicating peroxidative dama . . .ge and antioxidant enzymes SOD and CAT activity in tissues (p < 0.05), but 2 mg/Ni concentration caused a significant decrease in CAT activity in kidney tissues (p < 0.05). One of mechanism in the antioxidant defense system seems to be GSH, which increased in gill and kidney tissues of fish exposed to Ni (p < 0.05). NFkB immunopositivity was detected in all tissues. Ni exposure caused lamellar thickening, cellular infiltration in gill tissues, hydropic degeneration of hepatocytes in liver tissues, hyalinous accumulation within the glomeruli and tubular degeneration in kidney tissues. Our results suggested that Ni toxicity may disturb the biochemical and physiological functions of fish by causing changes in NFkB activity and oxidative and histopathological damage in the tissues of rainbow trout. This study can provide useful information for understanding of Ni-induced toxicity. - Keywords: Heavy metal; Nickel; Fish; NFkB; Toxicity; Oxidative stress; Histopatholog More less

Mehmet KOBYA

Article | 2021 | Chemosphere263

Co-occurrence of arsenic and anions in groundwater causes a severe health problems and combine effects of these pollutants significantly affect performance of treatment process. Thus, this study has been conducted to examine the combine effects of anions on arsenic removal using aerated electrocoagulation (EC) reactor with 3D Al electrodes in groundwater. A 3-level, six factors Box-Behnken experimental design (BBD) was applied to investigate the individual and combine effect of anions and operating time: phosphate (x(1): 1-10 mg L-1), silica (x(2): 20-80 mg L-1), bicarbonate (x(3): 130-670 mg L-1), fluoride (x(4): 2-10 mg L-1), boro . . .n (x(5): 5-10 mg L-1), and operating time (x(6): 8-22 min) on desired responses. The specified responses were effluent arsenic concentration (C-f,C-As), removal efficiency of arsenic (R-e), consumptions of energy and electrode (ENC and ELC), operational cost (OC), and adsorption capacity (q(e)). The optimum operating parameters predicted using BBD were found to be x(1): 1.0 mg L-1, x(2): 26.0 mg L-1, x(3): 651.5 mg L-1, x(4): 2.0 mg L-1, x(5): 9.9 mg L-1, and x(6): 10.5 min considering highest removal efficiency of arsenic and lowest operational cost. Under these operating conditions, the experimental values of C-f,C-As, R-e, ENC, ELC, OC, and q(e) were found to be 2.82 mu g L-1, 98.6?0.411 kWh m(-3), 0.0124 kg m(-3), 0.098 $ m(-3), and 17.65 mu g As (mg Al)(-1), respectively. Furthermore, mathematical modelling was conducted using quadratic regression model and response surface analysis was performed to understand the relationship between independent parameters and responses. (C) 2020 Elsevier Ltd. All rights reserved More less

Mehmet KOBYA

Article | 2022 | Chemosphere307 ( 3 )

This study compares the efficiencies of active (Ti/TiO2-RuO2-IrO2 (TIR)) and inactive (Ni/Boron Doped Diamond (BDD)) anodes in terms of pollutant treatment and by-product formation in pretreated (chemical coagulation) landfill leachate nanofiltration membrane concentrate (PLNC). PLNC has high chemical oxygen demand (COD:4900 mg/L), total organic carbon (TOC: 1874 mg/L), total Kjeldahl nitrogen (TKN: 520 mg/L), ammonium nitrogen (NH3-N: 21.35 mg/L), chloride (5700 mg/L) and sulfate (9000 mg/L - due to coagulant type). The parameters of COD, TOC, NH3-N, TKN, free and combined chlorine species, halogenated organic compounds (HOCs), ads . . .orbable organic halogens (AOX), and nitrate at different current density (J: 111-555 A/m(2)) and initial pH (pH(i):3.5-7) were compared for both anodes. The removal efficiencies at the optimum conditions (pH(i) 5.5, 333 A/m(2) and 8 h) were obtained as 86.4 COD, 77.4 TOC, 93.4 TKN, 94.4 NH3-N with BDD and 34.3 COD, 27.3 TOC, 93.7 TKN, 97.4 NH3-N with TIR. According to gas chromatography-mass spectrometry (GC-MS) results obtained under optimum conditions, haloalkane/alkene, halonitroalkane, halonitrile, haloketone, haloalcohols, haloacids, haloaldehydes, haloamines/amides on both electrodes were detected as species of HOCs. In addition, the highest nitrate concentration was observed at the TIR anode, while the highest AOX concentration was observed at the BDD anode More less

Mehmet KOBYA

Article | 2021 | Chemosphere287 ( 4 )

The aim of this study is to produce an electrode that can be used in H2O2 production and Electro-Fenton (EF) process by an effective, cheap, and easy method. For this reason, a superhydrophobic electrode with a higher PTFE ratio and high thickness was produced with a simple press. The produced electrode was used in the production of H2O2 and mineralization of Atrazine. First, the effect of pH, cathode voltage, and operation time on H2O2 production was evaluated. The maximum H2O2 concentration (409 mg/L), the highest current efficiency (99.80? and the lowest electrical energy consumption (3.16 kWh/kg) were obtained at 0.8 V, 7.0 of p . . .H, and 120 min, and the stability of the electrode was evaluated up to 720 min. Then, the effects of the operational conditions (pH, cathode voltage, operating time, and catalyst concentration) in electro-Fenton were evaluated. The fastest degradation of Atrazine (>99?was obtained at 2.0 V, 3.0 of pH, and 0.3 mM of Fe2 in 15 min. In the final part of the study, the degradation intermediates were identified, and the characterization of the electrode was evaluated by SEM, XRD, FT-IR, tensiometer, potentiostat, and elemental analyzer More less

Mehmet KOBYA

Article | 2022 | Chemosphere309 ( 1 )

In this study, a ternary layered double hydroxide containing Zn, Co, and Fe transition metals (ZnCoFe LDH) was developed using a co-precipitation procedure. The as-synthesized photocatalyst was evaluated for its perfor-mance in the degradation of methylene blue (MB) under visible light irradiation. The effects of various process conditions including photocatalyst dosage, pollutant concentration, pH, lamp distance, and lamp power were investigated. The ZnCoFe LDH achieved approximately 74 photodegradation efficiency owing to the narrow bandgap of 2.14 eV. The Langmuir-Hinselwood rate constants were calculated as 1.17 min-1 and 3.55 m . . .in-1 for photolysis by LED lamp alone and for photocatalysis by LED/ZnCoFe LDH, respectively. The photocatalytic ability of the LDH was attributed to the generation of radical species like center dot OH and O2 center dot-. The photocatalytic degradation intermediates of MB were determined by GC-MS analysis. The catalyst retained its performance throughout seven reuse cycles with only a 4.17 reduction in removal efficiency. The energy per order EEO of the ZnCoFe/LED process in 180 min treatment time was determined as 5.41 kWh.m- 3. order-1. This study shows that ZnCoFe LDH has sufficient activity and photostability for long-term application in photocatalytic water treatment More less