Quantification of trace heavy metals in environmental water, soil and atmospheric particulates with their bioaccessibility analysis

In this work, sulfhydryl (SH) functionalized magnetic covalent organic framework (COF) was synthesized by using 4-aldehyde phenyl butadiyne (DEBD) and 1,3,5-tris(4-aminophenyl) benzene (TAPB) as the monomers and ethanedithiol as the modifier, with the aid of thiol-alkyne "click" reaction. The prepared Fe3O4@COFTAPB-DEBD@SH exhibited relatively strong magnetism (32.8 emu g-1), good stability and selectivity to target analytes with a high sulfhydryl content (0.24 mmol g-1). Based on Fe3O4@COFTAPB-DEBD@SH, a method combining magnetic solid phase extraction with inductively coupled plasma mass spectrometry (ICP-MS) was developed for the quantitative analysis of trace metals. Under the optimal conditions, the method merited fast desorption kinetics (<2 min), adsorption kinetics (<20 min), fast phase separation (<1 min), high enrichment factor (100), and the detection limits for Cd, Hg, Pb and Bi were determined to be 1.18, 0.51, 4.91 and 0.39 ng L-1, respectively. A good resistance to complex matrices was demonstrated for the method in the analysis of soil, atmospheric particles and simulated pulmonary fluids samples. Certified reference materials (coal fly ash GBW08401 and soil GBW07427) were employed to validate the accuracy of the method. Four target metals in the range of 12.9-215 ng L-1, 0.06-24.6 μg g-1 and 0.52-33.1 ng m-3 were found in local water, soil and atmospheric particulates (PM), respectively. Additionally, artificial lysosome solution and gamble's solution were used to simulate human pulmonary fluid and the bioaccessibility of Cd, Hg, Pb and Bi in PM2.5 was evaluated to be 58.6-73.1 % and 1.3-7.1 %, respectively.

Synthesis of Boronate Affinity-Based Oriented Dummy Template-Imprinted Magnetic Nanomaterials for Rapid and Efficient Solid-Phase Extraction of Ellagic Acid from Food

Ellagic acid (EA) is a natural polyphenol and possesses excellent in vivo bioactivity and antioxidant behaviors, which play an important role in the treatment of oxidative stress-related diseases, such as cancer. Additionally, EA is also known as a skin-whitening ingredient. The content of EA would determine its efficacy. Therefore, the accurate analysis of EA content can provide more information for the scientific consumption of EA-rich foods and cosmetics. Nevertheless, the analysis of EA in these samples is challenging due to the low concentration level and the presence of interfering components with high abundance. Molecularly imprinted polymers are highly efficient pretreatment materials in achieving specific recognition of target molecules. However, the traditional template molecule (EA) could not be absolutely removed. Hence, template leakage continues to occur during the sample preparation process, leading to a lack of accuracy in the quantification of EA in actual samples, particularly for trace analytes. In addition, another drawback of EA as an imprinting template is that EA possesses poor solubility and a high price. Gallic acid (GA), called dummy templates, was employed for the synthesis of MIPs as a solution to these challenges. The approach used in this study was boronate affinity-based oriented surface imprinting. The prepared dummy-imprinted nanoparticles exhibited several significant advantages, such as good specificity, high binding affinity ((4.89 ± 0.46) × 10-5 M), high binding capacity (6.56 ± 0.35 mg/g), fast kinetics (6 min), and low binding pH (pH 5.0) toward EA. The reproducibility of the dummy-imprinted nanoparticles was satisfactory. The dummy-imprinted nanoparticles could still be reused even after six adsorption-desorption cycles. In addition, the recoveries of the proposed method for EA at three spiked levels of analysis in strawberry and pineapple were 91.0-106.8% and 93.8-104.0%, respectively, which indicated the successful application to real samples.

