Recognition of Actinides by Siderocalin.

Plain simulations and enhanced sampling unveil a novel siderocalin (Scn) recognition mode for An-Ent (where An = actinides and Ent = enterobactin) complexes and identify a "seesaw" relationship between actinide affinity to Ent and Scn recognition to an An-Ent complex. Electrostatic interactions predominantly govern competitive binding in both processes. Additionally, hydrolysis-induced negative charge, water expulsion-driven entropy, and Ent's conformational adaptability collectively enhance high-affinity recognition.

Computational Comparative Study of the Binding of Americium with N-Donor Ligands.

The accessibility of multiple valence states of americium (Am) inspired redox-based protocols aimed at efficient separation of trivalent Am (Am3+) from trivalent lanthanides (Ln3+) alternative to the traditional liquid-liquid extraction. This requires an extensive understanding of the coordination chemistry of Am in its various accessible valence states in the aqueous phase. In this work, by means of DFT calculations, the coordination of AmIII-VI with five typical N-donor ligands, i.e., terpyridine (tpy), bispyrazinylpyridine (dpp), bistriazinylpyridine (BTP), bistriazinyl bipyridine (BTBP), and bistrazinyl phenanthroline (BTPhen), was studied in terms of energy and topological analysis. The results show that the exchange of aqua ligands of hydrated ions by N-donor ligands is an entropy-driven process and enthalpically unfavorable. Topological analysis suggests a distinct mechanism of BTP to modulate the redox potential of Am(III) in that BTP can assist the relay of the leaving electron of AmIII, while the other N-donor ligands can detain the oxidation of Am by offering their electron instead. This comparative study enriches our understanding of the coordination chemistry of high-valent Am with N-donor ligands and recommends the ligand design toward the modulation of redox potentials of hydrated Am(III) ions.

Hydrologic Connectivity Regulates Riverine N2O Sources and Dynamics.

Indirect nitrous oxide (N2O) emissions from streams and rivers are a poorly constrained term in the global N2O budget. Current models of riverine N2O emissions place a strong focus on denitrification in groundwater and riverine environments as a dominant source of riverine N2O, but do not explicitly consider direct N2O input from terrestrial ecosystems. Here, we combine N2O isotope measurements and spatial stream network modeling to show that terrestrial-aquatic interactions, driven by changing hydrologic connectivity, control the sources and dynamics of riverine N2O in a mesoscale river network within the U.S. Corn Belt. We find that N2O produced from nitrification constituted a substantial fraction (i.e., >30%) of riverine N2O across the entire river network. The delivery of soil-produced N2O to streams was identified as a key mechanism for the high nitrification contribution and potentially accounted for more than 40% of the total riverine emission. This revealed large terrestrial N2O input implies an important climate-N2O feedback mechanism that may enhance riverine N2O emissions under a wetter and warmer climate. Inadequate representation of hydrologic connectivity in observations and modeling of riverine N2O emissions may result in significant underestimations.

Bio-Based Copolyester PEIFT: Enhanced Hydrophilicity, Rigidity, and Applications in Nanofibers.

The raw materials of Poly(ethylene terephthalate) (PET) are derived from petroleum-based resources, which are no sustainable. Therefore, previous researchers introduced biomass-derived 2,5-tetrahydrofurfuryl dimethanol (THFDM) into PET. However, its heat resistance has decreased compared to PET. In this paper, a novel bio-based copolyester, poly(ethylene glycol-co-2,5-tetrahydrofuran dimethanol-co-isosorbide terephthalate) (PEIFT), is prepared by introducing biomass-derived isosorbide (ISB) and THFDM into the PET chains through melting copolymerization process. With the introduction of ISB content, copolyesters' hydrophilicity and rigidity improve. Compared to PET, glass transition temperature (Tg) increases by over 5 °C. In addition, the toughness and spinning performance of PEIFT have also been improved as a result of the addition of THFDM components. The hydrophobicity of PEIFTs electrospinning is greatly improved, with a contact angle exceeding 135°. Finally, due to the good hydrophobicity of PEIFTs nanofibers, they have potential application value in the manufacture of hydrophobic nanofiber and filter films. Given its biomass source and excellent performance, they make it easier to replace materials derived from petroleum.

Structures of multinuclear U(VI) species on the hydroxylated α-SiO2(001) surface: insights from DFT calculations.

