Number Of Adsorption Sites Research Articles

Construction of a Bifunctional Redox-Site Conjugated Covalent-Organic Framework for Photoinduced Precision Trapping of Uranyl Ions.

The performance of covalent-organic frameworks (COFs) for the photocatalytic extraction of uranium is greatly limited by the number of adsorption sites. Herein, inspired by electronegative redox reactions, we designed a nitrogen-oxygen rich pyrazine connected COF (TQY-COF) with multiple redox sites as a platform for extracting uranium via combining superaffinity and enhanced photoinduction. The preorganized bisnitrogen-bisoxygen donor configuration on TQY-COF is entirely matched with the typical geometric coordination of hexavalent uranyl ions, which demonstrates high affinity (tetra-coordination). In addition, the presence of the carbonyl group and pyrazine ring effectively stores and controls electron flow, which efficaciously facilitates the separation of e-/h+ and enhances photocatalytic performance. The experimental results show that TQY-COF removes up to 99.8% of uranyl ions from actual uranium mine wastewater under the light conditions without a sacrificial agent, and the separation coefficient reaches 1.73 × 106 mL g-1 in the presence of multiple metal ions, which realizes the precise separation in the complex environment. Importantly, DFT calculations further elucidate the coordination mechanism of uranium and demonstrate the necessity of the presence of N/O atoms in the photocatalytic adsorption of uranium.

Treatment of seeds by cold ambient air plasma: combining impedance measurements with water sorption modeling to understand the impact of seed hydration

In this article, we focus on the plasma seed interaction and more specifically-on the feedback exerted by the seeds on the plasma properties. Dormant Arabidopsis seeds with different water contents (WC), namely 3%DW, 10%DW and 30%DW were exposed to cold ambient air plasma (C2AP) generated in a dielectric barrier device (DBD). It is found that increasing WC enhances the capacitive current of the DBD, generates a greater number of low energy streamers (characterized by current peaks lower than 10 mA) that preferentially interplay with the seeds. Since the resistive and capacitive components of the seeds modify the C2AP electrical properties, impedance measurements (also called LCRmetry) have been carried out to measure their main dielectric parameters before/after plasma exposure (seeds resistance, capacitance, complex relative permittivity, tangent loss and conductivity). It appears that WC significantly changes dielectric losses at low frequencies (<1 kHz) due to polarization relaxation of the polar molecules (i.e. water). LCRmetry further reveals that C2AP does not substantially alter seeds dielectric parameters, i.e. it neither adds or removes significant amounts of new materials, meaning that the relative starch, protein and lipid contents remain essentially unaffected. However, it cannot be discounted that some bulk properties of the Arabidopsis seeds may be modified, especially regarding their porosity. This characteristic could facilitate penetration of plasma-generated reactive oxygen species into the internal seed tissues, leading to the grafting of oxygenated groups. To corroborate this theory, water sorption isotherms have been achieved on Arabidopsis seeds and fitted with four thermodynamic models, including the Brunauer–Emmett–Teller model and the Generalized D’Arcy and Watt model. It is demonstrated that C2AP primarily strengthens water-seed affinity by modifying molecular interactions rather than changing the seed’s moisture layer. This occurs despite a potential decrease in the number of adsorption sites, indicating a significant increase in overall seed hydrophilicity after plasma treatment.

Fe3O4 nanochips loaded MXenes/g-C3N4 nanocomposite for ultrasensitive electrochemical detection of zinc (II), cadmium (II), lead (II), copper (II) and mercury (II) metal ions

The present work demonstrates a highly sensitive and efficient nanosensor for the simultaneous detection of zinc (II), cadmium (II), lead (II), copper (II) and mercury (II) metal ions using Ti3C2/Fe3O4/g-C3N4 nanocomposite. The Ti3C2/Fe3O4/g-C3N4 nanocomposite was prepared using co-prcepitation method followed by ultrasonication treatment containing Ti3AlC2, ferrous sulfate, ferric chloride and melamine as precursors. The as-prepared nanocomposites were successfully examined using XRD, FTIR, SEM and cyclic voltammetric techniques. Differential pulse anodic stripping voltammetry (DPASV) technique was applied for the simultaneous detection of Zn (II), Cd (II), Cu (II), Pb (II) and Hg (II) ions. The electrochemical variables including pH of the solution, amount of Ti3C2/Fe3O4/g-C3N4 on the GCE surface, supporting electrolyte and deposition time were optimized to get maximum sensitivity. Under optimal conditions, Ti3C2(HF)/Fe3O4/g-C3N4 sensor exhibited excellent performance for Zn (II), Cu (II), Cd (II), Pb (II) and Hg (II) in a range from 0.5 to 0.005 μM with detection limits 0.26 nM for Zn (II), 0.21 nM for Cd (II), 0.10 nM for Pb (II), 0.11 nM for Cu (II) and 0.12 nM for Hg (II) which are lower than the permissible limit recommended by the WHO guidelines. The sensor also shown outstanding selectivity in the presence of various foreign species (Ca2+, Mg2+, Na1+, Cl1-, NO31-, and 4-nitrophenol) and high resolution for simultaneous detection of Zn (II), Cd (II), Cu (II), Pb (II) and Hg (II) ions. The good electroanalytical performance and excellent selectivity and sensitivity of developed nanosensor can be attributed to the heterostructure and the coordination provided by MXene and Fe3O4/g-C3N4, resulting in enhanced interfacial charge transfer and number of adsorption sites. In addition, the developed sensor was applied for the detection of metal ions in tap water samples and satisfactory results were obtained. This study highlights a facile approach for designing MXene-supported magnetic NPs/ N containing carbon materials as sensing platform for the detection of other toxic heavy metal ions.

Preparation of coal tar pitch based adsorption materials: Understanding the adsorption mechanism by combining field energy theory and statistical physics models

A coal tar pitch based adsorbent(CTPA) was prepared. The structure of the CTPA adsorbate was analyzed using FTIR, Zeta potential, SEM and BET. We investigate the adsorption mechanism of cation dye contaminants by adsorbates. It has been shown that CTPA has superior adsorption properties for MB. Thermodynamic analysis and Zeta potential analysis have shown that electrostatic forces play a particularly prominent role in adsorption. Statistical physics model studies have shown that increasing the temperature increases the trapping power and the number of adsorption sites. According to the SED theory, MB adsorption is particularly strong at elevated energy sites.

Molecular simulation of the effects of activated carbon structure on the adsorption performance for volatile organic compounds in fumes from gasoline

AbstractImproving the adsorption performance of activated carbon can effectively reduce the emission of volatile organic compounds (VOCs). In this paper, the influences of pore size, functional groups, and water molecular content on the adsorption for four gasoline evaporation VOCs (n‐butane, n‐hexane, p‐xylene, and ethanol) were investigated in terms of equilibrium adsorption capacity and threshold pressure by molecular simulation. The simulation results show that capillary condensation can increase the equilibrium adsorption capacity of gas, while functional groups and water molecules will reduce the effective adsorption volume of activated carbon. On the other hand, the threshold pressure depends primarily on the interaction energy and the number of adsorption sites. The superposition effect of the adsorption force field makes the lowest threshold pressure of four VOCs. The threshold pressure of n‐butane, n‐hexane, and p‐xylene is increased by the presence of functional groups and water molecules, while functional group modification and a certain amount of water molecules can improve the adsorption capacity of ethanol at low pressure. The results of the study can provide a reference for the selection of activated carbon in vehicle carbon canisters and the development of high‐performance activated carbon.

Polarization-Dependent Sum-Frequency-Generation Spectroscopy for In Situ Tracking of Nanoparticle Morphology.

The surface structure of oxide-supported metal nanoparticles can be determined via characteristic vibrations of adsorbed probe molecules such as CO. Usually, spectroscopic studies focus on peak position and intensity, which are related to binding geometries and number of adsorption sites, respectively. Employing two differently prepared model catalysts, it is demonstrated that polarization-dependent sum-frequency-generation (SFG) spectroscopy reveals the average surface structure and shape of the nanoparticles. SFG results for different particle sizes and morphologies are compared to direct real-space structure analysis by TEM and STM. The described feature of SFG could be used to monitor particle restructuring in situ and may be a valuable tool for operando catalysis.

