Recyclable Fe3O4@UiO-66-PDA core-shell nanomaterials for extensive metal ion adsorption: Batch experiments and theoretical analysis

With the ever-increasing challenge of heavy metal pollution, the imperative for developing highly efficient adsorbents has become apparent to remove metal ions from wastewater completely. In this study, we introduce a novel magnetic core-shell adsorbent, Fe3O4@UiO-66-PDA. It features a polydopamine (PDA) modified zirconium-based metal-organic framework (UiO-66) synthesized through a simple solvothermal method. The adsorbent boasts a unique core-shell architecture with a high specific surface area, abundant micropores, and remarkable thermal stability. The adsorption capabilities of six metal ions (Fe3+, Mn2+, Pb2+, Cu2+, Hg2+, and Cd2+) were systematically investigated, guided by the theory of hard and soft acids and bases. Among these, three representative metal ions (Fe3+, Pb2+, and Hg2+) were scrutinized in detail. The activated Fe3O4@UiO-66-PDA exhibited exceptional adsorption capacities for these metal ions, achieving impressive values of 97.99 mg/g, 121.42 mg/g, and 130.72 mg/g, respectively, at pH 5.0. Moreover, the adsorbent demonstrated efficient recovery from aqueous solution using an external magnet, maintaining robust adsorption efficiency (>80%) and stability even after six cycles. To delve deeper into the optimized adsorption of Hg2+, density functional theory (DFT) analysis was employed, revealing an adsorption energy of -2.61 eV for Hg2+. This notable adsorption capacity was primarily attributed to electron interactions and coordination effects. This study offers valuable insights into metal ion adsorption facilitated, by magnetic metal-organic framework (MOF) materials.

Recent Progress on the Adsorption of Heavy Metal Ions Pb(II) and Cu(II) from Wastewater

With the processes of industrialization and urbanization, heavy metal ion pollution has become a thorny problem in water systems. Among the various technologies developed for the removal of heavy metal ions, the adsorption method is widely studied by researchers and various nanomaterials with good adsorption performances have been prepared during the past decades. In this paper, a variety of novel nanomaterials with excellent adsorption performances for Pb(II) and Cu(II) reported in recent years are reviewed, such as carbon-based materials, clay mineral materials, zero-valent iron and their derivatives, MOFs, nanocomposites, etc. The novel nanomaterials with extremely high adsorption capacity, selectivity and particular nanostructures are summarized and introduced, along with their advantages and disadvantages. And, some future research priorities for the treatment of wastewater are also prospected.

Highly efficient Cu(II) capture by salicylaldoxime functionalized magnetic polydopamine core-shell hybrids: Behavior and mechanism

Functionalized magnetic nanocomposites were considered as promising adsorbents owing to their abundant functional groups and ease of separation properties. Herein, we combined the solvothermal method with molecular copolymerization to synthesize a salicylaldoxime-grafted magnetic polydopamine (SMP) core-shell hybrid and exploited it for Cu(II) adsorption. The physicochemical properties of SMP were comprehensively studied by SEM, TEM, XRD, FT-IR, TGA, XPS, and VSM measurements. The results manifested that polydopamine acts as a bridge connecting magnetic iron oxide and salicylaldoxime to fabricated core-shell hybrids with rich functional groups. The batch experimental results showed that the Cu(II) adsorption was consumingly pH-reliant behavior, while adsorption data fitted the pseudo-second-order kinetic model and Langmuir isothermal model well, and the adsorption process achieved equilibrium within 60 min. Moreover, SMP exhibited remarkable anti-interference and can be recycled for 5 times with an inconspicuous decrease in adsorption performance. Importantly, salicylaldoxime functionalization endowed SMP with maximum Cu(II) adsorption capacity of 141.24 mg/g at pH 6.0 and 25 °C as compared with pure MP. Based on FT-IR and XPS study, the main adsorption mechanisms were proposed with a synergistic effect including a strong chemical chelation and partial Cu(II) reduction. Importantly, this strategy can be extended to multifunctional magnetic composites for Cu-contaminated wastewater cleanup.