Multinuclear U(VI) species may be dominant in aqueous solutions under environmental conditions, while the structures of the multinuclear U(VI) species on mineral surfaces remain unclear. This work reports the structural and bonding properties of the possible surface complexes of three aqueous multinuclear U(VI) species, i.e., (UO2)2(OH)3+, (UO2)2(OH)22+ and (UO2)3(O)(OH)3+, on the hydroxylated α-SiO2(001) surface based on density functional theory (DFT) calculations. The results show that (UO2)2(OH)22+ and (UO2)3(O)(OH)3+ tend to form end-on structures at SiO(H)SiO(H) sites, whereas (UO2)2(OH)3+ prefers a side-on structure at SiO(H)O(H)-SiO(H)O(H) sites. The main driving forces for the formation of the multinuclear U(VI) surface complexes are electrostatic interactions and partially covalent chemical bonds. The Os-2p orbital hybridizes strongly with U-5f and U-6d orbitals, with a decreasing binding strength in the sequence of (UO2)2(OH)3+ > (UO2)2(OH)22+ > (UO2)3(O)(OH)3+ for the adsorption at the same type of surface sites. For the adsorption of the same multinuclear U(VI) species, the binding energy increases with the deprotonation extent of the identical sites. In addition, hydrogen bonds between surface hydroxyls and coordination waters as well as the acyl oxygen of uranyl moieties contribute to the formation of the multinuclear U(VI) surface complexes. The U-5f electron delocalization of far-side U atoms in the end-on structures of (UO2)2(OH)22+ and (UO2)3(O)(OH)3+ surface complexes also contributes slightly to the overall binding energy. Overall, this study provides insights into the adsorption behavior of multinuclear U(VI) on silica.

Deep Potential Molecular Dynamics Study of Propane Oxidative Dehydrogenation.

Oxidative dehydrogenation (ODH) of light alkanes is a key process in the oxidative conversion of alkanes to alkenes, oxygenated hydrocarbons, and COx (x = 1,2). Understanding the underlying mechanisms extensively is crucial to keep the ODH under control for target products, e.g., alkenes rather than COx, with minimal energy consumption, e.g., during the alkene production or maximal energy release, e.g., during combustion. In this work, deep potential (DP), a neural network atomic potential developed in recent years, was employed to conduct large-scale accurate reactive dynamic simulations. The model was trained on a sufficient data set obtained at the density functional theory level. The intricate reaction network was elucidated and organized in the form of a hierarchical network to demonstrate the key features of the ODH mechanisms, including the activation of propane and oxygen, the influence of propyl reaction pathways on the propene selectivity, and the role of rapid H2O2 decomposition for sustainable and efficient ODH reactions. The results indicate the more complex reaction mechanism of propane ODH than that of ethane ODH and are expected to provide insights in the ODH catalyst optimization. In addition, this work represents the first application of deep potential in the ODH mechanistic study and demonstrates the ample advantages of DP in the study of mechanism and dynamics of complex systems.

An Editorial for the Special Issue "Actinoids in Biologic Systems and Catalysis".

The recent few decades witnessed a quick growth in our knowledge in actinoid chemistry, particularly in actinoids' behaviors in catalysis and biologic systems [...].

Single Unit-Cell Layered Bi2 Fe4 O9 Nanosheets: Synthesis, Formation Mechanism, and Anisotropic Thermal Expansion.

As an important multiferroic material, pure and low-dimensional phase-stable bismuth ferrite has wide applications. Herein, one-pot hydrothermal method was used to synthesize bismuth ferrite. Almost pure Bi2 Fe4 O9 , BiFeO3 , and their mixture were successfully obtained by controlling the KOH concentration in the hydrothermal solutions. The as-prepared Bi2 Fe4 O9 products were crystalline with Pbam space group, had nanosheet morphology, and tended to aggregate into nanofloret or random stacking. Each Bi2 Fe4 O9 nanosheet was a single crystal with (001) plane as its exposed surface. Single unit-cell layered Bi2 Fe4 O9 nanosheets had a uniform thickness of 1 nm. The surface energies of various (100), (010), and (001) planes were 3.6-4.0, 5.6-15.1, and 1.7-3.0 J m-2 , respectively, in the Bi2 Fe4 O9 crystal. The formation mechanism and structural model of the as-prepared single unit-cell layered Bi2 Fe4 O9 nanosheets have been given. The growth of Bi2 Fe4 O9 nanosheets was discussed. Thermal analysis showed that the Bi2 Fe4 O9 phase was stable up to 1260 K. The thermal expansion behavior of the Bi2 Fe4 O9 nanosheet was nonlinear. The thermal expansion coefficients of the ultrathin Bi2 Fe4 O9 nanosheets on the a-, b-, c-axes, and on the unit-cell volume V were determined, showing an anisotropic thermal expansion behavior. This study is helpful for the controllable synthesis of ultrathin Bi2 Fe4 O9 nanosheets.

