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.
Highlights
It is possible sible to differentiate between the phases magnetite maghemite even though they have to differentiate between the phases magnetite and and maghemite even though they have a a very similar spinel and distorted spinalstructure, structure,respectively respectively[26]
We have studied the Fe3 O4 /APTES multifunctional nanosorbents fabO4/APTES multifunctional nanosorbents fabriricated in different atmospheres (Ar and ambient) for environmental purposes, such as mbient) for environmental purposes, such as heavy metal or radioisotope removal by magnetic separation
The colloid stability of nanoadsorbents is essential since adsorption requires a well-dispersed state of NPs, while n requires a well-dispersed state of NPs, while controlled aggregation is favored in the removal step
Summary
Humic substances (HS), natural high-molecular-weight organic compounds [9], seem rather prospective to coat the nanoparticles, thereby preventing aggregation through either electrostatic or steric stabilization [10], due to an abundance of Nanomaterials 2021, 11, 1418. The resulting coulombic, hydrogen and other bonds between Fe3 O4 and HA seemed to provide low protection to prevent oxidation of NPs, especially in ambient conditions (UV, biota or groundwater chemistry, i.e., pH, redox potential, dissolved oxygen, alkalinity). After their release into the environment, magnetite-humic NPs undergo various transformations via interactions with different geochemical and biological components, which influence their behavior and potential toxicity
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