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    A combined process of chemical precipitation and aerobic membrane bioreactor for treatment of citric acid wastewater
    (Academic Press Ltd- Elsevier Science Ltd, 2023) Belibagli, Pinar; Isik, Zelal; Bouras, Hadj Daoud; Arslan, Hudaverdi; Dizge, Nadir
    The wastewater generated from citric acid production has a high organic loading content. The treatment and reuse of citric acid wastewater with high organic loading become extremely important. In this study, the performance of calcium hydroxide (Ca(OH)2) precipitation as a low-cost and environmentally friendly pre-treatment method and aerobic membrane bioreactor (MBR) combined treatment system was investigated for the treatment of citric acid (CA) wastewater. At the first step, optimization parameters such as agitation speed (100, 150, 200 rpm), temperature (30, 50, 70 degrees C), and reaction time (2, 4, 6 h) for Ca(OH)2 precipitation as a pre-treatment method were investigated using response surface methodology (RSM) to achieve maximum chemical oxygen demand (COD) removal. Experimental sets were designed using Box-Behnken Design. As a result of pre-treatment with Ca(OH)2 precipitation, a COD removal efficiency of 97.3% was obtained. Then, pre-treated CA wastewater was fed continuously to the MBR process for 10 days, which was the second stage of the combined process. As a result of the MBR process, 92.0% COD removal efficiency was obtained for 24 h HRT and 10 days SRT. In total, 99.8% COD removal efficiency was obtained when combined process was used and COD concentration decreased from 52,000-114 mg/L. For the treatment and reuse of wastewater from citric acid production, Ca(OH)2 precipitation and MBR combined treatment systems demonstrated an effective strategy.
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    A comprehensive review on the usability of black phosphorus in energy and wastewater treatment
    (Elsevier Inc., 2024) Kaya, Gul; Eskikaya, Ozan; Kucukosman, Ridvan; Ocakoglu, Kasim; Dizge, Nadir; Balakrishnan, Deepanraj; Singh Chohan, Jasgurpreet
    Increasing population and industrial development brings with it many problems that need to be solved, such as energy production, storage, saving, protection of limited reserves, and environmental pollution. Nanomaterials, which emerged with the introduction of nanotechnology into our lives, play an important role in many areas. The novel two-dimensional nanomaterial black phosphorus (BP) exhibits great potential in photocatalytic applications, energy technologies, and purification with properties such as broad light absorption spectrum, tunable direct band gap, and exceptionally high charge carrier mobility. This review gives a outline of the manufacturing techniques, structural, chemical, electrical and thermal properties of BP. Then, the success of BP derivatives with different dimensions and morphologies in environmental and energy applications is presented by comparing them with previous studies in these fields. The results show that heterojunction structures produced by combining BP with MoS2 and MOFs improve the electrochemical properties of BP, while carbonization processes increase its efficiency in battery and supercapacitor applications. Finally, in this review, a summary of BP's potential future uses, awareness of easy production methods, and its activities in environmental and energy applications are discussed in a broad context. © 2024
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    A hybrid process for leachate wastewater treatment: Evaporation and reverse osmosis/sequencing batch reactor
    (Wiley, 2022) Bouchareb, Raouf; Isik, Zelal; Ozay, Yasin; Karagunduz, Ahmet; Keskinler, Bulent; Dizge, Nadir
    In this study, a hybrid process for leachate wastewater treatment including evaporation and reverse osmosis (RO) membrane or biological treatment systems was suggested. Experiments were performed on a real landfill leachate wastewater. The leachate was subjected to evaporation; as a result, a distillate was obtained containing less organic matter and less substantial amounts of other pollutants, as ammonium salts and total phenols were removed. Tests were carried out at different evaporation temperatures and times. The initial leachate pH was adjusted and optimized. For optimum conditions, each of chemical oxygen demand (COD), total phenol, and ammonium salt concentrations were reduced to 99.99%, 95.00%, and 83.00%, respectively. The distillate of the first stage of the proposed process was then exposed to RO membrane system, as a first study, under different transmembrane pressure of 20, 30, and 40 bar and at different pH values of 7, 8, and 9. As a second suggested treatment system, the distillate was subjected to a biological treatment process for 30 days as a retention time, pH = 6, and room temperature 25 degrees C +/- 1 degrees C. At the end of the research study, a comparison was conducted between results obtained with RO membrane separation and biological treatment system as two distinct treatment systems proposed for leachate landfill wastewater treatment. Although both systems were effective for landfill leachate wastewater treatment, however, with the RO membrane separation system, COD removal efficiency reached 99.99%. In the other hand, with biological treatment process, COD elimination was as much as 90.00%. Certainly, evaporation and RO are not novel ways of landfill leachate treatment; however, few studies have attempted to use similar combined system for landfill leachate wastewater treatment and attained effective results of treated water. Practitioner Points A hybrid process of evaporation and RO membrane or biological treatment systems was suggested for leachate wastewater treatment. For optimum conditions, COD, total phenols, and ammonium salt reductions were achieved to 99.99%, 95%, and 83%, respectively, after the first evaporation stage. The distillate of the first stage of the proposed process was then exposed to RO membrane system and biological treatment system. Different transmembrane pressure and different pH values were optimized for RO.