Exploration of the fundamental factor for the synergistic modification of model waxy oil by EVA and asphaltene: An experiment and simulation study

It has been well documented that the synergistic effect of polymer pour point depressant (PPD) and asphaltenes improves the low-temperature rheology of waxy oil. However, the fundamental factor of this synergistic effect has been little studied. In this paper, we innovatively combine macroscopic rheology experiment, mesoscopic particle size test and microscopic molecular dynamics simulation, supplemented by crystallization exotherm test and wax crystal morphology observation, to investigate the effect of solvent composition on the synergistic modification ability between ethylene-vinyl acetate (EVA) PPD and asphaltene, and then reveal the fundamental factor of this synergistic effect. The results showed that the EVA's adsorption on the asphaltene surface is the key element influencing their synergistic effects. With the deterioration of asphaltene dispersion in the solvent, the ability of asphaltene and EVA to synergistically improve the low-temperature rheology of model waxy oil increases and then decreases. When the aromatic component in the solvent was too high, a large number of aromatic solvent molecules were distributed around the asphaltene molecules through π-π conjugation, which interfered with the adsorption of EVA on asphaltene due to the existence of spatial site resistance. When the content of saturated hydrocarbon component in the solvent was too high, the self-aggregation tendency of asphaltenes led to a decrease in the number of adsorption sites on their surfaces, resulting in the decline of the adsorption efficiency of EVA on the asphaltene surface, and the synergistic modification effect between them was reduced. This work offers fresh ideas for the design of waxy crude oil PPD, which is crucial for the efficient pipeline transmission of waxy crude oil.

Using the composite material of GO and g-C3N4 nanosheets as substrate to in-situ grow Co3O4 nanosheets for efficient Hg0 removal

Chemisorption is an effective method to remove Hg0 from coal-fired flue gas. During this process, Hg0 will convert to Hg2+ and be solidified on sorbent surface. The number of adsorption sites and the electron transfer between Hg0 and sorbents play an important role in the removal process. In the present work, GO with a rapid electron transfer was compounded with NS-g-C3N4 to improve the electron donating ability of NS-g-C3N4. After that, Co3O4 nanosheets were grown in-situ in the interlayer space of GO and NS-g-C3N4 composites. A series of sorbents were successfully synthesized by changing GO concentration. SEM and TEM results show that the corresponding Co3O4/GCN (GCN denote the GO and NS-g-C3N4 composites) sorbent has better Co3O4 nanosheet dispersibility when GO concentration is 5 mg/mL. This results in a large amount of chemisorbed oxygen, which is favor to the oxidation of Hg0 to HgO. In addition, XPS results show that the interaction between Co3O4 and GCN give a rapid electrons transfer from GCN to Co3O4, thus improving the activation of gaseous oxygen. Therefore, Co3O4/GCN-5 has excellent Hg0 removal efficiency of about 95 % at 200 °C and high stability under different flue gas conditions. A probable reaction path way was deduced by the results of XPS and Hg0 adsorption–desorption experiment.

Biomass inherent metal interfere carbothermal reduction modification of biochar for Cd immobilization

Metal salt laden are frequently used to enhance the heavy metal adsorption capacity of biochar. The present study indicates that CaS loading biochar can be modified from the carbothermal reduction reaction between CaSO3 (modification agent) and carbon matrix. The CaS transformation ratio as indicated by XPS spectra was significantly improved by the CaSO3 loading content. The coprecipitation reaction induced by the CaS in biochar can significantly enhance the adsorption capacity of heavy metals (Cd). And, the Cd adsorption capacity can be enhanced up to >100 mg/g and increases with increasing CaS ratio in the biochar. In addition, the adsorption process was rapid and could be balanced within several minutes (~ 5 min). Furthermore, the interaction reaction between the modification agent and the inherent metal in the biomass was examined in the biochar pyrolysis preparation process. Interestingly, MgCl2 inherent metal salt can combine with the original CaSO3 to produce a new mineral, resulting in a decrease in CaS. However, KCl, a more thermally stable biomass-derived metal salt, exhibited a weak combination ability with the modification agent. Accordingly, this type of secondary reaction reduces the Cd adsorption capacity owing to the decrease in the number of adsorption sites (CaS).