Recent progress in magnetic polydopamine composites for pollutant removal in wastewater treatment

Various water pollution issues pose a significant threat to human water safety. Magnetic polydopamine composites (MPCs), which can be separated by magnetic fields after the adsorption process, exhibit outstanding adsorption capacity and heterogeneous catalytic properties, making them promising materials for water treatment applications. In particular, by modifying the polydopamine (PDA) coating, MPCs can acquire enhanced high reactivity, antibacterial properties, and biocompatibility. This also provides an attractive platform for further fabrication of hybrid materials with specific adsorption, catalytic, antibacterial, and water-oil separation capabilities. To systematically provide the background knowledge and recent research advances in MPCs, this paper presents a critical review of MPCs for water treatment in terms of both structure and mechanisms of effect in applications. Firstly, the impact of different PDA positions within the composite structure is investigated to summarize the optimization of properties contributed by PDA when acting as the shell, core, or bridge. The roles of various secondary modifications of magnetic materials by PDA in addressing water pollution problems are explored. It is anticipated that this work will be a stimulus for further research and development of magnetic composite materials with real-world application potential.

Polydopamine-functionalized electrospun poly(vinyl alcohol)/chitosan nanofibers for the removal and determination of Cu(II)

Environmentally friendly and recycled polydopamine-functionalized electrospun poly(vinyl alcohol)/chitosan nanofibers (PVA/CS/PDA) were prepared through a low-energy-consumption procedure. The PDA coating endows PVA/CS/PDA nanofibers with good water stability. The PVA/CS/PDA nanofibers have a fibrillar and porous structure that is favorable for Cu(II) to access the active sites of the nanofibers. The adsorption isotherm and kinetics data preferably conform to the Liu isotherm and pseudo-second-order kinetic models, respectively. The maximum adsorption capacity of Cu(II) ions by PVA/CS/PDA nanofibers from the Liu isotherm model is 326.5 mg g-1. The PVA/CS/PDA nanofibers exhibit higher adsorption capacity than some other reported adsorbents. The adsorption mechanism study demonstrates that the Cu(II) adsorption is mainly ascribed to the complexation of Cu(II) with the imino, amino, and hydroxy moieties in PVA/CS/PDA nanofibers. The nanofibers can be employed for 5 cycles without significantly deteriorating performance. More interestingly, a fluorometry method based on the oxidation mimic enzyme activity of Cu(II) was developed to detect low concentrations of Cu(II) using the nanofibers as an adsorbent to preconcentrate Cu(II). The limit of detection is 0.42 mg L-1. The successful removal and detection of Cu(II) in Pearl River and mineral water samples demonstrates the great potential of PVA/CS/PDA nanofibers to remediate Cu(II)-polluted water.

Adsorption-precipitation-cross-linking immobilization of GDSL-type esterase from Aspergillus niger GZUF36 by polydopamine-modified magnetic clarity tetroxide nanocouplings and its enzymatic characterization

Recombinant INANE1 (rINANE1), a recombinant intracellular GDSL-type esterase from Aspergillus niger GZUF36, has high acetate substrate specificity. Here, rINANE1 was successfully immobilized on polydopamine (PDA)-modified magnetic ferric oxide nanoparticles (Fe₃O₄NPs) by adsorption-precipitation-cross-linking to obtain cross-linked enzyme aggregate (CLEA)-rINANE1-Fe₃O₄@PDA. Fe₃O₄, Fe₃O₄@PDA, and CLEA-rINANE1-Fe₃O₄@PDA were characterized by scanning electron microscopy, X-ray diffraction, vibrating-sample magnetometry, Fourier transform infrared (FTIR) spectroscopy, and zeta potential analysis. Upon immobilization, CLEA-rINANE1-Fe₃O₄@PDA, with a protein loading of 72.72 ± 1.01 mg/g, reached optimal activity recovery of 104.40 % ± 1.14 %. FTIR analysis showed that immobilization increased the relative content of β-folding in rINANE1 by 12.25 % and reduced irregular curl by 4.16 %, rendering the structure more orderly. Specifically, under an alkaline condition (pH 10), CLEA-rINANE1-Fe₃O₄@PDA performed over 100 % of initial activity. The optimum temperature increased by 5 °C, and over 55 % of the initial activity was observed after 12 h at 55 °C. CLEA-rINANE1-Fe₃O₄@PDA showed over 40 % of its relative activity, whereas free rINANE1 showed <10 % in acetonitrile. In addition, the relative activity of CLEA-rINANE1-Fe₃O₄@PDA was retained at about 80 % after eight cycles and maintained at 109 % after 45 days. The PDA-modified magnetic ferrite nanoparticles exhibited excellent stability and recyclability, providing a new avenue for developing industrial biocatalysts.

