Optimization of Photocatalytic Degradation of Rhodamine B and Indigo Carmine Dyes Using Eco‐Friendly Kaolinite‐Silver Oxide Quantum Dots Nanocomposite Under Sunlight Irradiation

ABSTRACT In this work, we present a simple method for the pyrofabrication of a new kaolinite‐ silver oxide quantum dots nanocomposite (Kao‐Ag 2 O/QDs) that is used for the degradation of rhodamine B (RhB) and indigo carmine (IC) dyes. A homogenous combination of kaolinite and silver nitrate was sintered up to 350 °C to create the extremely effective photocatalyst (Kao‐Ag 2 O/QDs). Various analytical techniques were employed to characterize the Kao‐Ag 2 O/QDs photocatalyst such as XRD, FTIR, XPS, SEM–EDX, TEM, DTA/TGA, ZP, BET, and UV–Vis DRS. The degradation of RhB and IC dyes through the photocatalyst was carried out in aqueous solutions utilizing several pH dye solutions and sustainable solar energy in atmosphere conditions. The nanocomposite that was prepared had shown an enhanced specific surface area of 53.3005 m 2 /g, a pore size of 8.1197 nm, and a total pore volume of 0.216 cm 3 /g. It also displayed an optical band gap energy of 2.9 eV. The study creates that employing the ideal dose of 2000 and 1500 mg/L of the Kao‐Ag 2 O/QDs photocatalyst at neutral conditions (pH = 7) resulted a maximum degradation effectiveness of RhB and IC of 91.06 and 93.46% after 90 min, respectively. RhB and IC dyes degradation followed Langmuir first‐order kinetics with a rate constant of 0.0217 and 0.0216 min −1 at pH = 7, respectively. The photocatalytic degradation activity for RhB dye is based on hydroxyl radicals (˙OH) and superoxide radicals (˙O 2 − ), while the mechanism of IC removal is based on superoxide radicals (˙O 2 − ), as revealed by scavenger‐based radical trapping studies. A triple reusability study found that the Kao‐Ag 2 O photocatalyst is highly stable with degradation efficiencies of RhB and IC dyes from the initial 91.09 to 90.04, 88.54, and 86.27% and from the initial 93.46 to 92.8, 91.4 and 89.32%, respectively. The optimal situations for the parameters were identified by the Box–Behnken design (BBD), which was well matched with photocatalytic degradation tests.