Metal Capture Research Articles

Site differentiation strategy for selective strontium uptake and elution within an all-inorganic polyoxoniobate framework

Selective uptake and elution of trace amounts of hazardous radioactive 90Sr from large-scale high-level liquid waste (HLW) is crucial for sustainable development. Here, we propose a site differentiation strategy, based on the presence of distinct selective metal capture sites (concavity site and tweezer site) within the giant polyoxoniobate (PONb) nanoclusters of an all-inorganic PONb framework (FZU-1). Through this strategy, FZU-1 can not only effectively remove 98.9% of Sr²⁺ from simulated nuclear liquid waste, performing best among the reported Sr adsorbents, but also achieve desorption of adsorbed Sr²⁺ ions by selectively loading Na⁺ ions, thus enabling the recycling of FZU-1. Based on the well-defined single-crystal structures and theoretical studies, it can be revealed that the rapid and selective uptake of Sr²⁺ is attributed to the strong binding energy between the Sr²⁺ ions and the concavity sites. The effective elution of Sr²⁺, on the other hand, stems from the preferential binding of Na⁺ ions at the tweezer sites, elevating the cluster’s electrostatic potential and indirectly facilitating the elution of Sr²⁺ ions. The exceptional stability of FZU-1, along with its rapid and selective Sr²⁺ capture and elution capabilities, positions it as a promising candidate for large-scale nuclear waste treatment and groundwater remediation applications.

Defect-Engineered MOF-801/Sodium Alginate Aerogel Beads for Boosting Adsorption of Pb(II).

Metal-organic frameworks (MOFs) are attractive adsorbents for heavy metal capture due to their superior stability, easy modification, and adjustable pore size. However, their inherent microporous structure poses challenges in achieving a higher adsorption capacity. Defect engineering is considered a simple method to create hierarchical MOFs with larger pores. Here, we employed l-aspartic acid as a mixed linker to bind Zr4+ clusters in competition with fumaric acid of MOF-801 to create defects, and the pore size was increased from 4.66 to 15.65 nm. Mercaptosuccinic acid was subsequently used as a postexchange ligand to graft the resultant MOF-801 by acid-ammonia condensation to further expand the pore size to 22.73 nm. Notably, the -NH2, -COOH, and -SH groups contributed by these two ligands increased the adsorption sites for Pb(II). The obtained defective MOF-801 with larger pores was thereafter loaded onto sodium alginate to form aerogel beads as adsorbents, and an adsorption capacity of 375.48 mg/g for Pb(II) was achieved, which is ∼51 times that of pristine MOF-801. The aerogel beads also exhibited outstanding reusability with a removal efficiency of ∼90.23% after 5 cycles of use. The adsorption mechanism of Pb(II) included ion-exchange interaction, as well as chelation interactions of Pb-O, Pb-NH2, and Pb-S. The versatile combination of defect engineering and composite beads provides novel inspirations for MOF modification for boosting heavy metal adsorption.

Sorbents Based on Natural Zeolites for Carbon Dioxide Capture and Removal of Heavy Metals from Wastewater: Current Progress and Future Opportunities

This review is dedicated to the potential use of natural zeolites for wastewater treatment and carbon dioxide capture. Zeolites, due to their microporous structure and high surface activity, are used as sorbents. One effective application of zeolites is in wastewater treatment, which leads to the removal of pollutants and improvement in water quality. Zeolites can also be used for carbon dioxide capture, which helps reduce its concentration in the atmosphere and addresses climate change issues. This review examines recent research on the use of natural zeolites for the removal of heavy metals from water and CO2 capture. It explores the broad applications of natural zeolites by understanding their adsorption capabilities and the mechanisms affecting their performance in water purification from heavy metals and CO2 capture.

BioMOF@PAN Mixed Matrix Membranes as Fast and Efficient Adsorbing Materials for Multiple Heavy Metals' Removal.

