Facile hydrothermal fabrication and performance tuning of rGO/LDH nanocomposites for efficient photocatalytic degradation of Congo Red

• The rGO/LDH nanocomposites with different wt% of rGO loading were synthesized by ecofriendly hydrothermal route. • The 3 wt% rGO/LDH nanocomposite exhibited excellent photocatalytic performance, achieving 98.4% removal of Congo Red dye within 90 minutes. • Photocatalytic kinetics and process optimization were systematically investigated using BBD-RSM. • The catalyst demonstrated outstanding reusability over five consecutive cycles. Water pollution is a critical global issue intensified by industrialization. The release of toxic organic pollutants severely impacts aquatic ecosystems and public health. This study reports the green hydrothermal synthesis of rGO/Cu/Fe/Al LDH nanocomposites with varying rGO contents and their evaluation for photocatalytic efficiency. To explore the morphology, composition, and optical behavior of the synthesized nanocomposites, a range of analytical tools such as FE-SEM, HR-TEM, XRD, FT-IR, Raman, UV–Vis DRS, TGA, BET, XPS, and zeta potential analyses were employed. Furthermore, Photocatalytic degradation investigations demonstrated that the 3 wt% rGO/LDH nanocomposite exhibited superior degradation efficiency of 98.4% for Congo Red (CR) within 90 minutes under solar light irradiation. Key experimental factors, including pH, dose of catalyst, contact time, and concentration of dye, were methodically optimized employing the response surface methodology (RSM) coupled with Box-Behnken Design (BBD) approach. The observed pseudo-first-order kinetic rate constant was calculated as 0.0181 min⁻¹. Structural analysis confirmed the nanocomposite’s hydrotalcite-like morphology, accompanied by a high specific surface area (SBET = 213.13 m²/g), pronounced solar light absorption, and a narrow band gap energy (Eg =1.9 eV). Under optimized reaction conditions—0.5 mg/mL catalyst loading, 70 ppm initial dye concentration, and natural solution pH of 5.8, 98.4% degradation of CR was achieved within 90 minutes. Stability tests revealed that the 3 wt% rGO/LDH nanocomposite maintained 84.9% of its photocatalytic activity after five successive cycles, demonstrating remarkable reusability. The addition of rGO significantly improved the photocatalytic activity of LDH, suggesting its potential for efficient and reusable environmental remediation.