Distribution Of Adsorption Sites Research Articles

Entrapment and Reactivation of Polysulfides in Conductive Amphiphilic Covalent Organic Frameworks Enabling Superior Capacity and Stability of Lithium-Sulfur Batteries.

Inhibiting the shuttle of polysulfides is of great significance for promoting the practical application of lithium-sulfur batteries (LSBs). Here, an imine-linked covalent organic framework@carbon nanotube (COF@CNT) interlayer composed of triazine and boroxine rings is constructed between the sulfur cathode and the separator for polysulfides reception and reutilization. The introduction of CNT imparts the conductor characteristic to the interlayer attributed to electron tunneling in thin COF shell, and creates a hierarchical porous architecture for accommodating polysulfides. The uniform distribution of amphiphilic adsorption sites in COF microporous structure not only enables efficient entrapment of polysulfides while allowing the penetration of Li+ ions, but also provides a stable electrocatalytic channel for bidirectional conversion of active sulfur to achieve the substantially improved capacity and stability. The interlayer-incorporated LSBs deliver an ultrahigh capacity of 1446mAg-1 at 0.1C and an ultralow capacity decay rate of 0.019% at 1C over 1500 cycles. Even at an electrolyte/sulfur ratio of 6µLmg-1, an outstanding capacity of 995mAhg-1 and capacity retention of 74.1% over 200 cycles at 0.2C are obtained. This work offers a compelling polysulfides entrapment and reactivation strategy for stimulating the study on ultra-stable LSBs.

K+ doped graphitic carbon nitride modified layered double oxide nanocomposite towards high-efficiency CO2 adsorption at intermediate temperature

As a novel medium-temperature CO2 adsorbent, K+ doped and graphitic carbon nitride modified layered double oxide composite (xK/CN-LDO, x = 15, 20, and 25 wt%) were prepared via in-situ synthesis and impregnation methods. Their adsorption performance was evaluated by thermal gravimetric analyzer. g-C3N4-modified LDO (CN-LDO) exhibited a CO2 adsorption capacity of 0.46 mmol/g, 1.39 times higher than the 0.33 mmol/g observed for LDO. This enhancement was attributed to the increased specific surface area and the exposure of additional extractable sites. Further doping with K significantly enhanced the adsorption uptake of xK/CN-LDO. Notably, 20 K/CN-LDO achieved the highest CO2 adsorption uptake of 0.82 mmol/g, representing a 2.48-fold increase compared to LDO. This further enhancement can be ascribed to K's ability to alter the distribution of chemical adsorption sites, thereby providing an optimal number of basic sites. In-situ DRIFTS analysis revealed that CO2 predominantly existed in the form of carbonate species, while adsorption kinetics studies show that the dominant mechanism is chemical adsorption, with external diffusion being the primary adsorption process. Furthermore, 20 K/CN-LDO exhibited significantly higher regeneration efficiency of 72.4 % after 10 cycles, showcasing its promising practical prospects for application in the SEWGS process.

Enhanced low-concentration phosphate adsorption using magnetic UiO-66@Fe3O4 composite with potential linker exchange

A magnetic FenUiO-66 adsorbent was created to achieve high phosphate adsorption capacity. The incorporation of Fe3O4 facilitated the precipitation and growth of UiO-66 during crystallization, resulting in a shift towards a multilayer heterogeneous distribution of adsorption sites. The increased Fe3O4 content notably enhanced the magnetic properties of FenUiO-66, while negligibly affecting its adsorption performance. The Fe1.5UiO-66 demonstrated exceptional phosphate adsorption capacity (136.54 mg/g), outstanding selectivity, and sustained reusability, with an 80% removal efficiency after nine cycles of treating actual water. The mechanism of phosphate adsorption by FenUiO-66 involved electrostatic attraction, ligand exchange, and linker exchange. Notably, while linker exchange significantly contributed to high adsorption capacity, it resulted in irreversible damage to the FenUiO-66 crystal. These unequivocal findings will serve as a solid foundation for further research and underline the critical role of linkers in the process of phosphate adsorption.