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    A novel green approach for Cr(VI) removal: application of tomato stem-based hydrochar assisted Fenton-like process
    (Taylor & Francis Ltd, 2024) Alterkaoui, Aya; Belibagli, Pinar; Gun, Melis; Isik, Zelal; Eskikaya, Ozan; Yabalak, Erdal; Dizge, Nadir
    Environmentally friendly catalysts have come to the forefront due to the cost of chemically produced catalysts and the formation of by-products harmful to the environment. Millions of tons of plant waste are produced every year, some of which is disposed directly. In this study, tomato stem hydrochar (TSCH) was produced from waste tomato stems by the hydrothermal carbonisation (HTC) method, and its use as a catalyst was investigated. The optimisation of Cr(VI) removal from water was carried out using a Fenton-like process with a TSCH catalyst and resulted in 100% of Cr(VI) removal efficiency at 10 mg/L of Cr(VI) concentration, pH 2.00, 0.2 g/L of TSCH catalyst, 10 mu L/L of H2O2 and 60 minutes of reaction time. Fenton-like thermodynamic and kinetic data were analyzed, and the results were found to comply with the second-order in Cr(VI) removal. The reusability of the TSCH catalyst in Cr(VI) removal was investigated and it was emphasized that it was reusable for more than 5 uses. In conclusion, TSCH, which is an environmentally friendly, inexpensive and effective catalyst for Cr(VI) treatment in a Fenton-like process, can be used as an alternative catalyst for wastewater treatment in terms of both waste management and economic and environmentally friendly.
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    Adsorption and Fenton oxidation of azo dyes by magnetite nanoparticles deposited on a glass substrate
    (Elsevier, 2019) Unal, Bahar Ozbey; Bilici, Zeynep; Ugur, Naz; Isik, Zelal; Harputlu, Ersan; Dizge, Nadir; Ocakoglu, Kasim
    Fenton oxidation is an efficient and useful method for wastewater treatment. To increase overall reaction efficiencies and inhibit environmental impacts, developing advanced catalysts are crucial in this matter. The main goal of this study was to investigate the catalytic activity of the magnetite (Fe2+Fe23+O42-, FeFe2O4, or Fe3O4) nanoparticles (NPs) coated borosilicate glass on the color removal of basic red 18 (BR18) and acid red 8 (AR88) azo dyes by adsorption and Fenton oxidation reaction. The efficiency of powder magnetite NPs was also tested to compare to magnetite NPs coated borosilicate glass. The effect of solution pH (2.5-9.0), catalyst loading (0.25-3.0 g/L), and dye concentration (0.1-0.3 mM) were tested to achieve maximum color removal efficiency using powder magnetite NPs. The color removal efficiencies were measured 44% at pH 9.0 and 76% at pH 3.5 for adsorption and Fenton oxidation of BR18 dye (0.1 mM). Moreover, the color removal efficiencies were measured 81% at pH 3.5 and 100% at pH 6.0 for adsorption and Fenton oxidation of AR88 dye (0.1 mM). The effect of hydrogen peroxide (H2O2) concentration (2.5-25 mM) was also optimized and 10 mM was found optimum H2O2 dosage for Fenton oxidation. However, magnetite NPs coated borosilicate glass enhanced maximum 77% and 82% color removal efficiencies for adsorption and Fenton oxidation of BR18 dye. Maximum 86% and 100% color removal efficiencies were obtained for adsorption and Fenton oxidation of AR88 dye. Stability of the powder magnetite NPs and magnetite NPs coated borosilicate glass catalyst was also investigated. The reusability of the catalyst showed that magnetite NPs coated borosilicate glass could be used at least 3 times without significant loss of activity compared to powder magnetite NPs for Fenton oxidation. The characterization of the catalyst was carried out using scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray powder diffraction (XRD), and zeta potential analyses before and after adsorption.
