Phyllosilicate Clay Blended with Semiconductor Nanocomposite for Enhanced Dye Removal and CO₂ Adsorption

Release of untreated synthetic dyes into aquatic systems, along with excessive atmospheric CO2, contributes to health hazards and global warming. Synchronize optimization of CO2 adsorption and a synergistic approach toward dye removal combining adsorption and degradation remains to be a critical gap in scientific research. Inspired by this notion, our work adopts a holistic approach to synthesize a clay-based nanocomposite, ZnO-TiO2–Sepiolite (ZTS), having its facets of application in dye adsorption, synergistic dye removal, and CO2 capture. The synthesized material was investigated comparably to pristine ZnO-TiO2 (ZT) with a particular focus on evaluating the influence of the clay support in the nanocomposite material. The synthesis involved ethanol as a solvent and NaOH as a reducing agent without the use of any external capping agent at 65 °C. The maximum adsorption capacities for ZTS nanocomposite were found to be 173.76 mg/g for Congo red (CR) and 45.68 mg/g for Methylene blue (MB). The ZTS nanocomposite showed synergistic removal of dyes with 99.5% efficiency for MB and 98.3% efficiency for CR, while maintaining its significance at variable pH and mixed dye conditions. The ZTS nanocomposite has shown considerable CO2 adsorption (19.23 cm3/g) at 288 K, exhibiting potential in CO2 removal as well. The plausible mechanism was elucidated using UV–vis, PL, TRPL, and XPS spectroscopy, along with active radical examination (ROS test) and oxygen vacant site investigation by EPR spectroscopy. Plausible mechanistic pathways for the degradation of MB and CR were drawn using the LC-MS chromatography technique by analyzing the degraded effluents. The study has developed an efficient nanocomposite system to tackle multiple pollutants synergistically, leading toward cost-effectiveness and sustainability.