Study on Phosphorus Adsorption Performance of Inorganic Modified Green Mudstone

Inorganic modified green mudstone (MGM) was prepared from the green mudstone (GM) residue of Fushun West Open Pit Mine and characterized by XRF, XRD, FTIR, and SEM of GM and MGM. According to the calculation of pore size and the BET equation, the pore size and specific surface area of the MGM were larger. The results of adsorption kinetics and isothermal adsorption experiments showed that the adsorption capacity of MGM for phosphate increased from 0.1 mg/g to 0.71 mg/g, which was obviously better than that of GM. The GM and MGM accorded with the quasi-second-order kinetic model. The isothermal adsorption data of GM accorded with the Freundlich model, and the isothermal data of MGM accorded with the Langmuir model, which indicated that the model of GM and MGM was an adsorption process from a double layer to a single layer. Thermodynamic data showed that the increase in temperature was beneficial to the adsorption of MGM. The internal diffusion model showed that due to the change of pore size structure after modification, the number of adsorption sites that could provide phosphate was increased, and at the same time, the change of internal elements led to the extension of the chemical reaction time by 700 min. Because of the ligand exchange and electrostatic interaction between phosphate, GM, and MGM, the adsorption results showed that acidity was better than alkalinity. To improve the recycling ability of MGM, hydrochloric acid with a concentration of 0.1 mol/L was determined as the best phosphorus resolving agent, and the resolving rate was still close to 80% after five cycles. The results showed that the MGM could be a promising adsorbent for the removal of phosphorus, providing a new way for resource utilization of mining waste residue.

Removal of Cd (II) and Pb (II) Ions from Aqueous Solutions Using Raw and Modified Activated Carbon

The main objective of this study is to investigate the feasibility of using raw and modified activated carbon with ammonia for the maximum removal of Pb2+ and Cd2+ ions from aqueous solutions and polluted water samples at optimized process parameters such as initial metal concentration, adsorbent dose, contact time and solution pH. The treatment of a commercial granular activated carbon by ammonia was performed to increase the power of the heavy metal ions removal from aqueous samples. In this work, the adsorption of these ions on raw and modified activated carbon was studied using the batch equilibrium technique, and the equilibrium adsorption data was described by Langmuir isotherm models. In the current work, Pb2+ and Cd2+ ions were adsorbed out of aqueous solutions using raw and modified activated carbon as an adsorbent. Investigations have been done into the effects of solution pH, contact time, initial metal ion concentrations, and adsorbent dosage on removal efficiency. The pH studies demonstrated that Pb2+ and Cd2+ ion removal efficiency is pH-dependent, increasing with increasing pH value, peaking at pH 6.5, and then remaining nearly constant. Due to an increase in the number of adsorption sites, an increase in adsorbent mass causes an increase in Pb2+ and Cd2+ adsorption. According to the data, activated carbon has removal efficiency (96.0 - 98.0%) for removing Pb2+ and Cd2+ ions from aqueous solutions in the initial metal concentration range of 10 to 50 mg/l. The experimental data suited the Langmuir and Freundlich adsorption isotherms well, and their constants were assessed. The effectiveness of Pb2+ ions removal by adsorption (starting Pb2+concentration ranging from 1 - 10 mg/l) is shown by the treatment results of various polluted water samples to be between (81.5 - 86.7%), between (91 - 98%), utilizing raw Activated carbon (R-AC) and modified activated carbon with ammonia (A-AC), respectively. the results for cadmium ions reveal that the effectiveness of Cd2+ ions removal by adsorption (starting Cd2+ concentration ranging from 1 to 10 mg/l) is ranged from (74.3 to 83.7%), and from (97.6 to 98.4%) when the raw activated carbon (R-AC) and modified activated carbon with ammonia (A-AC) are used, respectively.

Chestnut Shell-Activated Carbon Mixed with Pyrolytic Snail Shells for Methylene Blue Adsorption.

Activated carbon has been used to treat organic dyes in water systems; however, the adsorption capacity of the samples studied was limited by the specific surface area and influenced by the pH of the aqueous solution. In this study, a hybrid adsorbent consisting of a mixture (MCS) of activated chestnut shell biochar (CN) and pyrolyzed snail shell material (SS) was developed to solve this problem, with the waste snail shell samples being processed by pyrolysis and the chestnut shell samples chemically pretreated and then pyrolyzed. The BET and SEM results revealed that the SS had a mesoporous fluffy structure with a higher specific surface (1705 m2/g) and an average pore diameter of about 4.07 nm, providing a large number of sites for adsorption. In addition, XPS and FTIR results showed that the main component of SS was calcium oxide, and it also contained a certain amount of calcium carbonate, which not only provided an alkaline environment for the adsorption of biochar but also degradation and photocatalytic capabilities. The results showed that the MCS3-1 sample, obtained when CN and SS were mixed in the ratio of 3:1, had good capacity for adsorption for methylene blue (MB), with 1145 mg/g at an initial concentration of 1300 mg/L (92% removal rate). The adsorption behaviors were fitted with the pseudo-second-order kinetic model and Freundlich isotherm model, which indicated that the adsorption was multilayer chemisorption with a saturated adsorption capacity of 1635 mg/g. The photocatalytic capacity from the SS composition was about 89 mg/g, and the sorption of MB dye onto the sorbent reached equilibrium after 300 min. The results suggested that MCS3-1 has enormous potential for removing MB from wastewater.

