In-Situ Fixation of All-Inorganic Mo-Fe-S Clusters for the Highly Selective Removal of Lead(II)

Multifunctional magnetic tags with photocatalytic and enzyme-mimicking properties for constructing a sensitive dual-readout ELISA

ELISA has become the gold standard for detecting harmful substances due to its specific antibody recognition and sensitive enzyme-catalyzed reactions. In this study, multifunctional magnetic Prussian blue nanolabels (MPBNs) were synthesized using a simple gentle two-step method to achieve a dual-readout mode. The MPBNs provide a sensitive colorimetric signal by efficiently catalyzing the oxidation of TMB and exhibit prominent photocatalytic degradation activity towards Rhodamine B (RhB). Supplemented by the quenching effect of oxTMB, the fluorescence was enabled to serve as a sensitive second signal. The magnetic property of the labels facilitates the separation and enrichment of the target, thereby improving sensitivity. Utilizing the versatile MPBNs, the visual limit of detection (vLOD) for Staphylococcus aureus is as low as 100 CFU/mL, with a quantitative analysis range of 102-108 CFU/mL. The introduction of photocatalytic reactions into immunoassay has opened up a new signal response system with strong momentum for development and application.

Selective lead capture using amide-containing COFs: A novel strategy for efficient soil remediation

A critical consideration in the application of phytoremediation to remediate sludge soil contaminated with heavy metals is the potential for leaching risks that prevail prior to the efficient uptake of these metals by plants. The most cost-effective method is to use heavy metal stabilizers with selective adsorption. A novel amide-based COF material (COF-TH) has been synthesized as a heavy metal stabilizer for Pb. COF-TH exhibits significant selectivity for Pb in five-metal-mixed solutions, with a distribution coefficient KD as high as 3279 mL·g-1, which was more than 7.3 times that of other heavy metals. The maximum adsorption capacity of COF-TH for Pb was 189 mg·g-1. The adsorption fitted Langmuir model and intra-particle diffusion model, and satisfied pseudo-second-order kinetic model. The excellent selectivity and adsorption performance originate from the complexation between abundant amide groups and Pb ions. Pot experiments and leaching assays confirm that COF-TH decreased Pb leachate concentrations by 77.8 % without significantly decreasing total phytoextracted amounts of other heavy metals, due to the high selectivity of COF-TH to Pb. Additionally, its positive impact on plant growth and microbial diversity makes it a promising soil remediation agent. This investigation offers a novel approach to mitigate the leaching risk of a specific heavy metal Pb during sludge land application by integrating soil phytoremediation with stabilization techniques.

Facile synthesis of ATTM@ZIF-8 modified pullulan hydrogels for enhanced adsorption of Congo red and malachite green

Efficient capture of dyes from wastewater is of great importance for environmental remediation. Yet constructing adsorbents with satisfactory adsorption efficiency and low cost remains a major challenge. This work reports a simple and scalable method for the fabrication of functionalized porous pullulan hydrogel adsorbent decorated with ATTM@ZIF-8 for the adsorption of congo red (CR) and malachite green (MG). The embedding of ammonium tetrathiomolybdate (ATTM) into the ZIF-8 nanoclusters offered additional adsorption sites and enlarged the pore size of the resulting ATTM@ZIF-8. The homogeneous dispersion of the nanoparticles in the three-dimensional network of polysaccharide gels prevents their agglomeration and thus improves the affinity for dye molecules. The resulting adsorbent AZP-20 at optimized composite ratios exhibits high activity, selectivity, interference resistance, reusability and cytocompatibility in dye adsorption applications, and possesses high removal rate of dye in real water systems. Batch experiments demonstrated that the adsorption rate of AZP-20 for MG and CR was 1645.28 mg g-1 and 680.33 mg g-1, and would be influenced by pH conditions. Adsorption kinetics followed pseudo-second-order model. Adsorption isotherms followed Langmuir model for MG and Freundlich model for CR. The adsorption of dye molecules primarily relied on electrostatic interaction (MG) and π-π stacking interaction (CR). Conclusively, the prepared AZPs adsorbent illuminated good application prospects in the treatment of complex component dye wastewater.

Effective and selective recovery of Au(III) from WPCBs using quaternary phosphonium adsorbent synthesized by adjusting steric hindrance

With the gradual depletion of natural gold ore, waste printed circuit boards (WPCBs) have become one of the most attractive alternatives to gold ore. Here, a series of quaternary phosphonium adsorbents with a large size were successfully synthesized by adjusting the number of functional groups and carbon chain length of functional monomers, which can be used for selective recovery of gold(III) from WPCBs leaching solution. The quaternary phosphonium adsorbent (PS-TEP) prepared by the nucleophilic substitution reaction between triethyl phosphine with the smallest volume and chloromethylated polystyrene (PS-Cl) exhibited the best gold loading capacity (617.90 mg g-1). The adsorption mechanism of gold(III) on PS-TEP surface mainly involves anion exchange between AuCl4- and Cl- in the adsorbent. The charge level of the H atom closest to -CH2-P+ group directly determines the strength of the interaction between the adsorbent and the gold ion. Multiwfn and VMD programs visually confirm the weak interaction between PS-TEP+ and AuCl4-. After 5 adsorption-stripping cycles, the adsorption rate of gold(III) in solution remained at about 99 %. In addition, PS-TEP exhibited good gold(III) selectivity in both simulated and actual WPCBs gold leaching solutions. These results indicate that the large-particle PS-TEP with high capacity is suitable for selective gold recovery from WPCBs leaching solution.

