Characterization and evaluation catalytic efficiency of La05Ca0.5NiO3 nanopowders in removal of reactive blue 5 from aqueous solution

In the present study, nanoparticles of perovskite-type La0.5Ca05NiO3-delta (LCNO) were fabricated by sol-gel method in the presence of nitrate-metal-ethylene glycol (EG) polymerized complex. A series of analytical techniques were used to characterize the crystallinity, morphology, specific surface area and grain size of La0.5Ca0.5NiO3 powders. Thermal decomposition process of the complex precursor was examined by means of differential thermal analysis-thermal gravimetric analysis (DTA/fGA). X-ray diffraction (XRD) results showed that single perovskite phase has been completely formed after calcination at 750 C. In addition, transmission electron microscopy (TEM) images revealed that the average size of the particles is approximately 10-32 nm in diameter. The surface morphology and composition of these nanopowders were also investigated using scanning tunneling microscopy (STM). scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDX). LCNO nanoparticles showed the excellent adsorption efficiency towards reactive blue 5 (RB5) as a reactive dye in aqueous solution. The adsorption studies were carried out at different pH values, dye concentrations, various adsorbent dosages and contact time in a batch experiments. The dye removal efficiency was found to be decreased with increasing in initial pH of dye solution, and LCNO exhibited good dye removal efficiency at acidic pH specially pH 2. Experimental results indicated that the adsorption kinetic data follow a pseudo-second-order rate for tested dye. The isotherm evaluations revealed that the Langmuir model attained better fits to the experimental equilibrium data than the Freundlich model. Finally, the photocatalytic degradation of RB5 using LCNO under solar light and UV irradiation at pH 2 was also investigated. The results showed that the nanoparticles cannot act as pure photocatalyst and the degradation of RB5 dye follows only an adsorption process. (C) 2011 Elsevier B.V. All rights reserved.