Competitive adsorption behavior of typical heavy metal ions from acid mine drainage by multigroup-functionalization cellulose: qualitative and quantitative mechanism

In response to Cd, Pb, and Cu pollution in acid mine drainage (AMD), a multigroup cellulose material (TCIS) containing thiol (-SH), carboxyl (-COOH), and imine (-C = N) groups was prepared through oxidation and grafting reactions. At pH 5, the maximum Cd(II), Pb(II), and Cu(II) adsorption performances of TCIS were 53.60, 120.6, and 36.01 mg/g, respectively. In the binary system, the interaction between metal ions was mainly inhibited by competitive adsorption. Cu(II) exhibited the most fierce inhibitory effect and had a relatively stable adsorption performance. In the ternary system, the adsorption order was Cu(II) > Cd(II) > Pb(II). In density functional theory (DFT) calculations, we combined the molecular electrostatic potentials, binding energies, differential charges, and total potentials to illustrate the competitive behavior of metal ions at different binding sites. Moreover, X-ray photoelectron spectroscopy (XPS) and DFT analysis revealed that the adsorption process of TCIS was dominated by the above functional groups, which caused competitive adsorption among Cd(II), Pb(II), and Cu(II).

Removal of cadmium and lead ions from aqueous solutions by novel dolomite-quartz@Fe3O4 nanocomposite fabricated as nanoadsorbent

The elimination of heavy metal ion contaminants from residual waters is critical to protect humans and the environment. The natural clay (dolomite and quartz) based composite Fe₃O₄ nanoparticles (DQ@Fe₃O₄) has been largely explored for this purpose. Experimental variables such as temperature, pH, heavy metal concentration, DQ@Fe₃O₄ dose, and contact time were optimized in details. The DQ@Fe₃O₄ nanocomposite was found to achieve maximum removals of 95.02% for Pb²⁺ and 86.89% for Cd²⁺, at optimal conditions: pH = 8.5, adsorbent dose = 2.8 g L^-1, the temperature = 25 °C, and contact time = 140 min, for 150 mg L^-1 heavy metal ion initial concentration. The Co-precipitation of dolomite-quartz by Fe₃O₄ nanoparticles was evidenced by SEM-EDS, TEM, AFM, FTIR, XRD, and TGA analyses. Further, the comparison to the theoretical predictions, of the adsorption kinetics, and at the equilibrium, of the composite, revealed that they fit, respectively to, the pseudo-second-order kinetic, and Langmuir isotherm. These both models were found to better describe the metal binding onto the DQ@Fe₃O₄ surface. This suggested a homogenous monolayer sorption dominated by surface complexation. Additionally, thermodynamic data have shown that the adsorption of heavy metal ions is considered a spontaneous and exothermic process. Moreover, Monte Carlo (MC) simulations were performed in order to elucidate the interactions occurring between the heavy metal ions and the DQ@Fe₃O₄ nanocomposite surface. A good correlation was found between the simulated and the experimental data. Moreover, based on the negative values of the adsorption energy (Eads), the adsorption process was confirmed to be spontaneous. In summary, the as-prepared DQ@Fe₃O₄ can be considered a low-cost-effective heavy metals adsorbent, and it has a great potential application for wastewater treatment.

