Silica-coated magnetic nanoparticles modified with γ-mercaptopropyltrimethoxysilane for fast and selective solid phase extraction of trace amounts of Cd, Cu, Hg, and Pb in environmental and biological samples prior to their determination by inductively coupled plasma mass spectrometry

Functionalization of carbon from rubber fruit shells (Hevea brasiliensis) with silane agents and its application to the adsorption of bi-component mixtures of methylene blue and crystal violet

In this research, activated carbon was obtained from rubber fruit shells (ACRPs). The obtained activated carbon (ACRPs) was modified by magnetite particle coating and silanization with triethoxyiphenylsilane (TEPS) to produce a new magnetic adsorbent (ACRPs-MS). The affinity of as-prepared adsorbent (ACRPs-MS) toward methylene blue (MB) and crystal violet (CV) dyes was tested in mono-component and bi-component solutions. Structural characterization proves the success of the magnetite coating process and the silanization of ACRPs. In the infrared (IR) spectroscopy spectrum of ACRPs-MS, Si-O-Fe and Si-O-Si bonds were identified, which indicated the presence of magnetite and silane. This is also supported by the elemental composition contained in the energy-dispersive X-ray (EDX) diffractogram. In addition, the presence of the porous structure of the surface of the material and the increase in the specific surface area increase the accessibility of contaminants such as MB and CV dyes to be adsorbed to the ACRPs-MS adsorption site effectively. The experimental results showed that the adsorption of mono-component MB and CV dyes by ACRPs-MS was optimum at pH 8 and an interaction time of 60 min. The adsorption kinetics of mono-component MB and CV dyes by ACRPs-MS tended to follow pseudo-second-order kinetics (PSO) models with PSO rate constant (k2) values of 0.198 and 0.993 g mg-1 min-1, respectively. The adsorption of MB and CV dyes by ACRPs-MS in a bi-component mixture tends to follow the Langmuir isotherm model with adsorption capacity (qm) values of 85.060 and 90.504 mg g-1, respectively. Analysis of adsorption data on the bi-component mixture between MB and CV by ACRPs-MS with the Langmuir isotherm equation for a binary mixture resulted in qm of 22.645 × 10-3 mmol equiv g-1. ACRPs-MS material can be used repeatedly five times with adsorption ability > 80%. Desorption of MB and CV dyes was carried out using 0.05 M HCl solution. ACRPs-MS material was able to adsorb MB and CV dyes with a large adsorption capacity and could be used in repeated adsorption. Thus, it can be stated that ACRPs-MS can be used as an effective adsorbent for MB and CV dyes, either singly or in a bi-component mixture.

Rapid, easy and catalyst-free preparation of magnetic thiourea-based covalent organic frameworks at room temperature for enrichment and speciation of mercury with HPLC-ICP-MS

The complex and cumbersome preparation of magnetic covalent organic frameworks (COFs) nanocomposites on a small scale limits their application. Herein, a rapid and easy route was employed for the preparation of magnetic thiourea-based COFs nanocomposites. COFs were coated on Fe3O4 nanoparticles at room temperature without a catalyst within approximately 30 min. This method is suitable for the large-scale preparation of magnetic adsorbent. Using the as-prepared magnetic adsorbent (Fe3O4@COF-TpTU), we developed a simple, efficient, and sensitive magnetic solid-phase extraction-high performance liquid chromatography-inductively coupled plasma-mass spectrometry (MSPE-HPLC-ICP-MS) for the enrichment and determination of mercury species, including Hg2+, methylmercury (MeHg), and ethylmercury (EtHg). The effects of the experimental parameters on the extraction efficiency, including solution pH, adsorption and desorption time, composition and volume of the elution solvent, salinity, coexisting ions, and dissolved organic matter, were comprehensively investigated. Under optimised conditions, the limits of detection in the developed method were 0.56, 0.34, and 0.47 ng L-1 with enrichment factors of 190, 195, and 180-fold for Hg2+, MeHg, and EtHg, respectively. The satisfactory spiked recoveries (97.0-103%) in real water samples and high consistency between the certified and determined values in a certified reference material demonstrate the high accuracy and reproducibility of the developed method. The as-proposed method with simple operation, high sensitivity, and excellent anti-matrix interference performance was successfully applied to the enrichment and determination of trace levels of mercury species in the natural samples with complicated matrices, such as underground water, surface water, seawater and biological samples.