Selective adsorption of mercury ion from water by a novel functionalized magnetic Ti based metal-organic framework composite

In the context of industrialization and severe wastewater pollution, mercury ions pose a major threat due to their high toxicity. However, traditional adsorbents and common metal-organic framework (MOF) materials have limited effectiveness. This study focuses on combining magnetic materials with functionalized titanium-based MOF composite (SNN-MIL-125(Ti)@Fe3O4) to improve mercury ion adsorption. Through comprehensive characterization and analysis, the adsorption performance and mechanism of the material were studied. The optimal adsorption of the material was achieved at pH 5, exhibiting a pseudo-second-order adsorption model and the Hill theoretical capacity of 668.98 mg/g. Hill and Tempkin models confirmed the presence of chemical and physical adsorption sites on the material surface. Thermodynamic experiments showed a spontaneous endothermic process. Despite the presence of interfering ions, the material exhibited high selectivity for mercury ions. After four cycles, adsorption performance decreased by only 8%, indicating excellent reusability. Nitrogen- and sulfur-containing functional groups played a key role in mercury ion adsorption. In conclusion, SNN-MIL-125(Ti)@Fe3O4, as a magnetic MOF adsorption material, showed potential for effective remediation of mercury-contaminated wastewater. This study contributes to the development of efficient adsorption materials and enhances the understanding of their mechanism.

Preparation and Application Progress of Imprinted Polymers

Due to the specific recognition performance, imprinted polymers have been widely investigated and applied in the field of separation and detection. Based on the introduction of the imprinting principles, the classification of imprinted polymers (bulk imprinting, surface imprinting, and epitope imprinting) are summarized according to their structure first. Secondly, the preparation methods of imprinted polymers are summarized in detail, including traditional thermal polymerization, novel radiation polymerization, and green polymerization. Then, the practical applications of imprinted polymers for the selective recognition of different substrates, such as metal ions, organic molecules, and biological macromolecules, are systematically summarized. Finally, the existing problems in its preparation and application are summarized, and its prospects have been prospected.

Efficient synthesis of boronate affinity-based catecholamine-imprinted magnetic nanomaterials for trace analysis of catecholamine in human urine

Catecholamines, a class of cis-diol-containing compounds, play a major role in the central nervous system.

Application of Molecularly Imprinted Polymers in the Analysis of Waters and Wastewaters

The increase of the global population and shortage of renewable water resources urges the development of possible remedies to improve the quality and reusability of waste and contaminated water supplies. Different water pollutants, such as heavy metals, dyes, pesticides, endocrine disrupting compounds (EDCs), and pharmaceuticals, are produced through continuous technical and industrial developments that are emerging with the increasing population. Molecularly imprinted polymers (MIPs) represent a class of synthetic receptors that can be produced from different types of polymerization reactions between a target template and functional monomer(s), having functional groups specifically interacting with the template; such interactions can be tailored according to the purpose of designing the polymer and based on the nature of the target compounds. The removal of the template using suitable knocking out agents renders a recognition cavity that can specifically rebind to the target template which is the main mechanism of the applicability of MIPs in electrochemical sensors and as solid phase extraction sorbents. MIPs have unique properties in terms of stability, selectivity, and resistance to acids and bases besides being of low cost and simple to prepare; thus, they are excellent materials to be used for water analysis. The current review represents the different applications of MIPs in the past five years for the detection of different classes of water and wastewater contaminants and possible approaches for future applications.

A thiol-functionalized zirconium metal-organic cage for the effective removal of Hg2+ from aqueous solution

The mercury ions in waste water have threatened public health and environmental protection. In this sense, novel materials with outstanding performances for removal of Hg²⁺ are imperative. Herein, we demonstrate a thiol-functionalized zirconium metal-organic cage (MOC-(SH)₂) with excellent dispersion displays ideal properties for Hg²⁺ capture. MOC-(SH)₂ exhibits the ability of removing Hg²⁺ in aqueous solutions with a capacity of 335.9 mg_Hg2+/g_MOC-(SH)2, which surpasses that of classical Zr-based metal-organic framework Uio-66-(SH)₂ by 1.89 folds. The higher loading capacity of MOC-(SH)₂ is probably owing to the excellent dispersion of the discrete cage, which makes the accessibility of binding sites (thiol) easier. Additionally, 99.6% of Hg²⁺ can be effectively captured by MOC-(SH)₂ with the concentration decreased from 5 to 0.02 ppm reaching the permissible limit for Hg²⁺, outperforming the performance of Uio-66-(SH)₂. The excellent absorption property of MOC-(SH)₂ is also achieved in terms of superior selectivity under the presence of competitive metal ions. Meanwhile, the regenerated MOC-(SH)₂ can be reused without apparent loss of Hg²⁺ loading capacity. UV-vis absorption spectra, IR spectra and emission spectra further verified the strong chemical affinity between Hg²⁺ and the thiol of MOC-(SH)₂. The study lays the groundwork for using Zr-MOCs in the removal of toxic metal ions and environmental sustainability.

