As(III) adsorption on co-precipitated cobalt substituted ferrite nanoparticles

Abstract

We synthesized CoxFe3-xO4 (x = 0, 0.5 and 1.0) nanoparticles (NPs) for aqueous As(III) adsorption trough pH 5–9. The ferrite NPs were characterized by XRD and SEM, determining that ~ 20 nm mean size was predominant in Fe3O4, Co0.5Fe2.5O4, and CoFe2O4. XPS was used to find what the Co0.5Fe2.5O4 NPs are enriched for Fe3+ ions in the octahedral sites in comparison to CoFe2O4 and Fe3O4 NPs. Magnetometry revealed that the Co0.5Fe2.5O4 NPs were magnetically harder. Adsorption of arsenite on ferrite NPs freshly synthesized was formerly examined for linear intraparticle diffusion model (IPD). Then the nonlinear Pseudo First Order (PFO), Pseudo Second Order (PSO), and Elovich models were applied for As(III) adsorption kinetics. Once the system reached equilibrium, adsorption results were fitted through the nonlinear isotherm models of Freundlich and Langmuir. IPD model revealed that mass transfer from the bulk As(III) solutions (0.5–12 mg/L) toward ferrite NPs occurred immeasurably rapid so that IPD determined the main course of the adsorption process. Unlike PFO and PSO, the Elovich model did not fit adsorption data; PSO was the model that described better adsorption kinetics. Freundlich and Langmuir isotherm models fitted in good agreement equilibrium adsorption data. Arsenic adsorption and removal were affected by the type of NPs, whereas no effect was recorded for pH from 5 to 9, with arsenic removal rates as high as 95%–92% through increasing As(III) nominal concentrations. Co0.5Fe2.5O4 NPs exerted the highest arsenic removal and adsorption capacity, which was strongly related to NPs properties.