Photocatalytic studies of methylene blue dye degradation on synthesized Ni-doped strontium zirconate perovskite nanoparticles

Abstract

Perovskite oxides have been recognized as highly potent catalysts for photocatalytic water decontamination due to their potential to capture solar energy and drive catalytic reactions. In this report, Ni doped strontium zirconate perovskite photocatalyst nanoparticles was synthesized using simple method with low production cost was applied in visible light irradiation for the photocatalytic degradation of a model organic pollutant in aqueous medium. The photocatalyst was synthesized successfully using sol-gel Pechini method and annealed at 800 ℃ for 2 h. The sample was characterized using XRD, FESEM, EDX FTIR and UV-visible spectrophotometric techniques. The crystallite size ranged between 23.74 and 33.18 nm according to Scherrer equation and Williamson-Hall methods with a dislocation density, lattice strain, and microstrain of 1.77, 1.4 and 3.4 (x 10^-3) respectively. The sample exhibited smooth surface with no agglomeration. The composition of the perovskite indicated the presence of Sr, Zr, Ni and oxygen in their atomic weight. Metal-oxygen vibration was located at 648.55 cm-1 with traces of adsorbed atmospheric CO₂ and H₂O on the catalyst surface. The catalyst exhibited optical band gap energy of 5.15 eV. The photocatalytic activity was evaluated by the degradation of Methylene blue (MB) under simulated light at 420 nm. Photodegradation was highest in light irradiated reaction compared to dark conditions. The effects of the amount of catalyst, initial concentration of MB dye irradiation time and solution pH on the degradation and removal efficiency of the pollutant was investigated. Adsorption capacity was found to increase with increase in initial adsorbate concentration and irradiation time in acidic pH. In order to investigate the efficiency of MB dye adsorption on strontium nickel zirconate (SNZ) photocatalyst, pseudofirst order (PFO), pseudo-second order (PSO), Elovich and Intra-particle diffusion (IPD) kinetic models were evaluated. The adsorption kinetic was found to follow pseudo-second order model. The graphical correlation of equilibrium data were analyzed by Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Flory- Huggins and Redlich-Peterson models by using linear regression technique. The data were best represented by the Langmuir isotherm yielding maximum monolayer adsorption at 30 ℃ with a favorable condition (RL < 1). The adsorption process was found to be exothermic and spontaneous. Therefore, Sr(Ni₀.₁₀Zr₀.₉₀)O₃ nanoparticles can be used as photocatalyst for remediation of wastewater containing organic pollutants.