Preparation 2-hydroxy-1-naphthaldehyde cross-linked Fe3O4@chitosan-polyacrylamide nanocomposite for removal of everzol black from aqueous solutions

In this study, new 2-hydroxy-1-naphthaldehyde linked Fe₃O₄/chitosan-polyacrylamide nanocomposite (Fe₃O₄@CS@Am@Nph) were prepared. The synthesized nanocomposite was characterized by (FT-IR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), vibrating Sample Magnetometry (VSM) and Termogravimetric Analysis (TGA). The 2-hydroxy-1-naphthaldehyde modified Fe₃O₄@CS@Am@Nph nanocomposite was used as an effective adsorbent for removal of everzol black from aqueous solutions by batch adsorption procedure. The effects of important parameters on the surface absorption process of everzol black dye, including pH, contact time, adsorbent dosage and initial dye concentration were studied. The Langmuir, Freundlich and Temkin adsorption models were used to describe adsorption isotherms and constants. The equilibrium results revealed that the adsorption behavior of the everzol black dye on the Fe₃O₄@CS@Am@Nph nanocomposite fitted well with the Langmuir model. On the basis of the Langmuir analysis, the maximum adsorption capacity (qm) of the Fe₃O₄@CS@Am@Nph for everzol black was found to be 63.69 mg/g. The kinetic studies indicated that adsorption in all cases to be a pseudo second-order process. Further, the thermodynamic studies showed the adsorption to be a spontaneous and endothermic process.

Molecularly Imprinted Polymer-Based Biomimetic Systems for Sensing Environmental Contaminants, Biomarkers, and Bioimaging Applications

Molecularly imprinted polymers (MIPs), a biomimetic artificial receptor system inspired by the human body's antibody-antigen reactions, have gained significant attraction in the area of sensor development applications, especially in the areas of medical, pharmaceutical, food quality control, and the environment. MIPs are found to enhance the sensitivity and specificity of typical optical and electrochemical sensors severalfold with their precise binding to the analytes of choice. In this review, different polymerization chemistries, strategies used in the synthesis of MIPs, and various factors influencing the imprinting parameters to achieve high-performing MIPs are explained in depth. This review also highlights the recent developments in the field, such as MIP-based nanocomposites through nanoscale imprinting, MIP-based thin layers through surface imprinting, and other latest advancements in the sensor field. Furthermore, the role of MIPs in enhancing the sensitivity and specificity of sensors, especially optical and electrochemical sensors, is elaborated. In the later part of the review, applications of MIP-based optical and electrochemical sensors for the detection of biomarkers, enzymes, bacteria, viruses, and various emerging micropollutants like pharmaceutical drugs, pesticides, and heavy metal ions are discussed in detail. Finally, MIP's role in bioimaging applications is elucidated with a critical assessment of the future research directions for MIP-based biomimetic systems.

Sustainable application of nanoparticles in wastewater treatment: Fate, current trend & paradigm shift

Existing water and wastewater treatment techniques are becoming increasingly difficult to employ due to the discovery of new toxins, the rapid development of population and industrial activities, and the limited quantity of water resources. Treatment of wastewater is a critical need in modern civilization due to a scarcity of water resources and rising industrial activity. Some of the techniques utilized include adsorption, flocculation, filtration, and others, although they are only used for primary wastewater treatment. However, the development and deployment of modern wastewater management with high efficiency and low capitalization are critical in terms of mitigating the environmental consequences of waste. The employment of different nanomaterials in the treatment of wastewater has opened up a world of possibilities for heavy metal and pesticide removal, as well as the treatment of microbes and organic contaminants in wastewater. Nanotechnology is a rapidly evolving technology because of certain nanoparticle's outstanding physiochemical and biological capabilities as contrasted to bulk counterparts. Secondly, it has been established that this is a cost-effective treatment strategy with significant potential in wastewater management, transcending the limitations imposed by currently existing technology. Advances in nanotechnology to reduce water contamination have been presented in this review, including the use of various nanomaterials such as nanocatalysts, nanoadsorbents, and nanomembranes in the treatment of wastewater containing organic contaminants, hazardous metals, and virulent pathogens.

