Main Adsorption Sites Research Articles

Improving the adsorption properties of low surface area hardwood biochar for the removal of Fe+ and PO₄3- from aqueous solution.

Biochar produced from wood residues may provide a new method and material for managing the environment, particularly in terms of carbon sequestration and contaminant remediation. Additionally, biochar produced from wood residues is free of chemical fertilizers, likewise in rice straw, wheat straw, corn straw, etc. This study investigated the removal of iron from aqueous solutions by a novel low-cost and eco-friendly biochar made from hardwood trees and modified by adding MgCl2 for effective phosphate removal. Optimal adsorption conditions were determined through studies of adsorption time, pH, and adsorbent dosage. Batch equilibrium isotherm and kinetic experiments and pre/post-adsorption characterizations using FESEM-EDS, XRD, and FTIR suggested that the presence of carboxyl group elements and colloidal and nano-sized MgO (periclase) particles on the biochar surface were the main adsorption sites for aqueous iron and phosphate respectively. In this study, the HW and MgO-HW biochar showed excellent Dubinin-Radushkevich isotherm (D-R) maximum adsorption capacities of 289.45 and 828.82mg/g for iron and phosphate. The kinetic study for iron and phosphate adsorption was described well by pseudo second-order model and pseudo second-order model respectively. The HW biochar and the prepared MgO-HW biochar exhibited commendable iron adsorption (98.25%) performance at 10 pH units and phosphate (96.22%) at pH 6 respectively. Thus, this research reveals a waste-to-wealth strategy by converting hardwood waste into mineral-biomass biochar with excellent Fe and P adsorption capabilities and environmental adaptability.

Calcium silicate hydrate complex konjac glucomannan-based hydrogel selectively adsorbed phosphate in low alkalinity solution

The selective recovery of phosphate from wastewater can manage nutrients and realize the recycling of phosphorus resources. In this study, a novel konjac glucomannan/pectin/calcium silicate composite hydrogel (KP-CSH) was developed for efficient recovery of phosphate in aqueous solution. The amount of alkali released after the reaction of KP-CSH in a neutral solution was small (the pH of the solution after the reaction was < 9). In a wide initial pH range (3–10), the adsorption capacity of KP-CSH in 50 mg-P/L phosphate solution reached 39∼45 mg-P/g. Besides, even if the pH of the solution after the reaction was less than 8, it could still well adsorb phosphate. The kinetic and isothermal adsorption experiments indicated that the adsorption process of phosphate by KP-CSH was chemical adsorption, and the maximum adsorption capacity was 61.2 mg-P/g. KP-CSH preferentially adsorbed phosphate even in the presence of high concentrations of competitive ions. In the actual biogas slurry, KP-CSH also exhibited the strongest selectivity/affinity for phosphate, and its distribution coefficient (Kd) was significantly higher than that of other co-existing anions and cations. The adsorption mechanism analysis indicated that Ca was the main adsorption site of KP-CSH, and that the adsorption process of target pollutants mainly involved ligand exchange and the intra-sphere complexation. Further plant seed germination and seedling growth experiments suggested that KP-CSH after phosphate recovery did not exert a negative effect on the growth of plant seedlings, and increased the chlorophyll content of seedling leaves. These results demonstrate that KP-CSH is a potential adsorbent for efficient phosphate recovery, which can be used as a slow-release phosphate fertilizer after recovering phosphate.

