Efficient photodegradation of E124 dye using two-dimensional Zn-Co LDH: Kinetic and thermodynamic studies

Abstract

Under mild conditions with a cation ratio of 1:1, Zn-Co layered double hydroxide (LDH) nanosheets were synthesized by co-precipitation. The effect of temperature on the physicochemical properties of LDH at 80, 300, and 500 ∘C was studied using x-ray diffraction (XRD), BET surface area, High resolution-Transmission electron microscopy (HR-TEM), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDX), x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), optical properties, and electron spin resonance (ESR) techniques. The FE-SEM confirmed that the formed Zn-Co LDH was cubically stacked up to thickness of 55 nm. HR-TEM shows that the interspacing between the layers was in the range of 1.95-2.70 nm and that the size slightly increased with temperature. Ponceau 4R (E124) was removed more efficiently than the Tartrazine (E102) dye from water using LDH-300. Different parameters that affect the photo-degradation process were performed, as: different calcination temperatures, initial dye concentration, LDH dosage, pH, and reaction temperature. The Photocatalytic degradation and adsorption processes showed dye removal of 90 and 80%, respectively. The highest degradation rate of E124 dye removal has been achieved using LDH-300. The kinetic parameters of the degradation process indicate that the kinetic data fits with the first-order kinetic reaction. The activation energy was found to be 18.189 KJ/mol. Thermodynamic parameters showed that the photodegradation process was non-spontaneous and endothermic. The adsorption coefficient was found to be 0.002961. Surface properties, FTIR, XPS, and FESEM were studied after the photodegradation process. The total free radicals were calculated by ESR analysis.