A systematic study of hexavalent chromium adsorption and removal from aqueous environments using chemically functionalized amorphous and mesoporous silica nanoparticles.

ABSTRACT: We report on the synthesis and characterization of highly monodisperse amorphous silica nanoparticles (ASNs) and mesoporous silica nanoparticles (MSNs) with particle sizes of 15-60 nm. We demonstrate adsorption of Cr(VI) ions on amino-functionalized ASNs (NH₂-ASNs) and MSNs (NH₂-MSNs) and their removal from aqueous environments and show the specific surface area (SSA) of NH₂-MSNs is four times as larger as that of NH₂-ASNs and that more than 70% of the total SSA of NH₂-MSNs is due to the presence of nanopores. Analyses of Cr(VI) adsorption kinetics on NH₂-ASNs and NH₂-MSNs exhibited relatively rapid adsorption behavior following pseudo-second order kinetics as determined by nonlinear fitting. NH₂-ASNs and NH₂-MSNs exhibited significantly higher Cr(VI) adsorption capacities of 34.0 and 42.2 mg·g^-1 and removal efficiencies of 61.9 and 76.8% than those of unfunctionalized ASNs and MSNs, respectively. The Langmuir model resulted in best fits to the adsorption isotherms of NH₂-ASNs and NH₂-MSNs. The adsorption of Cr(VI) on NH₂-ASNs and NH₂-MSNs was an endothermic and spontaneous process according to the thermodynamic analyses of temperature-dependent adsorption isotherms. The removal efficiencies of NH₂-ASNs and NH₂-MSNs exhibited a moderate reduction of less than 25% of the maximum values after five regeneration cycles. Furthermore, NH₂-MSNs were also found to reduce adsorbed Cr(VI) into less harmful Cr(III).

SUBMITTER: Jang EH 

PROVIDER: S-EPMC7101345 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature