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

Area of Science:

• Materials Science
• Nanotechnology
• Environmental Science

Background:

• Growing demand for non-toxic, multifunctional magnetic nanoparticles (MNPs) with high stability and magnetization.
• Need for predictive models of chemical and colloidal stability in aqueous solutions for MNPs.
• Humic acids (HA) are explored as multifunctional coating agents for MNPs.

Purpose of the Study:

• To synthesize silica-coated MNPs using the sol-gel method under varying atmospheric conditions.
• To investigate the influence of synthesis atmosphere on MNPs' microstructure, colloidal stability, and HA loading.
• To establish a correlation between zeta potential and HA loading capacity for predicting material performance.

Main Methods:

• Sol-gel synthesis of silica-coated magnetite nanoparticles (MNPs) under inert and ambient atmospheres.
• Characterization using X-ray Diffraction (XRD) to determine stoichiometry.
• Assessment of colloidal stability and humic acid (HA) loading via zeta potential measurements across varying pH.

Main Results:

• XRD analysis revealed a decrease in stoichiometric Fe3O4 content from 78.8% (inert) to 42.4% (ambient) atmosphere synthesis.
• The isoelectric point of MNPs shifted from pH ~7 to pH 3 with increasing HA loading.
• Zeta potential reversal indicated complete HA molecule coverage, demonstrating a predictive relationship for HA loading capacity.

Conclusions:

• Ambient synthesis conditions significantly alter MNPs' composition and colloidal properties.
• Zeta potential measurements effectively predict humic acid polyanion loading capacity.
• Developed silica-coated MNPs offer potential as magnetically separable adsorbents for contaminant removal due to HA complexation and silica insolubility.