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    Antibacterial and antioxidant activity of gold and silver nanoparticles in dextran–polyacrylamide copolymers
    (Springer Link, 2024) Tkachenko, Anton; Özdemir, Sadin; Tollu, Gülşah; Dizge, Nadir; Ocakoglu, Kasım; Prokopiuk, Volodymyr; Onishchenko, Anatolii; ?humachenko, Vasyl; Virych, Pavlo; Pavlenko, Vadym; Kutsevol, Nataliya
    Search for new antimicrobial agents is of great significance due to the issue of antimicrobial resistance, which nowadays has become more important than many diseases. The aim of this study was to evaluate the toxicity and biological effects of a dextran-graft-polyacrylamide (D-PAA) polymer-nanocarrier with/without silver or gold nanoparticles (AgNPs/D-PAA and AuNPs/D-PAA, respectively) to analyze their potential to replace or supplement conventional antibiotic therapy. The toxicity of nanocomplexes against eukaryotic cells was assessed on primary dermal fibroblasts using scratch, micronucleus and proliferation assays. DPPH (2,2-diphenyl-1-picrylhydrazylradical) assay was used to evaluate the antioxidant capacity of D-PAA, AgNPs/D-PAA and AuNPs/D-PAA. DNA cleavage, antimicrobial and biofilm inhibition effects of nanocomplexes were investigated. Nanocomplexes were found to be of moderate toxicity against fibroblasts with no genotoxicity observed. AgNPs/D-PAA reduced motility and proliferation at lower concentrations compared with the other studied nanomaterials. AgNPs/D-PAA and AuNPs/D-PAA showed radical scavenging capacities in a dose-dependent manner. The antimicrobial activity of AgNPs/D-PAA against various bacteria was found to be much higher compared to D-PAA and AuNPs/D-PAA, especially against E. hirae, E. faecalis and S. aureus, respectively. D-PAA, AgNPs/D-PAA and AuNPs/D-PAA showed DNA-cleaving and biofilm inhibitory activity, while AgNPs/D-PAA displayed the highest anti-biofilm activity. AgNPs/D-PAA and AuNPs/D-PAA were characterized by good antimicrobial activity. According to the findings of the study, AgNPs/D-PAA and AuNPs/D-PAA can be evaluated as alternatives for the preparation of new antimicrobial agents, the fight against biofilms, sterilization and disinfection processes. Our findings confirm the versatility of nanosystems based on dextran-polyacrylamide polymers and indicate that AgNPs/D-PAA and AuNPs/D-PAA can be evaluated as alternatives for the preparation of novel antimicrobial agents.
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    Antifouling and antibacterial performance evaluation of polyethersulfone membranes modified with AZ63 alloy
    (Iwa Publishing, 2023) Ozay, Yasin; Alterkaoui, Aya; Kahya, Kursat; Ozdemir, Sadin; Gonca, Serpil; Dizge, Nadir; Ocakoglu, Kasim
    Antibacterial membranes have attracted researchers' interest in recent years as a possible approach for dealing with biofouling on the membrane surface. This research aims to see if blending AZ63 Mg alloy into a polyethersulphone (PES) membrane can improve antifouling and separation. The composite membranes' pure water flux continued to increase from pristine PES to PES/AZ63 2.00 wt%. The results showed that PES/AZ63 2.00 wt% membrane supplied the highest permeate flux of E. coli. The steady-state fluxes of AZ63 composite membranes were 113.24, 104.38 and 44.79 L/m(2)h for PES/AZ63 2.00 wt%, 1.00 wt%, and 0.50 wt%, respectively. The enhanced biological activity of AZ63 was studied based on antioxidant activity, DNA cleavage, antimicrobial, anti-biofilm, bacterial viability inhibition and photodynamic antimicrobial therapy studies. The maximum DPPH scavenging activity was determined as 81.25% with AZ63. AZ63 indicated good chemical nuclease activity and also showed moderate antimicrobial activity against studied strains. The highest biofilm inhibition of AZ63 was 83.25% and 71.63% towards P. aeruginosa and S. aureus, respectively. The cell viability inhibition activity of AZ63 was found as 96.34% against E. coli. The photodynamic antimicrobial therapy results displayed that AZ63 demonstrated 100% bacterial inhibition when using E. coli.
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    Antimicrobial activity and cytotoxicity study of cerium oxide nanoparticles with two different sizes
    (Wiley, 2023) Yefimova, Svetlana; Klochkov, Vladimir; Kavok, Nataliya; Tkachenko, Anton; Onishchenko, Anatolii; Chumachenko, Tatyana; Dizge, Nadir
    The control over bacterial diseases requires the development of novel antibacterial agents. The use of antibacterial nanomedicines is one of the strategies to tackle antibiotic resistance. The study was designed to assess the antimicrobial activity of cerium oxide (CeO2) nanoparticles (NP) of two different sizes (CeO2 NP1 [1-2 nm] and CeO2 NP2 [10-12 nm]) and their cytotoxicity towards eukaryotic cells. The antimicrobial activity, effects of nanoparticles on DNA cleavage, microbial cell viability, and biofilm formation inhibition were analyzed. The impact of cerium oxide nanoparticles on eryptosis of erythrocytes was estimated using annexin V staining by flow cytometry. The newly synthesized CeO2 NP1 and CeO2 NP2 displayed moderate antimicrobial activities. CeO2 NP1 and CeO2 NP2 exhibited single-strand DNA cleavage ability. CeO2 NPs were found to show 100% microbial cell viability inhibition at a concentration of 500 mg/L. In addition, CeO2 NP1 and CeO2 NP2 inhibited the biofilm formation of S. aureus and P. aeruginosa. Larger cerium oxide nanoparticles were found to be less toxic against erythrocytes compared with the smaller ones. CeO2 nanoparticles demonstrate moderate antimicrobial activity and low cytotoxicity towards erythrocytes, which make them promising antibacterial agents.
