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⁻¹which 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.

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.

Brevibacillus agri was immobilized onto an abundant natural clay through a simple synthesis route to develop a novel and efficient adsorbent for the removal of Pb(II) ions from aqueous media. The adsorption behavior of Brevibacillus agri-loaded clay (BLC) was evaluated using batch experiments by investigating the effects of initial solution pH, BLC dosage, contact time, initial Pb(II) concentration, temperature, 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 65.4 mg g-1. 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.

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.