Batch-Scale Study to Assess the Adsorption Potential of Locally Available Clay for Cationic Azo Dye from Water

Abstract

Basic blue 41 (BB41) dye discharge to water bodies is a potential concern to public health. In this study, an eco-friendly and cost-effective approach for removing BB41 dye from water using locally available raw clay (RC) was proposed. RC was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared (FTIR) spectroscopy, laser granulometry, and X-ray fluorescence (XRF). The average particle size was 26.42 µm, with a high silica (SiO₂: 32.08%) and alumina (Al₂O₃: 10.82%) contents. The effect of various experimental parameters such as pH, solid/liquid ratio, initial dye concentration, and temperature on adsorption performance were investigated. Isotherm studies followed the Langmuir isotherm model, with a maximum monolayer adsorption capacity (q_m) of 85.54 mg/g. Kinetic modelling confirmed the applicability of pseudo-second-order model, with intraparticle diffusion as the rate-limiting step. Thermodynamic modelling parameters such as standard free energy (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) indicated a spontaneous and exothermic adsorption process, with an activation energy (E_a) of 26.24 kJ/mol, confirming BB41 was through physical adsorption. These findings demonstrate the potential of RC as an efficient and sustainable adsorbent for BB41 removal, providing a cost-effective alternative for wastewater treatment applications.