A novel framework integrating AI model and enzymological experiments promotes identification of SARS-CoV-2 3CL protease inhibitors and activity-based probe.

The identification of protein-ligand interaction plays a key role in biochemical research and drug discovery. Although deep learning has recently shown great promise in discovering new drugs, there remains a gap between deep learning-based and experimental approaches. Here, we propose a novel framework, named AIMEE, integrating AI model and enzymological experiments, to identify inhibitors against 3CL protease of SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2), which has taken a significant toll on people across the globe. From a bioactive chemical library, we have conducted two rounds of experiments and identified six novel inhibitors with a hit rate of 29.41%, and four of them showed an IC50 value <3 µM. Moreover, we explored the interpretability of the central model in AIMEE, mapping the deep learning extracted features to the domain knowledge of chemical properties. Based on this knowledge, a commercially available compound was selected and was proven to be an activity-based probe of 3CLpro. This work highlights the great potential of combining deep learning models and biochemical experiments for intelligent iteration and for expanding the boundaries of drug discovery. The code and data are available at https://github.com/SIAT-code/AIMEE.

Chelation Behaviors of 3,4,3-LI(1,2-HOPO) with Lanthanides and Actinides Implicated by Molecular Dynamics Simulations.

The hydroxypyridinone ligand 3,4,3-LI(1,2-HOPO) (denoted as t-HOPO) is a potential chelator agent for decorporation of in vivo actinides (An), while its coordination modes with actinides and the dynamics of the complexes (An(t-HOPO)) in aqueous phase remain unclear. Here, we report molecular dynamics simulations of the complexes with key actinides (Am3+, Cm3+, Th4+, U4+, Np4+, Pu4+) to study their coordination and dynamic behaviors. For comparison, the complexation of the ligand with a ferric ion and key lanthanides (Sm3+, Eu3+, Gd3+) was also studied. The simulations show that the nature of metal ions determines the properties of the complexes. The t-HOPO in the FeIII(t-HOPO)1- complex ion formed a compact and rigid cage to encapsulate the ferric ion, which was hexa-coordinated. Ln3+/An3+ cations were ennea-coordinated with eight ligating oxygen atoms from t-HOPO and one from an aqua ligand, and An4+ cations were deca-coordinated with a second aqua ligand. The t-HOPO shows strong affinity for metal ions (stronger for An4+ than Ln3+/An3+) benefited from its high denticity and its flexible backbone. Meanwhile, the complexes displayed different dynamic flexibilities, with the AnIV(t-HOPO) complexes more significant than the others, and in the AnIV(t-HOPO) complexes, the fluctuation of the t-HOPO ligand was highly correlated with that of the eight ligating O atoms. This is attributed to the more compact conformation of the ligand, which raises backbone tension, and the competition of the aqua ligand against the t-HOPO ligand in coordinating with the tetravalent actinides. This work enriches our understanding on the structures and conformational dynamics of the complexes of actinides with t-HOPO and is expected to benefit the design of HOPO analogues for actinide sequestering.

Rigidity and Flexibility: Unraveling the Role of Fulvic Acid in Uranyl Sorption on Graphene Oxide Using Molecular Dynamics Simulations.

Using molecular dynamics simulations, this work targets a molecular understanding on the rigidity and flexibility of fulvic acid (FA) in uranyl sorption on graphene oxide (GO). The simulations demonstrated that both rigid Wang's FA (WFA) and flexible Suwannee River FA (SRFA) can provide multiple sites to cooperate with GO for uranyl sorption and act as "bridges" to connect uranyl and GO to form GO-FA-U (type B) ternary surface complexes. The presence of flexible SRFA was more beneficial to uranyl sorption on GO. The interactions of WFA and SRFA with uranyl were primarily driven by electrostatics, and the electrostatic interaction of SRFA-uranyl was significantly stronger owing to the formation of more complexes. The flexible SRFA could markedly enhance the bonding strength of uranyl with GO by folding itself to provide more sites to coordinate with uranyl. The rigid WFAs tended to be adsorbed on the GO surface in parallel due to π-π interactions, whereas the flexible SRFAs took more slant configurations resulting from intermolecular hydrogen bonds. This work provides new insights into the sorption dynamics, structure, and mechanism and addresses the effect of molecular rigidity and flexibility, with great significance for FA-based remediation strategies of uranium-contaminated sites.