Nano-immuno-conjugates inspired by hydrophilic perovskite fluorescent spheres and magnetic assisted for detection of hepatitis B surface antigen

The rampant hepatitis B virus (HBV) seriously endangers human health, and hepatitis B surface antigen (HBsAg) is its early diagnostic marker. Therefore, it is crucial to construct a fast and highly sensitive HBsAg detection method. Based on high-efficiency magnetic separation technology and fluorescent composite material labelling technology, an accurate, fast and sensitive fluorescent immunosensing system for HBsAg detection was developed. Immunomagnetic beads constructed from carboxyl-functionalized Fe3O4 nanoparticles (Fe3O4-COOH) with excellent magnetic response performance were used as efficient capture carriers for HBsAg. Immunofluorescence composite microspheres constructed based on ultra-stable polystyrene-coated CsPbBr3 perovskite nanocrystals (CPB@PSAA) with high hydrophilic properties, were excellent fluorescent markers for HBsAg. Using this sensitive sandwich fluorescence sensing system a good linear relationship within the range of 0.2-15 ng/mL was established between HBsAg concentration and fluorescence intensity with a limit of detection (LOD) of  0.05 ng/mL. The system obtained satisfactory results when tested on real human serum samples. The magnetic-assisted fluorescence immune-sandwich sensor system has broad application prospects in biomedicine such as rapid and early diagnosis and effective prevention of infectious diseases.

Activated nanosulfur for broad-spectrum heavy metals capture

Current problems of existing heavy metal-removing technologies, especially for nanomaterials-based ones, are typically single metal ion-specific, high-cost and collected difficult. Herein, facile modification of commercial sulfur creates a versatile adsorbent platform to address challenges. The versatile adsorbent can be easily prepared through solvothermal treatment of a saturated commercial sulfur solution, followed by water precipitation on a commercial foam that eliminates the need for separation. Interestingly, the solvothermal treatment endows the resulting nanosulfur with sulfate acid groups (hard Lewis base), sulfur anions (soft base), and sulfite groups (borderline base), promising the coordination of all types of heavy metal ions (Lewis acids). As such, this versatile adsorbent with well-distributed adsorption sites exhibits highly effective heavy metal adsorption capacity towards diverse heavy metal ions for both single-component and multi-component adsorption, including soft, hard, borderline Lewis metal ions, with ultra-high adsorption ability (e.g., 903.79 mg g-1 for Cu2+). These findings highlighted the potential of this low-cost sulfur-based adsorbent to address the arising challenges in ensuring clean water.

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.

Efficient and selective removal of Hg(II) from water using recyclable hierarchical MoS2/Fe3O4 nanocomposites

Developing practical and cost-effective adsorbents with satisfactory mercury (Hg) remediation capability is indispensable for aquatic environment safety and public health. Herein, a recyclable hierarchical MoS₂/Fe₃O₄ nanocomposite (by in-situ growth of MoS₂ nanosheets on the surface of Fe₃O₄ nanospheres) is presented for the selective removal of Hg(II) from aquatic samples. It exhibited high adsorption capacity (∼1923.5 mg g ^-1), fast kinetics (k₂ ∼ 0.56 mg g ^-1 min^-1), broad working pH range (2-11), excellent selectivity (K_d > 1.0 × 10⁷ mL g ^-1), and great reusability (removal efficiency > 90% after 20 cycles). In particular, removal efficiencies of up to ∼97% for different Hg(II) concentrations (10-1000 μg L ^-1) in natural water and industrial effluents confirmed the practicability of MoS₂/Fe₃O₄. The possible mechanism for effective Hg(II) removal was discussed by a series of characterization analyses, which was attributed to the alteration of the MoS₂ structure and the surface coordination of Hg-S. The accessibility of surface sulfur sites and the diffusion of Hg(II) in the solid-liquid system were enhanced due to the advantage of the expanded interlayer spacing (0.96 nm) and the hierarchical structure. This study suggests that MoS₂/Fe₃O₄ is a promising material for Hg(II) removal in actual scenarios and provides a feasible approach by rationally constructing hierarchical structures to promote the practical applications of MoS₂ in sustainable water treatments.