Heavy metal ions are a common source of water pollution. In this study, two novel membranes with biobased metal-organic frameworks (BioMOFs) embedded in a polyacrylonitrile matrix with tailored porosity were prepared via nonsolvent induced phase separation methods and designed to efficiently adsorb heavy metal ions from oligomineral water. Under optimized preparation conditions, stable membranes with high MOF loading up to 50 wt % and a cocontinuous sponge-like morphology and a high water permeability of 50-60 L m-2 h-1 bar-1 were obtained. The tortuous flow path in combination with a low water flow rate guarantees maximum contact time between the fluid and the MOFs, and thus a high heavy metal capture efficiency in a single pass. The performances of these BioMOF@PAN membranes were investigated in the dynamic regime for the simultaneous removal of Pb2+, Cd2+, and Hg2+ heavy metals from aqueous environments in the presence of common interfering ions. The new composite adsorbing membranes are capable of reducing the concentration of heavy metal pollutants in a single pass and at much higher efficiency than previously reported membranes. The enhanced performance of the mixed matrix membranes is attributed to the presence of multiple recognition sites which densely decorate the BioMOF channels: (i) the thioether groups, deriving from the S-methyl-l-cysteine and (S)-methionine amino acid residues, able to recognize and capture Pb2+ and Hg2+ ions and (ii) the oxygen atoms of the oxamate moieties, which preferentially interact with Cd2+ ions, as revealed by single crystal X-ray diffraction. The flexibility of the pore environments allows these sites to work synergically for the simultaneous capture of different metal ions. The stability of the membranes for a potential regeneration process, a key-factor for the effective feasibility of the process in real life applications, was also evaluated and confirmed less than 1% capacity loss in each cycle.

Bioinspired, Carbohydrate-Containing Polymers Efficiently and Reversibly Sequester Heavy Metals.

Water scarcity and heavy metal pollution are significant challenges in today's industrialized world. Conventional heavy metal remediation methods are often inefficient and energy-intensive, and produce chemical sludge. To address these issues, we developed a bioinspired, carbohydrate-containing polymer system for efficient and selective heavy metal removal. Using ring opening metathesis polymerization, we synthesized polymers bearing amphiphilic glucuronate side chains capable of selectively binding heavy metal cations in mixed media. In samples containing high concentrations of heavy metals (>550 ppb), these polymers rapidly form a filterable precipitate upon metal capture, reducing the concentration of cation to <1.5 ppb within 3 min, as measured by inductively coupled plasma mass spectrometry. This system effectively removes cadmium ions from highly contaminated solutions to levels below the Agency for Toxic Substances and Disease Registry limit for Cd2+ in drinking water and selectively removes both Cd2+ and Pb2+ from lake water spiked with trace amounts of metal. Acidification triggers protonation of the glucuronate groups, releasing the heavy metals and resolubilizing the polymer. This capture-and-release process can be repeated over multiple cycles without loss of binding capacity. As such, this study introduces a novel class of recyclable materials with pH-responsive properties, offering potential for applications in water remediation and beyond.

Simultaneous utilization of copper and non-metals from waste integrated circuits for precious metal melting capture and organics thermal detoxification

Waste integrated circuits, with underlying resource attributes and environmental risks, are complex in composition. Current processes suffer from high resource inputs, excessive pollutant emissions and incomplete treatment of varied species. Therefore, a comprehensive resource recycling and safe disposal process integrated with precious metal enrichment, non-metal resource utilization, and organic detoxification was proposed. The copper and non-metals from waste ICs served as in-situ precious metal collector, slagging former and reducing agent for alternative to partial chemical inputs. Batch experiments indicated that optimized parameters enabled the recycling efficiencies of 94.3 %, 96.8 % and 98.4 % for copper, gold and silver, respectively. Meanwhile, oxide component, yielded as silicate slag, was synthesized into glass ceramics via high-temperature sintering. Furthermore, organic conversion process revealed that high-temperature smelting catalyzed bromine removal and contaminant detoxification, with decomposed reductive hydrocarbons facilitating metal capture in turn. And the capture mechanism was disclosed form thermodynamics and microdroplet motion perspectives. As process evaluation indicates, proposed recycling route allows remarkable reductions in negative environmental response and economic investment. In this work, metal recycling, waste minimization and pollutant detoxification were attained synergistically without residue, which contributes a novel insight into the disposal of comparable e-wastes.