Ultrasonic assisted magnetic solid phase extraction of ultra-trace mercury with ionic liquid functionalized materials

Due to the agglomeration between particles, the inherent adsorption characteristics of magnetic powder materials are usually difficult to fully display. Taking ionic liquid functional materials as an example, the enrichment behavior of these adsorbents for trace mercury (Hg²⁺) in ultrasonic (US) assisted dispersion mode was systematically studied. The dissociation of protonic ionic liquids (IL) occur in the process of dispersion and the strong electrostatic attraction can improve the diffusion and adhesion of mercury on the adsorbent surface. Spectral measurement data showed that with the help of US, the more uniform dispersion of magnetic materials accelerated the adsorption of trace Hg²⁺. Ultrasonic intrinsic parameters such as frequency, power and radiation duration significantly affect the dispersion and apparent adsorption properties of magnetic functional materials. In the range of experimental parameters, the dye/paper image experimental results documents that there is a positive correlation between cavitation effect and ultrasonic frequency/power. The enrichment degree of fixed adsorbate (0.1 μg L^-1) under high frequency (59 kHz) or high-power input (100%) is 1-2 times higher than that under low frequency (40 kHz) or low power (60%) input. This is a valuable conclusion for the subsequent study of US dispersion of magnetic and even non-magnetic powder materials. In addition, the in-situ desorption and accurate measurement of adsorbed mercury were realized by combining slurry vapor generation atomic fluorescence spectroscopy (SVG-AFS). The constructed US assisted magnetic solid phase extraction (US-MSPE) method has the characteristics of low detection limit (0.36 ng L^-1), high recovery (>90%), sustainable utilization (>3) and reasonable measurement deviation (<5%), which can meet the requirements of ultra-trace Hg²⁺ (0.01-1.0 μg L^-1).

Synthesis of new functionalized magnetic nano adsorbents and adsorption performance for Hg(II) ions

Fe₃O₄@SiO₂-NH-nNG-SPTZ (including Fe₃O₄@SiO₂-NH-2NG-SPTZ, Fe₃O₄@SiO₂-NH-3NG-SPTZ) were prepared by 2-mercapto-5-(4-pyridyl)-1,3,4-thiadiazole and the reaction products of 3, 6-dichloropyridazine and cyanuric chloride with Fe₃O₄@SiO₂-NH₂ respectively. Fe₃O₄@SiO₂-S-nNG-SPTZ (including Fe₃O₄@SiO₂-S-2NG-SPTZ, Fe₃O₄@SiO₂-S-3NG-SPTZ) were prepared by 2-mercapto-5-(4-pyridyl)-1,3,4-thiadiazole and the reaction products of 3, 6-dichloropyridazine and cyanuric chloride with Fe₃O₄@SiO₂-SH respectively. Four novel adsorbents were characterized by SEM, TEM, FT-IR and XRD. Hg(II) ions removal efficiency of these adsorbents were more than 95%, in 15–20 min, at pH 7.0–8.0. It is easy to separate these adsorbents that adsorb mercury ions from the solution through magnets. These adsorbents have similar adsorption mechanism and have application value in the treatment of mercury ions in sewage and are worth studying.

A novel thiourea derivative for preconcentration of copper(II), nickel(II), cadmium(II), lead(II) and iron(II) from seawater samples for Flame Atomic Absorption Spectrophotometry

A novel adsorbent, 3-phenyl-1-(2-pyridyl)thiourea (PPTU) was synthesized and its adsorption capabilities were studied for Cu(II), Cd(II), Ni(II), Pb(II) and Fe(II) cations in the waters such as tap and polluted seawaters. The kinetics, Langmuir and Freundlich isotherms were discussed related to the adsorptions. The adsorption capacities of PPTU were found 9.4; 12.6; 90.9; 57.1 and 30.4 mg g^-1 and preconcentration with PPTU including the FAAS step yielded the LOQ values 0.46; 2.65; 1.12; 2.65 and 1.72 ng mL^-1 for Cu(II), Cd(II), Ni(II), Pb(II) and Fe(II), respectively. The adsorbent after the elutions and washings could be reused three times in the next adsorptions. The interferences on the adsorptions arising from the major cations of the seawater and the usability of PPTU for interested metals in the seawater were discussed. The proposed method is simple with highly efficient and green preconcentration procedure for trace analysis of the target metal ions.

Voltammetric picomolar determination of mercury, copper and cadmium using modified pencil graphite electrode with poly-L-cysteine and Fe3O4 nanoparticles

Cost-effective simultaneous determination of mercury, copper and cadmium ions was performed by differential pulse anodic stripping voltammetry (DPASV) using a pencil graphite electrode (PGE) modified with poly-L-cysteine (P-L-Cys) and Fe₃O₄ nanoparticles. Electropolymerization of L-cysteine was performed by cyclic voltammetry (CV) through applying different cycles. Also, Fe₃O₄ was deposited in a single step by applying a constant potential on the electrode surface in the presence of ferric nitrate. To enhance the sensitivity of measurement, several parameters such as monomer concentration, scan rate, number of cycles in electropolymerization, ferric nitrate concentration, Fe₃O₄ electrodeposition potential and time, and pH of the sample solution were optimized. The surface morphology of the modified electrode was examined by SEM and FTIR. Electrochemical impedance spectroscopy was conducted to investigate the impedance of the electrode surface. The linear ranges for cadmium, copper and mercury were 0.001‒2500, 0.0002‒3600 and 0.0001‒2500 nM with detection limits of 6.4 × 10^-13, 1.0 × 10^-13 and 9.0 × 10^-14 M, respectively. The stability and reproducibility of the electrode were investigated. Finally, the modified electrode was applied to determine mercury, copper and cadmium in real samples such as the groundwater, Caspian Sea and Tajan River water.