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.

Removal of mercury from polluted water by a novel composite of polymer carbon nanofiber: kinetic, isotherm, and thermodynamic studies

This work aims at the synthesis of a polymer of poly-trimesoyl chloride and polyethyleneimine grafted on carbon fibers (PCF) derived from palm. The obtained PCF was characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) for its structural properties. The obtained PCF was then evaluated for the removal of mercury (Hg(ii)) from aqueous solutions using batch adsorption studies at four different temperatures (298, 308, 318, and 328 K). The experimental parameters such as initial concentration, pH, dosage, and contact time were optimized on the mercury adsorption. The percentage removal was 100% with an adsorbent dosage of 100 mg L⁻¹ at a pH between 5 and 7 and temperature of 298 K and thus kinetic, isotherm, and thermodynamic studies were performed under these conditions. By the Langmuir adsorption isotherm, the maximum adsorption capacity of Hg(ii) by PCF was 19.2 mg g⁻¹. In addition, results fit the pseudo-second-order model, with R² > 0.99, to describe the adsorption kinetic mechanism. The adsorption process is spontaneous with an endothermic nature under the studied conditions.

This work aims at the synthesis of a polymer of poly-trimesoyl chloride and polyethyleneimine grafted on carbon fibers (PCF) derived from palm to remove mercury (ii) from aqueous solutions using batch adsorption studies at different temperatures.

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.

Al-Omar M. Synthesis and Characterization of CuFe2O4 Nanoparticles Modified with Polythiophene: Applications to Mercuric Ions Removal

In this research, CuFe₂O₄ nanoparticles were synthesized by co-precipitation methods and modified by coating with thiophene for removal of Hg(II) ions from aqueous solution. CuFe₂O₄ nanoparticles, with and without thiophene, were characterized by x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX), high-resolution transmission electron microscopy (HRTEM) and Brunauer-Emmett-Teller (BET). Contact time, adsorbent dose, solution pH, adsorption kinetics, adsorption isotherm and recyclability were studied. The maximum adsorption capacity towards Hg²⁺ ions was 7.53 and 208.77 mg/g for CuFe₂O₄ and CuFe₂O₄@Polythiophene composite, respectively. Modification of CuFe₂O₄ nanoparticles with thiophene revealed an enhanced adsorption towards Hg²⁺ removal more than CuFe₂O₄ nanoparticles. The promising adsorption performance of Hg²⁺ ions by CuFe₂O₄@Polythiophene composite generates from soft acid-soft base strong interaction between sulfur group of thiophene and Hg(II) ions. Furthermore, CuFe₂O₄@Polythiophene composite has both high stability and reusability due to its removal efficiency, has no significant decrease after five adsorption-desorption cycles and can be easily removed from aqueous solution by external magnetic field after adsorption experiments took place. Therefore, CuFe₂O₄@Polythiophene composite is applicable for removal Hg(II) ions from aqueous solution and may be suitable for removal other heavy metals.

Efficient synthesis of boronate affinity-based chlorogenic acid-imprinted magnetic nanomaterials for the selective recognition of chlorogenic acid in fruit juices

Chlorogenic acid (CGA), a cis-diol-containing compound, can exhibit anti-inflammatory, antiviral, antimicrobial and anti-oxidation properties.

