A magnetic Fe₃O₄@MgAl-layered double hydroxide (MLDH) nanocomposite was successfully synthesized and applied as an effective adsorbent for preconcentration of trace As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions from complex matrices. The quantification of the analytes was achieved using the inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The nanocomposite was then characterized using BET, FTIR, SEM, and EDS. Due to its high adsorption surface area, compared to traditional metal oxide-based adsorbents, MLDH nanocomposite exhibited high extraction efficiency. Several experimental parameters controlling the preconcentration of the trace metals were optimized using response surface methodology based on central composite design. Under optimum conditions, the linearity ranged from 0.1 to 500 µg L⁻¹ and the correlation of coefficients (R²) were higher than 0.999. The limits of detection (LODs) and quantification (LOQs) were 0.11–0.22 µg L⁻¹ and 0.35–0.73 µg L⁻¹, respectively. The intra-day (n = 10) and inter-day precisions (n = 5 working days) expressed in the form of percent relative standard deviations (%RSDs) were below 5%. The proposed method was successfully applied for the analysis of the As(III), Cd(II), Cr(III), Co(II), Ni(II), and Pb(II) ions in different environmental water samples.

In this study, Fe₃O₄-ZrO₂ functionalized with 3-aminopropyltriethoxysilane (Fe₃O₄-ZrO₂@APS) nanocomposite was investigated as a nanoadsorbent for the removal of Cd(II), Cu(II), Mn (II) and Ni(II) ions from aqueous solution and real samples in batch mode systems. The prepared magnetic nanomaterials were characterized using X-ray powder diffraction (XRD), scanning electron microscopy/energy dispersion x-ray (SEM/EDX) Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Factors (such as adsorbent dose and sample pH) affecting the adsorption behavior of the removal process were studied using the response surface methodology. Under optimized condition, equilibrium data obtained were fitted into the Langmuir and Freundlich isotherms and the data fitted well with Langmuir isotherms. Langmuir adsorption capacities (mg/g) were found to be 113, 111, 128, and 123 mg/g for Cd, Cu, Ni and Mn, respectively. In addition, the adsorption kinetics was analyzed using five kinetic models, pseudo-first order, pseudo-second order, intraparticle diffusion and Boyd models. The adsorbent was successfully applied for removal of Cd(II), Cu(II), Mn (II) and Ni(II) ions in wastewater samples.

Contamination of drinking water by metals remains a global threat to living organisms. Therefore, the current study describes variations of metal occurrence, water quality and human health risk assessment between the dry and wet seasons of a rural village located in the Eastern Cape Province, South Africa. The concentrations of major and trace metals were determined in drinking water samples using inductively coupled plasma-optical emission spectrometry (ICP-OES). The physicochemical parameters, water quality index (WQI), total water hardness (TWH) and health risk assessment (hazard quotient: HQ and chronic daily intake: CDI) were evaluated seasonally. The TWH results showed that the water was very hard with water hardness values ranging between 415 and 442. The water also contained several metals and metalloids such as Al (2.18–3.36 mg L⁻¹), As (0.17–0. 53 mg L⁻¹), Cd (0.0068–0.0134 mg L⁻¹), Cr (0.2481–0.2601 mg L⁻¹), Mn (0.387–1.582 mg L⁻¹), Pb (0.064–0.0802 mg L⁻¹), Sb (0.0496–0.1391 mg L⁻¹) and Se (0.075–0.148 mg L⁻¹) that exceeded the SANS and WHO permissible limits in drinking water. The health risk assessment revealed that the water may cause noncarcinogenic and carcinogenic health effects due to the presence of As, Cr, Sb, Tl and V in water samples, while the water quality index revealed that the water was of very poor quality.

Magnetic ion-imprinted polymers (MIIPs) are an innovative material that combines the selectivity of ion imprinting with the ease of separation provided by magnetic properties. Recent advancements in MIIPs have shown that they have higher selectivity coefficients compared to non-imprinted materials. The synthesis of MIIPs involves creating specific recognition sites for target ions in magnetic nanomaterials. Various nanomaterials, such as graphene oxide, carbon nanotubes, and silica, have been incorporated into the IIPs to improve their analytical performance for different environmental applications, including metal extraction, monitoring, detection, and quantification. This review stresses the need to develop new monomers with a high affinity for the target analyte and to find supporting materials with groups that facilitate the effective removal of the target analyte. It also explores the influence of experimental parameters on metal determination.

The presence of metallic pollutants presents a significant risk to human health, making their removal crucial. Magnetic halloysite nanotube (HNT@Fe₃O₄) nanocomposite was synthesised via co-precipitation, and then magnetic hydrogel (Fe₃O₄@HNT-SA and Fe₃O₄@HNT-CTS) nanocomposites were prepared using chitosan (CTS) and sodium alginate (SA) biopolymers. The structural, morphological, crystalline, surface, and thermal properties of the hydrogels were determined. The favourable adsorption performance of Fe₃O₄@HNT-SA and Fe₃O₄@HNT-CTS hydrogels towards As, Cd, Cr, Mo, Pb, Sb and V was established by optimising the factors affecting the sorption process. The results indicated that Fe₃O₄@HNT-CTS was suitable for the adsorption of As, Cr, Mo, Sb and V, while Fe₃O₄@HNT-SA had high adsorption affinity for Cd and Pb. The data for the adsorption of target analytes onto the hydrogels were mostly explained by both the Langmuir isotherm model and the pseudo-second order model. The maximum adsorption capacities of Fe₃O₄@HNT-SA hydrogel for Cd and Pb were 52.2 mg/g and 57.7 mg/g, respectively. On the other hand, the maximum capacities of the Fe₃O₄@HNT-CTS hydrogel for As, Cr, Mo, Sb, and V were 30.3 mg/g, 28.4 mg/g, 22.2 mg/g, 24.7 mg/g, and 19.9 mg/g, respectively. The Fe₃O₄@HNT-SA and Fe₃O₄@HNT-CTS hydrogels effectively removed the respective target analytes from river water samples.

A dual-template magnetic ion-imprinted polymer based on halloysite (Fe₃O₄@HNT-DIIP) was synthesised via surface imprinting and co-precipitation. This material was utilised in magnetic solid-phase extraction (MSPE) to selectively and simultaneously concentrate cadmium (Cd ²⁺ ) and lead (Pb ²⁺ ) from both aqueous samples and environmental water sources. The morphological structure, crystallinity, and surface characteristics were analysed using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a zetasizer. The maximum adsorption capacities of Fe ₃ O ₄ @HNT-DIIP for Cd ²⁺ and Pb ²⁺ ions were 44.4 and 58.5 mg/g. The adsorption kinetics exhibited a strong correlation with the pseudo-second-order model, and the Langmuir isotherm suggested that the Fe ₃ O ₄ @HNT-DIIP adsorbent facilitates monolayer sorption on uniform sites. The Fe ₃ O ₄ @HNT-DIIP adsorbent proved selective towards Cd ²⁺ and Pb ²⁺ ions in the presence of Co ²⁺ and Zn ²⁺ . Under optimum conditions, the Fe ₃ O ₄ @HNT-DIIP-MSPE coupled with inductively coupled plasma optical emission spectrometry (ICP-OES) exhibited wide linear ranges (0.712-100), acceptable limits of quantification (LOQs = 0.712–1.45 µg/L) and limit of detection (LODs = 0.214–0.440 µg/L) for Cd ²⁺ and Pb ²⁺ ions. The proposed method demonstrated excellent performance in preconcentrating and detecting trace metals in surface and groundwater samples, yielding recoveries of 95.5–102%.