Au Nanoparticles Decorated Graphene-Based Hybrid Nanocomposite for As(III) Electroanalytical Detection

Electrochemical sensors integrating hybrid nanostructured platforms are a promising alternative to conventional detection techniques for addressing highly relevant challenges of heavy metal determination in the environment. Hybrid nanocomposites based on graphene derivatives and inorganic nanoparticles (NPs) are ideal candidates as active materials for detecting heavy metals, as they merge the relevant physico-chemical properties of both the components, finally leading to a rapid and sensitive current response. In this work, a hybrid nanocomposite formed of reduced graphene oxide (RGO) sheets, surface functionalized by π-π interactions with 1-pyrene carboxylic acid (PCA), and decorated in situ by Au NPs, was synthesized by using a colloidal route. The hybrid nanocomposite was characterized by cyclic voltammetry and electrochemical impedance spectroscopy with respect to the corresponding single components, both bare and deposited as a layer-by-layer junction onto the electrode. The results demonstrated the high electrochemical activity of the hybrid nanocomposite with respect to the single components, highlighting the crucial role of the nanostructured surface morphology of the electrode and the PCA coupling agent at the NPs-RGO interphase in enhancing the nanocomposite electroactivity. Finally, the Au NP-decorated PCA-RGO sheets were tested by anodic stripping voltammetry of As(III) ion—a particularly relevant analyte among heavy metal ions—in order to assess the sensing ability of the nanocomposite material with respect to its single components. The nanocomposite has been found to present a sensitivity higher than that characterizing the bare components, with LODs complying with the directives established by the U.S. EPA and in line with those reported for state-of-the-art electrochemical sensors based on other Au-graphene nanocomposites.

A combination approach using two functionalized magnetic nanoparticles for speciation analysis of inorganic arsenic

Mercapto- and amino-functionalized magnetic nanoparticles, Fe₃O₄@SiO₂@MPTMS (SMNPs-MPTMS) and Fe₃O₄@SiO₂@APTES (SMNPs-APTES), have been applied as magnetic solid-phase extraction (MSPE) sorbents to directly extract arsenite (As(III)) and arsenate (As(V)) respectively, followed by inductively coupled plasma-mass spectrometry (ICP-MS) detection. Various MSPE parameters were optimized including dose of magnetic adsorbent, pH of sample solution, loading and elution conditions of analytes, adsorption capacity and reusability of SMNPs-MPTMS and SMNPs-APTES for As(III) and As(V) respectively. Under the optimized MSPE conditions, this combined scheme possesses excellent selectivity and strong anti-interference ability without any oxidation or reduction prior to capture of these two species. It is found that with a 25-fold enrichment factor, the limits of detection of As(III) and As(V) were 23.5 and 10.5 ng L^-1, respectively. To verify the reliability of the proposed protocol, a certified reference material of environmental water was analyzed, and the results for inorganic arsenic species were in close agreement with the certified values. The applicability of the combination strategy for speciation analysis of inorganic arsenic was evaluated in spiked tap, river, lake and rain water samples. Good recoveries of 89%-96% and 90%-102% were achieved for As(III) and As(V), respectively, with the relative standard deviation ranges of 3.2%-8.0% and 2.5%-7.6%. Through the characterization of functionalized magnetic nanoparticles and the optimization of MSPE experiment, it is confirmed that the existence of mercapto and amino groups on SMNPs-MPTMS and SMNPs-APTES sorbents are responsible for the extraction of As(III) and As(V), respectively, via coordination and electrostatic interactions.

Converting CO2 into heterocyclic compounds under accelerated performance through Fe3O4 grafted ionic liquid catalysts

Solid supported catalysts such as amines has high demand for chemical fixation of CO2 into commodity chemicals. Here, we demonstrate an accelerated platform for 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-ionic liquids (ILs) catalyzed CO2...