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    Antimicrobial and antioxidant activity of phenolic extracts from walnut (Juglans regia L.) green husk by using pressure-driven membrane process
    (Springer India, 2023) Arslan, Hudaverdi; Koc, Eda Ondul; Ozay, Yasin; Canli, Oltan; Ozdemir, Sadin; Tollu, Gulsah; Dizge, Nadir
    In this study, antioxidant (DPPH and metal chelating), DNA cleavage, biofilm, and antimicrobial properties of extracted phenol from the walnut green husk (WGH) and its different concentrate and permeate samples were evaluated. For maximum phenolic compound extraction from the WGH first, the effects of solvent type (deionized water, methanol, n-hexane, acetone, and ethanol), solvent temperature (25-75 degrees C), and extraction time (0.5-24 h) were optimized. Then to concentrate phenolic compounds a pressure-driven membrane process was used with four different membrane types. The phenol contents of the concentrate samples were found to be microfiltration (MF) concentrate 4400 mg/L, ultrafiltration (UF) concentrate 4175 mg/L, nanofiltration (NF) concentrate 8155 mg/L, and reverse osmosis (RO) concentrate 8100 mg/L. LC-MSMS was used to determine the quantification of phenolic compounds in permeate and concentrate streams. In addition, all of the concentrate samples with high phenol content showed a high antioxidant activity as 100% with MF concentrate, UF concentrate, NF concentrated and RO concentrated. Likewise, concentrate samples were found to have very high antibiofilm activity as 82.86% for NF concentrate againts S. aureus, 85.80% for NF concentrate against P. aureginosa, 80.95% for RO concentrate against S. aureus, and 83.61% for RO-concentrate against P. aureginosa. When the antimicrobial activity of the extracted phenol from WGH and its different concentrate and permeate samples were evaluated by micro dilution and disk diffusion methods, it was found that the ability of the concentrate samples to inhibit bacterial growth was much higher than permeate ones. In addition, extracted phenol from WGH and its different concentrate and permeate samples showed significant DNA nuclease activity.
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    Antimicrobial Effects of Nanostructured Rare-Earth-Based Orthovanadates
    (Springer, 2022) Gonca, Serpil; Yefimova, Svetlana; Dizge, Nadir; Tkachenko, Anton; Ozdemir, Sadin; Prokopiuk, Volodymyr; Klochkov, Vladimir
    The search for novel antimicrobial agents is of huge importance. Nanomaterials can come to the rescue in this case. The aim of this study was to assess the cytotoxicity and antimicrobial effects of rare-earth-based orthovanadate nanoparticles. The cytotoxicity against host cells and antimicrobial activity of LaVO4:Eu3+ and GdVO4:Eu3+ nanoparticles were analyzed. Effects of nanomaterials on fibroblasts were assessed by MTT, neutral red uptake and scratch assays. The antimicrobial effects were evaluated by the micro-dilution method estimating the minimum inhibitory concentration (MIC) of nanoparticles against various strains of microorganisms, DNA cleavage and biofilm inhibition. GdVO4:Eu3+ nanoparticles were found to be less toxic against eukaryotic cells compared with LaVO4:Eu3+. Both nanoparticles exhibited antimicrobial activity and the highest MIC values were 64 mg/L for E. hirae, E. faecalis and S. aureus shown by GdVO4:Eu3+ nanoparticles. Nanoparticles demonstrated good DNA cleavage activity and induction of double-strand breaks in supercoiled plasmid DNA even at the lowest concentrations used. Both nanoparticles showed the biofilm inhibition activity against S. aureus at 500 mg/L and reduced the microbial cell viability. Taken the results of host toxicity and antimicrobial activity studies, it can be assumed that GdVO4:Eu3+ nanoparticles are more promising antibacterial agents compared with LaVO4:Eu3+ nanoparticles.