Phosphorous recovery from sewage effluent by vanadium-substituted composite synthesized via reverse coprecipitation route

MgFe2O4/MgO (S-sample) and a novel V-modified MgFe2O4/MgO (V-sample) nanocomposites were successfully synthesized using the reverse coprecipitation method and were carefully characterized by X-ray diffractometry, Infrared and 57Fe Mössbauer spectroscopies, magnetization, electron microscopy (both transmission and scanning) and surface area analysis to comprehend their structural, morphological, hyperfine and magnetic properties before and after P adsorptions. MgFe2O4 and V-modified MgFe2O4 phases (with 30 nm average in “diameter”) govern the nanocomposite magnetic properties and these phases are chemically stable in phosphate-rich effluents. 50 nm in size MgO phase is responsible for P adsorption, but it showed chemical corrosion, as suggested by surface analysis. Adsorption kinetic revealed that there are two controlling steps: film and intraparticle diffusion. The nanocomposite materials fitted better to the Freundlich isotherm model, indicating that the adsorption site distribution for P is heterogeneous, and a multilayer adsorption mechanism is favored. Multicycle reuse experiments with secondary sewage effluent were performed, and the adsorption capability of the V-sample over 3 consecutive adsorption cycles was 11 mg g−1, a value 30 % higher than that found for the S-sample. The desorption efficiency of the V-sample was about 97 %, while the S-sample reached 76 %. The V-substituted composite is a promising nanoadsorbent for water remediation process in phosphate-rich effluents and should be also tested in remediation of other contaminants.

Synthesis of hydroxyapatite/activated carbon composite with bioactivity property and copper ion removal efficiency

Hydroxyapatite/activated carbon composite (HAP/AC) was synthesized via a one-pot method for an adsorption removal of copper ions (Cu2+) in water. The surface area, average pore size and pore volume of HAP/AC were found to be 296.41 m2 g−1, 3.5929 nm and 0.1509 cm3 g−1, respectively. The HAP/AC showed the Cu2+ removal efficiency of 99.68 % with the adsorption capacity of 299.05 mg g−1 at the initial concentration of 300 mg L−1, 50 °C and pH 5. The adsorption capacity of HAC/AC was higher than that of HAP and bare AC. The interaction between Cu2+ and HAP/AC adsorbent was suggested to be complexation, cation exchange, and electrostatic interaction. The adsorption followed the Freundlich isotherm model, indicating a non-uniform distribution of adsorption sites that led to multilayer adsorption with various binding energies. The adsorption kinetics fit well with the Pseudo-second order model with the amount of Cu2+ ions adsorbed at an equilibrium of 357.14 mgg−1. Thermodynamic studies indicated that the adsorption was spontaneous and endothermic with an increase in the randomness at the solid-liquid interface. In addition, the bioactivity test of HAC/AC showed that the growth of the newly-formed apatite increased with soaking time, demonstrating its potential in orthopedic implantology.

The impact of hydroxyapatite crystal structures and protein interactions on bone's mechanical properties

Hydroxyapatite (HAP) constitutes the primary mineral component of bones, and its crystal structure, along with the surface interaction with proteins, significantly influences the outstanding mechanical properties of bone. This study focuses on natural hydroxyapatite, constructing a surface model with calcium vacancy defects. Employing a representative model of aspartic acid residues, we delve into the adsorption mechanism on the crystal surface and scrutinize the adsorption forms of amino acid residues on HAP and calcium-deficient hydroxyapatite (CDHA) surfaces. The research also explores the impact of different environments on adsorption energy. Furthermore, a simplified sandwich structure of crystal-polypeptide-crystal is presented, analyzing the distribution of amino acid residue adsorption sites on the crystal surface of the polypeptide fragment. This investigation aims to elucidate how the stick–slip mechanism of polypeptide molecules on the crystal surface influences the mechanical properties of the system. By uncovering the interface mechanical behavior between HAP and osteopontin peptides, this article offers valuable theoretical insights for the construction and biomimetic design of biocomposites.

