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Context: SF6 gas has a strong greenhouse effect, and how to treat SF6 in an environmentally friendly way has been a hot topic of current research. In this paper, the adsorption behavior of SF6 on the surface of Pd-doped hydroxyl-terminated modified Ti3C2Tx (i.e., Ti3C2(OH)2) was investigated based on the density functional theory using two-dimensional MXene as the catalyst. The structures of different Pd-doped Ti3C2(OH)2 were analyzed and the most structurally stable doped structures were selected as the basis for subsequent calculations. A large number of adsorption configurations were constructed and geometrically optimized, and the adsorption energy, charge transfer, differential charge density, and density of states of the systems were calculated in order to analyze the gas–solid interactions and find the surface active sites; compared with the adsorption performance of undoped Ti3C2(OH)2 on SF6, it was found that Pd doping played a less inhibitory role in the adsorption of SF6 on the Ti3C2(OH)2 surface. The results of this study can provide theoretical support for the use of Pd-doped Ti3C2(OH)2 as a catalyst for the degradation of SF6. Methods: In this paper, simulations of SF6 adsorption on Ti3C2Tx surfaces are based on density functional theory and are carried out in the Dmol3 module of Material Studio. To better describe the non-uniform electron density of the actual system, the PBE functional in the generalized gradient approximation (GGA) was chosen for the optimization of the structure of the gas–solid interface system and the calculation of the relevant electronic properties, combined with the Grimme dispersion correction in the DFT-D dispersion correction for the electron exchange correlation term. Because both Pd and Ti are transition metal elements, the mode-conserving pseudopotential DNP basis set containing relativistic effects was chosen for the electronic wave function expansion. In this paper, an all-electron model is used for the inner core treatment of gas molecules and a density generalized semi-nuclear pseudopotential DSSP is used for the solid surface treatment. [ABSTRACT FROM AUTHOR]

In this paper, the effects of transition metal atom Pt doping on the structural parameters and electronic properties of the two-dimensional material Ti3C2Tx MXene (T = OH, O or F) as well as the adsorption interaction between the doped material and SF6 are investigated based on density functional theory calculations. To investigate the SF6 adsorption mechanism, the adsorption structure, adsorption energy, charge transfer, and density of states of Pt atom-doped Ti3C2Tx after the adsorption of SF6 molecules were analyzed. The results showed that the electronic properties and chemical activity of the doped Ti3C2Tx changed significantly compared to those before doping. In addition, Pt-doped Ti3C2(OH)2 has good adsorption ability on SF6 molecules, and its adsorption type is chemisorption; in the relevant sites, SF6 undergoes chemical bond breaking, and the doping of Pt improves the catalytic effect of Ti3C2(OH)2. The adsorption capacity of Pt-doped Ti3C2O2 and Ti3C2F2 for SF6 molecules is much weaker than that of Pt-doped Ti3C2(OH)2, physical adsorption occurred, and there was almost no degradation of SF6; the doping of Pt did not improve the catalytic effect of Ti3C2O2 and Ti3C2F2. [ABSTRACT FROM AUTHOR]

In gas-insulated equipment, the decomposition of SF6 is closely related to the residual traces of O2 and H2O in the equipment. However, the decomposition mechanism has not yet been clarified. In this paper, the adsorption and defluorination of SF6 on the preadsorbed Cu(111) surface were calculated based on density flooding theory and transition state theory. Besides, the influence mechanism of O atoms and H2O molecules on the defluorination process is analyzed by comparing the energy barrier, reaction heat, and density of states. The results show that pre-adsorption of O atoms changes the adsorption sites of SFx, but has no significant effect on the adsorption energy. In addition, the O atom has a certain inhibitory effect on the decomposition process, and SF → S + F is the key to determining the reaction rate. In contrast, H2O will not only promote the adsorption of SFx to the surface but also reduce the total reaction heat of the decomposition reaction by 135.37 kcal·mol−1, driving the decomposition process of SF6. In this paper, stable co-adsorption configurations of low-fluorosulfide and co-adsorption groups were determined, and the effects of O and H2O preadsorption on SF6/Cu gas–solid interactions were initially revealed. [ABSTRACT FROM AUTHOR]