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    Antioxidant activity, DNA cleavage ability, and antibacterial properties of ceramic membrane coated with cobalt nanoparticles
    (Elsevier Ltd, 2025) Belibagli, Pinar; Dogan, Ali Can; Kaya, Gul; Dizge, Nadir; Ocakoglu, Kasim; Özdemir, Sadin; Tollu, Gülsah
    Ceramic membranes are increasingly used in water/wastewater treatment due to their excellent filtration/separation performance, mechanical, thermal and long-term stability. In this study, ceramic clay membranes coated with cobalt nanoparticles (Co NP) were produced to increase the antibacterial properties of ceramic membranes produced using clay, a natural and cost-effective material. The morphological structure of Co NP ceramic clay membranes was determined by SEM analysis and the surface of the ceramic clay membrane coated with Co NP gained a smooth surface feature close to homogeneity. The antioxidant activity of CoNPs was 69.26 % at 100 mg/L. Plasmid DNA was entirely degraded at 50 mg/L nanoparticle concentrations. At a concentration of 100 mg/L, α-amylase inhibition of 86.39 % was exhibited by the CoNPs solution. CoNPs exhibited significant antimicrobial activities against L. pneumophila subsp. pneumophila, E. hirae, and E. faecalis (Minimum Inhibition concentration (MIC):16 mg/L). The cell viability inhibitory effect of the NPs was 98.27 % at 20 mg/L concentration against E. coli. The antibiofilm activities of the CoNPs were determined 82.13 % and 71.67 % against S. aureus and P. aeruginosa, respectively. Furthermore, the E. coli elimination performance of CoNP coated on the solid surface of the ceramic membrane was obtained as 94.64 %. In line with all these results, it has been clearly proven that Co NP ceramic clay membranes can be used in water and wastewater treatment due to their convenient, cheap, and effective antibacterial properties. © 2024 Elsevier Ltd and Techna Group S.r.l.
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    Boron-based magnesium diboride nanosheets preparation and tested for antimicrobial properties for PES membrane
    (Elsevier, 2023) Küçükosman, Rıdvan; Işık, Zelal; Ocakoğlu, Kasım; Dizge, Nadir; Özdemir, Sadin
    Antimicrobial resistance to antibiotics for current bacterial infection treatments is a medical problem. 2D nanoparticles, which can be used as both antibiotic carriers and direct antibacterial agents due to their large surface areas and direct contact with the cell membrane, are important alternatives in solving this problem. This study focuses on the effects of a new generation borophene derivative obtained from MgB2 particles on the antimicrobial activity of polyethersulfone membranes. MgB2 nanosheets were created by mechanically separating magnesium diboride (MgB2) particles into layers. The samples were microstructurally characterized using SEM, HR-TEM, and XRD methods. MgB2 nanosheets were screened for various biological activities such as antioxidant, DNA nuclease, antimicrobial, microbial cell viability inhibition, and antibiofilm activities. The antioxidant activity of nanosheets was 75.24 ± 4.15% at 200 mg/L. Plasmid DNA was entirely degraded at 125 and 250 mg/L nanosheet concentrations. MgB2 nanosheets exhibited a potential antimicrobial effect against tested strains. The cell viability inhibitory effect of the MgB2 nanosheets was 99.7 ± 5.78%, 99.89 ± 6.02%, and 100 ± 5.84% at 12.5 mg/L, 25 mg/L, and 50 mg/L, respectively. The antibiofilm activity of MgB2 nanosheets against S. aureus and P. aeruginosa was observed to be satisfactory. Furthermore, a polyethersulfone (PES) membrane was prepared by blending MgB2 nanosheets from 0.5 wt to 2.0 wt %. Pristine PES membrane also has shown the lowest steady-state fluxes at 30.1 ± 2.1 and 56.6 L/m2h for BSA and E. coli, respectively. With the increase of MgB2 nanosheets amount from 0.5 to 2.0 wt%, steady-state fluxes increased from 32.3 ± 2.5 to 42.0 ± 1.0 and from 15.6 ± 0.7 to 24.1 ± 0.8 L/m2h, respectively for BSA and E. coli. E. coli elimination performance of PES membrane coated with MgB2 nanosheets at different rates and the membrane filtration procedure was obtained from 96% to 100%. The results depicted that BSA and E. coli rejection efficiencies of MgB2 nanosheets blended PES membranes increased when compared to pristine PES membranes.