A Molecular Coordination Template Strategy for Designing Selective Porous Aromatic Framework Materials for Uranyl Capture

Uranium capture from seawater could solve increasing energy demand and enable a much needed relaxing from fossil fuels. Low concentration (∼3 ppb), competing cations (especially vanadium) and pH-dependent speciation prohibit highly efficient uranium uptake. Despite intensive research, selective extraction of uranyl ions over vanadyl units remains a tremendous challenge. Here, we adopted a molecular coordination template strategy to design a uranyl-specific bis-salicylaldoxime entity and decorated it into a highly porous aromatic framework (PAF-1) by programmable assembly. The superstructure (MISS-PAF-1) gives a strong affinity that removes 99.97% of uranium in 120 min. Notably, it binds to the uranyl ion at least 100 times more selectively than 14 different cations tested, including the vanadyl ion, in simulated seawater at ambient pH. Real seawater samples collected from the Bohai Sea achieve 5.79 mg g^-1 of uranium capacity over 56 days without PAF degradation, exceeding a 4-fold higher amount than commercial adsorbents.

Carboxymethyl cellulose thiol-imprinted polymers: Synthesis, characterization and selective Hg(II) adsorption

Sulfur containing ion imprinted polymers (S-IIPs) were applied for the uptake of Hg(II) from aqueous solution. Cysteamine which was used as the ligand for Hg(II) complexation, was grafted along the epichlorohydrin crosslinked carboxylated carboxymethyl cellulose polymer chain through an amide reaction. The adsorption ability of S-IIPs towards Hg(II) was investigated by kinetic and isotherm models, which, corresponding, showed that the adsorption process followed a pseudo-second-order, fitted well with the Langmuir isotherm with a maximum adsorption capacity of 80 mg/g. Moreover, thermodynamic studies indicated an endothermic and spontaneous reaction with the tendency of an enhanced randomness at the surface of the S-IIPs with temperature increases. S-IIPs indicated a high degree of selectivity towards Hg(II) in the presence of Cu²⁺, Zn²⁺, Co²⁺, Pb²⁺ and Cd²⁺. Furthermore, the efficiency of S-IIPs was also evaluated against real samples showing 86.78%, 91.88%, and 99.10% recovery for Hg(II) wastewater, ground water and tap water, respectively. In this study, the adsorbent was successfully regenerated for five cycles, which allows for their reuse without significant loss of initial adsorption capability.

Preparation of Poly (Allylthiourea-Co-Acrylic Acid) Derived Carbon Materials and Their Applications in Wastewater Treatment

Functional carbon materials have been developed and applied in various sewage treatment applications in recent years. This article reports the fabrication, characterization, and application of a new kind of poly (allylthiourea-co-acrylic acid) (PAT⁻PAC) hydrogel-based carbon monolith. The results indicated that the poly acrylic acid component can endow the PAT⁻PAC hydrogel with an increased swelling ratio and enhanced thermal stability. During the carbonization process, O⁻H, N⁻H, C=N, and ⁻COO⁻ groups, etc. were found to be partly decomposed, leading to the conjugated C=C double bonds produced and the clear red shift of C=O bonds. Particularly, it was found that this shift was accelerated under higher carbonization temperature, which ultimately resulted in the complex conjugated C=C network with oxygen, nitrogen, and sulfur atoms doped in-situ. The as-obtained carbon monoliths showed good removal capacity for Ni(II) ions, organic solvents, and dyes, respectively. Further analysis indicated that the Ni(II) ion adsorption process could be well described by pseudo-second-order and Freundlich models under our experimental conditions, respectively. The adsorption capacity for Ni(II) ions and paraffin oil was as high as 557 mg/g and 1.75 g/g, respectively. More importantly, the as-obtained carbon monoliths can be recycled and reused for Ni(II) ions, acetone, and paraffin oil removal. In conclusion, the proposed PAT⁻PAC-based carbonaceous monoliths are superior adsorbents for wastewater treatment.