Comparative study on the adsorption of lead ions by kaolin loaded chitosan by different modification methods

The adsorption effect of two modified kaolin-chitosan composites prepared by different modification methods (cross-linking method (GL-CS) and click reaction method (TGL-CS)) on lead ion wastewater was studied. The structure of TGL-CS has a denser pore structure than that of GL-CS, and the distribution of adsorption sites is more uniform. At 25 °C, pH 4, the adsorbent dosage of 0.05 g/dm3, reaction time of 4 h, and initial mass concentration of 150 mg/dm3, TGL-CS had the best effect on Pb2+ wastewater treatment, and the adsorption capacity was 76.159 mg/g. The adsorption studies of kinetic, thermodynamic, and ther-modynamic parameters showed that the adsorption on GL-CS and TGL-CS was best described by the Langmuir model. The adsorption mechanism is mainly chemical adsorption. The adsorption process is spontaneous. These results show that the adsorbent prepared by click reaction has obvious advantages, with more adsorption capacity and adsorption sites, faster adsorption rate, and better application potential.

Isotherm Study, Adsorption Kinetics and Thermodynamics of Lead Using Combination Adsorbent of Chitosan and Coffee Ground Activated Carbon

The presence of lead metal in water naturally due to its mobility can cause the nature of water to become toxic and endanger the environmental ecosystem because it bioaccumulates in the food chain. The purpose of this study was to study the maximum adsorption capacity through an isotherm model, to determine the rate of adsorption kinetics in the use of chitosan and coffee grounds adsorbents in reducing lead concentrations in industrial wastewater and to study its thermodynamic magnitude. The research method was carried out using experiments in the laboratory followed by quantitative data analysis to determine the isotherm model and adsorption kinetics. The results showed that the adsorption isotherm follows the Langmuir isotherm model with a correlation coefficient of 0.9970 with a maximum adsorption capacity of 1.0511 mg.g-1 which indicates that chemical adsorption occurs in the mono layer with a homogeneous distribution of adsorption sites with adsorption energy. constant and negligible interactions between lead metal molecules (adsorbate). Study of lead adsorption kinetics using chitosan-activated carbon coffee grounds following the Weber-Morris/intra-particle diffusion model with a correlation coefficient of 0.9920 with a diffusion rate of 76.512 g.mg-1.hour-1 indicating that intra-particle diffusion is the rate step limiting in the overall biosorption process. Negative ΔGo values ​​indicate that the adsorption reaction takes place spontaneously, ΔHo of 0.8130 indicates an endothermic reaction, and ΔSo of 4.1888 indicates an increase in the randomness of the adsorption process at the adsorbent interface and lead during adsorption.

Development of a Multicomponent Adsorption Isotherm Equation and Its Validation by Modeling.

Researchers have made significant efforts over the past few decades to understand adsorption by developing various simple adsorption isotherm models. However, though many contaminants usually occur as multicomponent mixtures in nature, multicomponent adsorption isotherms have received limited attention and remain an area of inadequate research. We have presented here in a new multicomponent adsorption isotherm model, named the Jeppu Amrutha Manipal Multicomponent (JAMM) isotherm, that can alleviate this problem. We first developed the JAMM multicomponent isotherm using our experimental data sets of arsenic and fluoride competitive adsorption on activated carbon. We then tested the JAMM multicomponent isotherm for a case study of cadmium and zinc competitive adsorption. Next, we further assessed the JAMM isotherm using another competitive adsorption case study of copper and chromium. Through extensive validation studies and error analysis, the JAMM isotherm was able to demonstrate its efficacy in predicting the adsorption behavior in several multicomponent adsorption systems accurately. The main advantage of JAMM isotherm over other multicomponent isotherms is that it utilizes and leverages the single-component adsorption parameters to simulate multicomponent isotherms. The proposed JAMM analytical isotherm model furthermore incorporates the interaction between the components, a mole fraction parameter, and a heterogeneity index, providing a more comprehensive modeling framework for multicomponent adsorption. The mole fraction term was introduced for the distribution of adsorption sites based on the relative number of molecules of each component. An additional term for interaction coefficient was introduced for the representation of interactions. During the validation of JAMM with three experimental case studies with negligible, small, and high competition systems of adsorbates, impressive predictions were exhibited, with the average normalized absolute percentage error as 6.05% and average R2 as 0.86, highlighting the model's robustness, versatility, and reliability. We propose that the new JAMM isotherm modeling framework might profoundly help in chemical engineering, environmental engineering, and materials science applications by providing a potent tool for analyzing and predicting multicomponent adsorption systems.

