Strategic innovation in CuBTC/PANI nanocomposites for dye remediation: a holistic approach for enhancing adsorption, isotherms, and kinetic studies †

Abstract

The environmental persistence of reactive blue 19 dye poses a significant challenge, driving the urgent need for efficient removal technologies to protect water quality. This study introduces a highly effective solution in the form of a copper benzene-1,3,5-tricarboxylate (CuBTC) composite integrated with polyaniline (PANI), designed for the adsorption of Reactive Blue-19 (RB19) dye. The CuBTC/PANI composite was synthesized at varying weight ratios (5%, 10%, and 15%) and meticulously analyzed using a suite of advanced techniques, including FESEM, EDS, FTIR, XPS, XRD, and BET surface area analysis. These characterization studies confirmed the composite's exceptional structural integrity, thermal stability, and high porosity. The adsorption efficiency of the composite was evaluated under various conditions, such as adsorbent dosage, dye concentration, pH, temperature, and contact time. Impressively, the composite achieved a 99% removal efficiency for 60 ppm RB19 at pH 2 within just 50 minutes. Reusability tests highlighted the material's remarkable durability, exhibiting consistent performance over six cycles. Five equilibrium isotherm models were employed to unravel the adsorption process. The Langmuir model (R² = 0.998) provided the best fit, suggesting that the adsorption process follows a monolayer pattern driven primarily by chemisorption. Post-adsorption FTIR analysis unveiled additional interactions, such as hydrogen bonding, π–π stacking, electrostatic forces, and pore filling, further elucidating the complex adsorption mechanism. Kinetic studies, based on four models revealed that the pseudo-second-order model (R² = 0.990) best describes the process, with a rate constant of 0.172 mg g⁻¹ min⁻¹, indicating that adsorption is governed by a chemical reaction. Thermodynamic analysis indicated that the process is endothermic (ΔH = 795.15 J mol⁻¹) and spontaneous (ΔG = −1.790 kJ mol⁻¹), and results in a decrease in randomness at the solid–liquid interface (ΔS = 3.082 J mol⁻¹ K⁻¹). This study provides a comprehensive chemical engineering analysis of the adsorption process, encompassing isotherm, kinetic, and thermodynamic models. The CuBTC/PANI composite emerges as a highly efficient and sustainable material for the removal of RB19, offering not only exceptional adsorption capacity and rapid kinetics but also impressive reusability. This work paves the way for a promising solution in the fight against dye-contaminated wastewater, outshining traditional methods and heralding a new era of water treatment technology.