Toward Integrating EBPR and the Short-Cut Nitrogen Removal Process in a One-Stage System for Treating High-Strength Wastewater.

Enhanced biological phosphorus removal (EBPR) is an economical and sustainable process for phosphorus removal from wastewater. Despite the widespread application of EBPR for low-strength domestic wastewater treatment, limited investigations have been conducted to apply EBPR to the high-strength wastewaters, particularly, the integration of EBPR and the short-cut nitrogen removal process in the one-stage system remains challenging. Herein, we reported a novel proof-of-concept demonstration of integrating EBPR and nitritation (oxidation of ammonium to nitrite) in a one-stage sequencing batch reactor to achieve simultaneous high-strength phosphorus and short-cut nitrogen removal. Excellent EBPR performance of effluent 0.8 ± 1.0 mg P/L and >99% removal efficiency was achieved fed with synthetic high-strength phosphorus wastewater. Long-term sludge acclimation proved that the dominant polyphosphate accumulating organisms (PAOs), Candidatus Accumulibacter, could evolve to a specific subtype that can tolerate the nitrite inhibition as revealed by operational taxonomic unit (OTU)-based oligotyping analysis. The EBPR kinetic and stoichiometric evaluations combined with the amplicon sequencing proved that the Candidatus Competibacter, as the dominant glycogen accumulating organisms (GAOs), could well coexist with PAOs (15.3-24.9% and 14.2-33.1%, respectively) and did not deteriorate the EBPR performance. The nitrification activity assessment, amplicon sequencing, and functional-based gene marker quantification verified that the unexpected nitrite accumulation (10.7-21.0 mg N/L) in the high-strength EBPR system was likely caused by the nitritation process, in which the nitrite-oxidizing bacteria (NOB) were successfully out-selected (<0.1% relative abundance). We hypothesized that the introduction of the anaerobic phase with high VFA concentrations could be the potential selection force for achieving nitritation based on the literature review and our preliminary batch tests. This study sheds light on developing a new feasible technical route for integrating EBPR with short-cut nitrogen removal for efficient high-strength wastewater treatment.

The contribution of wetland plant litter to soil carbon pool: Decomposition rates and priming effects.

Plant litter input is an important driver of soil/sediment organic carbon (SOC) turnover. A large number of studies have targeted litter-derived C input tracing at a global level. However, little is known about how litter carbon (C) input via various plant tissues affects SOC accumulation and mineralization. Here, we conducted laboratory incubation to investigate the effects of leaf litter and stem litter input on SOC dynamics using the natural 13C isotope technique. A 122-day laboratory incubation period showed that litter input facilitated SOC accumulation. Leaf and stem litter inputs increased soil total organic carbon content by 37.6% and 15.5%, respectively. Leaf litter input had a higher contribution to SOC accumulation than stem litter input. Throughout the incubation period, the δ13C values of stem litter and leaf litter increased by 1.5‰ and 3.3‰, respectively, while δ13CO2 derived from stem litter and δ13CO2 derived from leaf litter decreased by 4.2‰ and 6.1‰, respectively, suggesting that the magnitude of δ13C in litter and δ13CO2 shifts varied, depending on litter tissues. The cumulative CO2-C emissions of leaf litter input treatments were 27.56%-42.47% higher than those of the stem litter input treatments, and thus leaf litter input promoted SOC mineralization more than stem litter input. Moreover, the proportion of increased CO2-C emissions to cumulative CO2-C emissions (57.18%-92.12%) was greater than the proportion of litter C input to total C (18.7%-36.8%), indicating that litter input could stimulate native SOC mineralization, which offsets litter-derived C in the soil. Overall, litter input caused a net increase in SOC accumulation, but it also accelerated the loss of native SOC. These findings provide a reliable basis for assessing SOC stability and net C sink capacity in wetlands.

Effect of return activated sludge diversion ratio on phosphorus removal performance in side-stream enhanced biological phosphorus removal (S2EBPR) process.