Preparation of efficient adsorbent with dual adsorption function based on semi-coke: Adsorption properties and mechanisms

Solid waste oil shale semi-coke (SC) is considered as a potential material for the preparation of adsorbents due to its rich organic and inorganic components. However, the dense structure and the complex form of the components present make it unsatisfactory for adsorption. In this study, using Alkali corrosion under hydrothermal condition, SC was prepared as an adsorbent material PSSC with excellent adsorption performance for both anionic and cationic dyes. The related characterization analysis showed that most of the organic matter and silicates of SC reacted with inorganic matter to form silicon carbide. The specific surface area of PSSC increased significantly (from 7.47 m2/g to 1353.99 m2/g) leading to the maximum adsorption of PSSC on Methylene blue (MB) and Congo red (CR) reached at 974.66 mg/g and 562.41 mg/g, respectively, which far exceeded the adsorption of SC on both dyes. Finally, the adsorption mechanisms were revealed from the structural and energetic perspectives. The results showed that the modification process increased the type and number of adsorption sites, and that these adsorption sites exhibited different capturing abilities for the two dyes with the change of contact temperature.

Using a Modified Langmuir Equation to Estimate the Influence of Organic Materials on Phosphorus Adsorption in a Mollisol From Northeast, China

The use of organic materials has been increasing due to improving soil fertility by affecting phosphorus (P) adsorption and desorption behavior of soils. However, previous studies ignored the influences of increased P concentrations in equilibrium solutions caused by P released from applied organic materials in bath P adsorption experiments. To eliminate these influences, a modified Langmuir equation was applied to describe P adsorption properties in dairy manure composts and biosolids-incubated soils. The adsorption and desorption trends shifted around the initial P concentration of 70 mg/L. The fitted parameter of correlation coefficients showed that the modified Langmuir model fitted well for the adsorption data covering only the lower initial P concentrations (0–70 mg P/L) and covering the whole P concentrations applied in the present study (0–400 mg/L). For the fitted results covering the whole P concentrations, adding organic materials generally decreased both the Γmax (maximum adsorption capacity for P) and the MABC (maximum adsorption buffering capacity), except for the 20-g/kg biosolids incubation, indicating that the number of adsorption sites for P decreased as the organic materials applied, and the binding energy for the P adsorption to the soil also decreased to some extent with some fluctuation as reflected by K values which represent adsorption strength. Higher DOC content, lower molecular weight, and higher humic acid might result in the higher Γmax of 20-g/kg biosolids incubated soil. The linear equations are described well for P desorption. The constant a value of slope in a linear equation reflects the P desorption capacity of soils increased due to the application of organic materials, especially in high P concentrations with a value of 0.45 for the control soil increased to 1.02 for 10-g/kg biosolids treated soil. Thus, it would be important to control the P application amounts when the application of P fertilizers to the soils with organic materials applied, as the effects of organic materials on P adsorption and desorption characteristics were more efficient at high P concentrations.

Hydrogen interaction with Mn-doped Zr2Fe (101) surface: A DFT study

The metal getter materials play a pivotal role in the treatment of tritium-containing waste gas, which is one of the most important tasks in fusion reactions, owing to the characteristics of no tritiated water product and easy recovery by the form of reversible metal hydrides. As the most promising and attractive hydrogen isotopes trapping materials for metal getters, Zr2Fe alloy has the advantages of low thermal neutron absorption, high corrosion resistance, fast hydrogen absorption rate, and high absorption efficiency, which have attracted great attention. Though pristine/Mn-doped Zr2Fe have been widely used to trap tritium from nitrogen and inert gases, an atomic-scale description of the inherent interaction mechanism between hydrogen and pristine/Mn-doped Zr2Fe surface is still lacking. Herein, density functional theory (DFT) calculations were employed to study the effect of doping Mn on the adsorption, dissociation and diffusion of hydrogen on the Zr2Fe(101) surface. It is found that the number of adsorption sites and adsorption strength of hydrogen increase when a Fe atom is substituted by a Mn atom. In addition, the dissociation and diffusion barriers of hydrogen are lowered on the Mn-doped surface. The electronic structure analysis shows that the adsorptions of hydrogen molecules cause more electron transfer to the surfaces and there exists strong interaction between hydrogen and doping Mn. Consequently, this should enhance the hydrogen storage performance of Zr2Fe alloy, due to the surface adsorption and diffusion of hydrogen being improved by doping Mn. All these findings can provide insightful guidance for future research to improve the hydrogen storage capacity of Zr-based alloy materials and the design of metal getters for tritium-containing waste gas treatment.