Magnetic Molecularly Imprinted Polymers: Synthesis and Applications in the Selective Extraction of Antibiotics

Recently, magnetic molecularly imprinted polymers (MMIPs) have integrated molecular imprinting technology (MIT) and magnetic separation technology and become a novel material with specific recognition and effective separation of target molecules. Based on their special function, they can be widely used to detect contaminants such as antibiotics. The antibiotic residues in the environment not only cause harm to the balance of the ecosystem but also induce bacterial resistance to specific antibiotics. Given the above consideration, it is especially important to develop sensitive and selective methods for measuring antibiotics in the complex matrix. The combination of MMIPs and conventional analytical methods provides a rapid approach to separate and determine antibiotics residues. This article gives a systematic overview of synthetic approaches of the novel MMIPs materials, briefly introduces their use in sample pretreatment prior to antibiotic detection, and provides a perspective for future research.

Magnetic nanomaterials as sorbents for trace elements analysis in environmental and biological samples

This review focuses on magnetic nanomaterials as sorbents for trace elements analysis in environmental and biological samples. The design and preparation of magnetic nanomaterials with specific functional groups for trace elemental analysis are summarized, along with relevant adsorption mechanism. The application of these magnetic sorbents in different operation modes for the quantification of trace elements and their species in environmental and biological samples are discussed. The trend of development in this field is also prospected.

Synthesis and surface modification of magnetic Fe3O4@SiO2 core-shell nanoparticles and its application in uptake of scandium (III) ions from aqueous media

The main objective of this work is to produce an eco-friendly and economically nano-adsorbent which can separate scandium metal ions Sc from a model aqueous phase prior to applying these adsorbents in industrial filed. The magnetic core-shell structure Fe3O4@SiO2 nanoparticles were synthesized by modified Stöber method and functionalized with (3-aminopropyl) triethoxysilane APTES as a coupling agent and ethylenediaminetetraacetic acid (EDTA) as a ligand. Magnetic nano support adsorbents exhibit many attractive opportunities due to their easy removal and possibility of reusing. The ligand grafting was chemically robust and does not appreciably influence the morphology or the structure of the substrate. To evaluate the potential, the prepared hybrid nanoparticles were used as nano-adsorbent for Sc ions from model aqueous solutions due to the fact that rare earth elements (REEs) have a strong affinity for oxygen and nitrogen donors. The iron oxide nanoparticles were prepared by co-precipitation method at pH 10 and pH 11 to get the best morphology and nanoscale dimensions of iron oxide magnetic nanoparticles. The particle size, morphology, specific surface area, and surface modification were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), and X-ray powder diffraction (XRD). The results showed that the Fe3O4 nanoparticles with average particle size of 15 ± 3 nm were successfully synthesized at pH 11, and 25 °C. Moreover, the prepared Fe3O4 nanoparticles were coated with amorphous SiO2 and functionalized with amino and carboxyl groups. The adsorption study conditions of Sc are as follows: the initial concentrations of the Sc model solution varied 10-50 mg/L, 20 mL volume, 20-80 mg of the Fe3O4@SiO2-COO adsorbent, pH range of 1-5, and 5 h contact time at 25 °C temperature. The adsorption equilibrium was represented with Langmuir, Freundlich, and Temkin isotherm models. Langmuir model was found to have the correlation coefficient value in good agreement with experimental results. However, the adsorption process followed pseudo-second-order kinetics.

Selective aptamer conjugation to silver-coated magnetite nanoparticles for magnetic solid-phase extraction of trace amounts of Pb2+ ions

Herein, a novel aptamer-functionalized magnetic adsorbent was developed and combined with magnetic solid-phase extraction (MSPE) for the specific enrichment of Pb²⁺ ions prior to flame atomic absorption spectrometric detection.

Magnetic solid-phase extraction for speciation of mercury based on thiol and thioether-functionalized magnetic covalent organic frameworks nanocomposite synthesized at room temperature

A simple and practical magnetic solid-phase extraction high-performance liquid chromatography-inductively coupled plasma mass spectrometry (MSPE-HPLC-ICP-MS) method for extraction and determination of trace mercury species, including inorganic mercury (IHg), monomethylmercury (MeHg) and ethylmercury (EtHg), was developed. The MSPE adsorbent, urchin-like thiol and thioether-functionalized magnetic covalent organic frameworks (Fe₃O₄@COF-S-SH), was synthesized by coating covalent organic frameworks (COFs) on the surface of Fe₃O₄ nanoparticles at room temperature and then easily grafting 1,2-Ethanedithiol on the COFs. The as-prepared Fe₃O₄@COF-S-SH has strong adsorption capacity for IHg, MeHg and EtHg, with excellent static adsorption capacity: 571, 559 and 564 mg g^-1, respectively. The parameters influencing the extraction and enrichment had been optimized, including pH, adsorption and desorption time, composition and amount of the eluent, co-existing ions and dissolved organic materials etc. Under the optimized condition, the limit of detection (3δ) of the proposed method were 0.96, 0.17 and 0.47 ng L^-1 for IHg, MeHg and EtHg, and the developed method has high actual enrichment factors of 370, 395, 365-fold for IHg, MeHg and EtHg based on 200 mL samples, respectively. The high accuracy and reproducibility has been proved by the spiked recoveries (96.0‒108 %) in real water samples and determination of the certified reference material. Both the adsorption and desorption process can be completed within 5 min. The proposed method with simple operation, short pre-concentration time and high sensitivity has been successfully applied to mercury speciation at trace levels in the samples with complicated matrices, including underground water, surface water, sea water and fish samples.

