Sürdürülebilir Kalkınma Amaçları

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• Doktora TeziAçık Erişim2026/r/gumushane/21829
  Demlenmiş çay atığı ve fındık kabuğundan biyokömür üretimi, karakterizasyonu ve bazı ağır metallerin zenginleştirilmesinde kullanımı

  Serdal Şeker

  Bu tez çalışmasında, çevresel su numunelerinde eser düzeyde bulunan Cd(II), Pb(II), Ni(II) ve Co(II) iyonlarının Alevli Atomik Absorpsiyon Spektrofotometresi (FAAS) ile tayini öncesinde, bulundukları ortamdan ayrılması ve zenginleştirilmesi amacıyla katı faz ekstraksiyonu (SPE) yöntemleri geliştirilmiştir. Bu kapsamda düşük maliyetli biyokütle kaynakları olan demlenmiş çay atığı ve fındık kabuğundan piroliz yöntemiyle biyokömürler elde edilmiş ardından demlenmiş çay atığı biyokömürü (DÇAB) ve fındık kabuğu biyokömürü (FKB) manyetik nanopartiküller ile modifiye edilerek yeni manyetik kompozit adsorbanlar sentezlenmiştir. Sentezlenen adsorbanların yapısal ve yüzey özellikleri çeşitli enstrümantal yöntemlerle karakterize edilmiştir. Adsorpsiyon ve desorpsiyon verimini etkileyen sulu çözelti pH'ı, adsorban miktarı, temas süresi ile desorpsiyon çözeltisinin türü ve derişimi gibi deneysel parametreler, DÇAB/Fe3O4 adsorbanı için Merkezi Kompozit Tasarım (MKT) yaklaşımı kullanılarak optimize edilmiş ve elde edilen deneysel veriler kullanılarak yüzde geri kazanımı tahmin edebilen Yapay Sinir Ağı (YSA) tabanlı bir model geliştirilmiştir. DÇAB/CoFe2O4 ve FKB/NiFe2O4 adsorbanları için ise optimizasyon çalışmaları tek değişkenli yaklaşım (OVAT) kullanılarak yürütülmüştür. Geliştirilen yöntemin analitik performansı, zenginleştirme faktörü (ZF), bağıl standart sapma (BSS), gözlenebilme sınırı (GS) ve tayin sınırı (TS) kriterleri temel alınarak incelenmiştir. Sentezlenen adsorbanların maksimum adsorpsiyon kapasiteleri, Langmuir izoterm modeli kullanılarak her bir analit iyonu için belirlenmiş olup; DÇAB/Fe3O4 adsorbanında Cd(II) için 79.4 mg g-1, DÇAB/CoFe2O4 adsorbanında Cd(II), Pb(II) ve Ni(II) için sırasıyla 69.4, 185.2 ve 45.2 mg g-1, FKB/NiFe2O4 adsorbanında ise Cd(II), Pb(II) ve Co(II) için 20.4, 28.2 ve 21.7 mg g-1 olarak hesaplanmıştır. Farklı çevresel su numunelerinde gerçekleştirilen analit ekleme/geri kazanım testleri ile yöntemin doğruluğu ve güvenilirliği ortaya konulmuştur.

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• MakaleAçık Erişim2026/r/gumushane/19417
  Removal of Pb(II) ions from aqueous solutions by Brevibacillus agri-loaded clay: Kinetic, isotherm, and artificial neural network modeling

  Belduz, Ali Osman; Inan, Kadriye; Duran, Celal; Ozdes, Duygu; Ozeken, Sengul Tugba; Nalçaoğlu, Aleyna; Şeker, Serdal

  In this study, a novel and efficient adsorbent was developed by immobilizing inactivated Brevibacillus agri biomass onto an abundant natural clay via a simple synthesis route for Pb(II) removal from aqueous media. The adsorption behavior of inactivated Brevibacillus agri-loaded clay (BLC) was evaluated using batch experiments by investigating the effects of initial solution pH (2.0–6.0), BLC dosage (0.5–4.0 g/L), contact time (1–180 min), initial Pb(II) concentration (10–420 mg/L), temperature (25–80°C), and the presence of foreign ions. The optimum conditions were determined to be an initial solution pH of 5.0 and a contact time of 120 min. Isotherm models were applied to elucidate the interactions between Pb(II) ions and BLC, while kinetic studies were conducted to evaluate the adsorption performance and underlying mechanisms. The maximum adsorption capacity of BLC was determined as 65.4 mg/g according to the Langmuir isotherm model. Thermodynamic parameters revealed that Pb(II) adsorption on BLC was exothermic, feasible, and spontaneous at 25ºC. Artificial neural network (ANN) studies provided highly accurate predictions by modeling and confirmed the reliability and applicability of the model for Pb(II) removal in industrial applications. This study presents an innovative and sustainable approach for heavy metal removal, offering an effective solution applicable to environmental remediation processes.

