Ceria associated manganese oxide nanoparticles: Synthesis, characterization and arsenic(V) sorption behavior

Abstract

Four samples of ceria incorporated manganese oxide (NCMO) were prepared by co-precipitation-calcinations and sol–gel methods, and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, BET surface area etc. The synthetic samples were nanoparticle agglomerates with irregular surface morphology (Ce:Mn = 1:1). The NCMO-1b sample, prepared by the calcination of metal hydroxide at 573 K for 3.0 h, was a nano-crystalline (70–90 nm) and hydrated material having high BET surface area (116.96 m 2 g −1). The arsenic(V)-sorption by the samples at pH 7.0 (±0.2) and 30 °C showed that the NCMO-1b is a most efficient material. Optimum pH range for the arsenic(V) sorption is 3.0–7.0 at 303 (±1.0) K. Kinetics and equilibrium data obtained (pH = 7.0 ± 0.2, T = 303 ± 1.0 K and I = 0.01 M) had described the pseudo-second order kinetics and the Freundlich isotherm models well, respectively. Thermodynamics of the sorption reaction showed that the changes of enthalpy (Δ H°), entropy (Δ S°) and Gibbs free energy (Δ G°), respectively, were +23.901 kJ mol −1, +0.175 kJ mol −1 K −1 and −25.737 to −32.753 kJ mol −1 at T = 283–323 K. Estimation of the sorption energy ( E = 17.15 kJ mol −1) indicated that the arsenic(V) was chemisorbed on NCMO-1b. The phosphate only reduced the arsenic(V) removal efficiency of NCMO-1b.