CoS2@SC modified separator for high-performance lithium-sulfur batteries: suppression of polysulfide shuttling

ABSTRACT Due to their high energy density and cost-effective electrode materials, lithium sulfur batteries (LSBs) have been considered as one promising candidate of energy devices. However, the practical application is impeded by the shuttle effect of lithium polysulfides and slow redox kinetics of electrode. Here, we report a successful synthesis of CoS2@SC composite material via in-situ growth and sulfuration pyrolysis method and prepared CoS2@SC modified separator. The carbon matrix derived from sucrose carbonization with a porous structure promotes the uniform distribution of active adsorption sites. According to Lewis acid–base interaction, CoS2@SC separator exhibits strong chemisorption of lithium polysulfides, reducing the loss of active material during cycling. Furthermore, the enhanced wettability of the CoS2@SC separator with the electrolyte accelerates the ion transfer, improving the reaction kinetics. Compared with the blank separator, the cell with CoS2@SC separator has an initial specific capacity of 1135.5 mAh g−1 and notably, the capacity decay rate of the modified battery is only 0.052% per cycle after 800 long cycles at 0.5 C. This unique attribute ensures enhanced stability and durability of the battery system. Consequently, LSBs with the CoS2@SC separator exhibit an improved electrochemical performance.

Research on adsorption enhancement of formaldehyde over transition-sensitive carbon materials for fast purification

In order to simultaneously purify indoor air and exchange no pollutants with outdoor atmosphere, the method of adsorption purification for formaldehyde is brought up and its enhancement mechanism over graphene is theoretically investigated in this study via density functional theory (DFT). The distribution of adsorption sites, relationship between adsorption sites and adsorption forms, effects of dopant atoms on adsorption features of HCHO as well as transfer of weakly-adsorbed structures to strongly-adsorbed ones are main research contents of this study. The simulation results indicate that pure graphene barely shows affinity to HCHO molecules owing to lack of polar surface electron distributed on the adsorbent. When Al atoms are inserted in the graphene to replace some C atoms, polar electronic centers are formed and they can get HCHO chemically adsorbed while HCHO can be only weakly adsorbed on adsorption sites far away from polar centers and hardly transferred to strongly-adsorbed forms. However, after both N and Al atoms are doped in graphene, not only can HCHO be intensely adsorbed on more sites, but weak physisorption can be more easily transitioned into strong chemisorption, which makes accessible strong-adsorption areas of doped graphene for HCHO larger. This research supplies helpful information for utilization of graphene series to accomplish indoor air purification.

Phosphorus-Mediated Local Charge Distribution of N-Configuration Adsorption Sites with Enhanced Zincophilicity and Hydrophilicity for High-Energy-Density Zn-Ion Hybrid Supercapacitors.