Synthesis and Characterization of SPIONs Encapsulating Polydopamine Nanoparticles and Their Test for Aqueous Cu2+ Ion Removal

The removal of pollutants, such as heavy metals, aromatic compounds, dyes, pesticides and pharmaceuticals, from water is still an open challenge. Many methods have been developed and exploited for the purification of water from contaminants, including photocatalytic degradation, biological treatment, adsorption and chemical precipitation. Absorption-based techniques are still considered among the most efficient and commonly used approaches thanks to their operational simplicity. In recent years, polydopamine-coated magnetic nanoparticles have emerged for the uptake of heavy metals in water treatment, since they combine specific affinity towards pollutants and magnetic separation capacity. In this context, this work focuses on the synthesis of polydopamine (PDA)-coated Super Paramagnetic Iron Oxide Nanoparticles (PDA@SPIONs) as adsorbents for Cu²⁺ ions, designed to serve as functional nanostructures for the removal of Cu²⁺ from water by applying a magnetic field. The synthetic parameters, including the amount of SPIONs and PDA, were thoroughly investigated to define their effects on the nanostructure features and properties. Subsequently, the ability of the magnetic nanostructures to bind metal ions was assessed on Cu²⁺-containing solutions. A systematic investigation of the prepared functional nanostructures was carried out by means of complementary spectroscopic, morphological and magnetic techniques. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements were performed in order to estimate the Cu²⁺ binding ability. The overall results indicate that these nanostructures hold great promise for future bioremediation applications.

High-efficiency Hg(II) adsorbent: FeS loaded on a carbon black from pyrolysis of waste tires and sequential reutilization as a photocatalyst

Iron-sulfur nano compounds have been proven to be effective in mercury removal, but the agglomeration, poor dispersion and mobility, and easy oxidation challenges limit their application. Herein, carbon black originating from pyrolysis of waste tires was used as a carrier of nano-FeS to obtain an efficient adsorbent (C@PDA-FeS). It is found that the C@PDA-FeS shows outstanding adsorption ability, excellent selectivity, and high removal rate. A maximum adsorption capacity of 1754 mg/g is obtained, and the residual Hg(II) ion concentration is as low as 3.2 μg/L in the simulated industrial wastewater, which meets the industrial discharge standard under the optimal conditions. Meanwhile, the removal rate of Hg(II) ion can reach 99.8% after up to 10 cycles. More importantly, the C@PDA-FeS still shows good adsorption efficiency, and the removal rate of Hg(II) ion is over 99% (25 mg/L Hg(II) concentration) after 90 days of storage, demonstrating the long-term stability and promising future of the adsorbent. In addition, the waste adsorbent (C@PDA-FeS/HgS) is reused as a photocatalyst to degrade methylene blue, and the corresponding degradation rate is 92.9% (10 mg/L).

APTMS-BCAD modified magnetic iron oxide for magnetic solid-phase extraction of Cu(II) from aqueous solutions

Fe₃O₄@SiO₂-3-aminopropyltrimethoxysilane-1,8-bis (3-chloropropoxy) anthracene-9,10-dione was synthesized as a new, sustainable, and environmentally friendly adsorbent for magnetic solid-phase extraction of Cu(II) from aqueous solutions. The structure of the adsorbent was characterized by FTIR, XRD, SEM, EDX, and TEM analysis. Optimum conditions for Cu(II) adsorption were determined as adsorbent dose 0.04 g, pH 5.0, contact time 120 min, and beginning concentration of 30 mg/L in the adsorption process. The adsorption capacity for Cu(II) ions was 43.67 mg/g and the removal efficiency was 84.72 percent. The Langmuir isotherm and the pseudo-second-order model fit the experimental data better. Adsorption was a spontaneous and endothermic process based on the obtained thermodynamic properties such as ΔG°, ΔH°, and ΔS°. The results showed that the sorbent has good selectivity in the presence of competing ions. The method was determined to be accurate and effective using real water samples and CRM.

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Magnetic Fe₃O₄@SiO₂-3-aminopropyl-trimethoxysilane-1,8-bis(3-chloropro-poxy) anthracene-9,10-dione was synthesized as a new, sustainable, and environmentally friendly adsorbent for magnetic solid-phase extraction of Cu(II) from aqueous solutions.

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The results showed that the presence of competitor ions did not have a significant effect on the sorption of Cu(II) ion and the sorbent had good selectivity.

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Using real water samples and CRM, the method was found to be accurate and effective.

