RECYCLABLE Fe₃O₄–MgFe₂O₄ SORBENTS AND THEIR Fe/Mg RATIO OPTIMIZATION FOR WATER DECONTAMINATION

Abstract

Our research aims to investigate a series of Mg_xFe_3-xO₄ (x = 0-1) nanomaterials in the context of their application in both treating arsenic-rich groundwater, where they act as magnetic nanosorbents, and in the treatment of water contaminated with organic pollutants, where they serve as agents in magnetic hyperthermia. Magnetization measurements as a function of magnetic field strength and temperature reveal that these materials exhibit a superparamagnetic (SPM) behavior, making them suitable for advanced water purification technologies.

Magnetic hyperthermia is a process of induced heating of magnetic nanoparticles in an alternating magnetic field. One of the key aspects of this research was to examine how the substitution of Fe²⁺ with Mg²⁺ in the Fe₃O₄ structure (Mg_xFe_3-xO₄, x = 0-0.2) affects the hyperthermic properties of the samples, through the analysis of SLP (Specific Loss Power) and ILP (Intrinsic Loss Power) values. It was found that SLP values increase with frequency for all samples. The highest SLP at 728 kHz was observed for Mg₀.₂Fe₂.₈O₄ (818 W/g), whereas Fe₃O₄ at the same frequency exhibited 327 W/g. The Mg₀.₂Fe₂.₈O₄ sample has the highest ILP value at 728 kHz (1.404 nHm²/kg), making it the most efficient for hyperthermia applications. The excellent heating efficiency of Mg_xFe_3-xO₄ nanoparticles makes them suitable for applications in technologies for the degradation of organic contaminants based on magnetic hyperthermia.

Preliminary results of testing Mg_xFe_3-xO₄ as sorbents for arsenic removal from groundwater indicate their significant potential and the need for further optimization of the chemical composition and microstructural properties of the nanoparticles. It has been shown that arsenic concentration in groundwater can be reduced from 102 ppb to 14 ppb within 30 minutes using a sorbent concentration of only 0.1 g/L. At the same time, the phosphorus concentration decreased from 381 ppb to 83 ppb, indicating competitive adsorption between phosphate and arsenate ions on the sorbent surface. This suggests that phosphate anions occupy similar adsorption sites as arsenate, which may influence the efficiency of arsenic removal in real groundwater systems with varying phosphate concentrations. Although the phosphorus concentration after treatment remains above the normal range for drinking water, further studies are required to enhance the selectivity and capacity of the material, ensuring both effective arsenic removal and the production of safe drinking water.