Constructing 2D Polyphenols-Based Crosslinked Networks for Ultrafast and Selective Uranium Extraction from Seawater.

The role of tannins (TA), a well-known abundant and ecologically friendly chelating ligand, in metal capture has long been studied. Different kinds of TA-containing adsorbents are synthesized for uranium capture, while most adsorbents suffer from unfavorable adsorption kinetics. Herein, the design and preparation of a TA-containing 2D crosslinked network adsorbent (TANP) is reported. The ≈1.8-nanometer-thick TANP films curl up into micrometer-scale pores, which contribute to fast mass transfer and full exposure of active sites. The coordination environment of uranyl (UO2 2+) ions is explored by integrated analysis of U L3-edge XANES and EXAFS. Density functional theory calculations indicate the energetically favorable UO2 2+ binding. Consequently, TANP with excellent adsorption kinetics presents a high uranium capture capacity (14.62mg-Ug-Ads-1) and a high adsorption rate (0.97mgg-1day-1) together with excellent selectivity and biofouling resistance. Life cycle assessment and cost analysis demonstrate that TANP has tremendous potential for application in industrial-scale uranium extraction from seawater.

Mycoprotein nanoparticles in agriculture

A32 kDa protein from fungi can be used to produce nanoparticles which might be use as nanofertilisers needed by plants. There are large numbers of fungi which can be used for the efficient synthesis of nanofertiliser particles. Generally, the formation of nanoparticles by fungi involves metal capture, enzymatic reduction and capping on their surface. Metal ions are located either on the outer surface or inside fungal cells and then chemically reduced to nanoparticles in the presence of fungal enzymes. The best way to apply fungus-synthesised nanoparticles/nanofertiliser is to foliage but they can also be applied to soil or through seed soaking. They may also apply through drip, sprinkler, hydroponic, aeroponic and aquaponic. The major effects of nanoparticles as nanofertilisers are on the elevation of antioxidant enzyme activities and photosynthetic pigments. They help to improve in plant tolerance to stresses and defence against pest and diseases after retaining important physiological and biochemical functions. The net results are increased seed germination, vigour index, chlorophyll level, hormonal regulation, photosynthetic rate, electrolytic levels, plant biomass and crop yields. Mycoprotein nanoparticles may alter plant metabolic pathways, regulating energy dissipation, and improved membrane permeability and stability, at the same time as increasing plant health and growth kinetic traits. They are also known to trigger to produce more microbial polysaccharide from polysaccharide secreting fungi that help in soil aggregation, moisture retention, carbon build - up. However, they should be applied only in recommended doses to avoid adverse effects on plant growth and toxicity

Heavy Metal Detection and Removal by Composite Carbon Quantum Dots/Ionomer Membranes.

The combination of ion exchange membranes with carbon quantum dots (CQDs) is a promising field that could lead to significant advances in water treatment. Composite membranes formed by sulfonated poly(ether ether ketone) (SPEEK) with embedded CQDs were used for the detection and removal of heavy metal ions, such as lead and cadmium, from water. SPEEK is responsible for the capture of heavy metals based on the cation exchange mechanism, while CQDs detect their contamination by exhibiting changes in fluorescence. Water-insoluble "red" carbon quantum dots (rCQDs) were synthesized from p-phenylenediamine so that their photoluminescence was shifted from that of the polymer matrix. CQDs and the composites were characterized by several techniques: FTIR, Raman, UV/VIS, photoluminescence, XPS spectroscopies, and AFM microscopy. The heavy metal ion concentration was analyzed by inductively coupled plasma-optical emission spectroscopy (ICP-OES). The concentration ranges were 10.8-0.1 mM for Pb2+ and 10.0-0.27 mM for Cd2+. SPEEK/rCQDs showed a more pronounced turn-off effect for lead. The composite achieved 100% removal efficiency for lead and cadmium when the concentration was below a half of the ion exchange capacity of SPEEK. The regeneration of membranes in 1 M NaCl was also studied. A second order law was effective to describe the kinetics of the process.