Tailor-made carbonaceous-based cathodes with zincophilicity and hydrophilicity are highly desirable for Zn-ion storage applications, but it remains a great challenge to achieve both advantages in the synthesis. In this work, a template electrospinning strategy is developed to synthesize nitrogen and phosphorous co-doped hollow porous carbon nanofibers (N, P-HPCNFs), which deliver a high capacity of 230.7 mAh g-1 at 0.2 A g-1 , superior rate capability of 131.0 mAh g-1 at 20 A g-1 , and a maximum energy density of 196.10Wh kg-1 at the power density of 155.53W kg-1 . Density functional theory calculations (DFT)reveal that the introduced P dopants regulate the distribution of local charge density of carbon materials and therefore facilitate the adsorption of Zn ions due to the increased electronegativity of pyridinic-N. Ab initio molecular dynamics (AIMD)simulations indicate that the doped P species induce a series of polar sites and create a hydrophilic microenvironment, which decreases the impedance between the electrode and the electrolyte and therefore accelerates the reaction kinetics. The marriage of ex situ/in situ experimental analyses and theoretical simulations uncovers the origin of the enhanced zincophilicity and hydrophilicity of N, P-HPCNFs for energy storage, which accounts for the faster ion migration and electrochemical processes.

Removal of GenX by APTES functionalized diepoxyoctane cross-linked chitosan beads

Perfluoro-2-propoxypropanoic acid ammonium salt, commonly known as GenX, is a persistent, bioaccumulative, and toxic synthetic organofluorine compound utilized in producing various products. It has become a concern due to its extensive presence in the aquatic environment and its resistance to conventional water treatment methods. This study achieved effective adsorption of GenX by employing chitosan (CS) modified adsorbent. Cross-linked and aminated CS beads were synthesized using 1,2:7,8-diepoxyoctane (DEO) and 3-aminopropyl triethoxysilane (APTES). The prepared CS-DEO-APTES adsorbent exhibited an adsorption capacity of 825.9 mg/g, which was 2.26 times higher than that of CS beads (364.6 mg/g), attributed to its higher content of amino groups. Additionally, the CS-DEO-APTES adsorbent demonstrated excellent stability under acidic conditions (optimal pH= 4) due to the cross-linking process. Kinetic data, following a pseudo-second-order rate and isothermal data, fitting well with the Langmuir model, indicated that the interactions between GenX and CS-DEO-APTES were chemisorptive, with a nearly uniform distribution of adsorption sites. GenX-saturated beads were successfully regenerated for at least 6 cycles using a 1 % w/v aqueous NaCl and methanol solution (30:70 % v/v). Density functional theory (DFT) calculations suggested that electrostatic interactions primarily influence the adsorption of GenX. These results highlight the effectiveness of the CS-DEO-APTES adsorbent as a viable option for removing GenX from aqueous solutions.

Anomalous Diffusion of Polyelectrolyte Segments on Supported Charged Lipid Bilayers.

This work provides mesoscale models for the anomalous diffusion of a polymer chain on a heterogeneous surface with rearranging randomly distributed adsorption sites. Both the "bead-spring" model and oxDNA model were simulated on supported lipid bilayer membranes with various molar fractions of charged lipids, using Brownian dynamics method. Our simulation results demonstrate that "bead-spring" chains exhibit sub-diffusion on charged lipid bilayers which agrees with previous experimental observations for short-time dynamics of DNA segments on membranes. In addition, the non-Gaussian diffusive behaviors of DNA segments have not been observed in our simulations. However, a simulated 17 base pairs double stranded DNA, using oxDNA model, performs normal diffusion on supported cationic lipid bilayers. Due to the number of positively charged lipids attracted by short DNA is small, the energy landscape that the short DNA experiences during diffusion is not as heterogeneous as that experienced by long DNA chains, which results in normal diffusion rather than sub-diffusion for short DNA.

Leaf-like ionic covalent organic framework for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs: Adsorption performance and mechanism insights