Highly Fluorescent Magnetic ATT-AuNCs@ZIF-8 for All-in-One Detection and Removal of Hg2+: An Ultrasensitive Probe to Evaluate Its Removal Efficiency

The development of multifunctional materials for the synchronous detection and removal of mercury ions (Hg²⁺) is in high demand. Although a few multifunctional materials as a fluorescent indicator and adsorbent have achieved this aim, the feedback of their removal efficiency still depends on other methods. Herein, magnetic Fe₃O₄ nanoparticles (MNPs) and 6-aza-2-thiothymine-protected gold nanoclusters (ATT-AuNCs) were rationally assembled into a zeolitic imidazolate framework 8 (ZIF-8) structure via a one-pot method. The coordination assembly of ATT-AuNCs and ZIF-8 not only strengthened the aurophilic interactions of adjacent ATT-AuNCs but also induced the restriction of intramolecular motion of ATT with a six-membered heterocyclic structure. As a consequence, the fluorescence (FL) quantum yield of MNPs/ATT-AuNCs@ZIF-8 was 12.5-fold higher than that of pristine ATT-AuNCs. Benefiting from the enhanced FL emission, MNPs/ATT-AuNCs@ZIF-8 showed improved sensitivity for Hg²⁺ detection and therefore could evaluate the removal efficiency via FL detection, without relying on another detection method. Additionally, the nanocomposite also displayed a satisfactory removal capability for Hg²⁺, including a short capture time (20 min), a high removal efficiency (>96.9%), and excellent reusability (10 cycles). This work provides an approach for customizing functional nanocomposites to concurrently detect and remove Hg²⁺ with superior performance, especially for high detection sensitivity.

Design of Zr-MOFs by Introducing Multiple Ligands for Efficient and Selective Capturing of Pb(II) from Aqueous Solutions

The existence of lead ions seriously affects the quality of many metal products in metallurgical enterprises. Currently, the various methods of lead-ion removal tried by researchers will affect valuable metals in the removal process, thus resulting in low economic efficiency. In this study, a novel metal-organic framework adsorbent (UiO-FHD) which efficiently and selectively captures lead ions is developed by introducing multiple ligands. The maximum adsorption capacity of lead ions is 433.15 mg/g at pH 5. The adsorption process accords with the pseudo-second-order kinetic and the Langmuir isotherm models at room temperature. Thermodynamic experiments indicate that the removal of Pb(II) is facilitated by appropriate temperature reduction. The performance tests indicate that UiO-FHD maintains a high removal rate of 90.35% for Pb(II) after four consecutive adsorption-desorption cycles. The distribution coefficient of lead ions (26.7 L/g) shows that UiO-FHD has excellent selective adsorption for lead ions. It is revealed that the chelation of the sulfhydryl groups and the electrostatic interaction of the hydroxyl groups are the dominant factors to improve the removal rate of Pb(II) by density functional theory calculations. This study clarifies the value of self-designed novel organic ligands in metal-organic framework materials that selectively capture heavy-metal ions.

Boosting electron transport process over multiple channels induced by S-doped carbon and Fe7S8 NPs interface toward high-efficiency antibiotics removal

The enhancement of electron transport process on multiple channels of C-Fe and C-S-Fe bonds between dual-reaction centres was investigated for stimulating the antibiotics degradation in Fenton-like processes. Herein, multiple channels structure of sulfur-doped carbon coupled Fe₇S₈ cluster through C-Fe bond and C-S-Fe bond was constructed through density functional theory (DFT), and S-doped carbon framework coated Fe₇S₈ nanoparticles (Fe₇S₈/SC) Fenton-like catalyst was prepared through hydrothermal and subsequent sulfuration process. The DFT calculations revealed that electrons are thermodynamically transferred from carbon to iron along both C-Fe and C-S-Fe bonds. The optimized Fe₇S₈/SC catalyst exhibited desirable catalytic property for Fenton-like degradation for various antibiotics, the removal of amoxicillin, norfloxacin, and tetracycline hydrochloride reach 98.9%, 97.8%, and 99.3% respectively within 40 min under neutral pH, and catalyst also demonstrated excellent cycle stability after five runs. The excellent degradation effect of antibiotics by Fenton-like catalyst was attributed to the intensified electron transport process by multiple electron transfer channels between dual reaction centres, making Fe^II easier to regenerate. This study spreads a new route for the enhancement of electron transport process in Fenton-like catalysts by constructing multiple channels.

Photocatalytic removal of organic dye using green synthesized zinc oxide coupled cadmium tungstate nanocomposite under natural solar light irradiation

In this work, zinc oxide coupled cadmium tungstate (ZnO-CT) was prepared as a nano-photocatalyst through a green synthesis route using lemon leaf extract and characterized based on diverse microscopic and spectroscopic techniques. To explore the applicabilties of the prepared nanocomposite (NC), its photocatalytic activity has been investigated against Congo red (CR) dye under natural solar light irradiation conditions. ZnO- CT nano-photocatalyst showcases 97% photocatalytic degradation of the CR after 90 min of natural solar light irradiation with quantum yield of 1.16 × 10^-8 molecules photon^-1. The ZnO-CT NC has shown the enhanced photocatalytic degradation performance against CR when compared to its pristine forms (e.g., ZnO (70%) or CT (44%)). According to the free radical trapping and quenching experiments, the photocatalytic activity of ZnO-CT NC appears to be driven efficiently by superoxide and hydroxyl radicals. The photocatalytic degradation kinetics for CR dye was also studied using the pseudo-first-order, diffusional, and Singh models. The high photocatalytic activity of ZnO-CT NC can be accounted for by the presence of electron-withdrawing functional groups like acids (-COOH) and aldehydes (-CHO) on its surface which helped maintain the prolonged recombination of charge carriers and enhanced stability of ZnO-CT (with moderately low leaching rate of cadmium ions (∼2-5%)).

