Silica-coated magnetite nanoparticles core-shell spheres (Fe3O4@SiO2) for natural organic matter removal.

Elahe Karimi Pasandideh,Babak Kakavandi,Simin Nasseri,Amir Hossein Mahvi,Ali Esrafili,Roshanak Rezaei Kalantary,Ramin Nabizadeh

doi:10.1186/s40201-016-0262-y

Abstract

BackgroundIn this work, the magnetite (Fe3O4) nanoparticles (MNPs) and silica-coated magnetite nanoparticles (SMNPs) were synthesized as adsorbents for removing humic acid (HA) from water resources.MethodsThe adsorption processes were performed in batch experiments with which the influence of pH, reaction time, adsorbent dosage, initial concentrations of HA and temperature were investigated. Specific techniques were applied to characterize the features of both adsorbents (i. e. TECHNIQUES) (SEM, XRD, TEM, BET, EDX and VSM).ResultsThe maximum saturation magnetization for SMNPs was 30.2 emu/g, which made its separation from the solution by a magnetic field to be easier and faster. The HA adsorption process onto the both adsorbents were best described by the Freundlich isotherm and pseudo-second-order kinetic models. Highest adsorption efficiency of HA by MNPs an d SMNPs occurred at acidic conditions (pH ≈ 3). The mechanisms of adsorption process involved with a physisorption process such as (i. e. hydrogen bonding and electrostatic interaction). The predicted maximum monolayer adsorption capacities obtained by Langmuir isotherm model for MNPs and SMNPs were 96.15 and 196.07 mg/g, respectively.ConclusionHigher amount of HA adsorption onto the surfaces of SMNPs than MNPs surfaces was observed, reflecting that silica impregnated on MNPs enhances the efficiency of the adsorbent in removing HA.Electronic supplementary materialThe online version of this article (doi:10.1186/s40201-016-0262-y) contains supplementary material, which is available to authorized users.

Highlights

In this work, the magnetite (Fe3O4) nanoparticles (MNPs) and silica-coated magnetite nanoparticles (SMNPs) were synthesized as adsorbents for removing humic acid (HA) from water resources
Similar peaks were seen in the X-ray diffraction (XRD) diagrams of synthesized synthesize MNPs with silica based coating layer (SMNPs) composite, confirming that the cubic phase of MNPs is still kept after incorporating with the mesoporous silica
It was found that the average size of MNPs is 100 nm, confirming that the MNPs of Fe3O4 have been successfully synthesized at nano-size scales

Summary

Introduction

The magnetite (Fe3O4) nanoparticles (MNPs) and silica-coated magnetite nanoparticles (SMNPs) were synthesized as adsorbents for removing humic acid (HA) from water resources. The amount of natural organic matter (NOM) in drinking water resources is an important issue. It is best described as a complex mixture of organic compounds, included with humic and fulvic acids; and the other organic compounds, including proteins, lipids, carbohydrates, carboxylic acids, amino acids, and hydrocarbons [1]. Researchers have strived to remove NOM from the water resources In this regard, conventional treatment processes, including adsorption with different types of the adsorbents [5], coagulation [6], ion exchange [7], advanced oxidation [8], biodegradation [9]. Wide range of the adsorbents have been investigated with the effort to remove humic acid (HA) from water, including granular ferric hydroxide [12], magnetic chitosan nanoparticle [13], activated carbon, and newly developed nanoparticles (i. e. carbon nanotubes and chitosan/zeolite composites) [14, 15]

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