In recent years, ionic covalent organic frameworks (iCOFs) have become popular for the removal of contaminants from water. Herein, we employed 2-hydroxybenzene-1,3,5-tricarbaldehyde (TFP) and 1,3-diaminoguanidine monohydrochloride (DgCl) to develop a novel leaf-like iCOF (TFP-DgCl) for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs (NSAIDs). The uniformly distributed adsorption sites, suitable pore sizes, and functional groups (hydroxyl groups, guanidinium groups, and aromatic groups) of the TFP-DgCl endowed it with powerful and selective adsorption capacities for NSAIDs. Remarkably, the optimal leaf-like TFP-DgCl demonstrated an excellent maximum adsorption capacity (1100.08 mg/g) for diclofenac sodium (DCF), to the best of our knowledge, the largest adsorption capacity ever achieved for DCF. Further testing under varying environmental conditions such as pH, different types of anions, and multi-component systems confirmed the practical suitability of the TFP-DgCl. Moreover, the prepared TFP-DgCl exhibited exceptional reusability and stability through six adsorption–desorption cycles. Finally, the adsorption mechanisms of NSAIDs on leaf-like TFP-DgCl were confirmed as electrostatic interactions, hydrogen bonding, and π-π interactions. This work significantly supplements to our understanding of iCOFs and provides new insights into the removal of NSAIDs from wastewater.

A porous composite membrane for spontaneous moisture adsorption

Highly humid air is harmful to human health. The solution dehumidification can easily cause salt solution droplets release into the air while membrane dehumidification requires a significant driving force. This work aims to investigate the moisture adsorption performance of as-synthesized composite porous membranes in the absence of pressure driving force. Here, a series of PVDF/PVA/CaCl2 membranes were prepared. An open core-shell skeleton with a porous surface and PVA aggregated core was obtained, which serves as a permeation channel for mass transfer. Due to the uniform distribution of CaCl2 adsorption sites, the hydrophilic nature of PVA, and the porous structure, the membranes exhibited outstanding hygroscopic properties with the highest initial moisture adsorption rate of 0.053 g·g−1·min−1 and moisture adsorption capacity of 2.36 g·g−1 in the spontaneous state. The water vapor adsorption data of the M-4-5 sample was best fitted using the double constant kinetic model. Moreover, the core-shell skeleton provided excellent strength and a stable structure. The maximum dry strength of the composite membrane was 1.6 MPa and the maximum wet strength was 0.92 MPa. This work provides a new concept for designing the dehumidified membrane material, especially for non-pressure-driven condition.

Adsorption performance of layered double hydroxides for heavy metals removal in soil with the presence of microplastics

Microplastics (MPs) are widely presence in soil, and the uncertain influence of MPs is ineluctable. In this study, the influence of removal efficiency for heavy metals by LDHs with the presence of polyethylene (PE) and polypropylene (PP) is investigated. And the removal efficiency of heavy metals Cu2+, Pb2+, Zn2+, Ni2+ by LDHs from soil is investigated by contact time, initial concentration, PP/PE contents, pH and coexisting ions. The adsorption capacities of heavy metals with the presence of PP/PE are larger and the effects with high content of PP/PE is more obvious on removal of heavy metals. The isothermal experiment data are well described by the Generalized Langmuir isothermal model, denoting that the adsorption sites on the absorbents are certain, and the sites are inhomogeneous with different adsorption energy. In order to further explore the influence of PP/PE on the removal of heavy metals by LDHs, the interaction between LDHs and PP/PE is analyzed by XRD, FT-IR, Zeta potential and SEM. The sites energy distribution theory is employed to analyze the distribution of accessible adsorption sites and the heterogeneity of sites. The results show that with the presence of PP/PE in soil, LDHs interacts with PP/PE preferentially on account of electrostatic attraction, and the combination of LDHs and PP/PE increases the accessible adsorption sites for the removal of heavy metals and is beneficial to the adsorption process. These findings contribute to understanding environmental behavior of heavy metals with the presence of MPs and guide the application of LDHs in soil.