Corn stover could be pyrolysed to prepare biochar for removing pollutants in water and realizing the resource utilization of biomass. The aims of the present study were to investigate the optimal preparation and adsorption conditions of biochar and to reveal the adsorption characteristics and mechanisms of Cd2+ in water by biochar. For this purpose, with Cd2+ as the target pollutant, the pyrolysis conditions involved in the pyrolysis temperature, retention time, and heating rate were evaluated and optimized. Additionally, the characteristics, mechanisms and optimal adsorption conditions of Cd2+ by biochar were determined. A series of characterization techniques was employed, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and specific surface area analysis (SBET). The optimum pyrolysis parameters were a pyrolysis temperature of 700 °C, a retention time of 2.5 h, and a heating rate of 5 °C/min. Acid/base modification did not improve the adsorption capacity of biochar. The Langmuir and the Elovich model were the most suitable isotherm and kinetic models for equilibrium data, respectively. The maximum adsorption capacity fitted by Langmuir model was 13.4 mg/g. Furthermore, mineral precipitation and π electron interactions were shown to be the main adsorption mechanisms of Cd2+. The optimum adsorption conditions for Cd2+ in water were a CaCl2 electrolyte solution of 0.01 mol/L, a pH level of 6.7, and a biochar dosage of 0.4 g. Our results indicated that corn stover biochar was an appropriate approach for improving the status of water with Cd2+ contamination in the short term and for promoting a new perspective for the rational utilization of corn stover and the low-cost pollution control of heavy metals in water. [ABSTRACT FROM AUTHOR]

Poor contact is one of the main causes of the internal fault of SF6 gas insulated equipment. Taking the most common over-thermal decomposition process of SF6 caused by poor silver-plated copper contacts as an example, this article combines with density functional theory (DFT) and establishes the gas–solid contact interface adsorption model of SF6 and its main decomposition characteristic products (SO2F2, SO2, SOF2, HF, and H2S) with solid silver. Adsorption energy, charge transfer, and density of electronic state were used to analyze the reaction activity of SF6 and its main decomposition products with the Ag surface. It is found that SF6 and SO2 are chemically adsorbed on the Ag surface, and the reaction activity is relatively strong. When chemical adsorption occurs, SF6 bonds with the metal surface by the 2p orbitals of F atoms, and SO2 is bonded to the metal surface by the 2p orbitals of O atoms. There is also a strong reaction trend between HF and Ag (1 1 1), while SO2F2, SOF2, and H2S only physically absorbed with the Ag (1 1 1) surface. This indicates that under the local overheating failure caused by metal contacts, SF6 will first undergo chemical adsorption in the SF6/Ag (1 1 1) system and then undergo a decomposition reaction near the metal surface rather than in free space. The participation of Ag reduces the difficulty of the decomposition reaction to some extent. The results lay a foundation for finally revealing the interfacial reaction process of SF6-Ag. [ABSTRACT FROM AUTHOR]

A Co(II)-based MOF, {[Co3(L)2(bpb)(DMA)(H2O)]·Solvents}n (RH-1), with a unique interpenetrated framework has been solvothermally prepared. Because of its unsaturated metal sites and narrow pores inside the framework, RH-1 demonstrated excellent selective CO2 adsorption over N2 and CH4 and good performance in catalytic CO2 conversion to cyclic carbonates under mild conditions. [ABSTRACT FROM AUTHOR]

The dyeing and finishing industry inevitably produces a large amount of wastewater, and how to treat pollutants such as methylene blue (MB) in the wastewater is a huge challenge. In this paper, molybdenum disulfide (MoS 2) after simple ultrasonic treatment was added to the sodium alginate/Antarctic krill protein composite fiber (SAF) as an additive, and the MoS 2 -sodium alginate/Antarctic krill protein composite fiber (MSAF) was successfully prepared, which was used as an adsorbent for MB. The results indicated that MSAF had an excellent adsorption effect on MB, the maximum adsorption capacity in the experiment could reach 472.68 mg/g, which was 27 % higher than that of SAF, and the theoretical adsorption capacity calculated by fitting could reach 934.58 mg/g. Moreover, the MSAF still has high adsorption efficiency after five adsorption-desorption cycles. Based on the data of the present investigation, MSAF can be used as an efficient and reliable adsorbent and is expected to be used as a functional textile fabric in the fields of filtration and treatment of textile printing and dyeing wastewater. [Display omitted] [ABSTRACT FROM AUTHOR]

