Developing an efficient single‐atom material (SAM) synthesis and exploring the energy‐related catalytic reaction are important but still challenging. A polymerization–pyrolysis–evaporation (PPE) ...strategy was developed to synthesize N‐doped porous carbon (NPC) with anchored atomically dispersed Fe‐N4 catalytic sites. This material was derived from predesigned bimetallic Zn/Fe polyphthalocyanine. Experiments and calculations demonstrate the formed Fe‐N4 site exhibits superior trifunctional electrocatalytic performance for oxygen reduction, oxygen evolution, and hydrogen evolution reactions. In overall water splitting and rechargeable Zn–air battery devices containing the Fe‐N4 SAs/NPC catalyst, it exhibits high efficiency and extraordinary stability. This current PPE method is a general strategy for preparing M SAs/NPC (M=Co, Ni, Mn), bringing new perspectives for designing various SAMs for catalytic application.
Single‐atom catalyst: A polymerization–pyrolysis–evaporation (PPE) strategy was developed to synthesize N‐doped porous carbon (NPC) with anchored atomically dispersed Fe‐N4 sites. This material is a superior trifunctional catalyst for overall water splitting and Zn–air batteries. The PPE method is a general strategy for preparing M SAs/NPC (M=Fe, Co, Ni, Mn) materials.
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•Phosphoramide functionalized Fe3O4 sorbent was synthesized for uranium extraction.•A maximum sorption capacity of 95.2 mg of U/g of sorbent has been achieved.•>90% uranium extraction ...from tap water, drinking water and sea water was observed.•EXAFS studies suggests that uranium bind with oxygens of three PO group.•Sorbent is low cost having high sorption capacity and requires less contact time.
Phosphoramide functionalized Fe3O4 nanoparticles (NPs) were synthesized by a three step procedure and its application for uranium extraction from different enviornmental matrices has been demonstrated. A maximum adsorption capacity of 95.2 mg of U/g of the sorbent has been achieved which is higher as compared to many reported magnetic NPs. pH dependent adsorption studies were performed at 1 ppm uranium concentrations which suggests more than 80% adsorption in pH range of 4–8 with maximum adsorption at pH 6. Interestingly this is the pH range of most naturally occurring water bodies suggesting the potential of this material to extract uranium from real environmental samples. Adsorption studies were carried out with tap water, drinking water and sea water and more than 90% uranium extraction was observed. Desorption studies were performed with different reagents suggesting that the material can be reused again. EXAFS studies have been carried out which suggests that the uranium binds with oxygens of three PO group at the surface of phosphoramide functionalized NPs and based on this, binding mode of uranium with the synthesized sorbent is proposed.
We report detailed investigations on the synthesis, structural, morphology, electronic/atomic structure and photocatalyst properties of Cu doped TiO2, ZnO and Ni(OH)2 nanostructures. All of the ...samples were synthesized by using the chemical precipitation method. Samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and photocatalyst measurements. XRD studies revealed single phase nature of the samples and omitted the presence of trivial metallic or binary oxide phases. TiO2 set of samples have shown nanorod kind of morphology, however TEM images of ZnO and Ni(OH)2 set of samples depicted the spherical morphology of particles. XANES spectra at the Cu K-edge and Cu L-edge, along with the atomic multiplet calculations, revealed the predominance of Cu2+ ions in all of the samples, within the entire doping range. Ti L-edge and Ti K-edge XANES confirmed the existence of Ti4+ ions in the pure and Cu doped TiO2 samples with anatase local structure. Zn L-edge XANES results confirmed the divalent character of Zn ions in the pure and Cu doped ZnO, which is further validated by the Zn K-edge XANES. Ni L-edge and Ni K-edge XANES conveyed the +2 valence state of Ni ions in the pure and Cu doped Ni (OH)2 samples. EXAFS analysis at the Cu K-edge nullifies the formation of Cu metallic clusters and other trivial phases, suggesting random distribution of Cu atoms in the oxide materials. Though, local atomic arrangement of Cu ions is disparate in the different oxide compounds. As an application of the pure and Cu doped TiO2, ZnO and Ni(OH)2 nanostructures, towards the degradation of water pollutant dyes, we demonstrate that all of the samples can serve as effective photocatalyst materials towards the degradation of methyl orange aqueous pollutant dye under the UV-light irradiation.
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•Pure and Cu doped TiO2, ZnO and Ni(OH)2 photocatalyst were synthesized using co-precipitation method.•XRD, HR-TEM, XANES, EXAFS and photocatalysis measurements were performed.•Presence of Cu2+, Ti4+, Zn2+, Ni2+ ions was confirmed by XANES.•Atomistic local information on the bond length and coordination number was studied by experimental EXAFS and theoretical simulation.•Orbital hybridization of Cu and host metal (Ti, Zn and Ni) leads to superior photocatalyst performance.
