Fabrication, Microstructure and Colloidal Stability of Humic Acids Loaded Fe3O4/APTES Nanosorbents for Environmental Applications

Abstract

Nowadays, numerous researches are being performed to formulate nontoxic multifunctional magnetic materials possessing both high colloidal stability and magnetization, but there is a demand in the prediction of chemical and colloidal stability in water solutions. Herein, a series of silica-coated magnetite nanoparticles (MNPs) has been synthesized via the sol-gel method with and without establishing an inert atmosphere, and then it was tested in terms of humic acids (HA) loading applied as a multifunctional coating agent. The influence of ambient conditions on the microstructure, colloidal stability and HA loading of different silica-coated MNPs has been established. The XRD patterns show that the content of stoichiometric Fe3O4 decreases from 78.8% to 42.4% at inert and ambient atmosphere synthesis, respectively. The most striking observation was the shift of the MNPs isoelectric point from pH~ 7 to 3, with an increasing HA reaching up to the reversal of the zeta potential sign as it was covered completely by HA molecules. The zeta potential data of MNPs can be used to predict the loading capacity for HA polyanions. The data help to understand the way for materials’ development with the complexation ability of humic acids and with the insolubility of silica gel to pave the way to develop a novel, efficient and magnetically separable adsorbent for contaminant removal.

Sample preparation considerations for surface and crystalline properties and ecotoxicity of bare and silica-coated magnetite nanoparticles

“…The diameter of bare Fe 3 O 4 under argon condition changes after modification from 32.1 nm to 24.2 nm. 55 The same effect was observed for MNPs under ambient conditions: functionalization by APTES leads to size reduction from 30.2 nm to 23.3 nm. There sizes for bare and modified magnetic NPs are typical for superparamagnetic MNPs that correlate with the value of saturation magnetization and other magnetic properties.…”

“…As we have previously indicated in ref. 55 , the modification of APTES leads to the decrease of the lattice parameter from 8.3813 A for Fe 3 O 4 (Ar) to 8.3789 A for Fe 3 O 4 -APTES (Ar). In this case, the preparation and functionalization of Fe 3 O 4 under ambient conditions leads to the decrease of the lattice parameter to 8.3641 A for Fe 3 O 4 (air) and 8.3603 A Fe 3 O 4 -APTES (air), respectively.…”

“…Therefore, the phase composition and primary particle size of the samples were determined by X-ray diffraction (XRD) analysis in Bragg–Brentano geometry using a Philips X-pert diffractometer (Philips Analytical, Eindhoven, The Netherlands, Cr-Kα radiation, λ = 2.29106 Å) as described in ref. 55 . The full width at a half maximum (FWHM) of all reflections was used to determine particle size with the Scherrer equation.…”

Surface Modification of Magnesium Ferrite Nanoparticles for Selective and Sustainable Remediation of Congo Red

“…To address this shortcoming, we encapsulated the MgFe 2 O 4 –NH 2 NPs within a thin silica shell followed by amino functionalization (3-aminopropyltriethoxysilane, APTES) on the silica surface to increase the selectivity for CR. APTES was used as a surface modifier since not only it provides structural stability and inertness to redox reactions of the magnetic nanoadsorbent but also provides an amine group on the surfaces of the modified adsorbents, which offers the linking of a specific adsorbate. , Several characterization techniques (i.e., X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and ζ-potential analysis) were employed to characterize the modified nanoadsorbent. The adsorption behavior of anionic dyes, in particular IC and CR, in both single and binary systems was examined using the as-modified nanoparticles.…”

Hemocompatible Functionalized Hydrogen Substituted Graphdiyne Based Highly Durable Biosensor for Liver Cancer Detection

“…This negative charge is highly favorable for enhancing the binding strength with APTES. The surface charge on APTES/HsGDY was recorded to be +24.5 mV indicating the generation of highly positive ammonium sites after APTES functionalization, thus resulting in a strong electrostatic interaction between HsGDY and APTES. − Hence, the opposite polarities between HsGDY and APTES are of great advantage in formation of stable strong linkages with each other.…”