Heavy metal application of response surface optimized-lipopeptide biosurfactant produced by Pseudomonas aeruginosa strain CGA-02 in low-cost substrate

Cost-effective methods of biosurfactant production with minimal environmental impact are needed as global demand continues to increase. This study evaluated lipopeptide biosurfactant production in a Pseudomonas aeruginosa strain CGA-02 using a low-cost carbon substrate. The structural properties of the biosurfactant and applicability of the biosurfactant in heavy metal removal were evaluated. Response surface methodology (RSM) involving central composite design (CCD) was used to optimize process parameters to maximize biosurfactant production. The study identified sugar cane molasses and sodium nitrate as carbon and nitrogen sources of choice for bacterial growth and biosurfactant production, with a relatively 2.64-fold increase in biosurfactant yield under optimized conditions. Analysis of the biosurfactant measured a surface tension reduction of water from 72.2 ± 0.26 to 30.5 ± 0.2 mN/m at 40 mg/L critical micelle concentration. GC–MS and FTIR analysis revealed structural properties of the lipopeptide biosurfactant, with fatty acid components predominantly 9-octadecenoic acid (oleic acid), n-hexadecanoic acid, cyclotetrasiloxane and trimyristin, and infrared peaks belonging to amine, carboxyl, nitrile, alkanol, ether and carbonyl groups. Capture of heavy metals using the biosurfactant was evaluated in soil microcosms. Removal rates of 80.47, 100, 77.57, 100, and 97.57% were recorded for As, Pb, Hg, Cd and Cr respectively after 12 weeks of incubation. There was no significant difference (p < 0.05) in the removal efficiency of the biosurfactant and an analogous chemical surfactant, sodium dodecyl sulphate. First and second-order kinetic models described heavy metal removal rates by the biosurfactant. We demonstrate the production of a useful biosurfactant using low-cost waste carbon.

Comprehensive recycling of slag from the smelting of spent automotive catalysts

Spent automotive catalyst is a valuable source of platinum group metals (PGMs), making them crucial secondary resources. Currently, the main process for recovering PGMs from these catalysts is metal capture method. The smelting process would produce a significant amount of residual slags containing various components like SiO2, Al2O3, CaO, Fe2O3, Na2O, as well as high levels of heavy metals including Cr, Pb, and Ni. These slags are considered either solid waste or hazardous waste and usually disposed of in landfills, which can have detrimental effects on the environment. Furthermore, the smelting slags also contain approximately 2–5 % rare earth elements and trace amounts of precious metal elements. In this study, vacuum carbothermal reduction is employed to pretreat the smelting slags. This method not only successfully removes the heavy metal element lead, but also efficiently achieves the recovery of rare earths, and the enrichment of platinum group metals by mineral phase transformation of cerium-zirconium solid solution and in-situ iron capture. The lead removal rate exceeded 99 %, and the grade of precious metals in the enrichment process was approximately 12 times higher than the original material, with a recovery rate more than 90 %. The leaching rate of rare earths also increased from less than 50 % to more than 95 % after vacuum carbothermal reduction. The effect of vacuum carbothermal reduction pretreatment on the smelting slag phase was systematically studied, and the mechanism behind the increasing rare earth leaching rate due to this pretreatment was further analyzed.

