Removal of uranium(VI) from simulated wastewater by a novel porous membrane based on crosslinked chitosan, UiO-66-NH2 and polyvinyl alcohol

Cellulose acetate @ functionalized UiO-66-COOH as an affordable coating sorbent for the thin-film extraction of biogenic amines followed by HPLC-MS/MS; Application to various cheese and alcohol-free beverages

Biogenic amines are naturally occurring bioactive compounds synthesized by living organisms, playing vital roles in metabolism. High concentrations of these compounds in the human diet can lead to food poisoning. Therefore, it is crucial to measure the biogenic amines content in food samples to guarantee food safety and protect human health. In this study, a thin film dispersive solid phase extraction method combined with high-performance liquid chromatography-tandem mass spectrometry was proposed for the non-derivatization determination of some biogenic amines such as putrescine, cadaverine, histamine, tryptamine, and 2-phenylethylamine in various types of cheese samples and alcohol-free beverages. For this purpose, cellulose acetate functionalized UiO-66 with free COOH deposited on a stainless-steel mesh was effectively applied as an ultra-thin coating sorbent for the extraction and preconcentration of the target analytes. This resulted in an immense surface area containing a low sorbent amount, long lifetime and fast designing that directly extracted the desired analytes from complicated matrices. The developed design can be a reasonable alternative to electrospinning due to low energy consumption, saving time, and being a cost-effective technique. Under optimal conditions, the method provided wide linearity (5.6-1000 ng g-1) with high coefficients of determination, satisfactory extraction recoveries, and low limits of detection (0.7-1.7 ng g-1) and limits of quantification (1.6-5.6 ng g-1) with good precision (relative standard deviation less than 10%). This innovative method is expected to be applicable to the majority of metal-organic frameworks, which accelerates the advancement and utilization of nanomaterials-coated stainless steel.

Recent advances in chitosan-based nanocomposites for adsorption and removal of heavy metal ions

Due to the high concentration of various toxic and dangerous pollutants, industrial effluents have imposed increasing threats. Among the various processes for wastewater treatment, adsorption is widely used due to its simplicity, good treatment efficiency, availability of a wide range of adsorbents, and cost-effectiveness. Chitosan (CS) has received great attention as a pollutant adsorbent due to its low cost and many -OH and -NH2 functional groups that can bind heavy metal ions. However, weaknesses such as sensitivity to pH, low thermal stability and low mechanical strength, limit the application of CS in wastewater treatment. The modification of these functional groups can improve its performance via cross-linking and grafting agents. The porosity and specific surface area of CS in powder form are not ideal, so physical modification of CS via integration with other materials (e.g., metal oxide, zeolite, clay, etc.) leads to the creation of composite materials with improved absorption performance. This review provides reports on the application of CS and its nanocomposites (NCs) for the removal of various heavy metal ions. Synthesis strategy, adsorption mechanism and influencing factors on sorbents for heavy metals are discussed in detail.

Construction of oxime-functionalized PCN-222 based on the directed molecular structure design for recovering uranium from wastewater

The directed construction of productive adsorbents is essential to avoid damaging human health from the harmful radioactive and toxic U(VI)-containing wastewater. Herein, a sort of Zr-based metal organic framework (MOF) called PCN-222 was synthesized and oxime functionalized based on directed molecular structure design to synthesize an efficient adsorbent with antimicrobial activity, named PCN-222-OM, for recovering U(VI) from wastewater. PCN-222-OM unfolded splendid adsorption capacity (403.4 mg·g-1) at pH = 6.0 because of abundant holey structure and mighty chelation for oxime groups with U(VI) ions. PCN-222-OM also exhibited outstanding selectivity and reusability during the adsorption. The XPS spectra authenticated the -NH and oxime groups which revealed a momentous function. Concurrently, PCN-222-OM also possessed good antimicrobial activity, antibiofouling activity, and environmental safety; adequately decreased detrimental repercussions about bacteria and Halamphora on adsorption capacity; and met non-toxic and non-hazardous requirements for the application. The splendid antimicrobial activity and antibiofouling activity perhaps arose from the Zr6(μ3-O)4(μ3-OH)4(H2O)4(OH)4 clusters and rich functional groups within PCN-222-OM. Originally proposed PCN-222-OM was one potentially propitious material to recover U(VI) in wastewater on account of outstanding adsorption capacity, antimicrobial activity, antibiofouling activity, and environmental safety, meanwhile providing a newfangled conception on the construction of peculiar efficient adsorbent.