Turn-on fluorescence determination of sulfide based on site-occupying modulation of MOF-copper nanocluster interaction

A tunable interaction between Fe-MOFs (MIL-53(Fe) and kojic acid (KA)-functional copper nanoclusters (Cu NCs) has been studied. When introducing MIL-53(Fe), the Fe-O bonds can be formed between the KA on the surface of Cu NCs and MIL-53(Fe), which will induce the electron transfer from Cu NCs to MIL-53(Fe) and fluorescence quenching of Cu NCs. By introducing S^2- it occupies the Fe-site of MIL-53(Fe) and impede the interaction between Cu NCs and MIL-53(Fe), rendering a "turn-on" fluorescence signal. Thus, the KA-Cu NC/MIL-53(Fe) pair is designed as fluorescence sensing for S^2-, which displays a low detection limit of 18.6 nM and a wide linear detection range from 0.05 to 5 µM by fitting the fluorescence intensity at maximum wavelength of 500 nm with excitation at 400 nm. It was also applied to monitor S^2- in water samples and food additives with satisfactory results, demonstrating the practicability and reliability of the sensing strategy based on the tuable MOF-Cu NC interactions.

Highly efficient metal-organic frameworks adsorbent for Pd(II) and Au(III) recovery from solutions: Experiment and mechanism

With the boom of modern industry, the demand for precious metals palladium (Pd) and gold (Au) is increasing. However, the discharge of Pd(II) and Au(III) wastewater has caused environmental pollution and shortage of resources. Here, a new metal-organic frameworks adsorbent (MOF-AFH) was synthesized to efficiently separate Pd(II) and Au(III) from the water. The adsorption behavior of Pd(II) and Au(III) was explored at the same time. When gold and palladium are adsorbed separately, the adsorption capacity of gold and palladium is 389.02 mg/g and 191.27 mg/g, respectively. The equilibration time is 3 h. When gold and palladium coexist, the adsorption capacities of Au(III) and Pd(II) are 238.71 and 115.02 mg/g, respectively. The experimental results show that the adsorption of Pd(II) and Au(III) on MOF-AFH is a single-layer chemical adsorption, which is an endothermic process. MOF-AFH has excellent selectivity and after MOF-AFH is repeatedly used 4 times, the removal effect can still reach more than 90%. The adsorption mechanisms include reduction reaction and chelation with N and O-containing functional groups on the adsorbent. There is also electrostatic interaction for Au(III) adsorption. The adsorbent can be used to efficiently recover gold and palladium from wastewater.

Alkynyl functionalized MoS2 mesoporous materials with superb adsorptivity for heavy metal ions

Effective elimination of heavy metal ions from water is an arduous task for their toxic effects to aquatic ecosystem and human health. Herein, a novel alkynyl functionalized molybdenum disulfide (C-MoS₂) is fabricated via mechanochemical method with well interlayered spacing, meso porosity, and high surface area (~211 m²g^-1). Mineral MoS₂ was first peeled mechanically and oxidized in situ to MoS_2-xO_x, and then reduced by ball milling with CaC₂ to form the C-MoS₂ composite. The as-obtained C-MoS₂ shows extraordinary adsorptivity for heavy metal ions, viz. 1194 mg-Hg g^-1 (Hg(NO₃)₂ solution, pH= 5, 303.15 K, equilibrium Hg(II) concentration Ce= 36.9 μg·g^-1, ionic strength I= 17.2 mmolL^-1), and 442.3 mg-Pbg^-1 (Pb(NO₃)₂ solution, pH= 5, 303.15 K, equilibrium Pb(II) concentration Ce= 46.9μgg^-1, I= 5.8 mmolL^-1), respectively, along with excellent recyclability, representing one of the best sorbents till now. The adsorption isotherms of Hg(II) followed the Langmuir model and the adsorption kinetics followed the pseudo-second-order model. The adsorption is an endothermic and entropy driven spontaneous process. The excellent adsorption performance of C-MoS₂ is attributed to its very high S-content, availability, and soft acid-base interaction with mercury and lead anions. The C-MoS₂ is an advanced sorbent for Hg(II) and Pb(II) with excellent adsorption performance and recyclability.