Efficient phosphorus removal using the La-based perovskite oxides: Role of B-site metal for modulating the surface electronic structure

Highly efficient removal of phosphate from water bodies is of great importance to controlling eutrophication. Herein, the lanthanum-based perovskites (i.e., LaMnO3, LaFeO3) were synthesized and employed for phosphorus adsorption. Adsorption experiments showed that the phosphate removal by LaMnO3 was well fitted with the pseudo second-order kinetic model, with a multi-stage adsorption process. The LaMnO3 exhibited a maximum adsorption capacity of 51.3 mg/g for phosphate calculated using the Langmuir model, which was 2.1 times higher than that of LaFeO3 under neutral conditions. Characterization and DFT calculation results further revealed that the La element on the surface of perovskite was the main adsorption site via inner-sphere complex and/or electrostatic interactions, whereas the B-site metal (i.e. Mn element) could trigger the surface electronic structure modulation such as the reduction of surface bonding barrier, for further improving the phosphate adsorption. Additionally, the LaMnO3 adsorbent exhibited commendable performance in treating natural water with low phosphorus concentration and good regenerative capability. This work provides insight into the development of novel perovskite-type adsorbents for efficiently removing phosphorus in environmental remediation.

Quantum Confinement and End-Sealing Effects for Highly Sensitive and Stable Nitrogen Dioxide Detection: Homogeneous Integration of Ti3C2Tx-Based Flexible Gas Sensors.

The real-time and room-temperature detection of nitrogen dioxide (NO2) holds significant importance for environmental monitoring. However, the performance of NO2 sensors has been hampered by the trade-off between the high sensitivity and stability of conventional sensitive materials. Here, we present a novel fully flexible paper-based gas sensing structure by combining a homogeneous screen-printed titanium carbide (Ti3C2Tx) MXene-based nonmetallic electrode with a MoS2 quantum dots/Ti3C2Tx (MoS2 QDs/Ti3C2Tx) gas-sensing film. These precisely designed gas sensors demonstrate an improved response value (16.3% at 5 ppm) and a low theoretical detection limit of 12.1 ppb toward NO2, which exhibit a remarkable 3.5-fold increase in sensitivity compared to conventional Au interdigital electrodes. The outstanding performance can be attributed to the integration of the quantum confinement effect of MoS2 QDs and the conductivity of Ti3C2Tx, establishing the main active adsorption sites and enhanced charge transport pathways. Furthermore, an end-sealing effect strategy was applied to decorate the defect sites with naturally oxygen-rich tannic acid and conductive polymer, and the formed hydrogen bonding network at the interface effectively mitigated the oxidative degradation of the Ti3C2Tx-based gas sensors. The exceptional stability has been achieved with only a 1.8% decrease in response over 4 weeks. This work highlights the innovative design of high-performance gas sensing materials and homogeneous gas sensor techniques.

Competitive Adsorptive Mechanism of H2/N2 in LTA/FAU Zeolites by Molecular Simulations and Experiments.

For industrial tail gas to be converted into high-purity hydrogen, the H2-N2 mixture needs to be separated efficiently. This work examined the adsorption characteristics and competitive mechanisms of H2 and N2 on LTA- and FAU-type zeolites, at 77 K, 298 K, and 0.1-10 bar by thoroughly analyzing results of adsorption capacity experiments and molecular simulations. In the Grand Canonical Monte Carlo (GCMC) simulations, the force field causing a molecular dipole of H2 and the polarization force field of N2 are first applied. The accuracy of the force field was experimentally verified. The findings indicate that N2 and H2 loading on Ca-FAU (Ca-LTA) are higher than Na-FAU (Na-LTA). On NaX at 77 K, the highest adsorption selectivity (N2/H2) is observed; on NaA at 298 K, it is the opposite. The GCMC data findings demonstrate that H2 and N2 have remarkably similar adsorption sites, with framework oxygen atoms and non-framework cations serving as the main adsorption sites for adsorbate molecules. Furthermore, the rate at which H2 diffuses is higher than that of N2. The study of redistribution charge before and after adsorption demonstrated that N2 has a greater affinity for the framework oxygen atoms than H2. This study provides a molecular theoretical foundation for the adsorption behavior of H2-N2 mixture in zeolites.

Sulfur-Bridged Asymmetric CuNi Bimetallic Atom Sites for CO2 Reduction with High Efficiency.

