Investi̇gation of the adsorption of some dye substances on the clay of Beşi̇kdüzü in Trabzon

In today's world, where industrialization is rapidly accelerating, the environmental pollution caused by synthetic dyes used in textile, paint, and chemical industries has become a major concern. In this context, adsorption emerges as a cost-effective, environmentally friendly, and efficient method for dye removal. This thesis focuses on investigating the potential use of natural clay from the Beşikdüzü district of Trabzon as an adsorbent for the removal of common dyes such as methylene blue (MB) and crystal violet (CV) from aqueous solutions. At the beginning of the study, clay samples were collected from the Beşikdüzü region, washed with distilled water, dried, and ground into a fine powder. These pretreatment steps were carried out to eliminate impurities and enhance the adsorption capacity. The prepared samples were then subjected to detailed characterization analyses using techniques such as (BET) Surface Area Analysis, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Fluorescence (XRF), and Thermogravimetric-Differential Thermal Analysis (TGA-DTA). The results showed that the clay possessed a high specific surface area, suitable porosity, and stable chemical structure—features ideal for adsorption processes. Adsorption experiments were conducted under varying conditions of temperature, pH, contact time, initial dye concentration, and adsorbent dosage to identify the optimum operating parameters. The adsorption behavior of the system was evaluated using isotherm models such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R). Among these, the Langmuir model exhibited the best fit to the experimental data, suggesting that the adsorption occurred as a monolayer on a homogeneous surface with a finite number of identical sites. Thermodynamic parameters such as Gibbs free energy change (∆G°), enthalpy change (∆H°), and entropy change (∆S°) were calculated to understand the nature and spontaneity of the adsorption process. Negative ∆G° values indicated that the adsorption was spontaneous, while positive ∆H° values revealed that the process was endothermic. Additionally, positive ∆S° values suggested increased randomness at the solid-liquid interface during adsorption. In conclusion, the findings of this thesis demonstrate that the natural clay from Beşikdüzü, Trabzon, can serve as an effective and sustainable adsorbent for removing synthetic dyes such as methylene blue and crystal violet from wastewater. This study provides a valuable contribution to the field of environmental remediation by promoting the use of natural and locally available materials in water treatment technologies.