Adsorption Structure Research Articles

Designing activated carbon and porous carbon nanofibers for insight into their differences in adsorption affinity mechanisms of VOCs

The adsorption technology has been considered as an effective and economical strategy to control volatile organic compounds (VOCs) through various types of porous materials. As two potential porous materials, activated carbon and carbon nanofibers were synthesized as VOCs adsorbents. In order to investigate the difference in the adsorption of VOCs between activated carbon and carbon nanofibers, the specific surface area, pore structure and chemical functional groups of VOCs adsorbent were analyzed. In particular, the carbon nanofibers (CNF) activated at 800 ℃ showed an excellent specific surface area (2524 m2·g−1), abundant pores (1.66 mL·g−1), and rich functional groups (N: 8.29 at%). Meanwhile, the carbon nanofibers had a better adsorption performance for acetone (1069.82 mg·g−1) and toluene (427.72 mg·g−1) than activated carbon materials. Furthermore, the theoretical calculations were conducted to reveal the mechanism of favorable adsorption on the CNFs. The theoretical adsorption energies of CNF are −31.9 kJ·mol−1 (acetone) and −67.5 kJ·mol−1 (toluene), respectively, which have more favorable adsorption sites and stronger charge redistribution than activated carbon. This research guided the approach to obtain the porous carbon nanofibers and provided the evidence for CNFs (curved carbon) exhibiting a better adsorption ability to VOCs.

Unraveling pH-Dependent Changes in Adsorption Structure of Uranyl on Alumina (012).

Mitigating uranium transport in groundwater is imperative for ensuring access to clean water across the globe. Here, in situ resonant anomalous X-ray reflectivity is used to investigate the adsorption of uranyl on alumina (012) in acidic aqueous solutions, representing typical UVI concentrations of contaminated water near mining sites. The analyses reveal that UVI adsorbs at two distinct heights of 2.4-3.2 and 5-5.3 Å from the surface terminal oxygens. The former is interpreted as the mixture of inner-sphere and outer-sphere complexes that adsorb closest to the surface. The latter is interpreted as an outer-sphere complex that shares one equatorial H2O with the terminal surface oxygen. With increasing pH, we observe an increasing prevalence of these outer-sphere complexes, indicating the enhanced role of the hydrogen bond that stabilizes adsorbed uranyl species. The presented work provides a molecular-scale understanding of sorption of uranyl on Al-based-oxide surfaces that has implications for environmental chemistry and materials science.

Optimization and mechanism of the novel eco-friendly additives for solidification and stabilization of dredged sediment.

Solidification/stabilization technology is commonly used in the rehabilitation of dredged sediment due to its cost-effectiveness. However, traditional solidification/stabilization technology relies on cement, which increases the risk of soil alkalization and leads to increased CO2 emissions during cement production. To address this issue, this study proposed an innovative approach by incorporating bentonite and citrus peel powder as additives in the solidifying agent, with the aim of reducing cement usage in the dredged sediment solidification process. The research results showed that there is a significant interaction among cement, bentonite, and citrus peel powder. After response surface methodology (RSM) optimization, the optimal ratio of the cementitious mixture was determined to be 14.86 g/kg for cement, 5.85 g/kg for bentonite, and 9.31 g/kg for citrus peel powder. The unconfined compressive strength (UCS) of the solidified sediments reached 3144.84 kPa. The reaction products of the solidification materials, when mixed with sediment, facilitated adsorption, gelation, and network structure connection. Simultaneously, the leaching concentration of heavy metals was significantly decreased with five heavy metals (Zn, As, Cd, Hg, and Pb) leaching concentrations decreasing by more than 50%, which met the prescribed thresholds for green planting. This study demonstrated the ecological benefits of employing bentonite and citrus peel powder in the solidification process of dredged sediment, providing an effective solution for sediment solidification.

Optimized Intermediates Adsorption Configuration on Co-Doped Fe2P@NiP2 Heterojunction Interface for Enhanced Electrocatalytic Nitrate-To-Ammonia Conversion.