Double-atom catalysts (DACs) with asymmetric coordination are crucial for enhancing the benefits of electrochemical carbon dioxide reduction and advancing sustainable development, however, the rational design of DACs is still challenging. Herein, this work synthesizes atomically dispersed catalysts with novel sulfur-bridged Cu-S-Ni sites (named Cu-S-Ni/SNC), utilizing biomass wool keratin as precursor. The plentiful disulfide bonds in wool keratin overcome the limitations of traditional gas-phase S ligand etching process and enable the one-step formation of S-bridged sites. X-ray absorption spectroscopy (XAS) confirms the existence of bimetallic sites with N2Cu-S-NiN2 moiety. In H-cell, Cu-S-Ni/SNC shows high CO Faraday efficiency of 98.1% at -0.65V versus RHE. Benefiting from the charge tuning effect between the metal site and bridged sulfur atoms, a large current density of 550mAcm-2 can be achieved at -1.00V in flow cell. Additionally, in situ XAS, attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), and density functional theory (DFT) calculations show Cu as the main adsorption site is dual-regulated by Ni and S atoms, which enhances CO2 activation and accelerates the formation of *COOH intermediates. This kind of asymmetric bimetallic atom catalysts may open new pathways for precision preparation and performance regulation of atomic materials toward energy applications.

Tannic acid-assisted construction of amino-functionalized cellulose nanofiber composite aerogel for high-performance adsorption of Cr(VI), Cu(II) and Congo red: Experimental and DFT studies

With industrialization, heavy metals and dyes pose potential environmental and human health risks. Developing adsorbent materials with three-dimensional structures and abundant active sites is essential for removing these pollutants. In this study, we developed an environmentally friendly, high-adsorption composite aerogel (CNF-TA-PMMT-PEI) comprising cellulose nanofiber (CNF), polydopamine-modified montmorillonite (PMMT), tannic acid (TA), and polyethyleneimine (PEI). The introduction of TA and PEI increased the number of adsorbed active sites and the interaction between CNF and PMMT through strong hydrogen and chemical bonding. CNF-TA-PMMT-PEI has a honeycomb-like pore structure, high porosity (98.29 %), abundant functional groups, and showed rapid and excellent adsorption performance for Cr(VI), Cu(II), and Congo red (CR), with the Qm of 456.62, 289.86, and 3429.23 mg/g, respectively. The adsorption process followed the pseudo-second-order kinetic model and Langmuir model, indicating that the chemisorption of the monomolecular layer controlled the adsorption, and the thermodynamic adsorption indicated a spontaneous heat absorption reaction. The aerogel had good anti-interference properties and excellent adsorption performance in natural water. After 7 cycles, the removal of Cr(VI), Cu(II) and CR was maintained at 74.81 %, 68.23 % and 81.54 % of the initial performance, respectively. FTIR, XPS and DFT calculations revealed the amine group of the PEI and the phenolic hydroxyl group on TA are the main adsorption sites. The CR had the lowest adsorption energy (−4.23 Ha) compared to Cu(II) and Cr(VI), suggesting stronger interactions and greater stability on CNF-TA-PMMT-PEI. The adsorption mechanism for Cr(VI) involved electrostatic interactions, reduction, and chelation. For Cu(II), including chelation. For CR, adsorption through electrostatic attraction, π-π interactions, and Schiff base formation. In summary, CNF-TA-PMMT-PEI is an eco-friendly adsorbent with outstanding adsorption capacity and effective recovery performance for simulated wastewater.

Micro- and Mesoporous Structural Effects of Beta Zeolites for Volatile Organic Compound Sorption.