In this study, a lab-scale continuous flow side-stream enhanced biological phosphorus (P) removal (S2EBPR) reactor was operated for 247 days treating synthetic wastewater with influent carbon to phosphorus (C/P) ratio of 25.0 g COD/g P and influent PO43--P of 7.4 ± 0.3 mg P/L. The effect of the return activated sludge (RAS) diversion ratio on S2EBPR reactor was investigated by comparing P removal performance, microbial activity, and community structure. The results showed that the RAS diversion ratio of 8.0%, by yielding a side-stream sludge retention time (SRTSS) of ∼60 h, resulted in the lowest effluent PO43--P concentration of 0.5 ± 0.3 mg P/L. The results of in situ process profiles and ex situ P release and uptake batch tests under different RAS diversion conditions showed that the more anaerobic P release was obtained in the side-stream reactor, the higher the P removal efficiency and EBPR activity were achieved. The stoichiometric ratios observed in EBPR activity tests indicated a polyphosphate accumulating organisms (PAOs) metabolism mainly dependent on the glycolysis pathway. The results of microbial ecology analysis revealed that the optimized SRTSS would give a competitive advantage to PAOs in the S2EBPR process. By obtaining statistically reliable results, this study would provide guidance for wastewater treatment plants to achieve optimal P removal performance in S2EBPR configuration.

Treated wastewater and weak removal mechanisms enhance nitrate pollution in metropolitan rivers.

The focus of urban water environment renovation has shifted to high nitrate (NO3-) load. Nitrate input and nitrogen conversion are responsible for the continuous increase in nitrate levels in urban rivers. This study utilized nitrate stable isotopes (δ15N-NO3- and δ18O-NO3-) to investigate NO3- sources and transformation processes in Suzhou Creek, located in Shanghai. The results demonstrated that NO3- was the most common form of dissolved inorganic nitrogen (DIN), accounting for 66 ± 14% of total DIN with a mean value of 1.86 ± 0.85 mg L-1. The δ15N-NO3- and δ18O-NO3- values ranged from 5.72 to 12.42‰ (mean value: 8.38 ± 1.54‰) and -5.01 to 10.39‰ (mean value: 0.58 ± 1.76‰), respectively. Based on isotopic evidence, the river received a significant amount of nitrate through direct exogenous input and sewage ammonium nitrification, while nitrate removal (denitrification) was insignificant, resulting in nitrate accumulation. Analysis using the MixSIAR model revealed that treated wastewater (68.3 ± 9.7%), soil nitrogen (15.7 ± 4.8%) and nitrogen fertilizer (15.5 ± 4.9%) were the main sources of NO3- in rivers. Despite the fact that Shanghai's urban domestic sewage recovery rate has reached 92%, reducing nitrate concentrations in treated wastewater is crucial for addressing nitrogen pollution in urban rivers. Additional efforts are needed to upgrade urban sewage treatment during low flow periods and/or in the main stream, and to control non-point sources of nitrate, such as soil nitrogen and nitrogen fertilizer, during high flow periods and/or tributaries. This research provides insights into NO3- sources and transformations, and serves as a scientific basis for controlling NO3- in urban rivers.

Effects of organic substrates on sulfate-reducing microcosms treating acid mine drainage: Performance dynamics and microbial community comparison.

Bioremediation techniques utilizing sulfate-reducing bacteria (SRB) for acid mine drainage (AMD) treatment have attracted growing attention in recent years, yet substrate bioavailability for SRB is a key factor influencing treatment effectiveness and long-term stability. This study investigated the effects of external organic substrates, including four complex organic wastes (i.e., sugarcane bagasse, straw compost, shrimp shell (SS), and crab shell (CS)) and a small-molecule organic acid (i.e., propionate), on AMD removal performance and associated microbial communities during the 30-day operation of sulfate-reducing microcosms. The results showed that the pH values increased in all five microcosms, while CS exhibited the highest neutralization ability and a maximum alkalinity generation of 1507 mg/L (as CaCO3). Sulfate reduction was more effective in SS and CS microcosms, with sulfate removal efficiencies of 95.6% and 86.0%, respectively. All sulfate-reducing microcosms could remove heavy metals to different degrees, with the highest removal rate of >99.0% observed for aluminum. The removal efficiency of manganese, the most recalcitrant metal, was the highest (96%) in the CS microcosm. Correspondingly, SRB was more abundant in the CS and SS microcosms as revealed by sequencing analysis, while Desulfotomaculum was the dominant SRB in the CS microcosm, accounting for 10.8% of total effective bacterial sequences. Higher abundances of functional genes involved in fermentation and sulfur cycle were identified in CS and SS microcosms. This study suggests that complex organic wastes such as CS and SS could create and maintain preferable micro-environments for active growth and metabolism of functional microorganisms, thus offering a cost-efficient, stable, and environmental-friendly solution for AMD treatment and management.