Construction of cellulose-based hybrid hydrogel beads containing carbon dots and their high performance in the adsorption and detection of mercury ions in water

Cellulose-based adsorbents have been extensively developed in heavy metal capture and wastewater treatment. However, most of the reported powder adsorbents suffer from the difficulties in recycling due to their small sizes and limitations in detecting the targets for the lack of sensitive sensor moieties in the structure. Accordingly, carbon dots (CDs) were proposed to be encapsulated in cellulosic hydrogel beads to realize the simultaneous detection and adsorption of Hg (II) in water due to their excellent fluorescence sensing performance. Besides, the molding of cellulose was beneficial to its recycling and further reduced the potential environmental risk generated by secondary pollution caused by adsorbent decomposition. In addition, the detection limit of the hydrogel beads towards Hg (II) reached as low as 8.8 × 10−8 M, which was below the mercury effluent standard declared by WHO, exhibiting excellent practicability in Hg (II) detection and water treatment. The maximum adsorption capacity of CB-50 % for Hg (II) was 290.70 mg/g. Moreover, the adsorbent materials also had preeminent stability that the hydrogel beads could maintain sensitive and selective sensing performance towards Hg (II) after 2 months of storage. Additionally, only 3.3% of the CDs leaked out after 2 weeks of immersion in water, ensuring the accuracy of Hg (II) evaluation. Notably, the adsorbent retained over 80% of its original adsorption capacity after five consecutive regeneration cycles, underscoring its robustness and potential for sustainable environmental applications.

Controlled Magnetite Grafted Poly(glycidyl methacrylates) for Heavy Metal Absorption and Recovery via SET-LRP

A versatile magnetite based stringent polymer for effective metal capture was prepared by reacting iron oxide based initiator with glycidyl methacrylate monomer via single-electron transfer living radical polymerization (SET-LRP) technique. The versatile grafted polymer was successfully synthesized by metal catalyzed living radical polymerization using the catalyst system Cu/N,N,N',N'',N'''-pentamethyldiethylenetriamine as the ligand. The structural confirmation of the initiator and the grafted polymer was analyzed by using instrumentation methods such as proton nuclear magnetic resonance spectroscopy, UV-visible, TGA, SEM and gel permeation chromatography for molecular weight measurements. As the polymerization time increased, both the conversion and the molecular weight were observed to increase linearly with time. Narrow dispersed lower polydispersity index (PDI) and dispensable magnetite-g-PGMA was utilized for the extract of toxic lead from the wastewater. Sustained binding was observed due to the presence of epoxide ring in the repeating units of the polymer and recovered by magnetic effect. The material shows good stability as evident by TGA curves and better affinity to toxic lead as observed by UV-visible and SEM techniques.

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.

Pyrolysed sewage sludge for metal(loid) removal and immobilisation in contrasting soils: Exploring variety of risk elements across contamination levels

Efficient treatment of sewage sludge may transform waste into stable materials with minimised hazardous properties ready for secondary use. Pyrolysed sewage sludge, sludgechar, has multiple environmental benefits including contaminant sorption capacity and nutrient recycling. The properties of five sludgechars were tested firstly for adsorption efficiency in laboratory solutions before prospective application to soils. A wide variety of metal(loid)s (As, Cd, Co, Cr, Cu, Ni, Pb, Sb, and Zn) was involved. Secondly, the sludgechars (3 % v/v) were incubated in five soils differing in (multi)-metal(loid) presence and the level of contamination. The main aim was to evaluate the metal(loid) immobilisation potential of the sludgechars for soil remediation. Moreover, nutrient supply was investigated to comprehensively assess the material's benefits for soils. All sludgechars were efficient (up to 100 %) for the removal of metal cations while their efficiency for metal(loid) anions was limited in aqueous solutions. Phosphates and sulphates were identified crucial for metal(loid) capture, based on SEM/EDS, XRD and MINTEQ findings. In soils, important fluctuations were observed for Zn, being partially immobilised by the sludgechars in high-Zntot soils, while partially solubilised in moderate to low-Zntot soils. Moreover, pH showed to be crucial for material stability, metal(loid) adsorption ability and their immobilisation in soils. Although metal(loid) retention was generally low in soils, nutrient enrichment was significant after sludgechar application. Long-term evaluation of the material sorption efficiency, nutrient supply, and ageing in soil environments will be necessary in future studies.

Simultaneous coupling of metal removal and visual detection by nature-inspired polyphenol-amine surface chemistry.