Developing adsorbent materials based on biomass that can be easily recycled and reused to remove water pollutants has received widespread attention. A novel method for the preparation of calcium alginate/poly (vinyl alcohol)/boric acid (as–synthesized Ca-APB) aerogel fibers for highly efficient adsorption of methylene blue by directed freezing wet–spinning was presented in this paper. The Ca-APB-0.5 aerogel fibers exhibited a hierarchical structure consisting of a honeycomb micron pore structure with mesopores walls, with a maximum adsorption capacity of 508.99 mg/g in 5 h at 293 K. Meanwhile, the experimental data for Ca-APB-0.5 aerogel fibers showed the best fit to the Freundlich model and pseudo–second–order model. Moreover, the adsorption capacity was investigated for three consecutive cycles, with 469.37, 457.19, and 439.77 mg/g in the first, second, and third cycles, respectively. This paper proves that the hierarchical structure of alginate-based aerogel fiber is an effective dye adsorption material with high efficiency, reusability, and eco-friendliness. [Display omitted] • Robust alginate–based aerogel fibers via directed freezing–wet spinning. • Restriction of Ca2+ complexation by boric acid reduces the consumption of active groups. • Efficient adsorbent based on multi-active groups and hierarchical structure. • Micron macropores for channeling and nanopores for adsorption, inspired by soil pores. • Aerogel fibers realized high efficiency, reusability, and eco-friendliness. [ABSTRACT FROM AUTHOR]

CaO significantly influences the SNCR deNO x process. The adsorption and reaction mechanism of NH 3 + NO + O 2 system on the CaO surface were studied in this work. Results showed that NH 3 adsorbed onto the Lewis acid sites of CaO and the main ad-species were NH 2 and OH. With increased temperature, NH 2 dehydrogenation occurred and formed dinitride, which eventually desorbed as N 2 O; whereas OH reacted with H to form H 2 O. O 2 accelerated NH 3 conversion to NH 2 and oxidized dinitride. NO ad-species on the CaO surface were cis-dimer nitroso and monodentate nitrate. With increased temperature, cis-dimer nitroso decomposed and desorbed as NO, and monodentate nitrate eventually desorbed as N 2 O. O 2 had no influence on NO ad-species. When NH 3 and NO coexisted, they simultaneously adsorbed onto the CaO surface and formed the similar ad-species with their single adsorption. NO was reduced to N 2 by NH 2 , and the reaction followed Langmuir–Hinshelwood mechanism. NH 2 dissociation to dinitride simultaneously occurred with NO reduction in the NH 3 + NO system. In the NH 3 + NO + O 2 system, NH 3 conversion to NH 2 was determined by O 2 . The majority of NH 2 was oxidized by O 2 , and the remainder reacted with NO. NH 2 dissociation to dinitride was negligible in the presence of O 2 . [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesis conditions of S/YP-INPs@CB were optimized for three factors. • The specific surface area of the material was improved after sulfide modification. • The green synthesized S/YP-INPs@CB showed superior Cr(VI) removal (99.2%) efficiency. • The HCrO 4 - is adsorbed on S/YP-INPs@CB via Fe-O bonds and hydrogen bonds. • FeS had stronger electron transfer performance and greater adsorption energy. Sulfide Yali pear iron nanoparticles-loaded corn straw biochar (S/YP-INPs@CB) were synthesized using pear peel extract as the reductant. The synthesis method was optimized in terms of the sulfur-to-iron ratio, sulfurization time, and synthesis temperature. Characterization results reveal that, after vulcanization of the iron nanoparticles-loaded biochar, the material became coarser, and its specific surface area increased. FeS and other substances were loaded onto S/YP-INPs@CB, enhancing its ability to provide electrons. Experiments were conducted to study the effects of time, temperature, pH, initial Cr(Ⅵ) concentration, co-existing anions, and real water on the removal of Cr(Ⅵ). The results show that the optimized S/YP-INPs@CB was synthesized with a S/Fe ratio of 0.2:1, a synthesis temperature of 70 °C, and a sulfurization time of 60 min. At pH 5 and the temperature of 55 °C, the q e for Cr(Ⅵ) was 79.7 mg/g. The hexavalent chromium removal followed Langmuir and the quasi-second-order kinetics model, indicating chemical adsorption. S/YP-INPs@CB successfully removed Cr(Ⅵ) through different mechanisms such as electrostatic adsorption, reduction of Cr(Ⅵ), co-precipitation, etc. The removal process mainly occurred at the solid–liquid interface between the adsorbent and solution. DFT calculation shows that FeS had stronger electron transfer performance and greater adsorption energy for HCrO 4 - and Cr3+, and the adsorption was more stable, so the performance of S/YP-INPs@CB to remove Cr(VI) was enhanced. This study not only presents an environmentally friendly method for the preparation of adsorbent materials but also contributes to the surface science of cleaner materials. [ABSTRACT FROM AUTHOR]