Preparation of biologically activated lignite immobilized SRB particles and their AMD treatment characteristics

In response to the insufficient supply of carbon sources and the toxicity of heavy metal ions when using sulfate reducing bacteria (SRB) to treat acid mine wastewater (AMD), the immobilized particles are prepared with Rhodopseudomonas, SRB and lignite as the main raw materials. And based on single factor test and orthogonal test to determine the optimal ratio of biologically activated lignite fixed SRB particles. The adsorption characteristics of immobilized particles were studied under the optimal ratio, and the reaction kinetics and adsorption capacity of SRB particles immobilized on biologically activated lignite to different ions were analyzed. The results show that: lignite not only has good adsorption performance, but also can be used as the carbon source of SRB after being degraded by Rhodopseudomonas, solving the problems of low removal efficiency of SRB treatment of AMD and insufficient carbon source supply. When the dosage of lignite (particle size is 200 mesh), Rhodopseudomonas, and SRB are 3%, 10%, and 10% mesh, the prepared biologically activated lignite-immobilized SRB particles have the best effect on AMD treatment. The removal rates of SO42−, Zn2+, and Cu2+ were 83.21%, 99.59%, and 99.93%, respectively, the pH was increased to 7.43, the COD release was 523 mg/L, and the ORP value was − 134 mV. The reduction process of SO42− by the biologically activated lignite-immobilized SRB particles conforms to the pseudo-first-order kinetics, and the adsorption of Zn2+ is more in line with the Freundlich isotherm adsorption equation and the pseudo-second-order kinetic model. And it does not spread in a single form, both internal and external diffusion occur. SEM, FT-IR, and BET analysis of biologically activated lignite immobilized SRB particles showed that the pore structure is developed, has a large number of adsorption sites, and some activated groups participate in the reaction. The adsorption process of Zn2+ and Cu2+ in AMD meets the multi-layer adsorption theory.

3D-printed montmorillonite nanosheets based hydrogel with biocompatible polymers as excellent adsorbent for Pb(Ⅱ) removal

• 3D hydrogel with high Pb(II) handling capacity and specific geometry is fabricated via 3D-printing technology. • 3D hydrogel provides an open-access for Pb(II) to contact and react with the internal adsorption sites. • 3D hydrogel achieves the efficient adsorption for Pb(II) in both batch and column tests. Montmorillonite nanosheets (MMTNs), gelatin (GEL) and sodium alginate (SA) were used as the raw materials to synthesize the 3D porous hydrogel with high Pb(II) handling capacity and specific geometry via 3D-printing technology. MMTNs and GEL could bond with each other through the hydrogen bonding at the edge and electrostatic interactions on the surface of MMTNs, forming the stable organic–inorganic framework, and further forming the interpenetrating polymer network (IPN) with the crosslinking and intertwining interaction of SA. Characterizations shown that there were abundant macroporous and huge lamellas in hydrogel, offering an open-access for Pb(II) to contact and react with the internal adsorption sites. The batch adsorption experiments shown that Pb(II) adsorption onto hydrogel was a monolayer chemisorption process, which was controlled by the number of adsorption sites in adsorbent. The maximal adsorption capacity for Pb(II) could reach 134 mg/g (C 0 = 1000 mg/L, T = 25 ℃, M = 4 g/L, pH = 5), which was attributed to the coefficient of ion exchange, electrostatic interactions and surface complexation according to the XPS, FTIR and EDX tests. The hydrogel also has good filtering performance towards Pb(II) from aqueous solutions via the fix-bed column, showing the potential in practical application.