The extraction of ammonia (NH3) through electrocatalytic nitrate reduction reaction (NO3 -RR) represents a sustainable avenue in NH3 generation and utilization. However, the catalytic efficiency of the NO3 -RR is hindered by the sluggish kinetics. This study first theoretically found that phosphide-based heterostructure can alter the adsorption structure of intermediates in the nitrate-to-ammonia process, thereby achieving precise regulation of the energy barrier in the rate-determining step. Based on theoretical design, a novel Co-doped Fe2P@NiP2 heterojunction catalyst is successfully synthesized, which deliver a notable NH3 yield rate of 0.395mmolh-1cm-2 at -0.7V versus RHE, as well as a remarkable ammonia Faraday efficiency of 97.2% at -0.6V versus RHE. Experimental and theoretical results further confirm that redistributing electrons and shifting the center of the d-band upwards through interfacial doping modulate intermediates adsorption strength and inhibition of hydrogen evolution, leading to excellent performance in NO3 --to-NH3. Further integrating the Co-Fe2P@NiP2 catalyst into a Zn-nitrate battery exhibits a substantial voltage output of 1.49V and a commendable power density of 13.2mWcm-2. The heteroatom-doped heterojunction strategy provides a versatile route for developing advanced catalysts, thereby broadening the horizons of electrocatalytic methodologies for nitrate reduction and ammonia synthesis.

Hydrophilicity of Organically Modified Montmorillonite and Effect on Benzene Adsorption by the Molecular Dynamics Method.

Interlayer modification of layered materials with organocations has been known to endow the nanocomposite with hydrophobicity, and adsorption of aromatic compounds in the aqueous phase has been investigated for decades by using montmorillonite, a representative layered clay mineral, as the host material. Usage of the organocation has been believed to be effective due to the π-π interaction with the aromatic adsorbate, the presence of which is not verified spectroscopically in the water-immersed state. Considering that the organocation is generally regarded as a pillar to keep the interlayer space, the interaction between the organocation and adsorbate has not yet been clarified sufficiently. In the present study, we revealed the role of the organocation by the molecular dynamics method, where tetramethylammonium (TMA) and trimethylphenylammonium (TMPA) ions were selected as the representative and simple organocations, and benzene was the adsorbate to exclude the effect of the substitution group. Both H2O and benzene molecules were introduced in the interlayer of TMA- or TMPA-modified montmorillonite to model the water-immersed adsorption structure. It was found that H2O is preferentially distributed on the clay surface, followed by the center of the interlayer when the amount of H2O is large. In the adsorption model, benzene was vertically adsorbed on the clay surface. Radial distribution function analysis revealed that benzene is distributed around both the methyl and the phenyl groups in the TMA and TMPA cations, but the orientation of the phenyl ring is not consistent with that of benzene. Thus, benzene was found not to form the π-π interaction in montmorillonite modified with the TMPA cations in the water-immersed state. Furthermore, the surface was partly covered with the phenyl group in the TMPA cation, decreasing the adsorption area. Therefore, the experimental suggestion that benzene is adsorbed on the clay surface was reproduced by our simulation, and the interaction between the organocation and benzene and surface occupancy should be paid attention to maximize the adsorption property.

Lignin-impregnated biochar assisted with microwave irradiation for CO2 capture: adsorption performance and mechanism

Bamboo biochar was modified by lignin impregnation and microwave irradiation to enhance its performance for CO2 capture. The pore structure of lignin-impregnated biochar was significantly affected by the impregnation ratio. The maximum specific surface area of 377.32 m2 g−1 and micropore volume of 0.163 cm3 g−1 were observed on the biochar with an impregnation ratio of 1:20 (mass ratio of lignin to biochar). Lignin impregnation increased the CO2 adsorption capacity of biochar up to 134.46 mg g−1. Correlation analysis confirmed the crucial role of biochar’s pore structure in adsorption. The Avrami model fitted the CO2 capture curves well. The calculation of adsorption activation energy suggested that the adsorption process was dominated by physical mechanism assisted with partial chemical mechanism. Meanwhile, Langmuir isotherm analysis indicated that lignin impregnation transformed the larger pores of biochar into more uniform micropores, thereby making the adsorption process closer to monolayer adsorption. Both the high reusability (89.79–99.06%) after 10 successive cycles and the excellent CO2 selectivity in competitive adsorption confirmed that lignin-impregnated biochar is an outstanding adsorbent for CO2 capture.Graphical