Regulation of the Sulfur Environment in Clusters to Construct a Mn-Sn2S6 Framework for Mercury Bonding

The remarkable chemical activity of metal-sulfur clusters lies in their unique spatial configuration associated with the abundant unsaturated-coordination nature of sulfur sites. Yet, the manipulation of sulfur sites normally requires direct contact with other metal atoms, which inevitably changes the state of the coordinated sulfur. Herein, we facilely construct a Mn-Sn₂S₆ framework by regulating the sulfur environment of the [Sn₂S₆]^4- cluster with metal ions. Mn-Sn₂S₆ showed superior removal performance to gaseous elemental mercury (Hg⁰) at low temperatures (20-60 °C) and exhibited high resistance against SO₂. Moreover, Mn-Sn₂S₆ can completely remove liquid Hg²⁺ ions with low or high concentrations from acid wastewater. In addition, the adsorption capacities of Mn-Sn₂S₆ toward Hg⁰ and Hg²⁺ reached 21.05 and 413.3 mg/g, respectively. The results of physico-chemical characterizations revealed that compared with Cu²⁺, Co²⁺, and Fe²⁺, the moderate regulation of Mn²⁺ led to the special porous spherical structure of Mn-Sn₂S₆ with uniform element distribution, due to the difference of electrode potentials [E^θ(Mn²⁺/Mn) < E^θ(S/S^2-) < E^θ(Sn⁴⁺/Sn²⁺)]. The porous structure was beneficial to Hg⁰ and Hg²⁺ adsorption, and the presence of Mn⁴⁺/Mn³⁺ and S^1- promoted the oxidation of Hg⁰, resulting in stable HgS species. The constructed Mn-Sn₂S₆, thus, is a promising sorbent for both Hg⁰ ang Hg²⁺ removal and provides guidelines for cluster-based materials design and tuning.

Construction of MoS2 nanoarrays and MoO3 nanobelts: Two efficient adsorbents for removal of Pb(II), Au(III) and Methylene Blue

Toxic heavy metal ions, valuable noble metal ions and organic dyes are significant concerns in wastewater treatment. In this work, MoO₃ nanobelts (MoO₃ NBs) prepared by solvothermal method and MoS₂ nanoarrays (MoS₂ NAs) constructed using MoO₃ NBs precursor were proposed to effectively remove heavy/noble metal ions and organic dyes, such as Pb^(II), Au^(III) and Methylene Blue (MB). The two adsorbents exhibited the excellent adsorption capacity towards Pb^(II), Au^(III) and MB. The maximum removal capacity of Pb^(II) and MB on MoO₃ NBs was 684.93 mg/g and 1408 mg/g, respectively, whereas that of Au^(III) and MB on MoS₂ NAs was 1280.2 mg/g and 768 mg/g, respectively. Furthermore, the thermodynamic parameters were calculated from the temperature-dependent curves, suggesting that the removal of Pb^(II) and Au^(III) on both adsorbents was spontaneous and endothermic. The new adsorbents introduced here were high adsorption activity, ease of fabrication, high scalability, good chemical stability, great repeatability and abundant and cheap supply, which were highly attractive for wastewater treatment.

Photothermal-boosted effect of binary CuFe bimetallic magnetic MOF heterojunction for high-performance photo-Fenton degradation of organic pollutants

Overcoming the relatively low catalytic activity and strict acid pH condition of common photo-Fenton reaction is the key to alleviate the serious global burden caused by common organic pollutants. Herein, a binary homologous bimetallic heterojunction of magnetic CuFe₂O₄@MIL-100(Fe, Cu) metal-organic frameworks (MCuFe MOF) with photothermal-boosted photo-Fenton activity is constructed as an ideal practical photo-Fenton catalyst for the degradation of organic pollutants. Through an in-situ derivation strategy, the formed homologous bimetallic heterojunction with binary redox couples can simultaneously improve the visible light harvesting capacity and expedite the separation and transfer of photogenerated electrons/holes pairs, leading to the continuous and rapid circulation of both Fe^III/Fe^II and Cu^II/Cu^I redox couples. Notably, the heterojunction shows intrinsic photo-thermal conversion effect, which is found to be beneficial to boost the photo-Fenton activity. Impressively, MCuFe MOF shows remarkable catalytic performance towards the degradation of various organic pollutants by comprehensively increasing H₂O₂ decomposition efficiency and decreasing the required dosage of MCuFe MOF (0.05 g L^-1) with a wide pH range (3.0-10.0). As such, a photo-Fenton catalyst consisting of binary homologous bimetallic heterojunction is first disclosed, as well as its photothermal-enhanced effect, which is expected to drive great advance in the degradation of organic pollutants for practical applications.