To fully exploit pore engineering in the design of more efficient zeolite adsorbents for volatile organic compound (VOC) treatment, the roles of meso- and micropores need to be clarified to provide the theoretical basis and feasible measures. In this work, the three VOC sorption properties of conventional and hierarchical porous beta zeolites were comparatively investigated to study the roles of meso- and micropores. There is a division of functions between micro- and mesopores, with micropores being the main VOC adsorption sites and mesopores greatly enhancing VOC diffusion and adsorbent reusability. On the one hand, micropores should be preserved as much as possible because obtaining mesopores by sacrificing micropores (i.e., alkali treatment) results in 28-60% decreases in adsorption capacities. On the other hand, mesopore introduction is highly desirable, which results in an enhancement of VOC intraparticle diffusion rates by 1.3-2.3 times (at the VOC concentration of 600 ppm) and chlorobenzene adsorption capacity on the 20th cycle increasing from 78% of the initial value to 89 and 93%. The findings may provide valuable information about zeolite-based adsorbents for adsorption removal or recovery of VOCs.

In-situ precipitation zero-valent Co on Co2VO4 to activate oxygen vacancies and enhance bimetallic ions redox for efficient detection toward Hg(II)

Despite the widespread utilization of variable valence metals in electrochemistry, it is still a formidable challenge to enhance the valence conversion efficiency to achieve excellent catalytic activity without introducing heterophase elements. Herein, the in-situ precipitation of Co particles on Co2VO4 not only enhanced the concentration of oxygen vacancies (Ov) but also generated a greater number of low-valence metals, thereby enabling efficient reduction towards Hg(II). The electroanalysis results demonstrate that the sensitivity of Co/Co2VO4 towards Hg(II) was measured at an impressive value of 1987.74 μA μM−1 cm−2, significantly surpassing previously reported results. Further research reveals that Ov acted as the main adsorption site to capture Hg(II). The redox reactions of Co2+/Co3+ and V3+/V4+ played a synergistic role in the reduction of Hg(II), accompanied by the continuous supply of electrons from zero-valent Co to expedite the valence cycle. The Co/Co2VO4/GCE presented remarkable selectivity towards Hg(II), with excellent stability, reproducibility, and anti-interference capability. The electrode also exhibited minimal sensitivity fluctuations towards Hg(II) in real water samples, underscoring its practicality for environmental applications. This study elucidates the mechanism underlying the surface redox reaction of metal oxides facilitated by zero-valent metals, providing us with new strategies for further design of efficient and practical sensors.

Insight into the role of reactive species on catalyst surface underlying peroxymonosulfate activation by P–Fe2MnO4 loaded on bentonite for trichloroethylene degradation

In this study, bentonite supporting phosphorus-doped Fe2MnO4 (BPF) was synthesized and applied for PMS activation to degrade TCE. Morphology and structure characterization results indicated the successfully synthesized of BPF, and the BPF/PMS system not only featured high TCE removal (97.4%) but also high reaction rate constant (kobs = 0.0554 min−1) and PMS utilization (70.4%, kobs = 0.0228 min−1). According to the results of various experiments, massive oxygen vacancies on P–Fe2MnO4 alter its charge balance and facilitate the electron transfer process named adjacent transfer (direct electron capture by adsorbed PMS from adjacent TCE). Mn(III) is the main adsorption site for PMS, and the hydroxyl groups on the catalyst (Fe sites of P–Fe2MnO4, Si and Al sites of bentonite) can also offer binding sites for PMS. The hydrogen-bonded PMS on Fe(III) and Mn(III) sites will subsequently accept the discharged electrons to generate free radicals and high-valent metal species. Meanwhile, electron loss of HSO5− that chemically bonded to hydroxyl groups on bentonite will generate SO5•−, which will further produce 1O2 through self-bonding. the active species on the catalyst surface contribute 65% of TCE degradation in the heterogeneous catalytic oxidation system.