Effect of inorganic material surface chemistry on structures and fracture behaviours of epoxy resin

The mechanisms underlying the influence of the surface chemistry of inorganic materials on polymer structures and fracture behaviours near adhesive interfaces are not fully understood. This study demonstrates the first clear and direct evidence that molecular surface segregation and cross-linking of epoxy resin are driven by intermolecular forces at the inorganic surfaces alone, which can be linked directly to adhesive failure mechanisms. We prepare adhesive interfaces between epoxy resin and silicon substrates with varying surface chemistries (OH and H terminations) with a smoothness below 1 nm, which have different adhesive strengths by ~13 %. The epoxy resins within sub-nanometre distance from the surfaces with different chemistries exhibit distinct amine-to-epoxy ratios, cross-linked network structures, and adhesion energies. The OH- and H-terminated interfaces exhibit cohesive failure and interfacial delamination, respectively. The substrate surface chemistry impacts the cross-linked structures of the epoxy resins within several nanometres of the interfaces and the adsorption structures of molecules at the interfaces, which result in different fracture behaviours and adhesive strengths.

Study on the Effects of Wettability and Pressure in Shale Matrix Nanopore Imbibition during Shut-in Process by Molecular Dynamics Simulations.

Shut-in after fracturing is generally adopted for wells in shale oil reservoirs, and imbibition occurring in matrix nanopores has been proven as an effective way to improve recovery. In this research, a molecular dynamics (MD) simulation was used to investigate the effects of wettability and pressure on nanopore imbibition during shut-in for a typical shale reservoir, Jimsar. The results indicate that the microscopic advancement mechanism of the imbibition front is the competitive adsorption between "interfacial water molecules" at the imbibition front and "adsorbed oil molecules" on the pore wall. The essence of spontaneous imbibition involves the adsorption and aggregation of water molecules onto the hydroxyl groups on the pore wall. The flow characteristics of shale oil suggest that the overall push of the injected water to the oil phase is the main reason for the displacement of adsorbed oil molecules. Thus, shale oil, especially the heavy hydrocarbon component in the adsorbed layer, tends to slip on the walls. However, the weak slip ability of heavy components on the wall surface is an important reason that restricts the displacement efficiency of shale oil during spontaneous imbibition. The effectiveness of spontaneous imbibition is strongly dependent on the hydrophilicity of the matrix pore's wall. The better hydrophilicity of the matrix pore wall facilitates higher levels of adsorption and accumulation of water molecules on the pore wall and requires less time for "interfacial water molecules" to compete with adsorbed oil molecules. During the forced imbibition process, the pressure difference acts on both the bulk oil and the boundary adsorption oil, but mainly on the bulk oil, which leads to the occurrence of wetting hysteresis. Meanwhile, shale oil still existing in the pore always maintains a good, stratified adsorption structure. Because of the wetting hysteresis phenomenon, as the pressure difference increases, the imbibition effect gradually increases, but the actual capillary pressure gradually decreases and there is a loss in the imbibition velocity relative to the theoretical value. Simultaneously, the decline in hydrophilicity further weakens the synergistic effect on the imbibition of the pressure difference because of the more pronounced wetting hysteresis. Thus, selecting an appropriate well pressure enables cost savings and maximizes the utilization of the formation's natural power for enhanced oil recovery (EOR).

First-principles study on the effect of pressure on the adsorption of H2O on the Mg-montmorillonite (010) surface