Wood-inspired nanocellulose aerogel adsorbents with excellent selective pollutants capture, superfast adsorption, and easy regeneration

Heavy metal ions can cause a series of hazards to environment and humans. Herein, we developed a wood-inspired nanocellulose aerogel adsorbent with excellent selective capability, superfast adsorption, and easy regeneration. The premise for the design is that the biomimetic honeycomb architecture and specific covalent bonding networks can provide the adsorbent with structural and mechanical integrity yet superfast removal of target contaminants. The as-obtained adsorbent showed the maximum adsorption capacity for Pb(II), Cu(II), Zn(II), Cd(II), and Mn(II) of 571 mg g^-1, 462 mg g^-1, 361 mg g^-1, 263 mg g^-1, and 208 mg g^-1, respectively. The adsorbent could remove Pb(II) species with super-rapid speed (87% and 100% of its equilibrium uptake in 2 min and 10 min, respectively). Furthermore, the adsorption isotherm and kinetics models were in accord with the Langmuir and pseudo-second-order models, indicating that the adsorption behavior was dominated by monolayer chemisorption. The aerogel adsorbent had better affinity for Pb(II) than other coexisting ions in wastewater and could be regenerated for at least five cycles. Such a wood-inspired aerogel adsorbent holds great potential in the application of contaminant cleaning.

CaFu MOF as an efficient adsorbent for simultaneous removal of imidacloprid pesticide and cadmium ions from wastewater

Heavy metal ions and pesticides are the noteworthy toxic substances which must be removed from contaminated water for safeguarding public health. The higher levels of these substances in natural water may adversely affect the human health, climate and the eco-framework. The adsorptive removal of hazardous constituents employing metal organic frameworks has drawn considerable attention of researchers during the last decade. From this point of view, single crystal of calcium fumarate [Ca(C₄H₄O₄)_1.5 (H₂O)(CH₃OH)₂] has been developed and analyzed by single crystal X-ray crystallography which confirmed the formation of 3-D metal organic frameworks (MOFs). The synthesized MOFs was employed for simultaneous adsorptive removal of imidacloprid, a high consumption pesticide, and highly toxic Cd (II) from aqua ecosystem. The effect of variation in experimental conditions such as solution pH, adsorbent dosage, contact time, initial concentration and temperature on adsorption was systematically evaluated. Both the imidacloprid and Cd(II) exhibited maximum adsorption at pH 6.5 and 7.8, respectively. The equilibrium empirical data was fitted into Langmuir, Freundlich and Temkin isotherms. The adsorption capacity of CaFu MOFs was observed to be 467.23 and 781.2 mg g^-1 for imidacloprid and cadmium ions, respectively. The adsorbed pollutants were desorbed from the adsorbent using dilute HCl, and the material was reused for five adsorption-desorption cycles without any appreciable loss of adsorption capacity. Therefore, the 3-D CaFu MOFs could be utilized as a novel material for adsorptive removal of imidacloprid pesticide as well as Cd (II) from wastewater.

Disulfide Cross-Linked Poly(Methacrylic Acid) Iron Oxide Nanoparticles for Efficiently Selective Adsorption of Pb(II) from Aqueous Solutions

The efficient selectivity of heavy metal ions from wastewater is still challenging but gains great public attention in water treatment on a world scale. In this study, the novel disulfide cross-linked poly(methacrylic acid) iron oxide (Fe3O4@S-S/PMAA) nanoparticles with selective adsorption, improved adsorption capability, and economic reusability were designed and prepared for selective adsorption of Pb(II) ions in aqueous solution. In this study, nuclear magnetic resonance, dynamic light scattering, scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry, and thermogravimetric analysis were utilized to study the chemophysical properties of Fe3O4@S-S/PMAA. The effect of different factors on adsorption properties of the Fe3O4@S-S/PMAA nanoparticles for Co(II) and Pb(II) ions in aqueous solution was explored by batch adsorption experiments. For adsorption mechanism investigation, the adsorption of Fe3O4@S-S/PMAA for Co(II) and Pb(II) ions can be better fitted by a pseudo-second-order model, and the adsorption process of Fe3O4@S-S/PMAA for Co(II) and Pb(II) matches well with the Freundlich isotherm equation. Notably, in the adsorption experiments, the Fe3O4@S-S/PMAA nanoparticles were demonstrated to have a maximum adsorption capacity of 48.7 mg·g-1 on Pb(II) ions with a selective adsorption order of Pb2+ > Co2+ > Cd2+ > Ni2+ > Cu2+ > Zn2+ > K+ > Na+ > Mg2+ > Ca2+ in the selective experiments. In the regeneration experiments, the Fe3O4@S-S/PMAA nanoparticles could be easily recovered by desorbing heavy metal ions from the adsorbents with eluents and showed good adsorption capacity for Co(II) and Pb(II) after eight recycles. In brief, compared to other traditional nanoadsorbents, the as-prepared Fe3O4@S-S/PMAA with improved adsorption capability and high regeneration efficiency demonstrated remarkable affinity for adsorption of Pb(II) ions, which will provide a novel technical platform for selective removal of heavy metal ions from actual polluted water.