Competitive adsorption-diffusion coupling process of helium-nitrogen mixture in shale kerogen nano-slit

Helium, as a probe gas with low adsorption capacity, is widely used for measuring porosity, permeability, and specific surface area in reservoir rocks of unconventional gas such as shale and coal. The pretreatment duration of these rock samples determines the amount of residual nitrogen in their pores, and the competitive adsorption and diffusion of residual nitrogen with the probe gas has a significant impact on the measurement results of their physical properties. This work aims to reveal the mechanisms involved in the competitive adsorption-diffusion coupling process of nitrogen-helium mixtures. Brief experiments were conducted to demonstrate the competitive adsorption between nitrogen and helium in shale. Subsequently, molecular dynamics simulation was employed to investigate this process and provide necessary details. Meanwhile, a theoretical model was developed to describe the diffusion of gas molecules in this process. Our results indicate that helium rapidly permeates shale samples and reaches an equilibrium distribution. However, the competitive adsorption between nitrogen and helium can slow down the helium permeation process, which can be attributed to the main adsorption sites occupied by nitrogen. The agreement between FEM computations and MD simulations validates our model for various mechanisms. Furthermore, our model can be applied to a wider range of porous materials and gas mixtures in related fields.

A novel mycelial pellet applied to remove polycyclic aromatic hydrocarbons: High adsorption performance & its mechanisms

Mycelial pellets formed by Penicillium thomii ZJJ were applied as efficient biosorbents for the removal of polycyclic aromatic hydrocarbons (PAHs), which are a type of ubiquitous harmful hydrophobic pollutants. The live mycelial pellets were able to remove 93.48 % of pyrene at a concentration of 100 mg/L within 48 h, demonstrating a maximum adsorption capacity of 285.63 mg/g. Meanwhile, the heat-killed one also achieved a removal rate of 65.01 %. Among the six typical PAHs (pyrene, phenanthrene, fluorene, anthracene, fluoranthene, benzo[a]pyrene), the mycelial pellets preferentially adsorbed the high molecular weight PAHs, which also have higher toxicity, resulting in higher removal efficiency. The experimental results showed that the biosorption of mycelial pellets was mainly a spontaneous physical adsorption process that occurred as a monolayer on a homogeneous surface, with mass transfer being the key rate-limiting step. The main adsorption sites on the surface of mycelia were carboxyl and N-containing groups. Extracellular polymeric substances (EPS) produced by mycelial pellets could enhance adsorption, and its coupling with dead mycelia could achieve basically the same removal effect to that of living one. It can be concluded that biosorption by mycelial pellets occurred due to the influence of electrostatic and hydrophobic interactions, consisting of five steps. Furthermore, the potential applicability of mycelial pellets has been investigated considering diverse factors. The mycelia showed high environmental tolerance, which could effectively remove pyrene across a wide range of pH and salt concentration. And pellets diameters and humic acid concentration had a significant effect on microbial adsorption effect. Based on a cost-effectiveness analysis, mycelium pellets were found to be a low-cost adsorbent. The research outcomes facilitate a thorough comprehension of the adsorption process of pyrene by mycelial pellets and their relevant applications, proposing a cost-effective method without potential environmental issues (heat-killed mycelial pellets plus EPS) to removal PAHs.

Efficacy and Mechanism of Tetracycline Adsorption by Boron-doped Mesoporous Carbon

