Photocatalytic degradation of Ponceau 4R by ZnAl‐layered double hydroxide nanostructures obtained with and without polyvinyl alcohol

Abstract

AbstractIn this work, zinc‐aluminum layered double hydroxides were synthesized with and without the presence of polyvinyl alcohol by co‐formation and co‐precipitation methods, respectively. The photocatalytic activity of the obtained nanocomposites was studied and a comparative analysis was performed. The mechanism of photocatalytic decomposition of Ponceau 4R (P4R) on the nanocomposites has been explained in detail by relating it to the compositional and structural properties of the nanocomposite. The structural and optical properties of nanocomposites are characterized by XRD, UV–vis, PL, and SEM in a pure state, dye loaded and after photodegradation. The bandgap of nanocomposites (Eg = 3,23 eV) was reduced after sorption (Eg = 3,1 eV) and photocatalytic degradation (Eg = 2,87 eV) of P4R. This result is in good agreement with basal spacing determined by XRD. To study the sunlight degradation of P4R at different initial concentrations (8, 12, 16, 20, 30, 40, 50 mg L−1), firstly sorption was developed with Langmuir and other isothermal models. The Langmuir constant value (KL = 0,102) of ZnAl‐LDH/PVA is close to the Langmuir–Hinshelwood constant (KL‐H = 0,094) obtained from the kinetics of the photodegradation in sunlight. The photocatalytic degradation of P4R onto the obtained nanocomposites follows the Langmuir‐Hinshelwood kinetic model.