Recent advances in metal-organic frameworks for pesticide detection and adsorption

The large-scale use of pesticides such as organophosphate pesticides (OPPs) and organochlorine pesticides (OCPs) has led to serious environmental problems worldwide, and their high toxicity could cause serious damage to human health. It is crucial to remove and track them precisely in the environment and food resources. As novel nanomaterials, metal-organic frameworks (MOFs) have attracted significant attention in the fields of adsorption and luminescence sensing due to their rich topology, tunable pore size and shape, high surface area, and abundant active sites. Luminescent metal-organic frameworks (LMOFs) have sprung up as great potential chemical sensors to detect pesticides with fast response, high sensitivity, high selectivity and easy operation. Therefore, in this highlight, we focus on recent progress of MOFs in sensing and adsorbing pesticides, as well as in the possible mechanism of sensing, so as to attract more attention to pesticide detection and adsorption.

Superselective Removal of Lead from Water by Two-Dimensional MoS2 Nanosheets and Layer-Stacked Membranes

Point-of-use (POU) devices with satisfactory lead (Pb²⁺) removal performance are urgently needed in response to recent outbreaks of lead contamination in drinking water. This study experimentally demonstrated the excellent lead removal capability of two-dimensional (2D) MoS₂ nanosheets in aqueous form and as part of a layer-stacked membrane. Among all materials ever reported in the literature, MoS₂ nanosheets exhibit the highest adsorption capacity (740 mg/g), and the strongest selectivity/affinity toward Pb²⁺ with a distribution coefficient K_d that is orders of magnitude higher than that of other lead adsorption materials (5.2 × 10⁷ mL/g). Density functional theory (DFT) simulation was performed to complement experimental measurements and to help understand the adsorption mechanisms. The results confirmed that the cation selectivity of MoS₂ follows the order Pb²⁺ > Cu²⁺ ≫ Cd²⁺ > Zn²⁺, Ni²⁺ > Mg²⁺, K⁺, Ca²⁺. The membrane formed with layer-stacked MoS₂ nanosheets exhibited a high water flux (145 L/m²/h/bar), while effectively decreasing Pb²⁺ concentration in drinking water from a few mg/L to less than 10 μg/L. The removal capacity of the MoS₂ membrane is a few orders of magnitude higher than that of other literature-reported membrane filters. Therefore, the layer-stacked MoS₂ membrane has great potential for POU removal of lead from drinking water.

CTAB-intercalated molybdenum disulfide nanosheets for enhanced simultaneous removal of Cr(VI) and Ni(II) from aqueous solutions

The treatment of heavy metal pollution in aquatic environment, especially the pollution caused by multiple heavy metal ions, has been a growing global concern for decades. To address this problem, it is urgent to explore effective and low cost adsorbents which can remove multiple heavy metal ions simultaneously. Herein, Cr(VI) and Ni(II) removal from water by MoS₂ with widened interlayer spacing was systematically investigated in comparison with pure MoS₂. A series of techniques, including X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area and porosimetry analysis were applied to characterize the nanocomposites. The XRD results confirmed the enlarged interlayer spacing of MoS₂ by intercalating cetyl trimethyl ammonium bromide (CTAB) into the interlamination. The maximum adsorption capacities of Cr(VI) and Ni(II) for MoS₂/CTAB were 79.4 mg g^-1 and 88.3 mg g^-1, respectively. Moreover, a synergistic effect in the simultaneous removal of Cr(VI) and Ni(II) was observed. A new Cr(VI) removal mechanism involving redox reaction between Cr(VI) and Mo(IV) in MoS₂/CTAB was verified. The removal efficiencies of Cr(VI) and Ni(II) still remained high at the end of fifth cycle, indicating that MoS₂/CTAB has a great potential to remove heavy metals from wastewater.

A sustainable and nondestructive method to high-throughput decolor Lycium barbarum L. polysaccharides by graphene-based nano-decoloration

Lycium barbarum L. polysaccharides (LBPs) with outstanding biological activities are of increasing interest. Traditional purification approaches are time-consuming and often involve toxic solvents that destroy the functionality and structure of polysaccharides. Herein, we report a sustainable and nondestructive strategy for purifying LBPs using graphene-based nano-decoloration. The amination of graphene oxide (GO) enables the resulted aminated reduced GO (NH₂-rGO) with abundant sp²-hybridized carbon domains, displaying high adsorption capacity toward pigments in crude polysaccharides. As such, within 5 min, NH₂-rGO can highly effectively and fast to decolor LBPs, with a high decoloration ratio of 98.72% and a high polysaccharides retention ratio of 95.62%. Importantly, compared with traditional decoloration methods, NH₂-rGO is nondestructive toward LBPs and has good reusability. Moreover, it exhibited widespread-use decoloration performance to decolor several common plant species. Overall, our proposed nano-decoloration approach is a general-purpose, sustainable, and nondestructive method to purify LBPs.