Using coconut shell and boric acid as raw materials， a new boron-doped coconut shell mesoporous carbon material （B-CSC） was prepared using a simple one-step pyrolysis method for efficient adsorption and removal of tetracycline pollutants in water. The effects of pyrolysis temperature and boron-carbon mass ratio on the adsorption performance under key preparation conditions were systematically studied， and their microstructure and physicochemical properties were characterized using a specific surface area and pore size analyzer （BET）， field emission scanning electron microscopy （SEM）， X-ray photon spectroscopy （XPS）， Raman spectrometer （Raman）， and Zeta potentiometer （Zeta）. The effects of initial pH， different metal cations， and different background water quality conditions on the adsorption effect were systematically investigated. Combined with material characterization and correlation analysis， the enhanced adsorption mechanism was discussed and analyzed in depth. The results showed that one-step pyrolysis could incorporate boron into the surface and crystal lattice of coconut shell charcoal， resulting in a larger specific surface area and pore volume， and the main forms of boron introduced were H3BO3， B2O3， B， and B4C. The adsorption capacity of B-CSC to tetracycline reached 297.65 mg·g-1， which was 8.9 times that of the original coconut shell mesoporous carbon （CSC）. At the same time， the adsorption capacity of B-CSC for rhodamine B （RhB）， bisphenol A（BPA）， and methylene blue （MB）， common pollutants in aquatic environments， was as high as 372.65， 255.24， and 147.82 mg·g-1， respectively. The adsorption process of B-CSC to tetracycline was dominated by physicochemical interaction， mainly involving liquid film diffusion， surface adsorption， mesoporous and microporous diffusion， and active site adsorption， and H3BO3 was the main adsorption site. The adsorption strengthening mechanism mainly reduced the chemical inertness of the carbon network and enhanced its π-π interaction and hydrogen bonding with tetracycline molecules.

Construction of defective hydroxyl-rich metal–organic framework for effective capture of borate ion

Developing high-efficiency adsorbents for borate ion still remains up to now. Herein, a facile and green method is used to obtain serial hydroxyl functionalized UiO-66-(OH)2-AA-X (AA, acetic acid; X, AA usage) by using AA as a modulator. The addition of AA can induce the generation of defect units in the adsorbents due to its partial substitution for the organic linkers. It is found that the defect degree as well as the porosity can be neatly regulated by the AA amount. In particular, UiO-66-(OH)2-AA-20 with the most defects exhibits a high adsorption capacity (891.1 mg g−1) towards borate ion, outperforming the most previously reported adsorbents. The adsorption reaches equilibrium at 600 min. The adsorption behavior can be well described by the Langmuir isotherm model and pseudo-second-order model. Besides, UiO-66-(OH)2-AA-20 possesses a wide pH (3–10) tolerance, excellent anti-interference ability, and good reusability. A combination of experimental characterization and density functional theory calculation indicates the free hydroxyl groups serve as the main adsorption sites, and the adsorption-driven forces involve electrostatic, coordination, hydrogen bonds and π–π stacking interactions. On these basis, our work may provide a guideline for constructing high-efficiency defective adsorbents for borate ions via a modulated strategy.

Simultaneous removal of various organic dyes from aqueous solutions using a UiO-67-type metal–organic framework

Water pollution has become increasingly critical with recent economic and industrial developments. Highly efficient methods are required to remove diverse pollutants in factory and domestic wastewater. For efficient wastewater treatment, the removal of various compounds in a single step is desirable. In this study, the adsorption characteristics of UiO-67 were evaluated using four organic dye compounds with different molecular sizes and electrostatic properties, i.e., methylene blue, rhodamine B, methyl orange, and Acid Red 52. UiO-67 showed high adsorption capacity for the four organic dye compounds regardless of ionicity or molecular size. Further, the equilibrium analysis revealed that not only methylene blue and methyl orange but also rhodamine B and Acid Red 52 with large molecular sizes were adsorbed in the pores (main adsorption sites) of UiO-67. The recycling resistance of UiO-67 was studied using a mixture of methylene blue and methyl orange, and UiO-67 was found to exhibit high adsorption capacity for both methylene blue and methyl orange even after four times of recycling. Therefore, UiO-67 is a promising adsorbent that can simultaneously remove compounds with different ionicities and molecular sizes.