Sulfur-decorated Fe/C composite synthesized from MIL-88A(Fe) for peroxymonosulfate activation towards tetracycline degradation: Multiple active sites and non-radical pathway dominated mechanism.

Peroxymonosulfate (PMS)-mediated advanced oxidation processes gain growing attention in degrading antibiotics (e.g., tetracycline (TC)) in wastewater for their high capacity and relatively low cost, while designing efficient catalysts for PMS activation remains a challenge. In this study, a sulfur-doped Fe/C catalyst (Fe@C-S) synthesized from iron metal-organic frameworks (Fe-MOFs) was developed for PMS activation towards TC removal. Under optimal conditions, the TC removal efficiency of Fe@C-S150/PMS system within 40 min was 91.2%. Meanwhile, the k value for Fe@C-S150/PMS system (0.2038 min-1) was 3.36-fold as high as the S-free Fe@C-based PMS system. Also, Fe@C-S150/PMS system showed high robustness in different water matrices. Further studies found that the TC degradation mechanism was mainly ascribed to the non-radical pathway (1O2 and electron transfer). Fe nanoparticles, S and CO groups on the catalyst all participated in the generation of reactive oxygen species (ROS). Besides, S species could enhance the Fe2+/Fe3+ redox cycle and accelerate the electron transfer process. This work highlights the critical role of S in enhancing the catalytic performance of Fe/C-based catalysts for PMS activation, which would provide meaningful insights into the design of high-performance PMS activators for the sustainable remediation of emerging contaminants-polluted water bodies.

Recent Advances in the Study of Trivalent Lanthanides and Actinides by Phosphinic and Thiophosphinic Ligands in Condensed Phases.

The separation of trivalent actinides and lanthanides is a key step in the sustainable development of nuclear energy, and it is currently mainly realized via liquid-liquid extraction techniques. The underlying mechanism is complicated and remains ambiguous, which hinders the further development of extraction. Herein, to better understand the mechanism of the extraction, the contributing factors for the extraction are discussed (specifically, the sulfur-donating ligand, Cyanex301) by combing molecular dynamics simulations and experiments. This work is expected to contribute to improve our systematic understanding on a molecular scale of the extraction of lanthanides and actinides, and to assist in the extensive studies on the design and optimization of novel ligands with improved performance.

Biphasic Behaviors of Nd3+ Bound with Cyanex272, Cyanex301, and Cyanex302: A Molecular Dynamics Simulation Study.

By means of molecular dynamics simulations, this work addresses the conformational flexibility and migration of trivalent neodymium (Nd3+) coordinated with three or six titled (thio)phosphinic ligands and shows that the fluxionality of the complexes enables them to adapt to the solvent environment during the migration. Cyanex272 forms a more compact complex than the other two types of ligands and screens more significantly the interaction between the water solvent and the metal ion in the complex, which weakens the detainment of the aqueous environment. This results in faster motion of the Nd(C272)3 complex both in its translation and rotation than the other complexes when migrating to the organic phase and wins over the other two ligands in transporting the metal ions from the aqueous phase to the organic phase. Depending on the solvent environment, these complexes may take two types of conformations to balance the forces from the environment benefited from their fluxionality. The migration of the M:L = 1:6 complexes, Nd[H(C272)2]3 and Nd[H(C301)2]3, was also investigated. The rich presence of the alkyl groups in the complexes screens the influence of the aqueous environment and benefits the transportation of metal ions to the interface. This work is expected to contribute to the community of inorganic chemistry interested in the coordination chemistry of metal ions and their behaviors in the condensed phase.

The Speciation of Americium Cations in Neat Water Implicated from DFT Studies.

The recent observed manipulatable redox potential of trivalent americium ion in the aqueous phase by modifying an electrode offers an alternative to accomplish the separation. In order to understand extensively the speciation of Am, which is the prerequisite to understanding the mechanism of the oxidation of Am, we conducted a density functional study to identify the potential species of Am in its tri-, tetra-, and pentavalent states in aqueous phase. Based on the speciation analysis, the calculations implicate a stepwise mechanism for the oxidation of hydrated Am(III), which predominantly exists in its hydrated monatomic cationic form (Am3+(aq)). The two sequential one-electron oxidation processes first produce AmO2+(aq), which may establish an equilibrium with Am4+(aq), and the AmO2+(aq) may then evolve to the dioxo americyl(V) ion. These results suggest the copresence of Am4+(aq) and AmO2+(aq), which builds a bridge for the conversion of americium ion from a monatomic ion to dioxo americyl(V).