Recent advances on functional nucleic acid-based biosensors for detection of food contaminants

It has seen increasing development of reliable, robust, and flexible biosensors for rapid food-safety analysis in the past few decades. Recently, functional nucleic acid-based biosensors have attracted attention because of their programmability, bottom-up characteristics, and structural switches. However, few systematic reviews devoted to categorizing the potential of DNA nanostructures and devices were found for detecting food contaminants. Hence, the applications of functional nucleic acid-based biosensors were reviewed for analyzing food contaminants, including foodborne pathogen bacteria, biotoxins, heavy metals, and et al. In addition to categorizing the various biosensors, multiple signal readout strategies, such as optical, electrochemical, and mass-based signals were also examined. Finally, the future changes and potential opportunities, as well as practical applications of functional nucleic acid-based biosensors were discussed.

Nano-sized magnetic Ni particles based dispersive solid-phase extraction of trace Cd before the determination by flame atomic absorption spectrometry with slotted quartz tube: a new, accurate, and sensitive quantification method

In this study, a new analytical strategy was developed to determine trace cadmium in aqueous samples with high sensitivity and accuracy. A combination of magnetic nickel nanoparticles (Ni-MNPs) based dispersive solid-phase extraction (DSPE) and flame atomic absorption spectrometry fitted with a slotted quartz tube (SQT-FAAS) lowered the detection limit of cadmium. The magnetic Ni nanoparticles were synthesized, characterized, and thoroughly optimized in a stepwise approach. The quartz tube was custom cut in the laboratory to suit the specifics of the flame burner. Using the optimized conditions, a limit of detection value of 0.58 μg/L and limit of quantification value of 1.93 μg/L were obtained. To demonstrate accuracy and applicability of the developed method, well water samples were analyzed for their Cd content, and matrix effect on the extraction yield was investigated. The percent recovery results calculated ranged from 93.8 to 108.2%, with corresponding standard deviation values ranging from 1.7 to 7.7. These results established the developed method as sensitive, accurate, and precise for determination of cadmium at trace levels.

Mitigation of environmentally-related hazardous pollutants from water matrices using nanostructured materials - A review

An unprecedented rise in population growth and rapid worldwide industrial development are associated with the increasing discharge of a range of toxic and baleful compounds. These toxic pollutants including dyes, endocrine-disrupters, heavy metals, personal care products, and pharmaceuticals are destructing nature's balance and intensifying environmental toxicity at a disquieting rate. Therefore, finding better, novel and more environmentally sound approaches for wastewater remediation are of great importance. Nanoscale materials have opened up some new horizons in various fields of science and technology. Among a range of treatment technologies, nanostructured materials have recently received incredible interest as an emerging platform for wastewater remediation owing to their exceptional surface-area-to-volume ratio, unique electrical and chemical properties, quantum size effects, high scalability, and tunable surface functionalities. An array of nanomaterials including noble metal-based nanostructures, transition metal oxide nanomaterials, carbon-based nanomaterials, carbon nanotubes, and graphene/graphene oxide nanomaterials to their novel nanocomposites and nanoconjugates have been attempted as the promising catalysts to overcome environmental dilemmas. In this review, we summarized recent advances in nanostructured materials that are particularly engineered for the remediation of environmental contaminants. The toxicity of various classes of relevant tailored nanomaterials towards human health and the ecosystem along with perspectives is also presented. In our opinion, an overview of the up-to-date advancements on this emerging topic may provide new ideas and thoughts for engineering low-cost and highly-efficient nanostructured materials for the abatement of recalcitrant pollutants for a sustainable environment.

A Wide Bandgap Ag/MgO@Fe3O4 Nanocomposite as Magnetic Sorbent for Cd(II) in Water Samples

Background:

The magnetic nanocomposites are very important as a reusable sorbents for the extraction of Cd(II) and other toxic metals from water samples.