The effect of pressure on H2O adsorption on the montmorillonite surface is a crucial issue in geomechanics and high-pressure physics. In this paper, the effect of pressure on adsorption capability were calculated based on density-functional theory (DFT) for pressures ranging from 0 to 18 GPa, and the adsorption energies and structures of the H2O molecules were analyzed with different surface coverages (0 < Θ ≤ 1.0 ML). Firstly, the clean (010) surface of Mg-montmorillonite was modelled at different pressures from an atomic perspective, then the calculations demonstrated that single H2O molecules were stably adsorbed on the top, bridge, hollow and interlayer bridge sites, independent of pressure. However, the adsorption energies at different sites were significantly influenced by the pressure and showed different trends. For the hollow and bridge sites, the adsorption energy increased within the pressure range 0–2 GPa but decreased within the pressure range 2–18 GPa. Conversely, for the top sites, the adsorption energy decreased with increasing pressure within the range 0–2 GPa but increased with increasing pressure within the range 2–18 GPa. For increasing coverage with H2O molecules, the adsorption energy was almost constant at 0 GPa but decreased within the range 0 < Θ ≤ 1.0 ML at 2, 10, and 18 GPa. Furthermore, the adsorption energies for the bridge sites all increased with increasing coverage but decreased with increasing coverage for the interlayer bridge sites at the four pressures. In addition, other characteristics of the H2O and Mg-montmorillonite (010) surface were discussed, including bonding, changes in the electronic density of states, the charge distribution, and the structure of the atomic interlayer at different pressures.

Accelerated Lignocellulosic Molecule Adsorption Structure Determination.

Here, we present a study combining Bayesian optimization structural inference with the machine learning interatomic potential Neural Equivariant Interatomic Potential (NequIP) to accelerate and enable the study of the adsorption of the conformationally flexible lignocellulosic molecules β-d-xylose and 1,4-β-d-xylotetraose on a copper surface. The number of structure evaluations needed to map out the relevant potential energy surfaces are reduced by Bayesian optimization, while NequIP minimizes the time spent on each evaluation, ultimately resulting in cost-efficient and reliable sampling of large systems and configurational spaces. Although the applicability of Bayesian optimization for the conformational analysis of the more flexible xylotetraose molecule is restricted by the sample complexity bottleneck, the latter can be effectively bypassed with external conformer search tools, such as the Conformer-Rotamer Ensemble Sampling Tool, facilitating the subsequent lower-dimensional global minimum adsorption structure determination. Finally, we demonstrate the applicability of the described approach to find adsorption structures practically equivalent to the density functional theory counterparts at a fraction of the computational cost.

Interactions of Acetylene-Derived Thioester Collectors with Gold Surfaces: A First-Principles Study

The high reactivity of the acetylene group enables the formation of strong chemical bonds with active sites on mineral surfaces, thereby improving the flotation performance of gold minerals. This study utilized density functional theory (DFT) to analyze the quantum chemical parameters of structure, Mulliken population, and the frontier orbitals of a thioester collector containing an acetylene group, PDEC (prop-2-yn-1-yl diethylcarbamodithioate). PDEC was compared with analogous thioester collectors Z-200 and Al-DECDT. The interaction mechanism of PDEC on the Au(1 1 1) surface was simulated, followed by empirical validation through adsorption experiments. The findings indicate that the S atom of PDEC in the carbon–sulfur group exhibits shorter covalent bond lengths, and has reduced carbon–sulfur double bonds and Mulliken population, resulting in enhanced electron localization. This confers greater selectivity to PDEC during its adsorption on mineral surfaces. Frontier orbital analysis shows that the electrons of the acetylene group possess a notable electron-accepting capacity, significantly influencing the frontier orbital energy of PDEC and playing a pivotal role in the bonding interaction with mineral surfaces. Both the S atom in the carbon–sulfur group and its acetylene group establish stable adsorption structures with the A(111) surface in a single coordination mode. The adsorption energy sequence is PDEC &gt; Al-DECDT &gt; Z-200. Partial density of states demonstrates that the S 3p orbit of the carbon–sulfur group hybridizes with the Au 5d orbit, while the C 2p orbit of the acetylene group engages in weaker back-donation bonding with the Au 5d orbit. This is corroborated by the electron density difference and post-adsorption Mulliken population analyses, revealing that the S atom of the carbon–sulfur group in PDEC donates electrons to the Au atom, forming dominant positive coordination bonds, whereas the acetylene group accepts partial electrons from the Au atom, resulting in weaker back-donation bonds. The adsorption experiments align with the DFT adsorption energy results.

First-principles study of the effects of doping B, N, and O on the photoelectric properties of Cr adsorbed GaS.