Removal of sulfonamide antibiotics by non-free radical dominated peroxymonosulfate oxidation catalyzed by cobalt-doped sulfur-containing biochar from sludge

The reuse of activated sludge as a solid waste is severely underutilized due to the limitations of traditional treatment and disposal methods. Given that, the sulfur-containing activated sludge catalyst doped with cobalt (SK-Co(1.0)) was successfully prepared by one-step pyrolysis and calcinated at 850 ℃. The generation of CoSx was successfully characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), indicating that the sulfur inside the sludge was the anchoring site for the externally doped cobalt. Cobalt (Ⅱ) (Co2+), as the main adsorption site for peroxymonosulfate(PMS), formed a complex (SK-Co(1.0)-PMS* ) and created the conditions for the generation of surface radicals. The SK-Co(1.0)/PMS system showed high degradation efficiency and apparent rate constants for Sulfamethoxazole (SMX) (91.56% and 0.187 min−1) and Sulfadiazine (SDZ) (90.73% and 0.047 min−1) within 10 min and 30 min, respectively. Three sites of generation of 1O2, which played a dominant role in the degradation of SMX and SDZ in the SK-Co(1.0)/PMS system, were summarized as：sulfur vacancies (SVs), the Co3+/Co2+ cycles promoted by sulfur(S) species, oxygen-containing functional groups (C-O). The degradation mechanisms and pathways had been thoroughly investigated using DFT calculations. In view of this, a new idea for the resource utilization of activated sludge solid waste was provided and a new strategy for wastewater remediation was proposed.

Synergistic effects between Mn and Co species in CO2 hydrogenation over xCo/MnO catalysts

CO2 hydrogenation technology has great potential for mitigating the greenhouse effect and creating a green economy. The development of catalysts plays a key role in the progress of CO2 hydrogenation technology. In this study, the xCo/MnO catalysts for CO2 hydrogenation reaction were prepared by the impregnation method using MnOx as the catalyst support. And the effects of the Co loading on the CO2 hydrogenation performances of the prepared xCo/MnO catalysts were investigated. The active Co0 species on the xCo/MnO catalysts surface are the main active centers for the CO2 hydrogenation reaction, and the medium basic sites on the xCo/MnO catalysts are the main CO2 adsorption sites. The MnOx support possesses a large number of medium basic sites, which can enhance the CO2 molecules adsorption ability of the xCo/MnO catalysts. An effective regulation of the basic and hydrogenation active site numbers on the xCo/MnO catalysts surface can be achieved by changing the Co loading amount, which in turn can affect the CO2 molecules adsorption, activation and hydrogenation abilities of the xCo/MnO catalysts. Moreover, the Mn1-yCoyO solid solution was found to be formed in the prepared xCo/MnO catalysts, which is conducive to the dispersion of metal Co nanoparticles on the MnO surface and the generation of oxygen-deficient sites. The CO2 desorption amount on the 12Co/MnO catalyst reached 1.76 mmol/g, which provided the catalyst with strong CO2 adsorption and activation abilities, enabling it to exhibit great CO2 hydrogenation performance. Under the conditions of atmosphere and 420 °C, the CO2 conversion and CH4 selectivity on the prepared 12Co/MnO catalyst reached 57.5 % and 78.8 %, separately. Furthermore, the CO2 conversion was able to consistently remain at the initial 57.5 %, and the CH4 selectivity was maintained above 70.0 % in the 10 times CO2 hydrogenation cycle tests on the 12Co/MnO catalyst. Our study highlights the potential of using MnOx as catalyst support in the CO2 hydrogenation reaction, and the findings will provide convenient for the future studies.

Effect of ligands regulation on Al-based metal organic frameworks for selective adsorption of xenon from spent fuel