Surface migration of Pb(II) from water and soil using an aerogel/graphite felt primary cell system

To develop a zero energy consumption electrokinetic remediation method of Pb(II) in water and soil, a primary cell system was constructed via synergistic effects of the electromigration, ion exchange, precipitation and hydrogen bond. The primary cell system used cathode of calcium alginate aerogel/graphite felt (CAA/GF) and another piece of CAA/GF was placed on the top of the water and soil. Thus the electric field in the system could drive positively charged Pb(II) towards the top of and thus Pb(II) was surface migrated, promoting removal of Pb(II). This system achieved Pb(II) removal efficiency of 97.8% and maximum power density of 32.1 mW m^-2. Additionally, the CAA/GF presented a good reusability. This work provides a promising and facile method to remove heavy metals from water and soil, which might have a huge application prospect.

Differentiating Nanomaghemite and Nanomagnetite and Discussing Their Importance in Arsenic and Lead Removal from Contaminated Effluents: A Critical Review

Arsenic and lead heavy metals are polluting agents still present in water bodies, including surface (lake, river) and underground waters; consequently, the development of new adsorbents is necessary to uptake these metals with high efficiency, quick and clean removal procedures. Magnetic nanoparticles, prepared with iron-oxides, are excellent candidates to achieve this goal due to their ecofriendly features, high catalytic response, specific surface area, and pulling magnetic response that favors an easy removal. In particular, nanomagnetite and maghemite are often found as the core and primary materials regarding magnetic nanoadsorbents. However, these phases show interesting distinct physical properties (especially in their surface magnetic properties) but are not often studied regarding correlations between the surface properties and adsorption applications, for instance. Thus, in this review, we summarize the main characteristics of the co-precipitation and thermal decomposition methods used to prepare the nano-iron-oxides, being the co-precipitation method most promising for scaling up processes. We specifically highlight the main differences between both nano-oxide species based on conventional techniques, such as X-ray diffraction, zero and in-field Mössbauer spectroscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism, the latter two techniques performed with synchrotron light. Therefore, we classify the most recent magnetic nanoadsorbents found in the literature for arsenic and lead removal, discussing in detail their advantages and limitations based on various physicochemical parameters, such as temperature, competitive and coexisting ion effects, i.e., considering the simultaneous adsorption removal (heavy metal-heavy metal competition and heavy metal-organic removal), initial concentration, magnetic adsorbent dose, adsorption mechanism based on pH and zeta potential, and real water adsorption experiments. We also discuss the regeneration/recycling properties, after-adsorption physicochemical properties, and the cost evaluation of these magnetic nanoadsorbents, which are important issues, but less discussed in the literature.

Fabrication, functionalization and advanced applications of magnetic hollow materials in confined catalysis and environmental remediation

Magnetic hollow-structured functional hybrid materials with unique architectures and preeminent properties have always been an area of extensive research. They represent a subtle collaboration of hollow architecture, mesoporous nanostructure and magnetic character. Owing to the merits of a large void space, low density, high specific surface area, well-defined active sites and facile magnetic recovery, these materials present promising application projections in numerous fields, such as drug delivery, adsorption, storage, catalysis and many others. In this review, recent progress in the design, synthesis, functionalization and applications of magnetic hollow-meso/nanostructured materials are discussed. The first part of the review has been dedicated to the preparation and functionalization of the materials. The synthetic protocols have been broadly classified into template-assisted and template-free methods and major trends in their synthesis have been elaborated in detail. Furthermore, the benefits and drawbacks of each method are compared. The later part summarizes the application aspects of confined catalysis in organic transformations and environmental remediation such as degradation of organic pollutants, dyes and antibiotics and adsorption of heavy metal ions. Finally, an outlook of future directions in this research field is highlighted.

Synthesis of potential Ca-Mg-Al layered double hydroxides coated graphene oxide composites for simultaneous uptake of europium and fulvic acid from wastewater systems