To lessen the impact of the dangerous metal Cr, this paper applies the first principles to investigate the adsorption behavior and photoelectric properties of GaS on Cr. The effects of doped GaS on Cr adsorption behavior are investigated with four GaS systems, which are pure, boron (B)-doped, nitrogen (N)-doped, and oxygen (O)-doped, in order to maximize the characteristics of GaS for use in novel sectors, to obtain understanding of the impact of doping on the electronic structure and optical properties of GaS adsorption of Cr, as well as to promote the development of the material. Four GaS adsorbed Cr systems, pure, B-doped, N-doped, and O-doped, are optimized, and the optimized results show that the stable adsorption position of Cr on both pure and doped GaS is the top position of Ga atoms, whereas doped elements B, N, and O can promote the adsorption of Cr on GaS, and the order of the strength of this promotion is B > N > O. In this paper, molecular simulation calculations and analyses using the CASTEP module in the software Materials Studio are performed to simulate the structure optimization of GaS-adsorbed Cr materials doped with B, N, and O atoms by using the generalized gradient approximation (GGA) plane-wave pseudopotential approach [1] and the Perdew-Burke-Ernzerhof (PBE) generalized function [2]. From the convergence test, it is reasonable to set the K-point network to 4 × 4 × 1 and the truncation energy to 500eV [3]. In this paper, a 3 × 3 × 1 supercell structure with 18 S atoms and 18Ga atoms is selected. The convergence value of the iterative accuracy is 1.0e - 5eV/atom, and all the atomic forces are less than 0.02eV/Å. A vacuum layer of 16Å is also set in the C direction to avoid interlayer interactions of GaS. First, we optimize the geometry of the model and then analyze the nature of the adsorption energy and electronic structure corresponding to the model.

Unveiling the enhancement mechanism of Fe ion for muscovite flotation: Adjustment of surface potential and agent dispersion

Metal ions have been used to improve the flotation recovery of muscovite, while the enhancement mechanism is still unclear. In this paper, density functional theory (DFT) calculations and molecular dynamics (MD) simulations were employed to investigate the adsorption structure of sodium oleate (NaOL) on muscovite surface, and the diffusivity and foaming of NaOL in the pulp system, in presence of Fe3+ at different pH range. DFT calculation results suggested that the adsorption of iron ions, include FeOH2+ and Fe(OH)2+, could change the surface charge from negative to positive, thus enhancing binding performance for OL−. Moreover, MD simulations indicated that the distribution of iron ions in aqueous solution can significantly affect the dispersion of sodium oleate molecules. Specifically, FeOH2+ may lead to the complexation of oleate ions and result in the agglomeration, which is not conducive to its dispersion in solution. However, Fe(OH)2+ can significantly inhibit the aggregation of OL− molecules, and accelerate the dispersion of OL− in flotation pulp. This work reveals atomic-level mechanism of Fe ion on the dispersion and adsorption of sodium oleate in pulp, which is helpful to the understanding of minerals flotation behavior in presence of metal ions.

Molecular Self-Assembly and Adsorption Structure of 2,2'-Dipyrimidyl Disulfides on Au(111) Surfaces.

The effects of solution concentration and pH on the formation and surface structure of 2-pyrimidinethiolate (2PymS) self-assembled monolayers (SAMs) on Au(111) via the adsorption of 2,2'-dipyrimidyl disulfide (DPymDS) were examined using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). STM observations revealed that the formation and structural order of 2PymS SAMs were markedly influenced by the solution concentration and pH. 2PymS SAMs formed in a 0.01 mM ethanol solution were mainly composed of a more uniform and ordered phase compared with those formed in 0.001 mM or 1 mM solutions. SAMs formed in a 0.01 mM solution at pH 2 were composed of a fully disordered phase with many irregular and bright aggregates, whereas SAMs formed at pH 7 had small ordered domains and many bright islands. As the solution pH increased from pH 7 to pH 12, the surface morphology of 2PymS SAMs remarkably changed from small ordered domains to large ordered domains, which can be described as a (4√2 × 3)R51° packing structure. XPS measurements clearly showed that the adsorption of DPymDS on Au(111) resulted in the formation of 2PymS (thiolate) SAMs via the cleavage of the disulfide (S-S) bond in DPymDS, and most N atoms in the pyrimidine rings existed in the deprotonated form. The results herein will provide a new insight into the molecular self-assembly behaviors and adsorption structures of DPymDS molecules on Au(111) depending on solution concentration and pH.