Morphological and Elemental Investigations on Co\u2013Fe\u2013B\u2013O Thin Films Deposited by Pulsed Laser Deposition for Alkaline Water Oxidation: Charge Exchange Efficiency as the Prevailing Factor in Comparison with the Adsorption Process

Mixed transition-metals oxide electrocatalysts have shown huge potential for electrochemical water oxidation due to their earth abundance, low cost and excellent electrocatalytic activity. Here we present Co–Fe–B–O coatings as oxygen evolution catalyst synthesized by Pulsed Laser Deposition (PLD) which provided flexibility to investigate the effect of morphology and structural transformation on the catalytic activity. As an unusual behaviour, nanomorphology of 3D-urchin-like particles assembled with crystallized CoFe2O4 nanowires, acquiring high surface area, displayed inferior performance as compared to core–shell particles with partially crystalline shell containing boron. The best electrochemical activity towards water oxidation in alkaline medium with an overpotential of 315 mV at 10 mA/cm2 along with a Tafel slope of 31.5 mV/dec was recorded with core–shell particle morphology. Systematic comparison with control samples highlighted the role of all the elements, with Co being the active element, boron prevents the complete oxidation of Co to form Co3+ active species (CoOOH), while Fe assists in reducing Co3+ to Co2+ so that these species are regenerated in the successive cycles. Thorough observation of results also indicates that the activity of the active sites play a dominating role in determining the performance of the electrocatalyst over the number of adsorption sites. The synthesized Co–Fe–B–O coatings displayed good stability and recyclability thereby showcasing potential for industrial applications.Graphic

A new model for soil water vapor sorption isotherms considering adsorption and condensation

AbstractA new model, which was based on the Do and Do (2000) model, was developed to describe soil water vapor sorption isotherms (SWSIs) including both adsorption and condensation processes. The model performance was evaluated using measured SWSIs of 33 soil samples with a wide range of clay contents (0.08–0.72 g g−1), clay mineralogy (montmorillonite, kaolinite, and mixed clay samples), and organic C contents (0.001–0.070 g g−1). The new model produced satisfactory fits to measured SWSIs, with the mean relative percentage deviation modulus less than 6.2%. For a given clay mineral type, the adsorption sites and condensation capacity increased with increasing clay content. At a given clay content, the number of adsorption sites was in the order of montmorillonitic samples (ML)&gt;mixed clay samples (MX)&gt;kaolinitic samples (KA), and the condensation capacities of ML and MX were lower than that of KA. For soils with low clay content (&lt;0.12 g g−1) and similar clay mineralogy, the adsorption sites and condensation capacities were positively related to organic C. The model parameter S0 had the potential for deriving cation exchange capacity, specific surface area, and clay content. The C/S0 values could potentially be used as a proxy of the dominant clay mineral type in a sample.

Adsorption process and mechanism of heavy metal ions by different components of cells, using yeast (Pichia pastoris) and Cu2+ as biosorption models.

Microbial biomass has been recognized as an essential biosorbent to remove heavy metal ions, but the biosorption process and mechanism of different components of microbial cells have not been elucidated. In present study, Pichia pastoris X33 and Cu2+ was used as a biosorption model to reveal the biosorption process and mechanism of different components of microbial cells. For the biosorption of whole cells, the maximum removal efficiency was 41.1%, and the adsorption capacity was 6.2 mg g−1. TEM-EDX analysis proved the existence of Cu2+ on the cell surface and cytoplasm. The maximum Cu2+ removal efficiency of the cell wall, cell membrane and cytoplasm were 21.2%, 20.7% and 18.5%, respectively. The optimum pH of Cu2+ biosorption of the P. pastoris cell, cell wall, cell membrane and cytoplasm was 6. Moreover, the maximum adsorption capacity of the cell, cell wall, cell membrane and cytoplasm was 16.13, 11.53, 10.97 and 8.87 mg g−1, respectively. The maximum removal efficiencies of P. pastoris biomass treated with proteinase K and P. pastoris biomass treated with β-mannanase were 18.1% and 28.2%, respectively. The maximum removal efficiencies of mannan and glucan were 34% and 12%, respectively. The FTIR spectra showed that the amino group (N–H), hydroxyl (O–H), carbon oxygen bond (C–O), –CH, C–N and carbonyl group (C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O) of a ketone or aldehyde may interact with Cu2+. Thus, our work provides guidance for further understanding the effect of different cell components on biosorption.