The recovery of uranium from wastewater and safe treatment of U(VI)-containing wastewater are of great important to ensure the sustainable development of nuclear-related energy. Although abundant ...studies of U(VI) sorption on various adsorbents have been widely achieved, U(VI) sorption at extreme pH and trace concentration is challenging issues due to limited sorption activity of natural adsorbents. The development of novel materials with highly efficient and excellent selectivity for capturing U(VI) from nuclear-related wastewater and seawater is highly desirable. In this study, amidoxime/carbon nitride (AO/g-C3N4) was fabricated and captured U(VI) under a variety of water chemistry. We demonstrated that AO/g-C3N4 exhibited the high adsorption capacities (312 mg/g at pH 6.8), fast removal equilibrium (>98% at 10 min) and superior selectivity for U(VI) compared with the other radionuclides (e.g., 19.76 mg/g of Cs(I)). In addition, AO/g-C3N4 exhibited the high uranium extraction capacity from natural seawater (9.55 mg/g at saturation time of 5.5 days) compared to vanadium (1.85 mg/g). U(VI) adsorption behavior at different pH can be excellently fitted by the surface complexation modeling with three inner sphere surface complexes (i.e., SOUO2(CO3)23−, SO(UO2)3(OH)50 and SOUO2+ species). According to XPS (X-ray Photoelectron Spectroscopy) analysis, the strong complexation of U(VI) with AO groups retained in C3N4 nanosheet. The split of U-Oeq2 subshell and the occurrence of U–C shell further demonstrated inner-sphere surface complexation by EXAFS (X-Ray Absorption Fine Structure) spectra analyses. These results revealed that the high potential of AO/g-C3N4 materials for selective U(VI) capture from wastewater and seawater.
•The amidoxime/carbon nitride was fabricated and captured U(VI) in solution.•AO/g-C3N4 exhibited the high adsorption capacities and superior selectivity.•U(VI) adsorption behavior could be fitted by the surface complexation modeling.•The strong complexation of U(VI) and AO groups retained in C3N4 nanosheet.
Magnetic biochar composites were successfully fabricated by pyrolysis of siderite and rice husk under N2 condition. The results of a variety of characterization implied magnetic biochar displayed ...porous structures with larger specific surface area. The batch adsorption experiments showed high adsorption properties of magnetic biochar composites toward U(VI) (52.63 mg/g at pH 4.0), whereas U(VI) adsorption was significantly influenced by Na2CO3 and HA. U(VI) adsorbed onto magnetic biochar was reduced to U(IV) by Fe3O4 according to XPS and XANES analyses. In addition, no significant effect of ionic strength of NaCl and EXAFS results, illustrated the inner-sphere surface complexation of U(VI) on magnetic biochar. Owing to the simple synthesis procedure, low cost, high adsorption efficiency, easy separation and environmental friendly, magnetic biochar can be considered as a potential adsorbent for the purification of U(VI)-bearing wastewater in environmental remediation.
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•Magnetic biochar was obtained by pyrolysis the rice husk and siderite.•The magnetic biochar has the advantages of low cost and high efficiency.•The interaction mechanism of U(VI) on magnetic biochar was adsorption and reduction.
A stable site‐isolated mononuclear platinum catalyst with a well‐defined structure is presented. Platinum complexes supported in zeolite KLTL were synthesized from Pt(NH3)4(NO3)2, oxidized at 633 K, ...and used to catalyze CO oxidation. IR and X‐ray absorption spectra and electron micrographs determine the structures and locations of the platinum complexes in the zeolite pores, demonstrate the platinum‐support bonding, and show that the platinum remained site isolated after oxidation and catalysis.
In the right spot: A site‐isolated mononuclear platinum catalyst is supported in the zeolite KLTL with a stable and well‐defined structure. This catalyst was examined spectroscopically and imaged with STEM (see picture) to show locations of the platinum complexes (blue circles) within the zeolite pores.
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•MXene-derived hierarchical titanate nanostructures (HTNs) were prepared by a mild in situ chemical conversion method.•HTNs can efficiently remove Eu(III) with large adsorption ...capacities (more than 200 mg/g).•The ion-exchange behavior of Eu(III) with Na+ or K+ was confirmed.•The exchanged Eu(III) ions were confined in the nanoscale interlayers of HTNs and then immobilized.