Electrostatic coupling and water bridging in adsorption hierarchy of biomolecules at water–clay interfaces

Clay minerals are implicated in the retention of biomolecules within organic matter in many soil environments. Spectroscopic studies have proposed several mechanisms for biomolecule adsorption on clays. Here, we employ molecular dynamics simulations to investigate these mechanisms in hydrated adsorbate conformations of montmorillonite, a smectite-type clay, with ten biomolecules of varying chemistry and structure, including sugars related to cellulose and hemicellulose, lignin-related phenolic acid, and amino acids with different functional groups. Our molecular modeling captures biomolecule-clay and biomolecule-biomolecule interactions that dictate selectivity and competition in adsorption retention and interlayer nanopore trapping, which we determine experimentally by NMR and X-ray diffraction, respectively. Specific adsorbate structures are important in facilitating the electrostatic attraction and Van der Waals energies underlying the hierarchy in biomolecule adsorption. Stabilized by a network of direct and water-bridged hydrogen bonds, favorable electrostatic interactions drive this hierarchy whereby amino acids with positively charged side chains are preferentially adsorbed on the negatively charged clay surface compared to the sugars and carboxylate-rich aromatics and amino acids. With divalent metal cations, our model adsorbate conformations illustrate hydrated metal cation bridging of carboxylate-containing biomolecules to the clay surface, thus explaining divalent cation-promoted adsorption from our experimental data. Adsorption experiments with a mixture of biomolecules reveal selective inhibition in biomolecule adsorption, which our molecular modeling attributes to electrostatic biomolecule-biomolecule pairing that is more energetically favorable than the biomolecule-clay complex. In sum, our findings highlight chemical and structural features that can inform hypotheses for predicting biomolecule adsorption at water-clay interfaces.

Effect of Water Components on Aggregation and Sedimentation of Polystyrene Nanoplastics

The aggregation and sedimentation of micro/nano-plastics significantly affect their migration and distribution in the environment. This study investigated the effects of Na+ and natural organic matter （NOM） on the aggregation and sedimentation of polystyrene nano-plastics （PS-NPs） in the aqueous phase. Six types of water， such as seawater， lake water， and domestic sewage， were used to evaluate the above effects and other potential influencing factors. The results indicated that Na+ could facilitate the sedimentation of PS-NPs when it was less than 80 mmol·L-1， whereas it could promote the aggregation and suspension of PS-NPs when the concentration was greater than 80 mmol·L-1. NOM molecules affected the aggregation and sedimentation of PS-NPs by changing the ζ potential and relative density of particles via forming a multilayer adsorption structure with Na+ on the particle surface. It was observed that NOM greater than 10 mg·L-1 enhanced the dispersion and suspension of PS-NPs， which might have been attributed to the decrease in relative density of the particles as a large amount of NOM was absorbed onto the surface. Compared with synthetic waters， environmental waters enhanced the aggregation of PS-NPs， which may have been related to the amino acid， protein， and other organic macro-molecules in the water.

Metal (Ni, Pd, and Pt)-Doped BS Monolayers as a Gas Sensor upon Vented Gases in Lithium-Ion Batteries: A First-Principles Study.

Real-time monitoring of the vented gases emitted by the thermal runaway of lithium-ion batteries (LIBs) is of great significance to the normal use of LIBs. We study systematically the adsorption and sensing performances of pristine and metal-doped BS monolayers to five typical gases (CO, CO2, CH4, C2H2, and C2H4) emitted from LIBs employing the first-principles method. The adsorption structure and energetics, charge transfer, band structure, density of states, sensitivity, and recovery time are simulated and analyzed. Outstanding sensing properties are predicted for the Ni-, Pd-, and Pt-doped BS monolayers, although their recently synthesized pristine counterpart shows little sensing potential for those gases. The magnitude of the adsorption energy increases from 0.249 eV to 2.32 eV (Ni-BS), 1.954 eV(Pd-BS), and 2.994 eV (Pt-BS) for the CO gas after doping. Besides, significant variation of band gap is observed after gas adsorption in doped BS nanosheets, which leads to huge theoretical values of the sensitivity. The sensitivity for CO, CO2, CH4, C2H2, and C2H4 on Pt-BS may reach up to 5.87 × 105, 1.57 × 106, 1.81 × 105, 8.33 × 104, and 8.18 × 103, respectively. In addition, the calculated recovery times indicate that the doped BS monolayers have strong selectivity for the adsorption and detection of these five gases. The three metal-doped BS monolayers should have great potential for application in sensors monitoring the gases emitted from LIBs.