• Thermal stability analysis of As clarifies dominance of chemical adsorption. • As amount adsorbed by ash in flue gas is far less than ash's adsorption capacity. • Chemical adsorption by ash is mainly through the joint action of Ca and Fe in ash. • As Adsorption by high-Ca ash increases with temperature due to the stable product. • Instability of Fe 2 O 3 product make As amount adsorbed by high-Fe ash peak at 800 °C. Arsenic (As) transformation during flue-gas cooling process determines terminal As emission. In this study, the dominant role of chemical adsorption in gaseous As transformed to ash was confirmed. Dynamic curves of As 2 O 3 adsorption by ash at 500–900 °C were obtained. The adsorbed As amount increased linearly with time, far from reaching saturation, and the maximum amount was approximately 10 times the As content in ash collected from power plant dust collectors, indicating that the actual capacity of ash was far higher. Analysis of As form and elemental distribution directly proved that chemical adsorption by ash was mainly through the joint action of Ca and Fe, and its correlation with other components was weak. At 500–900 °C, as temperature increased, the amount of As adsorbed by CaO gradually increased, whereas that of Fe 2 O 3 first increased and then decreased. The adsorption product of CaO was stable, whereas certain forms of products of Fe 2 O 3 released at 800 °C. Therefore, as temperature increased, the amount of As adsorbed by ash with high Fe content first increased and then decreased, reaching a maximum at 800 °C °C, whereas that of ash with higher Ca content kept increasing. The strong adsorption capacity of ash with high Ca and Fe contents helps reduce terminal As emission. [ABSTRACT FROM AUTHOR]

[Display omitted] • The adsorption of CS 2 and COF 2 on the surface of α-Al 2 O 3 (0 0 0 1) presents a state of energy release. • CS 2 is more easily adsorbed on the α-Al 2 O 3 (0 0 0 1) Surface by C atoms ;the surface of α-Al 2 O 3 (0 0 0 1) has a good adsorption effect on all three atom adsorption directions of COF 2 gas. • It is believed that new bonds may be generated during the adsorption process of the CS 2 and COF 2 gas molecules, and the structure after adsorption is more stable. As the typical carbon-containing decomposition components of SF 6 under partial discharge in high-voltage insulation devices, CS 2 and COF 2 , will not only corrode devices, but also pollute the environment. Remove these gases through SF 6 adsorbent is an effective approach to eliminate the above hazards. In this paper, the adsorption performance of CS 2 and COF 2 on α-Al 2 O 3 (0 0 0 1) surface was calculated by first-principle based density functional theory, including the adsorption enthalpy change, charge transfer and structural parameters, and five relatively stable adsorption structures were initially obtained through analysis. Results indicate that all adsorption processes are exothermic. To further understand the adsorption mechanism, the density of states, frontier molecular orbital and deformation charge density diagram were analyzed. Calculations show that both CS 2 and COF 2 has a fine adsorption effect on α-Al 2 O 3 (0 0 0 1) surface, besides, for CS 2 , it is easier to be adsorbed on α-Al 2 O 3 (0 0 0 1) surface through C atom while there is no significant difference in performance parameters of the adsorption configuration for COF 2. Furthermore, frontier molecular orbital analysis also confirmed that the adsorbed system is more stable. This work provide theoretical basis for the experiments of SF 6 adsorbents adsorbing typical carbon-containing decomposition components. [ABSTRACT FROM AUTHOR]