Improvement in Heavy Metal Removal from Wastewater Using an External Magnetic Inductor

Abstract

Magnetite nanoparticles (Fe3O4) of 12 ± 4 nm diameter are electrochemically synthesized for the adsorption and magnetic harvesting of Cr(VI) from contaminated simulated solutions. The removal of Cr(VI) from aqueous media follows pseudo-second-order kinetics. The adsorption efficiency is evaluated in three different scenarios. In standard conditions, i.e., at room temperature; in a thermal bath working at 60 °C, where the temperature could be considered homogeneous within the solution; and finally, under magnetic induction heating, while adjusting the frequency and magnetic field used to attain the same temperature as in the bath experiments. Two benefits of using a magnetic inductor are demonstrated. First, the removal efficiency is almost doubled in comparison to that of the room temperature experiments, and it is higher by 30% compared to that of the bath setup. At the same time as the adsorption occurs, a redox reaction occurs on the surface of the nanoparticles, and Cr(VI), the predominant species in the contaminated solution, is significantly reduced to Cr(III). Through X-ray photoelectron spectroscopy, it is shown that a greater reduction effect is achieved when working in induction conditions than at room temperature. This is the first time that this synergistic effect using magnetic induction heating has been demonstrated for heavy metal decontamination of wastewater.

Magnetic Nanoparticles: Synthesis, Anisotropy, and Applications

“…273 Besides conversion, controllable magnetic heating can be applied to improve reaction selectivity, as demonstrated in hydrodeoxygenation reactions and cleavage of lignocellulose-derived products by Ni/FeNi 3 NPs (Figure 39C), 274 which achieves full conversion and 100% selectivity for 2-methylfuran from furfural and 2,5-dimethylfuran from 5-hydroxymethylfurfural. Magnetic heating has also been applied to remove Cr(VI) 275 and to degrade methyl blue dye. 276 These examples highlight the important aspects of magnetic heating: it can make the catalytic process potentially not only safer and cleaner but also more efficient and controllable.…”

Nanoadsorbants for the Removal of Heavy Metals from Contaminated Water: Current Scenario and Future Directions

“…They measured an adsorption capacity of up to 12.4 mg/g. The regeneration cycles of the magnetic nanomaterials showed a slight decrease (about 4%) in the removal efficiency, concluding that the nanomaterial can be reused for up to 4 cycles continuously [134]. Tao et al, showed an effective removal of heavy metal ions (Hg 2+ and Pb 2+ ) using thiol-functionalized magnetic mesoporous microspheres [135].…”

Magnetic Iron Oxide Colloids for Environmental Applications

“…Apart of the fact that IONPs can be efficiently recovered with an external magnetic field, facilitating its regeneration and reuse, environmental processes like the presented in previous sections can also be enhanced by taking advantage of the magnetic heating power of IONPs in the presence of AMF. In the case of adsorption with IONPs, Rivera et al presented the improvement of the adsorption capacity of chromium under an AMF [95]. Here, they showed much higher adsorption yields for IONP systems heated up with AMF than with common thermal heating even though both systems were set at the same global temperature.…”