Effect of Elemental Doping on the Adsorption Behavior and the Mechanism of Hydrogen Adsorption on the Zirconium Surface

This study used the Monte Carlo (MC) and density functional theory (DFT) methods to simulate the adsorption process of a H atom on element (vacancy, Cr, Sn, and Fe)-doped Zr(0001) surfaces and further analyzed the adsorption site distribution, adsorption energy, charge transfer, and electronic structure, etc. of the doped zirconium surface model. Simulated results indicated that (i) although the doping of vacancy, Cr, Sn, and Fe had a significant effect on the adsorption site distributions of the H atom on the Zr(0001) surface, they showed completely different distribution patterns. (ii) Vacancy doping promoted the adsorption of the H atom on the Zr(0001) surface. The H atom would penetrate the zirconium matrix along the vacancy and then occupy the octahedral gap stably. On the contrary, the doping of Cr, Sn, and Fe inhibited Zr(0001) surface hydrogen uptake in the order of Fe > Cr > Sn, where the effect of Sn could be negligible. (iii) Fe doping had the greatest effect on the chemical reaction mechanism of H adsorption on the Zr(0001) surface, which significantly converted the chemical reaction from Zr–H- to Fe–H-dominated, while Cr doping caused the formation of the Cr–H and Zr–H coaction mechanism, and Sn doping had almost no effect on the mechanism of H adsorption on the Zr(0001) surface.

Improving the phosphate adsorption performance of layered manganese oxide by ammonia plasma surface modification

The introduction of excessive phosphate to natural water bodies often results in serious eutrophication. Adsorption is thought to be one of the best methods for phosphate recovery and removal from water. The abundance of surface functional groups and high particular surface part of layered manganese oxide (LMO) makes it an ideal agent to remove pollutants from wastewater. However, since the surface of LMO is normally negatively charged at neutral pH, it cannot efficiently clear anionic contaminants like phosphate. This study brings forward a novel development of phosphate sorbents that help remove phosphate from water. Specifically, the modification of LMO with plasma technology in the presence of ammonia (NH3) has yielded promising results. These outcomes indicated that NH3-LMO exhibited an ultrathin and transparent layered structure with numerous graphene-like wrinkles and folds. The adsorption of phosphate by NH3-LMO was very fast and followed pseudo-second-order kinetics. Due to the uniform distribution of adsorption sites on the surface of NH3-LMO, the Langmuir isotherm model could clearly support the phosphate adsorption onto NH3-LMO. The presence of chloride, sulfate, nitrate, and dissolved humic acid exerted a slight influence on the phosphate removal efficiency of NH3-LMO. Furthermore, the adsorption of phosphate by NH3-LMO was highly pH-dependent. This is mainly attributed to the transformation of pHIEP from 2.2 for LMO to 6.6 for NH3-LMO, which is positively charged at neutral pH. For the NH3-LMO reuse, the adsorption function was relatively stable after four adsorption-desorption cycles. Collectively, our research showed that NH3-LMO could be adopted as a potential adsorbent for the phosphate removal from water.

Tracking single adatoms in liquid in a transmission electron microscope.

Single atoms or ions on surfaces affect processes from nucleation1 to electrochemical reactions2 and heterogeneous catalysis3. Transmission electron microscopy is a leading approach for visualizing single atoms on a variety of substrates4,5. It conventionally requires high vacuum conditions, but has been developed for in situ imaging in liquid and gaseous environments6,7 with a combined spatial and temporal resolution that is unmatched by any other method-notwithstanding concerns about electron-beam effects on samples. When imaging in liquid using commercial technologies, electron scattering in the windows enclosing the sample and in the liquid generally limits the achievable resolution to a few nanometres6,8,9. Graphene liquid cells, on the other hand, have enabled atomic-resolution imaging of metal nanoparticles in liquids10. Here we show that a double graphene liquid cell, consisting of a central molybdenum disulfide monolayer separated by hexagonal boron nitride spacers from the two enclosing graphene windows, makes it possible to monitor, with atomic resolution, the dynamics of platinum adatoms on the monolayer in an aqueous salt solution. By imaging more than 70,000 single adatom adsorption sites, we compare the site preference and dynamic motion of the adatoms in both a fully hydrated and a vacuum state. We find a modified adsorption site distribution and higher diffusivities for the adatoms in the liquid phase compared with those in vacuum. This approach paves the way for in situ liquid-phase imaging of chemical processes with single-atom precision.