The interplay between polyphenols, amines, and metals has broad implications for surface chemistry, biomaterials, energy storage, and environmental science. Traditionally, polyphenol-amine combinations have been recognized for their ability to form adhesive, material-independent thin layers that offer a diverse range of surface functionalities. Herein, we demonstrate that a coating of tannic acid (TA) and polyethyleneimine (PEI) provides an efficient platform for capturing and monitoring metal ions in water. A unique feature of our PEI/TA-coated microbeads is the 'Detection-Capture' (Detec-Ture) mechanism. The galloyl groups in TA coordinate with Fe(III) ions (capture), initiating their oxidation to gallol-quinone. These oxidized groups subsequently react with PEI amines, leading to the formation of an Fe(II/III)-gallol-PEI network that produces a vivid purple color, thereby enabling visual detection. This mechanism couples metal capture directly with detection, distinguishing our approach from existing studies, which have either solely focused on metal removal or metal detection. The metal capturing capacity of our materials stands at 0.55 mg g-1, comparable to that of established materials like alginate and wollastonite. The detection sensitivity reaches down to 0.5 ppm. Our findings introduce a novel approach to the utility of metal-polyphenol-amine networks, presenting a new class of materials suited for simultaneous metal ion detection and capture in environmental applications.

Heterogeneous Capture and Release of Energy Metals Using Carborane-Tethered Electrodes

Li and U are the only trace metals dissolved in seawater that are proposed to be economical to extract. Both are at very low concentrations (Li (0.17 ppm), U (3.3 ppb)); however, their total content are approximately 10,000 and 1,000 times higher than in land-based reserves, respectively, representing huge untapped resources which could be collected in an environmentally friendly manner. With surging demand for Li-ion batteries for energy storage, it is estimated that current production methods will soon not meet market demands. In addition, low-carbon nuclear energy production is also expected to increase dramatically in many major countries.Previous studies have shown that reduction of the substituted closo-carborane polyhedral cluster, 1,2-L2-C2B10H10, to the nido-carborane, [1,2-L2-C2B10H10]2-, resulted in the rupture of the C–C bond, cage opening, and an increased bite angle, Θ (Scheme). This talk will start by describing how we used this redox-controlled chelation for the selective electrochemical capture and release of UO2 2+ from mixed-metal mixtures mimicking spent nuclear fuel in monophasic and biphasic media (Scheme; M = UO2 2+; L = Ph2PO).1-2 We will then discuss our current efforts to target other metals of energy importance, in particular M = Li+, for seawater extraction by incorporating Li-selective donating groups, L (Scheme). This talk will then focus heavily on our current work on anchoring these carboranes onto electrode surfaces using anchoring groups – e.g., allyl, pyrene, or thiols – for heterogeneous capture and release using galvanostatic charge/discharge cycles. Recent, soon-to-be published results demonstrate the successful application of this redox-controlled chelation for heterogeneous, selective capture of UO2 2+ from mixed-metal mixtures. Keener, M.; Hunt, C.; Carroll, T. G.; Kampel, V.; Dobrovetsky, R.; Hayton, T. W.; Ménard, G. Redox-switchable carboranes for uranium capture and release. Nature 2020, 577, 652-655.Keener, M.; Mattejat, M.; Zheng, S.-L.; Wu, G.; Hayton, T. W.; Ménard, G. Selective electrochemical capture and release of uranyl from aqueous alkali, lanthanide, and actinide mixtures using redox-switchable carboranes. Chem. Sci. 2022, 13, 3369-3374. Figure 1

Rapid and efficient removal of multiple heavy metals from diverse types of water using magnetic biochars derived from antibiotic fermentation residue