Developing versatile materials that rapidly and efficiently adsorb radionuclides is an urgent objective for environmental remediation in response to radioactive contamination. Herein, we report the preparation of hierarchical titanate nanostructures (HTNs) by a in situ chemical conversion strategy using a two-dimensional MXene crystal precursor. These HTNs are very stable and can efficiently remove Eu(III) with large sorption capacities, owing to well-maintained layered structures and abundantly exchangeable guest cations. The replacement of sodium or potassium ions with Eu(III) in HTN interlayers has been confirmed by X-ray diffraction (XRD), photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). The extended X-ray sorption fine structure (EXAFS) results, in combination with density functional theory (DFT) calculations, further indicate that the sequestration of Eu(III) is realized by forming inner-sphere surface complexes in nano-confined space, evidenced by the decrease of Eu-O distances (R) and coordination numbers (N). The finding of the inner-sphere complexation induced by Ti−O/Ti−OH coordination and confinement effect provides new insights into the interaction mechanism between radionuclides and titanates. Given their extraordinary sorption capacity and facile synthesis under mild conditions, these HTNs are promising candidates for the efficient removal of trivalent lanthanides and actinides from aqueous solutions during the cleanup of radioactive pollution in the environment.
Higher affinity of CNFs for Pb(II) than Ni(II) and Cu(II).
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•Inner-sphere complexation dominated sorption Pb(II), Cu(II) and Ni(II) on CNFs.•Pb(II) exhibited greater inhibition of the ...sorption of Cu(II) and Ni(II) on CNFs.•Competitive sorption was predicted quite well by surface complexation modeling.•Sorption of heavy metals on CNFs were covalent bonding by EXAFS analyses.
The competitive sorption of Pb(II), Cu(II) and Ni(II) on the uniform carbonaceous nanofibers (CNFs) was investigated in binary/ternary-metal systems. The pH-dependent sorption of Pb(II), Cu(II) and Ni(II) on CNFs was independent of ionic strength, indicating that inner-sphere surface complexation dominated sorption Pb(II), Cu(II) and Ni(II) on CNFs. The maximum sorption capacities of Pb(II), Cu(II) and Ni(II) on CNFs in single-metal systems at a pH 5.5±0.2 and 25±1°C were 3.84 (795.65mg/g), 3.21 (204.00mg/g) and 2.67 (156.70mg/g)mmol/g, respectively. In equimolar binary/ternary-metal systems, Pb(II) exhibited greater inhibition of the sorption of Cu(II) and Ni(II), demonstrating the stronger affinity of CNFs for Pb(II). The competitive sorption of heavy metals in ternary-metal systems was predicted quite well by surface complexation modeling derived from single-metal data. According to FTIR, XPS and EXAFS analyses, Pb(II), Cu(II) and Ni(II) were specifically adsorbed on CNFs via covalent bonding. These observations should provide an essential start in simultaneous removal of multiple heavy metals from aquatic environments by CNFs, and open the doorways for the application of CNFs.
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•Electrospun PVA/PAA membranes were studied for dynamic adsorption of Pb(II).•Breakthrough curves were dependent on the feed concentration and flow rate.•The dose-response model could ...precisely predict the breakthrough curves.•The column effectively removed lead from tap water by adsorption and filtration.•Molecular-level structure and removal mechanism were revealed by EXAFS analysis.
Poly(vinyl) alcohol/poly(acrylic) acid (PVA/PAA) nanofiber membranes were fabricated using electrospinning and showed good water stability and mechanical strength. Their application in lead (Pb(II)) removal from water was evaluated in a continuous fixed-bed column under varying conditions. The filtration was more efficient with a low feed concentration and low flow rate in terms of the elevated adsorption capacity and better bed utilization efficiency. The dynamic adsorption process was independent of bed height, so the fibers can be used as multilayer membranes in a fixed-bed column. The saturated column material could be regenerated and reused. The breakthrough curves were well fitted with the dose-response model, and the maximum adsorption capacity was 288 mg/g with the initial Pb(II) concentration of 1 mg/L. When tap water was used, the amount of water that can be treated before the effluent reached 15 μg/L increased by three times compared to the treatment of NaCl solutions, and a very high improvement was observed at pH 7 (4.5 L) than pH 5 (2.0 L) in tap water. These differences were further confirmed by the extended X-ray absorption fine structure (EXAFS) spectroscopy, where a decreased coordination number and decreased interatomic distance between Pb and C were observed for tap water. This study provides valuable insights in the application of PVA/PAA nanofiber membranes in a dynamic system for Pb(II) removal, and sheds light on the interatomic behavior between Pb(II) and the nanofiber membranes in a flow-through system.
•Antimony adsorption depended on the Sb species, pH, and the type of iron oxides.•Sb(V) adsorption favored at acidic pH, Sb(III) adsorption optimized in wider pH.•Antimony was adsorbed onto the iron ...oxides by the inner-sphere surface complex.•Bidentate mononuclear (2E) was the dominant form of Sb incorporated into HFO.•XAFS and XPS indicated Sb(III) adsorbed was slowly oxidized to Sb(V).
Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb–Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0–1.9 attributed to bidentate mononuclear edge-sharing (2E) between Sb and HFO.