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    Caustic recovery from caustic-containing polyethylene terephthalate (PET) washing wastewater generated during the recycling of plastic bottles
    (Nature Portfolio, 2025) Alterkaoui, Aya; Eskikaya, Ozan; Keskinler, Bulent; Dizge, Nadir; Balakrishnan, Deepanraj; Hiremath, Pavan; Naik, Nithesh
    To prevent water scarcity, wastewater must be discharged to the surface or groundwater after being treated. Another method is to reuse wastewater in some areas after treatment and evaluate it as much as possible. In this study, it is aimed to recover and reuse the caustic (sodium hydroxide, NaOH) used in the recycling of plastic bottles from polyethylene terephthalate (PET) washing wastewater. Chemical substances used in the industry will be significantly reduced with chemical recovery from wastewater. Ultrafiltration (UP150) and nanofiltration (NP010 and NP030) membranes were used for this purpose in our study. Before using nanofiltration membranes, pre-treatment was performed with coagulation-flocculation process to reduce the pollutant accumulation on the membranes. Different coagulants and flocculants were used to find suitable coagulants and flocculants in pre-treatment. The pre-treated wastewater using aluminum oxide, which supplied the highest chemical oxygen demand (COD) removal (76.0%), was used in a dead-end filtration system to be filtered through NP010 and NP030 membranes at different pressures (10-30 bar). In the same filtration system, raw wastewater was filtered through a UP150 membrane. Among these treatment scenarios, the best method that could remove pollutants and provide NaOH recovery was selected. After each treatment, pH, conductivity, COD, and NaOH analyses were performed. The maximum NaOH recovery (98.6%) was obtained with the UP150 membrane at 5 bar.
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    Comparison of Cr(VI) adsorption and photocatalytic reduction efficiency using leonardite powder
    (Pergamon-Elsevier Science Ltd, 2022) Arslan, Hudaverdi; Eskikaya, Ozan; Bilici, Zeynep; Dizge, Nadir; Balakrishnan, Deepanraj
    It is very important to treat Cr(VI) from the aquatic environment due to its toxic and harmful effects. Conventional treatment methodology involving biological pathways is generally ineffective for wastewater containing Cr(VI). Therefore, it is necessary to develop environmentally friendly and economical methods to remove Cr(VI) from the aquatic environment. In this study, leonardite, which is a natural mineral that has no harmful effects on the environment, was used for Cr(VI) removal. Leonardite was used in both adsorption and photocatalytic treatment systems by only pulverizing without any chemical treatment. Characterizations of leonardite were obtained using X-ray fluorescence (XRF), fouirer transform infrared spektrofotometre (FTIR), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) analyses methods. The effects of solution pH (2-10), particle size (45-300 mu m), adsorbent dose (0.25-3 g/L), and initial concentration (10-30 mg/L) on Cr(VI) removal efficiency were investigated in both adsorption and photocatalytic experiments. In the adsorption process, a complete removal efficiency (100%) was obtained for 3 g/L of adsorbent dose with an initial Cr(VI) concentration of 10 mg/L at pH 2 for 2 h. In the photocatalytic process, 100% removal efficiency of Cr(VI) was obtained when four times less adsorbent dosage was used under the same conditions. In addition, the reuse of leonardite powder was also investigated under optimum experimental conditions. Leonardite powder preserved approximately 70% of its activity in the photocatalytic process while it lost 50% of its activity after 5 reuses in adsorption process.
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    Development of Ruthenium Oxide Modified Polyethersulfone Membranes for Improvement of Antifouling Performance Including Decomposition Kinetic of Polymer
    (Springer, 2023) Yigit, Basak; Ozay, Yasin; Emen, Fatih Mehmet; Kutlu, Emine; Ocakoglu, Kasim; Dizge, Nadir
    In this study, RuO2-embedded PES membrane was prepared and it was used for protein separation. The antifouling properties of the fabricated composite membranes were also investigated using bovine serum albumin (BSA) as protein solution. The mean roughness increased proportionally by introducing RuO2 particles. The porosity of the composite membranes was higher than that of the pristine PES membrane. On the other hand, composite membranes has smaller average pore size after addition of RuO2 particles. The blending of RuO2 particles to the PES membrane caused to increase the hydrophilicity. The contact angle was measured 76.67 +/- 1.21 degrees, 73.23 +/- 0.84 degrees, 70.28 +/- 0.77 degrees, and 67.13 +/- 0.80 degrees for pristine PES, PES/RuO2 0.50 wt%., PES/RuO2 0.75 wt%., and PES/RuO2 1.00 wt%, respectively. The pure water flux of the membranes decreased from 439.7 to 379.3 L/m(2)/h for the pristine PES and PES/RuO2 1.00 wt%. The pore size was calculated as 16.47 nm for the pristine PES and pore size decreased up to 6.05 nm when RuO2 particles increased up to 1.00 wt%. BSA fluxes were 84.1 +/- 2.1, 86.3 +/- 2.5, and 93.9 +/- 3.2 L/m(2)/h for pristine, PES/RuO2 0.50 wt%, and PES/RuO2 0.75 wt% membranes, respectively. PES/RuO2 1.00 wt%. membrane supplied the lowest BSA flux (73.6 +/- 3.1 L/m(2)/h). BSA rejection efficiencies increased from 45.5 +/- 1.8% to 92.6 +/- 1.5% when blended RuO2 particles increased from 0 to 1.00 wt%. The results depicted that R-ir values decreased while R-r values increased after the blending of RuO2. The thermal studies of the PES/RuO2 membranes were also performed by DTA/TG. The Activation Energy (E-a) values of the PES/RuO2 membranes were found to be 57.67-641.34 kJ/mol for Flynn-Wall-Ozawa (FWO) and 55.13-659.10 kJ/mol for Kissenger-Akahira-Sunose (KAS).