Methods:

The Ag/MgO@Fe3O4 nanocomposite was synthesized by the coprecipitation method and characterized by the XRD, EDX, SEM, UV-vis spectroscopy and FTIR. This nanocomposite was used to extract Cd(II) from water samples prior to its quantitative analysis with FAAS. Different variables, i.e. pH, temperature, amount of nanosorbent, adsorption/desorption and dilution were optimized.

Results:

The method was successfully applied to determine Cd(II) in real water samples with excellent recoveries (98%). The present method has lower detection (0.29) and quantification limit (0.97 ng mL-1).

Conclusions:

The Ag/MgO@Fe3O4 nanocomposite based magnetic extraction is a simple, fast, reproducible, less expansive and efficient technique for the Cd(II) extraction in water samples. The developed sorbent can be recycled and reused (20 times).

Activated carbon/diatomite-based magnetic nanocomposites for magnetic solid-phase extraction of S-phenylmercapturic acid from human urine

In this study, activated carbon/diatomite-based magnetic nancomposites (denoted as AC/DBMNs) were synthesized and applied as an adsorbent for magnetic solid-phase extraction of S-phenylmercapturic acid (S-PMA) from human urine prior to high-performance liquid chromatography. The surface morphologies and structures of AC/DBMNs were characterized by Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, vibrating sample magnetometer and ζ-potential measurements. The experimental parameters including sample volume, sample pH, adsorbent amount, extraction time, elution solvent and desorption time were investigated in detail. Under the optimum conditions, the method exhibited good linearity (r > 0.9993) within the concentration ranges of 0.03-1.0 mg/L. Moreover, the limits of detection and quantification were 0.01 and 0.03 mg/L, respectively. The enrichment factor was 5, and good recoveries (88.9-97.3%) with relative standard deviations in the range of 5.6-6.8% (n = 6) for inter-day and 6.3-8.1% (n = 6) for intra-day were achieved. The developed method was successfully applied to the analysis of S-PMA in urine samples. In addition, this accurate and sensitive method has great potential to be applied in the early screening and clinical diagnosis of the workers exposed to benzene.

Diverse Surface Chemistry of Cobalt Ferrite Nanoparticles to Optimize Copper(II) Removal from Aqueous Media

Water pollution by heavy metals is one of the most serious worldwide environmental issues. With a focus on copper(II) ions and copper complex removal, in the present study, ultra-small primary CoFe₂O₄ magnetic nanoparticles (MNPs) coated with octadecylamine (ODA) of adequate magnetization were solvothermally prepared. The surface modification of the initial MNPs was adapted via three different chemical approaches based on amine and/or carboxylate functional groups: (i) the deposition of polyethylimide (PEI), (ii) covalent binding with diethylenetriaminepentaacetic acid (DTPA), and (iii) conjugation with both PEI and DTPA, respectively. FT-IR, TGA, and DLS measurements confirmed that PEI or/and DTPA were successfully functionalized. The percentage of the free amine (−NH₂) groups was also estimated. Increased magnetization values were found in case of PEI and DTPA-modified MNPs that stemmed from the adsorbed amine or oxygen ligands. Comparative UV–Vis studies for copper(II) ion removal from aqueous solutions were conducted, and the effect of time on the adsorption capacity was analyzed. The PEI-modified particles exhibited the highest adsorption capacity (164.2 mg/g) for copper(II) ions and followed the pseudo-second-order kinetics, while the polynuclear copper(II) complex Cu_x(DTPA)_y was also able to be immobilized. The nanoadsorbents were quickly isolated from the solution by magnetic separation and regenerated easily by acidic treatment.

Simultaneous enrichment and determination of cadmium and mercury ions using magnetic PAMAM dendrimers as the adsorbents for magnetic solid phase extraction coupled with high performance liquid chromatography

In present study, a sensitive and efficient method based on magnetic PAMAM dendrimers as the sorbents for magnetic solid-phase extraction (MSPE) coupled with high performance liquid-phase chromatography and ultraviolet variable wavelength detector (HPLC-VWD) was developed for simultaneous determination of trace cadmium and mercury ions. Sodium diethyldithiocarbamate (DDTC-Na) was used as the chelating agent during the elution process. Parameters that would affect the extraction efficiency including PAMAM generation, adsorbent dosage, adsorption time, elution time and volume, pH and coexisting ions were investigated to achieve the best adsorption efficiency. Under the optimal conditions, good linear relationship was obtained in the range of 0.05-200 μg L^-1 for Cd²⁺ and 0.1-200 μg L^-1 for Hg²⁺, and the limits of detection were 0.016 and 0.040 μg L^-1, respectively. The spiked recoveries of Cd²⁺ and Hg²⁺ were satisfied in the range of 91.5-105% (n = 3). The proposed method was proved to be an alternative and reliable method to determine trace Cd²⁺ and Hg²⁺ in water samples.