Pyrolysis is a promising method to treat antibiotic fermentation residue (AFR), a hazardous waste in China, with the benefits of detoxification and resource recycling. However, the application of the AFR-derived biochar has been limited yet, restricting the use of pyrolysis to treat AFR. Herein, for the first time, we reported the use of magnetic biochars derived from vancomycin fermentation residue to rapidly and efficiently co-adsorb multiple heavy metals from diverse types of water with complex matrices. The biochar prepared at 700 °C (labeled as VBC700) exhibited high affinity and selectivity for multiple heavy metals, especially for Ag(I), Hg(II), Pb(II), and Cu(II). The kinetics for Ag(I), Hg(II), and Pb(II) were ultrafast with an equilibrium time of only 5 min, while those for Cu(II) were relatively slower. The maximum adsorption capacity calculated from the Langmuir model for Ag(I), Hg(II), Pb(II), and Cu(II) reached 177.4, 105.9, 387.1, 124.5 mg/g, respectively, which were superior to much previously reported adsorbents. Impressively, Na(I), K(I), Ca(II), Mg(II), and salinity did not affect the capture of these heavy metals, and thus >99% of Ag(I), Pb(II), and Cu(II) were concurrently removed from complex water matrices including seawater, which has rarely been reported before. Furthermore, VBC700 remained high adsorption performance at pH ≥ 3. The adsorption mechanisms included ion exchange, precipitation, and inner-sphere complexation. Overall, the results demonstrate that VBC700 would be an excellent adsorbent to co-capture multiple heavy metals from diverse types of water, highlighting the feasibility of using pyrolysis to achieve a win-win goal for AFR management and heavy metal pollution control.

Robust nitrogen-rich covalent polymeric networks for ultra-efficient and selective palladium capture under harsh conditions

Selective capture of palladium (Pd) from high-level liquid waste (HLLW) is one of the frontier issues in materials science in order to alleviate the Pd resource scarcity and guarantee the safe disposal of radioactive wastes. However, this task remains a great challenge in HLLW treatment associated with low capacity, poor selectivity, and limited stability of materials in strongly acidic and radioactive environments. Here we conquer this challenge by designing covalent polymeric networks (CPNs) equipped with abundant bidentate (CPN-1) or tridentate (CPN-2) nitrogen-rich moieties as specific nano-traps for Pd(II). These CPNs are constructed through efficient and facile click reactions, among which CPN-1 bearing plentiful pyridinyl-triazolyl moieties sets a new record for Pd(II) uptake capacity (535 mg g−1), notably surpassing all the reported materials for Pd(II) separation from HNO3 solutions to date. Moreover, CPN-1 features additional attractive merits including good reusability, feasible dynamic column separation, outstanding Pd(II) selectivity over 17 coexisting cations, and excellent stability under highly acidic and radioactive conditions, making it highly promising for practical applications. This work provides a facile way to customize CPN adsorbents with superior performance and highlights the great potential of the prepared materials for metal capture applications.

Elucidating influences of defects and thermal treatments on CO2 capture of a Zr-based metal–organic framework

Carbon capture and storage (CCS) technology is currently an essential response to the global warming problem caused by excessive CO2 emissions. Efficient and reproducible adsorbents for flue gas treatment play an important role in CCS technology, and metal–organic frameworks (MOFs) are considered to be ideal candidates by virtue of their designable CO2 sorption sites. However, carbon capture performance evaluation and reproducibility of MOFs still hinder their application promotion in industrial production. In this work, an extended UiO-66-type MOF based on 1,4-naphthalenedicarboxylate, was successfully synthesized in both a near defect-free form (UiO-66N) and a defect-rich form (DUiO-66N), for exploring the influence of crystalline defects and thermal treatments on carbon capture performance. Although powder X-ray diffraction showed that UiO-66N and DUiO-66N possessed the same crystalline phase, transmission electron microscopy, thermalgravimetric analyse and gas/dye sorption confirmed the presence of crystalline defects and the variation of porosity in DUiO-66N. CO2 sorption isotherms and flue gas breakthrough experiments revealed the defect-induced improved carbon capture performance, which was also supported by density functional theory. Meanwhile, the metastability of defects required low thermal treatment temperatures for activation and regeneration thus maintaining the superior carbon capture performance. These findings suggested that in reproducing and evaluating the carbon capture performance of MOFs, it cannot rely only on the global crystalline phase judgment, but needs to identify the local fine structure as well as optimize activation and regeneration conditions.