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    Effects of hydrogen peroxide, temperature and treatment time on degradation properties of polyethersulfone ultrafiltration membrane
    (TUBITAK, 2022) Özay, Yasin; Yabalak, Erdal; Dizge, Nadir
    Oxidative cleaning agents such as hydrogen peroxide (H2O2) and sodium hypochlorite (NaClO) used in water and wastewater treatment play an important role in the degradation and rapid aging of the polymeric membranes. In addition, when the temperature is above the maximum operating range of the membrane, it negatively affects the membrane performance. H2O2, which is also known as a green and environmentally friendly strong oxidant because of releasing only water as a by-product, can provide good cleaning efficiency under temperature, but its influence on membrane aging is not fully understood. In this study, the aging of polyethersulfone (PES) ultrafiltration (UF) membrane using H2O2 under high-temperature conditions and degradation of the polymeric membrane were systematically investigated using response surface methodology (RSM). The effects of H2O2 concentration, temperature, and treatment time were tested on membrane flux, contact angle, pore size, and porosity for decomposed membrane. The results showed that normalized permeability was significantly changed approximately 2.34-folds by H2O2 concentration at an exposure dose of 5 mM and 373 K temperature. Moreover, the largest pore sizes as 161.23 nm and 160.73 nm were obtained at the conditions of 2.5 mM H2O2 concentration and 373 K temperature. The lowest contact angle (54.76°) and porosity (61.88%) were obtained at the same conditions. The results depicted that H2O2 can be used for membrane cleaning with minimum membrane degradation at moderate conditions. © TÜBİTAK
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    Enhanced biogas yield in anaerobic digestion of citric acid wastewater by pre-treatment: The effect of calcium hydroxide precipitation and electrocoagulation process
    (Elsevier, 2024) Belibagli, Pinar; Akbay, Habibe Elif Gulsen; Arslan, Salih; Mazmanci, Birgul; Dizge, Nadir; Senthilkumar, Natarajan; Balakrishnan, Deepanraj
    During the production and use of citric acid (CA), which is frequently used in food, chemistry, metallurgy and other related industries, wastewater with high organic load and acidity is generated. Discharge of these wastewaters into the receiving environment without adequate purification causes serious pollution problems. However, treating such wastewater with hybrid processes allows both the formation of valuable by-products and an increase in the degree of purification. In this study, the biogas production potential of citric acid wastewater (CAWW), which was pre-treated by chemical precipitation and electrocoagulation (EC) processes, was investigated. Pre-treatment experiments were designed using Box-Behnken Design (BBD) and chemical oxygen demand (COD) concentrations after hydrated lime (Ca(OH)2) precipitation and EC processes were determined as 4960 mg/L and 5120 mg/L, respectively. The pre-treated CAWW were finally used for the secondary treatment by anaerobic digestion (AD) process. After AD process COD degradation determined as 67% and 98% for Ca (OH)2 precipitation and EC process, respectively. In addition, the biogas production of the pre-treated CAWW increased approximately 2 and 7 times for the Ca(OH)2 precipitation and EC processes, respectively, compared to the untreated. The methane (CH4) content of the produced biogas increased by 18% and 50% for Ca(OH)2 precipitation and EC processes, respectively. According to 48-hour acute toxic test result, daphnia mortality decreased from 50% concentration of CAWW after AD, even 10% concentration is non-toxic to daphnia. In conclusion, the complementarity of Ca(OH)2 precipitation and EC processes with AD promoted both the removal of organics from wastewater and the production of valuable by-products.