Effect of synthesis conditions on the porous texture of activated carbons obtained from Tara Rubber by FeCl3 activation

This paper presents the results of an unique analysis of the influence of the mass ratio of activator FeCl3 to precursor and the temperature of the activation process on the formation of the porous structure of activated carbons obtained from Tara Rubber by FeCl3 activation. The study used the new numerical clustering based adsorption analysis method and the quenched solid density functional theory, taking into account, among other things, the heterogeneity of the analysed surface which is a new approach rarely used in the analysis of the porous structure of adsorbents. On the basis of the calculation results, it was concluded that the activated carbon with the most developed porous texture was obtained at a mass ratio (FeCl3:Tara Rubber) of 2, at an activation process temperature of 800 °C. This activated carbon is also characterised by the lowest degree of surface heterogeneity and at the same time, however, the widest range of micropores compared to activated carbons obtained at other mass ratios. The analyses carried out further demonstrated the valuable and complementary information obtained from the structure analysis methods and their high utility in practical applications, especially in the development of new industrial technologies for the production of adsorbents and the selection of optimal conditions for their production.

Molecular geochemistry of radium: A key to understanding cation adsorption reaction on clay minerals

Adsorption reactions of various cations on clay minerals have different effects on their environmental behaviors depending on the molecular-scale adsorption structure. Some cations form outer-sphere complexes via hydration, while others create inner-sphere complexes through dehydration. This preference dictates their environmental impact. However, the factors controlling these complex formations remain unclear. Furthermore, research on the adsorption preferences of radium (Ra) is lacking. Thus, this study conducted the first EXAFS study of Ra2+ adsorbed on clay minerals and showed that Ra2+ forms inner-sphere complexes on vermiculite, which can be surprising because Ra2+ is a divalent cation and prefers to be hydrated. In order to investigate the factors controlling the complex formations, this study conducted systematic EXAFS measurements and DFT calculations for alkali and alkaline earth metal cations. The results showed the importance of the size-matching effect between the adsorbed cation and the cavity of the tetrahedral sheets and that the complex formation can be estimated by the combination of the ionic radius and hydration enthalpy of the adsorbed cation. Furthermore, this study also analyzed environmental core samples. Their results showed the fixation of Ra2+ by clay minerals and the controlling factors can effectively predict cation environmental behavior.

Utilizing gamma radiation to induce polymerization of acrylonitrile/methacrylic acid on nonwoven fibers and its potential use in metal recovery

In this research, the focus was on creating new polymeric adsorbents through radiation-induced synthesis to effectively eliminate zinc from aqueous solutions in batch processes. The study explored the radiation-induced grafting method, a novel approach for producing polymer adsorbents, due to its advantages of process control and the absence of initiators. During the simultaneous irradiation process, acrylonitrile, methacrylic acid monomers, and phosphoric acid were grafted onto polypropylene nonwoven fiber as functional groups. To enhance zinc adsorption, the grafted polymers were modified with different amines, including diethylamine, triethylamine, ethanolamine, tributylamine, and tripropylamine. Among these, the modification with diethylamine exhibited the most promising results for zinc adsorption. After characterizing the adsorbent structure through SEM, FTIR, and TG analysis, the impact of various factors such as pH, contact time, adsorbent mass, and solution concentration on the adsorption process was investigated. Notably, under acidic conditions (pH=3) and an initial concentration of 40 ppm, a remarkable adsorption rate of over 98 % was achieved. To optimize the adsorption process, the response surface method (RSM) based on the central composite design was used to determine the ideal adsorption state. The Langmuir isotherm and the pseudo-second-order model yielded the best fit (R2=0.995) for describing the adsorption process and rate.