Green preparation of magnetic ferroferric oxide-polyvinyl alcohol-alginate coated UiO-67 nanospheres: Characterization, adsorption properties and adsorption mechanism of methylene blue

In this paper, a kind of magnetic ferric oxide/polyvinyl alcohol/calcium alginate/UiO-67 (Fe3O4/PVA/CA/UiO-67) nanospheres with homogeneous surface interconnecting structures was prepared by using macromolecular polymer polyvinyl alcohol and sodium alginate as carriers and zirconium organic skeleton as nanocrystals. The properties of magnetic nanospheres were studied by SEM, FT-IR, TGA, XRD, BET, VSM and Zeta potential. The impression of diverse temperatures, MB concentrations, interaction time, pH, and magnetic aerogel sphere dose on MB removal was studied. The optimum adsorption temperature and pH of magnetic nanospheres for MB were 298 K, and 10, respectively. Langmuir simulated that the maximum removal of MB by magnetic nanospheres at room temperature (298 K) was 1371.8 mg/g. The removal of MB by magnetic nanospheres complied with the pseudo-first-order kinetic model. The isotherm simulation can infer that the Langmuir model was more comply with MB adsorption on magnetic aerogel spheres. Thermodynamic studies have confirmed that the removal of MB by magnetic nanospheres was exothermic and spontaneous. The interaction mechanism of MB on magnetic nanospheres can be deduced by FT-IR and BET, including hydrogen bond, π-π bond, electrostatic interaction, and mesoporous pore flow. The removal rate of nanospheres for MB still reached 70.06 % after six cycles.

Highly Selective Extraction of U(VI) from Solutions by Metal Organic Framework-Based Nanomaterials through Sorption, Photochemistry, and Electrochemistry Strategies

With the rapid development of nuclear technology and peaceful utilization of nuclear energy, plentiful U(VI) not only is required to be extracted from solutions for a sustainable nuclear fuel supply but also is inevitably released into the surrounding environment to result in pollution and threaten human health. Thereby, realizing selective extraction of U(VI) from aqueous solutions is crucial for U(VI) pollution control and a sustainable nuclear industry. Metal organic frameworks (MOFs) have gained multidisciplinary attention due to their excellent properties including large specific surface areas, tunable pore structures, easy functionalization, etc. This Review comprehensively summarizes the research progress of MOFs and MOF-based materials on U(VI) removal from aqueous solutions by sorption, photocatalysis, electrocatalysis, membrane separation, etc. The efficient high extraction ability is dependent on the intrinsic properties of MOFs and the techniques used. The removal properties of MOF-based materials as adsorbents, photocatalysts, and electrocatalysts for U(VI) are discussed. Information about the interaction mechanisms between U(VI) and MOF-based materials are analyzed in-depth, including experiments, theoretical calculations, and advanced spectroscopy analysis. The removal properties for U(VI) of various MOF-based materials are assessed through different techniques. Finally, a summary and perspective on the direction and challenges of MOF-based materials and various pollutant removal technologies are proposed to provide some significant information on designing and fabricating MOF-based materials for environmental pollution management.

Electrospun mesh pattern of polyvinyl alcohol/zirconium-based metal-organic framework nanocomposite as a sorbent for extraction of phthalate esters

Herein, an electrospun composite polyvinyl alcohol/zirconium-based metal-organic frameworks (PVA@UiO-66) nanofiber coating was prepared on the surface of stainless steel mesh (SSM) and then utilized as novel sorbent for the extraction of phthalate esters (PEs) in milk and water samples. Gas chromatography equipped with a flame ionization detector (GC-FID) was used for the quantitative determination of extracted analytes. The SSM coated with PVA@UiO-66 was used in a polypropylene syringe to fabricate the solid-phase extraction (SPE) device. The PVA@UiO-66 nanofiber coating was confirmed using X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy analysis (FT-IR), and field emission scanning electron microscopy (FESEM). The effective parameters of the extraction efficiency including volume and type of desorption solvent, sample volume, ionic strength, pH, extraction flow rate, and desorption flow rate were optimized. At the optimal extraction conditions, the calibration plots for phthalate esters were linear within the range of 0.05-100 ng mL-1 and, low detection limits (0.015-0.06 ng mL-1). Finally, this semi-automated SPE was used for the extraction and detection of phthalate esters (PEs) in milk and various environmental real water samples. The results showed good precision with acceptable and satisfactory extraction recovery values ranging from 89.5 to 99.2% and relative standard deviations (RSDs%) ranging from 4.5 to 6.9%.

