Nagihan Soyer

This study presents a combined model-based and molecular-level assessment of methyl orange uptake by a hazelnut shell-based carbonaceous adsorbent. Batch experiments were conducted under previously optimized conditions, namely a dye concentration of 42.65 mg/L, adsorbent loading of 1.29 g/L, temperature of 30.4 °C, and pH 3.0. Kinetic, diffusion, equilibrium, apparent thermodynamic, surface charge, Fourier-transform infrared spectroscopy, and density functional theory analyses were used to evaluate the macroscopic adsorption behavior and to support possible molecular interaction pathways. The nonlinear pseudo-first-order model provided the most suitable empirical description of the kinetic profile, yielding qe = 32.62 ± 0.51 mg/g, k1 = 1.28 × 10−2 ± 5.63 × 10−4 min−1, and R2 = 0.9963. Weber–Morris and Boyd analyses suggested that the uptake behavior was consistent with coupled surface attachment, film diffusion, and intraparticle diffusion rather than a single rate-controlling step. Freundlich modeling suggested a heterogeneous adsorption description, with the Freundlich constant increasing from 15.05 to 46.09 (mg/g)(L/mg)1/n and n rising from 2.24 to 3.37 with increasing temperature. Negative apparent Gibbs free energy changes and positive apparent enthalpy and entropy changes suggested a favorable, endothermic, and entropy-favored tendency under the investigated conditions. Surface charge measurements, infrared spectral changes, and quantum chemical results collectively supported the possibility that acidic conditions favored electrostatic attraction, while π–π stacking, dispersion forces, and localized hydrogen bonding may have contributed to stabilization of the adsorbed state. Overall, the hazelnut shell-based carbonaceous adsorbent exhibited effective dye-removal performance, as supported by combined experimental and computational evidence.

The thermodynamic and structural properties of biomimetic monolayers composed of cholesterol, dipalmitoylphosphatidylcholine, and hydrophobic magnetite (Fe₃O₄) nanoparticles were investigated under varying cholesterol molar fractions and pH conditions (4.8 and 7.4). Langmuir monolayer experiments were performed to analyze surface pressure-area isotherms, excess molecular area, excess Gibbs free energy of mixing, and compressibility modulus to assess lipid monolayer phase behavior, molecular organization, and mechanical stability. The results confirm that cholesterol enhances monolayer condensation up to a cholesterol molar fraction of 0.50, particularly at pH 7.4, where stronger lipid-lipid interactions promote molecular ordering and increase monolayer rigidity. At cholesterol molar fractions of 0.75 and higher, steric hindrance and phase separation effects emerge, disrupting monolayer homogeneity. pH significantly influences monolayer stability, with pH 7.4 favoring lipid condensation, whereas pH 4.8 induces monolayer expansion and molecular disorder. Excess molecular area and Gibbs free energy of mixing analyses indicate the strongest cholesterol-lipid interactions at a cholesterol molar fraction of 0.25 for pH 4.8 and 0.50 for pH 7.4, confirming these compositions as the most thermodynamically stable. Compressibility modulus analysis demonstrates that cholesterol enhances monolayer rigidity, with pH 7.4 producing higher values. However, at high cholesterol molar fractions, compressibility modules slightly decrease, suggesting steric constraints and lateral phase separation. The incorporation of magnetite nanoparticles increases molecular area and slightly reduces monolayer rigidity at low cholesterol molar fractions due to steric disruptions, but at cholesterol molar fractions of 0.50 and higher, cholesterol stabilizes the monolayer, counteracting nanoparticle-induced perturbations. These findings provide insight into the thermodynamic and structural regulation of biomimetic lipid monolayers by cholesterol and magnetite nanoparticles, with implications for nanomedicine, membrane biophysics, and lipid-based nanostructures.

Bisphenol A is a widely recognized endocrine disruptor that persists in ecosystems, harms aquatic organisms, and contributes to ecological degradation, raising global environmental concerns. Numerous studies have explored β-cyclodextrin–based adsorbents for Bisphenol A removal; however, their regeneration remains a major challenge, often relying on energy-intensive processes and excessive use of organic solvents. In this study, Bisphenol A was selected as a model pollutant, and its adsorption onto β-cyclodextrin nanosponges was investigated. After adsorption, Bisphenol A was efficiently recovered from the saturated β-cyclodextrin nanosponges using an innovative and sustainable supercritical CO₂-based green process, which simultaneously regenerated the adsorbent. The adsorption process achieved an efficiency of 95.51 ± 0.82% under optimized conditions (C₀ = 150 mg/L, m_β-CDNS = 0.15 g, T = 25 °C, and N = 200 rpm), with a maximum adsorption capacity of 47.75 ± 0.28 mg/g. The regeneration process achieved over 99% efficiency at 60 °C and 300 bar, with 10% (v/v) ethanol as a co-solvent, nearly fully restoring the adsorbent’s performance. Unlike conventional regeneration techniques, this green approach eliminates the need for environmentally harmful organic solvents while preserving the adsorbent’s structural integrity, making it a highly efficient and sustainable alternative. This study is the first to demonstrate the effective application of supercritical CO₂-based regeneration for β-cyclodextrin nanosponges in Bisphenol A removal, providing a scalable and environmentally sustainable solution for wastewater treatment. Furthermore, characterization analyses confirmed that the adsorbent retained its chemical and morphological stability after adsorption and regeneration.

In this study, cyclodextrin-based nanostructures (CDNSs) were synthesized through the cross-linking of cyclodextrin (CD) with epichlorohydrin (ECH) as a cross-linker. Two types of CDNSs, α-CDNS and β-CDNS, were prepared to systematically investigate the influence of reaction parameters—such as the solubilization time of α-CD and β-CD, the molar ratio of ECH to CD, and NaOH concentration—on the physicochemical properties of the final product. Naproxen (NAP), a poorly water-soluble drug, was selected as a model compound to assess the drug-loading capacity of the synthesized CDNSs. The effect of each reaction parameter on NAP integration into the CDNSs was examined at varying weight ratios. The optimal reaction conditions were determined to be a solubilization time of 6 h, an ECH/CD molar ratio of 8/1, and an NaOH concentration of 33%. Under these conditions, the NAP loading efficiency of α-CDNSs was calculated as 67.12%. Comparative analysis revealed that α-CDNSs outperformed β-CDNSs in terms of drug-loading capacity. Additionally, the synthesized CDNSs and NAP-loaded CDNSs were characterized using FTIR, DSC, XRD, SEM, and Zetasizer analyses, while the NAP concentration was determined by HPLC.