Preparation of highly selective magnetic cobalt ion-imprinted polymer based on functionalized SBA-15 for removal Co2+ from aqueous solutions

In this research, a novel magnetic cobalt ion imprinted adsorbent (Co(II)-MIIP) was synthesized by use of magnetic SBA-15 core-shell. It was functionalized by dithizone, and after identification by various techniques was used for removal of cobalt from aquatic systems. The uptake of cobalt proceeded very fast and achieved to equilibration within 5 min at which 74 mg g-1 of cobalt was adsorbed at pH = 8 with adsorbent dose of 0.15 g. The ion imprinted sorbent exhibited good selectivity towards cobalt ions. Separation and recovery of the used sorbent was carried out respectively by use of magnetic field and by use of HNO3 (0.1 M), and 85% of the initial capacity was obtained after seven 7 regeneration cycles. Different isotherm models, and error analysis were used to evaluate the experimental data. Thermodynamic, and kinetic evaluations showed that sorption process was endothermic, and described by second order kinetic model (R2 > 0.99). The equilibrium was established within five min.

Magnetic Particles-Based Analytical Platforms for Food Safety Monitoring

Magnetic nanoparticles (MNPs) have attracted growing interest as versatile materials for the development of analytical detection and separation platforms for food safety monitoring. This review discusses recent advances in the synthesis, functionalization and applications of MNPs in bioanalysis. A special emphasis is given to the use of MNPs as an immobilization support for biomolecules and as a target capture and pre-concentration to increase selectivity and sensitivity of analytical platforms for the monitoring of food contaminants. General principles and examples of MNP-based platforms for separation, amplification and detection of analytes of interest in food, including organic and inorganic constituents are discussed.

Preconcentration of Pb with Aminosilanized Fe3O4 Nanopowders in Environmental Water Followed by Electrothermal Atomic Absorption Spectrometric Determination

A new preconcentration method to determine lead in environmental waters using the aminosilanized magnetite Fe3O4 powder sorbent has been developed. The preconcentration method was combined with electrothermal atomization atomic absorption spectrometry (ETAAS) and a graphite atomizer. Trace amount of sorbent (3 mg) could be applied into the preconcentration of Pb. According the preconcentration, the detection limits were 14 and 19 pg·mL−1 with bare and aminosilanized Fe3O4, respectively. The effect of interferent elements such as Al, Ca, Co, Fe, K, Mg, Na, Ni, and Zn (1000 ng·mL−1 versus Pb 1 ng·mL−1) on the preconcentration of Pb using bare magnetite was evaluated, and some elements (Al, Ni, and Zn) were found to interfere with the Pb preconcentration. The aminosilanized Fe3O4 sorbent was found to be effective in eliminating the severe interferences. The enrichment factors were 34 for the preconcentration with aminosilanized Fe3O4. The recovery of spiked Pb in the case of the sorbent with aminosilanized Fe3O4 was in the range of 75 to 110%. From the analytical data, the preconcentration technique was found to be useful for the determination of trace lead in environmental waters.

An OFF-ON detection method for copper(ii) ions using a AgAu-NG nanocomposite modified electrode

An OFF-ON detection method for Cu²⁺ was developed at the AgAu bimetallic nanoparticle decorated nitrogen-doped graphene (AgAu-NG) nanocomposite modified electrode. The measurement was based on the copper-catalyzed oxidation of cysteamine (Cys) to regulate the oxidation peak current of Ag. In the absence of Cu²⁺, Cys can bind to the surface of AgAu-NG via the Ag-S or Au-S bond, thus leading to an obvious decrease of the oxidation peak current of Ag. However, in the presence of Cu²⁺, Cu²⁺ can greatly catalyze the oxidation of Cys by dissolved O₂ to form cystamine, which would fall off the surface of AgAu-NG nanocomposites, leading to the partial recovery of the oxidation peak current of Ag. With the increase in the concentration of Cu²⁺, the oxidation peak current of Ag in the presence of Cys increases accordingly. So, the concentration of Cu²⁺ can be measured. By using the optimum conditions, this method can detect Cu²⁺ concentrations down to 0.3 nM (S/N = 3) with a linear response range of 1 nM-1 mM. Furthermore, this method was applied to determine Cu²⁺ concentrations in river water samples and showed excellent analytical performance.