Synthesis, characterization and application of Zeolite/Bi2O3 nanocomposite in removal of Rhodamine B dye from wastewater

Abstract

Many factories use a variety of colours to enhance product aesthetics, leading to untreated wastewater being discharged into natural water bodies. This wastewater not only poses a threat to aquatic life but also endangers human health, causing issues like skin diseases, as some dyes are carcinogenic. Rhodamine B dye (RhB) is commonly used in industries such as textiles, paper, etc. This study focuses on synthesizing, characterizing, and applying Zeolite/Bi₂O₃ nanocomposites to efficiently remove RhB dye. Nanocomposites were synthesized using the sol-gel method and characterized using techniques including FTIR, SEM-EDS, XRD, DLS, point of zero charge determination, and surface resonance analysis. The removal process in an aqueous solution achieved its maximum efficiency of 100% under the following optimal conditions: initial concentration of RhB dye (0.5 mg/L), time (10 min), adsorbent dose (0.55 g), pH (4), and temperature (298 K). Real wastewater testing confirmed the nanocomposite's efficiency, removing a significant 98.12% of RhB dye. Reusability tests showed stability, with removal efficiencies of 100%, 97.08%, and 88.9% over three cycles. Isotherm analysis adhered to the Freundlich Isotherm Model (R² = 0.9953), signifying favourable adsorption behaviour. Kinetic analysis supported the pseudo-second-order model, indicating a chemisorption mechanism. Thermodynamic analysis suggested spontaneous (negative ΔG°) and endothermic (positive ΔH°) adsorption, with reduced randomness (negative ΔS°) at the solid-liquid interface. In conclusion, wastewater dye removal, especially Rhodamine B, is vital for environmental and public health protection. The Zeolite/Bi₂O₃ nanocomposite emerges as an efficient, sustainable, and eco-friendly adsorbent for Rhodamine B dye removal in both synthetic solutions and real wastewater.