High background electrolyte and natural organic matter are favorable to migration of hazardous radionuclides in geochemical repository. Herein, Ca-Mg-Al layered double hydroxide coated onto graphene oxide (Ca-Mg-Al LDH/GO) composites were successfully synthesized, characterized and adopted to decontaminate Eu(III) and fulvic acid (FA) under diverse experimental conditions. Diverse concentration gradients and different addition sequences on Eu(III) and FA were also obtained, which revealed different interaction mechanisms. The experimental results displayed that the coexistence of FA and Eu(III) respectively promoted adsorption performance of Eu(III) and FA under the ternary systems. The acquired Ca-Mg-Al LDH/GO composites were adopted to remove Eu(III) and FA, which further illustrated excellent chemo-physical stability and adsorption capacity of 1.12 × 10^-3 mol/g and 3.54 × 10^-4 mol/g, respectively. The remarkable adsorption performances of Ca-Mg-Al LDH/GO were confirmed through kinetic procedures and depending-temperature isotherms, illustrating that the kinetics processes were simulated using pseudo-second-order pattern, and the adsorption isotherms were splendidly simulated using Langmuir pattern. XPS spectrum analysis revealed that these containing oxygen groups took significant part in the restricting of Eu(III) and FA onto the surfaces of Ca-Mg-Al LDH/GO composites. In view of experimental results, the Ca-Mg-Al LDH/GO composites can be as potential adsorbents with availably recycled reusability for the decontamination of Eu(III) and FA from nuclear fuel partition or nuclear wastewater systems.

Integration of covalent organic frameworks into hydrophilic membrane with hierarchical porous structure for fast adsorption of metal ions

Covalent organic frameworks (COFs) including their preparation and application as research focus have attracted attention of researchers. Most of COFs exhibit the powder form, therefore they inevitably suffer many difficulties during use of catalysis, separation and so on. In previous study, our group have fabricated COF-based monoliths through ring-opening polymerization in which the micropores/mesopores of COF were easily blocked by unreacted monomer and solvent resulting in low specific surface area of COF-based monoliths. Herein, we designed and fabricated two kinds of hydrazone-linked COF-integrated chitosan membranes (CM@COF and COF@CM) with hierarchical porous structure using chitosan, poly(ethylene glycol) diglycidyl ether (PEGDE), 1,3,5-triformylphloroglucinol (TP), oxalyldihydrazide (ODH) in the presence of mesitylene and 1,4-dioxane, and acetic acid as catalyst. The resulting CM@COF is monolithic material to overcome disadvantages of COF powder, meanwhile it possessed hierarchical porous structure containing mesoporous and macroporous structure and higher specific surface area (117.4 m² g^-1) than chitosan membrane (0.4 m² g^-1). And the CM@COF was applied to adsorption of heavy metal ion, and its adsorption capacities for Cu(II) and Cr(VI) ions were 144 mg g^-1 (pH = 7) and 388 mg g^-1 (pH = 6), respectively, indicating that the CM@COF had potential for fast removal of heavy metal ions.

Facile synthesis of core-shell phase-transited lysozyme coated magnetic nanoparticle as a novel adsorbent for Hg(II) removal in aqueous solutions

Adsorption using nanomaterials is considered an effective method for controlling the levels of toxic heavy metal in wastewater. Herein, a novel adsorbent, core-shell phase-transited lysozyme film-coated magnetic nanoparticles (Fe₃O₄@SiO₂@PTL) for Hg(II) ions removal from aqueous solutions was explored via facile and fast phase transformation and self-assembly process of lysozyme. The physiochemical properties of Fe₃O₄@SiO₂@PTL were investigated using various characterization techniques. The adsorption performances such as kinetics, isotherms, selectivity, the effect of coexisting ions, and regeneration were evaluated. Fe₃O₄@SiO₂@PTL showed an extremely high Hg(II) uptake rate and achieved more than 90% equilibrium adsorption capacity in 5 min. Hg(II) adsorption was followed by a pseudo-second-order kinetic model and fitted the Langmuir model by achieving a maximum uptake of 701.51 mg/g. Furthermore, excellent Hg(II) selectivity was obtained in a mixed solution containing various heavy metal ions, along with good chemical stability owing to the high adsorption capacity maintained after five cycles. The adsorption analyses indicated that the amino, imino, amide, hydroxyl, carboxyl, and thiol groups exposed on the surface of Fe₃O₄@SiO₂@PTL were vital for Hg(II) removal. Consequently, this work will significantly assist in the development of an easily available, eco-friendly, and selective adsorbent material to remove heavy metal ions from wastewater.