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    Fabrication and characterization of polyethersulfone membranes functionalized with zinc phthalocyanines embedding different substitute groups
    (Elsevier, 2021) Bilici, Zeynep; Ozay, Yasin; Yuzer, Abdulcelil; Ince, Mine; Ocakoglu, Kasim; Dizge, Nadir
    In this study, a novel polyethersulphone (PES) composite membrane incorporated with two different zinc phthalocyanines (ZnPc), tetra-iodo and octa(2,6-diphenylphenoxy), was fabricated through the phase inversion approach. Three different concentrations of zinc phthalocyanines (0.5, 1.0, and 2.0 wt.%) were blended into the PES membrane. The morphology and performance of the fabricated composite membranes were systematically studied by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) mapping, atomic force microscopy (AFM), porosity, water contact angle, antifouling, and rejection measurements. Hydrophobicity of the pristine membrane decreased from 79.67 degrees to 77.03 degrees and from 79.67 degrees to 67.57 degrees after blending of 2.0 wt.% tetra-iodo ZnPc (TI-ZnPc) and octa(2,6-diphenylphenoxy) ZnPc (DP-ZnPc), respectively. Furthermore, the porosity and mean pore radius decreased due to the introducing of ZnPc. Porosity of the pristine membrane decreased from 60.60 % to 44.96 % and 42.21 % after blending of TI-ZnPc and DP-ZnPc, respectively. Mean pore size of the pristine membrane decreased from 22.70 nm to 9.11 nm and 17.93 nm after blending of TIZnPc and DP-ZnPc, respectively. BSA filtration mostly affected the flux of pristine membrane and caused it to decrease from 133.5 to 87.1 L/m(2)h (relative flux reduction (RFR) of 34.7 %). RFR decreased up to 19.2 % and 17.3 % for TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes. Pristine PES membrane rejected 45.8 % BSA. However, TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes supplied 91.0 % and 70.6 % BSA rejections, respectively. In comparison to pristine PES membrane, the total resistance (R-t) values of the composite membranes decreased. The pristine PES membrane showed the lowest flux recovery ratio (FRR, 71.89 %) against BSA, while all-composite membranes showed promising antifouling properties. FRR increased up to 97.44 % and 89.06 % for TI-ZnPc 2.0 wt% and DP-ZnPc 2.0 wt% composite membranes, respectively. The pristine PES membrane showed the lowest FRR against activated sludge, while all composite membranes showed promising antifouling properties. Moreover, ZnPc-embedded PES composite membranes were irradiated with appropriate wavelengths of light in the presence of oxygen to generate reactive oxygen species to clean fouled membranes' surface. The results showed that photo-cleaning was very effective to recover membrane flux.
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    Heterogeneous catalyst production from waste cucumber stems and investigation of production potential in biodiesel
    (Elsevier, 2025) Alterkaoui, Aya; Belibagli, Pinar; Arslan, Hudaverdi; Dizge, Nadir; Balakrishnan, Deepanraj
    The use of heterogeneous catalysts obtained from waste in biodiesel production is of great importance in terms of waste management and waste recovery. In this study, heterogeneous catalyst was successfully obtained from waste cucumber stems (WCS) and its potential for biodiesel production via transesterification was investigated. The heterogeneous catalyst contains Ca, K, Mg, Si elements that play a role in biodiesel production. Biodiesel production potential was designed by selecting different temperature, time, methanol/oil molar ratio, and catalyst amount using response surface methodology (RSM). Waste cooking oil (WCO) was used for biodiesel production. The optimum values of these parameters were found to be 70 degrees C, 120 min, 15 wt% and 20:1, respectively. 93.7 % FAME yield was obtained using the obtained CaO catalyst. The heterogeneous catalyst obtained from WCS showed multiple reuse capacity up to 5 cycles. All these results showed that the heterogeneous catalyst obtained from WCS has strong biodiesel production activity and this approach has great potential in biodiesel production with its economic, sustainability and environmental benefits.
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    Hydrothermal Synthesis of Waste Black Tea Pulp and Tomato Stem Hydrochars and Comparison of Their Adsorption Performance of Safranin Dye
    (Springer Int Publ Ag, 2023) Alterkaoui, Aya; Belibagli, Pinar; Gun, Melis; Isik, Zelal; Dizge, Nadir; Yabalak, Erdal
    In this study, hydrochar prepared from black tea (BT) and tomato stem (TS) using subcritical water (SW) conditions was used as an adsorbent for color removal from Safranin-O (SO-Basic Red 2) dye wastewater. The use of black tea hydrochar (BTH) and tomato stem hydrochar (TSH) was investigated in the removal of Safranin-O dye from aqueous solutions by the adsorption process. In optimization studies, variables impacting the adsorption process such as adsorbent size, pH, dye concentration, adsorbent dosage, and shaking time were examined. As a result of optimization studies, removal efficiencies of 85.15% for BTH and 81.5% for TSH were achieved. In this study, the reuse cycle was also examined. Adsorption isotherm models, adsorption kinetic models, and thermodynamic studies have been studied to explain the relationships between the adsorption processes taking place. Data appropriate for the Freundlich and D-R isotherm models as well as the PSO kinetic model were obtained for TSH while defining the Freundlich isotherm model and the pseudo-second-order (PSO) kinetic model for BTH.