Effective separation of inert gas such as Xe and Kr from used nuclear fuel is significant for maintaining ecological environment safety and recycling nuclear fuel. In this study, Al-CDC and Al-BDC with similar linear ligands were synthesized to reveal the influence of ligand regulation on Xe separation under different pressure conditions. The results displayed that the adsorption capacity of Al-BDC for Xe could reach 2.66 mmol g-1 under normal pressure, which is 1.11 times higher than that of Al-CDC, depending on its higher specific surface area and bigger pore volume. On the contrary, the Xe adsorption capacity of Al-CDC with the feature of narrow micropore structure and saturated C-H or oxygen-containing functional groups reached 1.44 mmol g−1 at 0.1 bar, which was 2.82 times higher than that of Al-BDC, resulting in a remarkable difference in Xe working capacity between Al-CDC (0.43 mmol g−1) and Al-BDC (0.073 mmol g−1) through dynamic breakthrough experiments. Meanwhile, the Henry’s selectivity of Al-CDC for Xe/Kr and Xe/N2 was up to 13.97 and 110.31, Compared with most porous adsorbents in previous reports, Al-CDC exhibits both high adsorption capacity and high selectivity. Innovatively, we analyzed the advantage in capacity and selectivity by the perspective of ligands, and the calculation results of the complete cell also proved that the saturated C-H group and benzene ring center on cyclohexane are the main adsorption sites of Al-CDC and Al-BDC for Xe, respectively. Therefore, a higher polar ligand in Al-CDC could lead to strong static binding energy and single cell binding energy which attribute to a high selective Xe adsorption. These results revealed the key structural characteristics for selective Xe adsorption under different pressure conditions, providing valuable suggestions for the design of separation materials from spent fuel.

Molecular simulation of the adsorption and diffusion properties of CH4 and CO2 in the microporous system of coal

Micropores are the main adsorption sites for gases in coal. The research of the adsorption and diffusion pattern of gases in micropores is important for CO2-ECBM engineering and other measures to improve production. In this study, a multiscale microporous system with intramolecular pores, intermolecular pores, and slit pores is proposed. Adsorption and diffusion characteristics of CH4 and CO2 in different microporous systems were investigated. The results show that the adsorption of different microporous systems is basically consistent at low pressures (<2 MPa). Upon further increase in pressure, adsorption increases with increasing slit pore size. Gas molecules in coal are preferentially adsorbed in the intramolecular and intermolecular pores, and gas molecules in the slit pores are preferentially adsorbed in the slit pore walls. The increase in gas pressure and slit pore size decreases the proportion of gases adsorbed in the intramolecular and intermolecular pores and also increases the proportion adsorbed in the slit pores. Increase in size of the slit pores and decrease in adsorption will result in an increase in self-diffusion coefficients of gases. The results of self-diffusion coefficients of pores with different scales indicate that slit pores have the largest self-diffusion coefficients, followed by the intermolecular pores, and the smallest for the intramolecular pores. The isosteric heat of gases tends to decrease and then increase with increasing adsorption. The increase of slit pore size will decrease interaction energy. This study gives a reference for adsorption and diffusion mechanisms of gases in microporous systems, as well as a basis for gas injection displacement studies.

Preparation of chitosan mesoporous membrane/halloysite composite for efficiently selective adsorption of Al(III) from rare earth ions solution through constructing pore structure on substrate

The removal of impurity Al(III) from rare earth ion solution by selective adsorption method was one of the challenging tasks. Herein, calcination and acid dissolution treatment were used to construct the pore structure for the halloysite substrate (Hal-650-H) and provide conditions for the formation of the chitosan mesoporous membrane to prepare composite (Hal-H-2CS). The selective adsorption properties and mechanism of the Hal-H-2CS for Al(III) in the rare earth ion solution were studied. The results showed that the formation of mesoporous structures for chitosan provided abundant sites for the adsorption of Al(III). Hal-H-2CS showed remarkable selective adsorption properties for Al(III) in a wide pH range and the binary mixtures with high content of Al(III) or La(III). The maximum adsorption capacity of Al(III) was 106 mg/g, while the adsorption capacity of La(III) was only 1.41 mg/g at pH 4.0. In addition, the Hal-H-2CS exhibited excellent regeneration and structural stability. The remarkable selective properties of Hal-H-2CS was achieved by the synergistic effect between chitosan mesoporous membrane and Hal-650-H, the main adsorption sites were the OH, NH2, CONH2 of chitosan and the oxygen sites of the Hal-650-H. This work provides a new strategy for the design and preparation of outstanding selective adsorbent for Al(III).