Designed Core-Shell Fe3O4@Polydopamine for Effectively Removing Uranium(VI) from Aqueous Solution

Adsorbents with the combination of magnetic separation and removal performance are expected for reducing the adverse impact of nuclear pollution. In this study, the core-shell Fe₃O₄@polydopamine (Fe₃O₄@PDA) was successfully synthesized and used for removal of uranium (U(VI)) ion from aqueous solution. The abundant N-containing groups derived from PDA exist as the chelate sites for U(VI) and contribute greatly for U(VI) removal. Experimental results show that Fe₃O₄@PDA (56.39 mg g^-1) exhibits greater sorption capacity for U(VI) removal compared with the pure Fe₃O₄ (9.17 mg g^-1). The sorption isotherm can be well fitted with Freundlich model and the sorption process is endothermic and spontaneous. The removal of U(VI) can be explained by the complexation of U(VI) with -NH-, -NH₂ and C-O in the surface of Fe₃O₄@PDA by X-ray photoelectron spectroscopy (XPS) analysis.

A novel magnetic solid-phase extraction method for detection of 14 heterocyclic aromatic amines by UPLC-MS/MS in meat products

The current study developed a cheap and effective method for the simultaneous extraction of 14 heterocyclic aromatic amines (HAAs) in food matrix. Core-shell Fe₃O₄@PDA nanoparticles were constructed and acted as the magnetic solid-phase extraction adsorbent to separate and purify HAAs from meat products for the first time. Then, UPLC-MS/MS technique was employed to identify and quantify the HAAs easily. Fe₃O₄@PDA nanoparticles were synthesized and characterized successfully. Totally 14 HAAs were completely separated in 19.99 min with good regression coefficients. LODs and LOQs were in the range of 0.013-0.247 ng/g and 0.056-0.803 ng/g, respectively. The intra-day precisions and inter-day precisions were below 9%. Except for IQ[4,5-b], Phe-p-1, PhIP, other 11 types of HAAs (DMIP, 1,5,6-TMIP, IQ, IQx, MeIQ, MeIQx, 7,8-DiMeIQx, AαC, MeAαC, Harman, Norharman) could acquire relatively high recoveries (71.06%-108.49%). The proposed method was successfully devoted to the evaluation of HAAs levels in 8 commercial meat products to verify the adaptability.

Novel conjugated hybrid material for efficient lead(II) capturing from contaminated wastewater

An efficient material is always welcoming for the water treatment due to the need of clean water to safe the human health. The conjugate adsorbent (CJA) was fabricated by functional ligand embedded onto the highly porous silica material for selective lead (Pb(II)) ion monitoring and removal from wastewater. The study was achieved not only investigating the beginning material but also the performing extrusion as novel conjugate material, this defining the material novelty of this study considers to the modern state-of-art. The fabricated material was characterized in all aspects and then the experimental works for Pb(II) ion assessing were carried in batch mode. The CJA was exposed the color and signal intensity upon addition of Pb(II) ion from low to high concentrations. The optimum pH was considered at 5.50 based on the sensitivity, the color formation ability and high adsorption of Pb(II) ion. The determined limit of low detection was 0.18 μg/L, which was the extraordinary performance for the Pb(II) ion monitoring ability by the CJA. The adsorption efficiency, specific attention was remunerated to the influence of solution pH, reaction time, foreign ion, initial Pb(II) amounts and regeneration. The CJA was exhibited high kinetic performances and showed high adsorption Pb(II) ion compared with the different forms of material. The adsorption was completely fitted with the Langmuir adsorption as defining the monolayer coverage as expected of the homogeneous porosity of the CJA. The maximum adsorption was determined as high as 175.16 mg/g. In addition, the foreign ions were not affected in the Pb(II) adsorption by the CJA, and the adsorbent was regenerated using 0.20 M HCl for several cycles used without significant loss of the initial performance. Considering these advantages, the CJA demonstrated the potential low-cost material for competitive use in wastewater remediation, especially in the developing countries.

Macroscopic and microscopic investigation of uranium elimination by Ca–Mg–Al-layered double hydroxide supported nanoscale zero valent iron

Ca–Mg–Al-LDH/nZVI nanocomposites showed excellent U(vi) removal performance from aqueous solutions through the coordination of reduction and adsorption reactions.