Sustainable Remediation of Synthetic Azo Dyes: Enhanced Adsorption Performance of Titanium Dioxide-Modified Kaolin Clay in Wastewater Treatment

This study aims to assess the effectiveness of both activated and inactivated clay in removing synthetic azo dyes from industrial wastewater. Due to their toxicity and persistence, dyes such as Congo Red, Sudan Black, Methyl Orange, and Methylene Blue pose serious environmental threats. Conventional treatment methods are often costly and unsustainable, making it necessary to explore more affordable and eco-friendly alternatives. This research investigates the adsorption potential of kaolin clay under different conditions, including variations in adsorbent dosage, contact time, pH, temperature, and initial dye concentration. Furthermore, the study examines adsorption kinetics and thermodynamic behavior to gain a deeper understanding of the mechanisms involved in dye removal. To achieve this, the clay adsorbent was characterized using analytical techniques such as Xray Diffraction (XRD), X-ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDX) to determine its structural, chemical, and physical properties. Batch adsorption experiments were conducted to evaluate dye removal efficiency. The adsorption process was analyzed using kinetic models, including pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. Additionally, thermodynamic parameters such as enthalpy, entropy, and Gibbs free energy were assessed to determine the feasibility and spontaneity of adsorption. The effects of key factors such as adsorbent dosage (0.5g–2.5g), pH (2–11), contact time (30–75 minutes), temperature (30°C–70°C), and dye concentration (50–150 mg/L) were examined to optimize adsorption conditions. The results demonstrate that both kaolin with titanium dioxide and plain kaolin effectively remove dyes, with activated clay exhibiting superior adsorption performance due to its increased surface area and porosity. The adsorption process follows pseudo-second-order kinetics, indicating that chemisorption is the primary mechanism. Isotherm studies suggest monolayer adsorption, with the Langmuir and Freundlich models providing insights into adsorption capacity and surface heterogeneity. Thermodynamic analysis confirms that adsorption is spontaneous and exothermic, with higher efficiency at lower temperatures. These findings highlight the potential of clay as an inexpensive and sustainable solution for treating dye-contaminated wastewater, offering a practical alternative to conventional treatment methods.