Heavy Metal Adsorption Using Magnetic Nanoparticles for Water Purification: A Critical Review

Research on contamination of groundwater and drinking water is of major importance. Due to the rapid and significant progress in the last decade in nanotechnology and its potential applications to water purification, such as adsorption of heavy metal ion from contaminated water, a wide number of articles have been published. An evaluating frame of the main findings of recent research on heavy metal removal using magnetic nanoparticles, with emphasis on water quality and method applicability, is presented. A large number of articles have been studied with a focus on the synthesis and characterization procedures for bare and modified magnetic nanoparticles as well as on their adsorption capacity and the corresponding desorption process of the methods are presented. The present review analysis shows that the experimental procedures demonstrate high adsorption capacity for pollutants from aquatic solutions. Moreover, reuse of the employed nanoparticles up to five times leads to an efficiency up to 90%. We must mention also that in some rare occasions, nanoparticles have been reused up to 22 times.

Retraction: Zhao, S.; Lee, S. Biomaterial-Modified Magnetic Nanoparticles γ-Fe2O3, Fe3O4 Used to Improve the Efficiency of Hyperthermia of Tumors in HepG2 Model. Appl. Sci. 2021, 11, 2017

The authors and journal retract the article, “Biomaterial-Modified Magnetic Nanoparticles γ-Fe2O3, Fe3O4 Used to Improve the Efficiency of Hyperthermia of Tumors in HepG2 Model” [...]

Bio-Specific Au/Fe3+ Porous Spongy Nanoclusters for Sensitive SERS Detection of Escherichia coli O157:H7

For sensitive and fast detection of Escherichia coli O157:H7, organic and inorganic hybrid Au/Fe3+ nanoclusters (NCs) were synthesized for the first time using gold nanoparticles (GNPs), bovine serum albumin, ferric chloride, phosphate-buffered saline, and antibodies. The Au/Fe3+ porous spongy NCs with large surface area showed excellent bio-specific capability for E. coli O157:H7. GNPs in Au/Fe3+ NCs functioned as signal enhancers, significantly increasing the Raman signal via the metathesis reaction product of Prussian blue and obviously improving the detection sensitivity. We combined the novel Au/Fe3+ NCs with antibody-modified magnetic nanoparticles to create a biosensor capable of sensitive detection of E. coli O157:H7, which showed a good linear response (101 to 106 cfu/mL), high detection sensitivity (2 cfu/mL), and good recovery rate (93.60–97.50%) in spiked food samples. These results make the biosensor well-suited for food safety monitoring. This strategy achieves the goal of sensitive and quantitative detection of E. coli O157:H7.

Magnetic Solid-Phase Extraction using Ionic Liquid-Modified Magnetic Nanoparticles for The Simultaneous Extraction of Cadmium and Lead in Milk Samples; Evaluation of Measurement Uncertainty

In the present study, a new, sensitive, and rapid method was developed for extraction and determination of the trace amounts of Pb (II) and Cd (II) ions in milk samples through magnetic solid-phase extraction using DABCO based-ionic liquid-modified magnetic nanoparticles (Fe3O4/[DABCO-PDO]Cl NPs). Herein, Pb (II) and Cd (II) contents were quantified with flame atomic absorption spectroscopy (FAAS). The effect of different empirical parameters (such as sample pH, adsorbent amount, type and amount of the elution, extraction and desorption times, and the ligand concentration) was evaluated and optimized for simultaneous extraction and pre-concentration Pb (II) and Cd (II) ions. The calibration curve was linear under the optimum condition in the concentration range of 0.4-200 µgL-1 for Cd, and 0.5-120 µgL-1 for Pb, respectively. The pre-concentration factor was 67, with the detection limit of 0.09 and 0.07 µgL-1 for Pb and Cd, respectively. The relative standard deviation values (RSD %) of the proposed method were lower than 2.6 %. The developed method was successfully used to determine lead and cadmium content in milk samples. The information obtained from the method validation has been used to estimate the expanded uncertainty for the determination of Pb (II) and Cd (II) at trace levels in commercial milks. Resumen. En este trabajo, se ha desarrollado un nuevo, sensible y rápido procedimiento para la extracción y determinación de iones Pb(II) y Cd(II) a nivel de trazas en leche, mediante extracción en fase sólida utilizando nanopartículas magnéticas modificadas con líquido iónico basado en DABCO (Fe3O4/[DABCO-PDO]Cl NPs). La determinación de ambos metales se llevó a cabo por espectrometría de absorción atómica con atomización en llama. Se ha evaluado el efecto de diferentes parámetros empíricos (tales como pH, cantidad de adsorbente, tipo y cantidad de solvente de elución, tiempo de extracción y desorción, y concentración del ligando); estos parametros fueron optimizados enfocándose en la extracción y preconcentración simultanea de ambos iones. Empleando las condiciones establecidas, se obtuvo buena linealidad de las curvas de calibración en el intervalo de concentraciones 0.4-200 µgL-1 para Cd, y 0.5-120 µgL-1 para Pb, respectivamente. Se logró el factor de preconcentración 67, con los límites de detección 0.09 y 0.07 µgL-1 para Pb y Cd, respectivamente. Los valores de desviación estandar relativa (RSD %) en el procedimiento propuesto no sobrepasaron 2.6 %. En el análisis de leche, se obtuvieron resultados satisfactorios. Los datos obtenidos en etapa de validación se utilizaron para estimar la incertidumbre expandida en la determinación de Pb y Cd a nivel de trazas en leche.