Preparation of metal organic frameworks modified chitosan composite with high capacity for Hg(II) adsorption

In this study, a novel modified chitosan composite adsorbent (UNCS) was prepared by crosslinking between chitosan and metal organic frameworks (MOFs) material UiO-66-NH₂ using epichlorohydrin as crosslinker. The influence of the prepared conditions was investigated. The structure and morphology of the composite were characterized by FT-IR, XRD, SEM, TGA, BET and zeta potential analysis. Effects of different variables for adsorption of Hg(II) on this adsorbent were explored. The kinetic studies indicated that the adsorption process followed the pseudo-second-order kinetic model and the adsorption equilibrium could be reached within 2 h. The adsorption was mainly controlled by chemical process. Adsorption isothermal studies illustrated that the adsorption fitted Langmuir isotherm model, implying the homogeneous adsorption on the surface of the adsorbent. The adsorbent exhibited high uptake and the maximum capacity from Langmuir model could reach 896.8 mg g^-1 at pH 6. Thermodynamic studies showed the spontaneous nature and exothermic nature of the adsorption process. Additionally, the removal of Hg(II) on UNCS could achieve over 90 %. The adsorption-desorption cycled experiments indicated the appropriate reusability of the adsorbent. Hence, this adsorbent would be promising for the removal of Hg(II) from wastewater.

Microwave-Assisted Synthesis of Porous Composites MOF-Textile for the Protection against Chemical and Nuclear Hazards

Since the emergence of chemical, biological, radiological, and nuclear risks, significant efforts have been made to create efficient personal protection equipment. Recently, metal-organic framework (MOF) materials have emerged as new promising candidates for the capture and degradation of various threats, like chemical warfare agents (CWAs) or radioactive species. Herein, we report a new synthesis method of MOF-textile composites by microwave irradiation, with direct anchoring of MOFs on textiles. The resistance of the composite has been tested using normed abrasion measurements, and non-stable samples were optimized. The protection capacity of the MOF-textile composite has been tested against dimethyl 4-nitrophenyl phosphate, a common CWA simulant, showing short degradation half-life (30 min). Radiological/nuclear protection has also been tested through uranium uptake (up to 15 mg g^-1 adsorbent) and the capture of Kr or Xe gas at 0.9 and 2.9 cm³/g, respectively.

Amidoxime modified Fe3O4@TiO2 particles for antibacterial and efficient uranium extraction from seawater

Uranium extraction and recovery play a critical role in guaranteeing the sustainable nuclear energy supply and protecting the environmental safety. The ideal uranium sorbents possess high adsorption capacity, excellent selectivity and reusability, as well as outstanding antimicrobial property, which are greatly desired for the real application of uranium extraction from seawater. To address this challenge, a novel magnetic core-shell adsorbent was designed and fabricated by a facile method. The obtained amidoximed Fe₃O₄@TiO₂ particles (Fe₃O₄@TiO₂-AO) achieved equilibrium in 2 h and the maximum adsorption capacity calculated from Langmuir model is 217.0 mg/g. The adsorption kinetics followed the pseudo-second-order model. Meanwhile, the Fe₃O₄@TiO₂-AO exhibited great selectivity when competitive metal ions and anions coexisted. In addition, the magnetic Fe₃O₄@TiO₂-AO could be conveniently separated and collected by an external magnetic field, the regeneration efficiency maintained at 78.5% even after ten adsorption-desorption cycles. In natural seawater, the uranium uptake reached 87.5 μg/g in 33 days. Furthermore, the TiO₂ contained adsorbent showed effective photo induced bactericidal properties against both E. coli and S. aureus. The Fe₃O₄@TiO₂-AO with great U(VI) adsorption performance is highly promising in uranium extraction and reclamation.