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• MakaleAçık Erişim2026/r/gumushane/13721
  Enhanced cationic dye adsorption using Stenotrophomonas indicatrix -modified MnFe2O4: performance evaluation and adsorption mechanism

  Ozdes, Duygu; Dede, Alper; Turfan, Fatma Asya; Seker, Serdal

  In this study, MnFe2O4 magnetic nanoparticles were modified with the Stenotrophomonas indicatrix bacteria for the first time in the literature to develop an effective and novel bio-adsorbent for the remediation of toxic cationic dyes, specifically Rhodamine 6G (R6G) and Methylene Blue (MB), from contaminated aqueous media. MnFe2O4 and bacteria-loaded MnFe2O4 were thoroughly characterized using FTIR, XRD, and SEM-EDX analyses. XRD results confirmed that the cubic spinel structure of MnFe2O4 was preserved after bacterial modification, while FTIR spectra evidenced the successful incorporation of biological functional groups, including –NH, –OH, amide, and phosphate moieties, onto the nanoparticle surface. Adsorption performance of the dyes was evaluated in terms of parameters including aqueous solution pH, equilibrium time, bacteria-loaded MnFe2O4 dosage, and initial R6G and MB concentration. After investigating the effect of salt on adsorption efficiency, the applicability of the proposed adsorbent was assessed using real water samples. According to the experimental results, the optimum pH and equilibrium period for the uptake of both dyes were determined to be 8.0 and 60 min, respectively. Kinetic analyses showed that the pseudo-second order kinetic model exhibited a superior fit in representing the adsorption rates of both dyes, while isotherm studies indicated that both Langmuir and Freundlich isotherm models fit the experimental data well. While the adsorption capacities of pure MnFe2O4 for MB and R6G were 19.5 mg g− 1 and 15.3 mg g− 1, respectively, these values reached 67.6 mg g− 1 and 59.5 mg g− 1 for the bacteria-loaded MnFe2O4. The obtained data revealed that bacterial modification significantly increased the adsorption capacity of MnFe2O4, suggesting that the developed bio-adsorbent stands out as an effective and promising candidate for the remediation of dye-contaminated effluents.

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• MakaleYayıncıda açık erişim2026/r/gumushane/13551
  Boric acid-activated carbon derived from Scots pine sawdust for phenol removal: adsorption mechanism, linear and nonlinear kinetic and isotherm modeling, and artificial neural network prediction

  Ozdes, Duygu; Turfan, Fatma Asya; Seker, Serdal; Kavgaci, Gonca; Onal, Yunus

  In this study, a sustainable activated carbon was successfully prepared from Scots pine sawdust via boric acid activation (H3BO3-AC-SPS) and evaluated for phenol adsorption from aqueous solutions. The physicochemical characteristics of the adsorbent were investigated using FTIR, SEM-EDX, XRD, and BET analyses, while the effects of solution pH, contact time, adsorbent dosage, initial phenol concentration, temperature, ionic strength, and reusability without regeneration on the adsorption performance were systematically examined. H3BO3-AC-SPS exhibited excellent adsorption performance over a wide pH range (5–8), showed good tolerance to coexisting inorganic ions and organic contaminants, and retained appreciable adsorption efficiency over five consecutive adsorption cycles without regeneration. Phenol uptake increased with temperature, and NaOH enabled partial desorption of phenol. The adsorption kinetics and equilibrium data were analyzed using both linear and nonlinear regression approaches and comparatively evaluated based on the coefficient of determination (R2), sum of squared errors (SSE), and root mean square error (RMSE). The pseudo-second order kinetic model and the Langmuir isotherm exhibited the best predictive performance, with the Langmuir model estimating a maximum adsorption capacity of 65.4 mg g−1. The adsorption mechanism may involve π–π interactions, hydrogen bonding, pore filling, and hydrophobic interactions. In addition, an artificial neural network (ANN) model accurately predicted the adsorption behavior, yielding a high correlation coefficient (R = 0.9789). The applicability of H3BO3-AC-SPS was further demonstrated in stream water and mining wastewater. These findings demonstrate that boric acid activation is an effective strategy for converting Scots pine sawdust into a high-performance adsorbent and that integrating linear and nonlinear adsorption modeling with statistical error analysis provides a reliable framework for interpreting adsorption behavior. This journal is

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• MakaleAçık Erişim2026/r/gumushane/12320
  Waste to resource approach: CoFe2O4-modified spent tea waste for magnetic solid-phase extraction of toxic metal ions from water samples