Nonprecious bimetallic (Mo, Fe)-N/C nanostructures loaded on PVDF membrane for toxic CrVI reduction from water

Nonprecious bimetallic molybdenum and iron embedded into N-doped carbon (MoFe-NC) hybrids were designed and fabricated by pyrolysis of mixed precursors and then immobilized on poly (vinylidene fluoride) (PVDF) films via a phase inversion process to obtain novel catalytic membranes (MoFe-NC@PVDF) for toxic Cr^VI reduction. The catalytic membranes are highly active for aqueous Cr^VI reduction using formic acid (FA) as a sacrificial electron donor under mild conditions. The results demonstrated that the parameters of synthesis process can efficiently adjust the morphology and textural properties of the as-synthesized MoFe-NC@PVDF membrane, and thus have a significant impact on the catalytic behavior. Cr^VI reduction rates significantly increased with increasing FA concentrations (0.234-0.936 M) and reaction temperature (5-35℃), but declined with the increase of Cr^VI concentrations (5-40 mg/L) and pH values of solution (1.87-4.62). Mo-N_x, Fe-N_x, and C-N_x are the active sites, boosting the dissociation of FA molecules into active H* species for effective catalytic reduction of Cr^VI. The catalytic PVDF membrane exhibited distinct porous structure and numerous interaction sites, which not only stabilized metallic nanoparticles, but also promoted mass transfer across the membrane. This cost-effective catalytic membrane provides a new approach toward the treatment of Cr^VI-containing water.

Copper metal-organic frameworks loaded on chitosan film for the efficient inhibition of bacteria and local infection therapy

Although multiple advanced antibacterial and sterilization materials are available, bacterial infections still remain a big challenge in wound healing as they usually induce serious complications and cannot be thoroughly eliminated. Herein, we report an antibacterial film composed of the naturally derived polysaccharide chitosan (CS) and a copper metal-organic framework (HKUST-1) as a multifunctional platform for antibacterial and local infection therapy applications. As expected, the as-prepared HKUST-1/CS film possessed versatile abilities such as slow release of copper ions and reduced cytotoxicity; moreover, fluorescent staining and morphological changes of the bacteria treated with the HKUST-1/CS film confirmed the antibacterial activity of the fabricated film. Furthermore, in vivo results revealed that the HKUST-1/CS film could simultaneously kill bacteria and promote vessel regeneration; this resulted in an enhanced wound closure rate during the local infection therapy process. Overall, these results highlight that the HKUST-1/CS film exhibits significant potential as a suitable and promising wound dressing.

Removal and Recovery of Heavy Metal Ions by Two-dimensional MoS2 Nanosheets: Performance and Mechanisms

We investigated the removal of heavy metals from water by two-dimensional MoS₂ nanosheets suspended in aqueous solution, and restacked as thin film membranes, respectively. From these studies we elucidated a new heavy metal ion removal mechanism that involves a reduction-oxidation (redox) reaction between heavy metal ions and MoS₂ nanosheets. Ag⁺ was used as a model species and MoS₂ nanosheets were prepared via chemical exfoliation of bulk powder. We found that the Ag⁺ removal capacity of suspended MoS₂ nanosheets was as high as ∼4000 mg/g and adsorption accounted for less than 20% of removal, suggesting the reduction of Ag⁺ to metallic silver as a dominant removal mechanism. Furthermore, we demonstrated that MoS₂ membranes were able to retain a similar high removal capacity, and attribute this capability to the formation of a conductive, permeable multilayer MoS₂ structure, which enables a corrosion-type reaction involving electron transfer from a MoS₂ site inside the membrane (anode) to another site on membrane surface (cathode) where heavy metal ions are reduced to metallic particles. The membrane surface remains active to efficiently recover metallic particles, because the primary oxidation products are soluble, nontoxic molybdate and sulfur species, which do not form an insulating oxide layer to passivate the membrane surface. Therefore, MoS₂ membranes can be used effectively to remove and recover precious heavy metals from wastewater.

Interfacial growth of nitrogen-doped carbon with multi-functional groups on the MoS2 skeleton for efficient Pb(II) removal

Lead(II) is a highly toxic upon accumulation in the human body and a thorough cleanup of this pollutant in water resources has become a rising worldwide concern. In this study, multi-functional nitrogen-doped carbon-MoS₂ (NC-MoS₂) nanohybrid composite was successfully synthesized by a step-by-step approach and applied as an effective heavy metal ions adsorbent. Scanning electron microscopy and energy dispersive X-ray spectrometer analysis presents multilayer irregular nanosheets and reveals the uniform distribution of C, N and O elements in the fabricated nanomaterials, respectively. Powder X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the functionalization of oxygen-containing functional groups arising from the nitrogen-doped carbon. Particularly, the NC-MoS₂ possesses an excellent adsorption capacity (439.09mgg^-1) for Pb(II), which attributes to the integrated physicochemical adsorption resulting from the oxygen-containing functional groups on the surface of nanohybrid composites. The as-prepared NC-MoS₂ exhibits good chemical stability and can be reused 7 times with a slight fading over 80% during cycling, which is essential for its practical applications. All of these demonstrate that NC-MoS₂ can be an efficient material for selectively removal of Pb(II), which suggest its great potential in the utilization of environmental cleanup.