Molecularly Imprinted Polymers for Removal of Metal Ions: An Alternative Treatment Method

Aquatic and terrestrial environment and human health have been seriously threatened with the release of metal-containing wastewater by the rapid growth in the industry. There are various methods which have been used for removal of ions from the environment, such as membrane filtration, ion exchange, membrane assisted liquid extraction and adsorption. As a sort of special innovation, a polymerization technique, namely molecular imprinting is carried out by specific identification for the target by mixing it with a functional monomer. After the polymerization occurred, the target ion can be removed with suitable methods. At the end of this process, specific cavities, namely binding sites, are able to recognize target ions selectively. However, the selectivity of the molecularly imprinted polymer is variable not only because of the type of ligand but also charge, size coordination number, and geometry of the target ion. In this review, metal ion-imprinted polymeric materials that can be applied for metal ion removal from different sources are discussed and exemplified briefly with different metal ions.

Determination of subnanomolar levels of mercury (II) by using a graphite paste electrode modified with MWCNTs and Hg(II)-imprinted polymer nanoparticles

Mercury ion-imprinted polymer nanoparticles (Hg-IP-NPs) were synthesized via precipitation polymerization by using itaconic acid as a functional monomer. A carbon paste electrode was impregnated with the synthesized Hg-IP-NPs and MWCNTs to obtain a highly sensitive and selective electrode for determination of Hg(II). Mercury ion is first accumulated on the electrode surface via an open circuit procedure. After reduction of Hg(II) ions to its metallic form at a negative pre-potential, square wave anodic stripping voltammetry was applied to generate the electrochemical signal. The high affinity of the Hg-IP-NPs for Hg(II) was substantiated by comparing of the signals of electrodes with imprinted and non-imprinted polymer. The beneficial effect of MWCNTs on the voltammetric signal is also demonstrated. Under the optimized conditions and at a typical working potential of +0.05 V (vs. Ag/AgCl), the electrode has a linear response in the 0.1-20 nmol L^-1 Hg(II) concentration range and a 29 pM detection limit. The electrochemical sensitivity is as high as 1441 A·M^-1·cm^-2 which is among the best values known. The electrode was applied to the determination of Hg(II) in water samples. Graphical abstract Schematic representation of the sensor electrode modified with mercury-imprinted polymer nanoparticles, and the recognition and voltammetric determination steps.

Preparation of Palladium(II) Ion-Imprinted Polymeric Nanospheres and Its Removal of Palladium(II) from Aqueous Solution

Three kinds of functional monomers, 4-vinylpridine(4-VP), 2-(allylthio)nicotinic acid(ANA), and 2-Acetamidoacrylic acid(AAA), were used to synthetize palladium(II) ion-imprinted polymeric nanospheres (Pd(II) IIPs) via precipitation-polymerization method in order to study the effects of different functional monomers on the adsorption properties of ion-imprinted materials. The results of UV spectra in order to study the interaction between template ion PdCl₄^2- and functional monomers showed that there were great differences in structure after the template reacted with three functional monomers, 4-VP and ANA caused a large structural change, while AAA basically did not change. Further results on the adsorption performance of Pd(II) IIPs on Pd(II) confirmed 4-VP was the most promising candidate for the synthesis of Pd(II) IIPs with an adsorption capacity of 5.042 mg/g as compared with ANA and AAA. The influence of operating parameters on Pd(II) IIP's performance on Pd(II) adsorption was investigated. There was an increase in the adsorption capacity of Pd(II) IIPs at higher pH, temperature, and initial concentration of Pd(II). The results of multi-metal competitive adsorption experiments showed that Pd(II) IIPs had selectivity for Pd(II). An adsorption equilibrium could be reached at 180 min. Kinetic analysis showed that the adsorption test data fitted best to the pseudo-second order kinetic model, and the theoretical equilibrium adsorption capacity was about 5.085 mg/g. The adsorption isotherms of Pd(II) by Pd(II) IIPs agreed well with the Freundlich equation, suggesting a favorable adsorption reaction under optimal conditions. These results showed that Pd(II) IIPs have potential application in the removal of Pd(II) from aqueous solutions and may provide some information for the selection of functional monomers in the preparation of Pd(II) IIPs.