  Seker, Serdal; Ozdes, Duygu; Duran, Celal

  In this research, within the framework of a waste-to-resource conversion approach, biochar obtained from spent tea waste (STWB), a widely available and cost-free biomass source, was modified with magnetic CoFe2O4 nanoparticles to develop an environmentally friendly adsorbent (CoFe2O4/STWB). The applicability of this material for efficient separation and preconcentration of Cd(ii), Pb(ii), and Ni(ii) ions from mining wastewater, stream water, and wastewater samples collected from an organized industrial zone was systematically investigated using the solid phase extraction (SPE) method. Optimization of the experimental variables was conducted to enhance the extraction performance of the target analyte ions. The fact that the adsorption and desorption equilibrium times occur in less than 1 min demonstrates the rapid and highly efficient extraction performance of the developed adsorbent. Langmuir isotherm model analysis revealed that CoFe2O4/STWB exhibits adsorption capacities of 69.4 mg g−1 for Cd(ii), 185.2 mg g−1 for Pb(ii), and 45.2 mg g−1 for Ni(ii). In contrast, the corresponding adsorption capacities obtained for unmodified STWB were considerably lower, with values of 42.9, 75.8, and 16.8 mg g−1 for Cd(ii), Pb(ii), and Ni(ii), respectively. These results clearly demonstrate that modification with CoFe2O4 significantly enhances the adsorption performance of STWB. Consequently, CoFe2O4-modified spent tea waste can be regarded as an effective, economical, and sustainable adsorbent for trace heavy metal analysis in environmental water samples, owing to its rapid extraction kinetics, high adsorption capacity, and low detection limits. This journal is

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• MakaleAçık Erişim2025/r/gumushane/11575
  Sol–Gel Synthesized CuFe2O4-Modified Biochar Derived from Tea Waste for Efficient Ni(II) Removal: Adsorption, Regeneration, and ANN Modeling

  Duran, Celal; Ozeken, Sengul Tugba; Seker, Serdal; Ozdes, Duygu

  In the present research, a novel magnetic adsorbent was developed via the sol–gel method by coating CuFe2O4 nanoparticles on biochar sourced from brewed tea waste. The synthesized adsorbent was utilized for the removal of Ni(II) ions from aqueous media. The adsorption efficiency of Ni(II) ions was assessed under crucial experimental conditions such as initial solution pH, contact time, adsorbent dosage, and initial Ni(II) concentration. The adsorbent exhibited rapid adsorption kinetics, achieving equilibrium in approximately 15 min, and maintained high efficiency across a wide pH range. Adsorption experiments were conducted for Ni(II) solutions at their natural pH (5.6) to minimize chemical usage and enhance process simplicity. An impressive maximum adsorption capacity of 232.6 mg g−1 was recorded, outperforming many previously reported adsorbents. Furthermore, desorption studies demonstrated nearly 100% recovery of Ni(II) ions using 1.0 M HCl solution, indicating excellent regeneration potential of the adsorbent. Additionally, the prediction performance of an artificial neural network (ANN) model was evaluated to predict Ni(II) removal efficiency based on experimental variables, showing strong agreement with experimental data. Isotherm and kinetic models were also applied to the data to estimate the adsorption mechanisms. These findings demonstrate the promise of CuFe2O4-modified tea waste biochar for sustainable water treatment applications.

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• MakaleAçık Erişim2022/r/gumushane/11936
  Insights into brewed tea waste as a green and low-priced adsorbent for solid-phase extraction of Cd(II) ions: isotherm, kinetic, and artificial neural network approach

  Ozdes, Duygu; Tilki, Nida; Seker, Serdal; Duran, Celal

  In the present research, brewed tea waste (BTW) was utilized as a green, low-priced, and abundant adsorbent for separation/preconcentration of Cd(II) ions through solid-phase extraction method from water and foods for the first time. BTW was applied as a natural adsorbent, without using any chelating agent to bind Cd(II) ions or any chemical reagent for its modification. A three-layer artificial neural network model using backpropagation algorithm was utilized to explicate a prediction model for the extraction performance of Cd(II) ions by selecting the input parameters as solution pH, quantity of BTW, sample volume, eluent concentration and volume, and equilibrium time for desorption. The preconcentration factor, relative standard deviation, and detection limit were attained as 100, 3.03%, and 0.56 µg L−1, respectively. It was decided that the Langmuir isotherm model is acceptable to characterize the retention of Cd(II) ions on BTW. This result pointed out that the active binding sites on the BTW surface are homogeneously distributed. Adsorption capacity of BTW was achieved as 41.5 mg g−1 which is higher than several expensive and difficult-to-prepare adsorbents. Adsorption kinetics was elucidated by pseudo-second order kinetic model. After confirmed the accuracy of the method with spike/recovery studies, it was employed for Cd(II) determination in water (stream and sea water) and food (eggplant, lettuce, parsley, apple, and apricot) samples with high accuracy. The inferences of the study proved that the BTW offers a magnificent application prospect in the extraction of Cd(II) ions.

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