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The detection of the identities and concentrations of sulfur hexafluoride, SF 6 , decomposition products is important for evaluating the conditions of SF 6 -gas-insulated equipment. This study is a preliminary test of the use of cassiterite (110) for detecting SF 6 and SF 6 decomposition gases, including HF, H 2 S, SO 2 , SOF 2 , SO 2 F 2 , CF 4 , CO, and CO 2 . First-principles calculations were adopted to investigate the adsorption mechanism of SF 6 decomposition gases on a cassiterite (110) surface, using adsorption energy, geometrical structure, frontier molecular orbitals, electron density, density of states, potential energy, and work functions. We found that the adsorption of H 2 S made a noticeable change in the electronic properties of the (110) surface. The adsorption of SO 2 strongly influenced the charge distribution of the cassiterite (110) surface and made the greatest decrease in the work function of the nine gas molecules tested. Conversely, changes in the cassiterite's electronic properties induced by other gases, especially SF 6 , were slight. Therefore, cassiterite could be a promising candidate for highly selective and sensitive sensors to detect H 2 S and SO 2 in SF 6 decomposition gases. [ABSTRACT FROM AUTHOR]

Abstract: An anion-imprinted material with high performance for recognizing chromate anion was prepared by adopting the novel molecule surface-imprinting technique put forward by our research group previously. Functional macromolecule polyvinylimidazole (PVI) was first grafted on the surfaces of micron-sized silica gel particles, forming the grafted particle PVI/SiO2. Afterwards, the ion imprinting was carried out towards the grafted macromolecule PVI by using anion as template and 1,6-dibromohexane as crosslinking agent, and chromate ion surface-imprinted material IIP-PVI/SiO2 was obtained. The binding characteristic of IIP-PVI/SiO2 towards anion was studied with both static and dynamic methods. The experimental results show that IIP-PVI/SiO2 has excellent binding affinity and high recognition selectivity for chromate anion. Before imprinting, the grafted particles PVI/SiO2 have similar adsorption capacities for both two anions, chromate anion and phosphate anion that was used as a contrast anion. However, after imprinting, the binding capacity of IIP-PVI/SiO2 towards phosphate anion decreases remarkably, whereas the binding capacity of IIP-PVI/SiO2 for chromate anion still remains very high, leading to a high selectivity coefficient (7.78) of IIP-PVI/SiO2 for anion with respect of ion. [Copyright &y& Elsevier]

Density functional theory (DFT) calculation was used to study the potential applications of pure and metal-doped C 24 N 24 fullerene as highly sensitive and selective gas sensors. It is found that gases commonly existing in the air, including NO 2 , CO, NO, NH 3 , N 2 and CO 2 , are weakly adsorbed on pure C 24 N 24. The adsorption strength is increased when they are adsorbed on the metal-doped (Co-, Cr-, Cu-, K-, Li-, Fe-, Ni-, Pd-, Ti-, Mn-, Na-, Zn-, V-) C 24 N 24. The pure and metal-doped C 24 N 24 have a specific response to certain gas according to adsorption energy, charge transfer, band gap and the density of states analyses. Among various metal-doped C 24 N 24 , the adsorption energies of NO 2 on K- and Na-doped C 24 N 24 are apparently lager than those of other gas molecules, which fall between the suitable range of strong physical adsorption and weak chemical adsorption. Upon NO 2 adsorption, the band gap changes of K- and Na-doped C 24 N 24 which corelate with its conductivity reach −12.75% and −26.67%, respectively. In accordance with the band gap changes, the density of states changes and charge transfer for NO 2 adsorption on K- and Na-doped C 24 N 24 are most obvious. Sensor performance analysis further shows K- and Na-doped C 24 N 24 are highly selective in NO 2 detection. The recycle time of Na–C 24 N 24 under ambient condition is also in the suitable range (1.80 s). This study concludes the potential application of the Na-doped C 24 N 24 as high-performance NO 2 sensor. [ABSTRACT FROM AUTHOR]

Abstract: In this study, 5-aminosalicylic acid (5-ASA) was successfully grafted onto the poly(glycidyl methacrylate) (PGMA) macromolecular chains of PGMA/SiO2 to obtain adsorbent ASA-PGMA/SiO2. The adsorption properties of ASA-PGMA/SiO2 for phenolic compounds were studied through batch and column methods. The experimental results showed that ASA-PGMA/SiO2 possesses strong adsorption ability for phenolic compounds, and its adsorption capacity for phenol, 4-chlorophenol, and p-nitrophenol reaches 1.0, 1.1, and 1.32mmolg−1, respectively. In addition, pH has a great influence on the adsorption capacity. The adsorption isotherm data obeyed the Langmuir model well than Freundlich model. The desorption of phenolic compounds from the ASA-PGMA/SiO2 adsorbent was most effectively achieved in a 0.1molL−1 sodium hydroxide solution. Consecutive adsorption–desorption experiments showed that the ASA-PGMA/SiO2 adsorbent could be reused almost without any loss in the adsorption capacity. [Copyright &y& Elsevier]

Biochar is regarded as a promising new class of materials due to its multifunctional character and the possibility of effectively coupling different properties. With increasing introduction into the environment, environmental chemicals such as surfactants will load onto the released biochar and change its physicochemical characteristics and adsorption behavior toward pollutants. In this study, sodium dodecyl sulfate (SDS), as one type of anionic surfactant, was coated onto biochar with different loading amounts. The influence of SDS loading onto biochar's physicochemical properties were investigated by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, zeta potential and Brunauer–Emmett–Teller (BET) surface area and pore size distribution analysis. Results showed that the pore size of the biochar decreased gradually with the increase of SDS loading because of the surface-adsorption and pore-blocking processes; the pH of the point of zero charge (pH PZC ) decreased with increasing SDS loading. Although surface-coating with SDS decreased the pore size of the biochar, its adsorption capacity toward Methylene Blue (MB) significantly increased. The biochar-bound SDS introduced functional groups and negative charges to the biochar surface, which could thus enhance the adsorption of MB via hydrogen bonding and electrostatic interaction. The results can shed light on the underlying mechanism of the influence of anionic surfactants on the adsorption of MB by biochar. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 @SiO 2 -Chitosan/GO (MSCG) nanocomposite was investigated by various techniques (SEM, TEM, XRD, VSM, FT-IR, XPS) for the removal of tetracycline (TC). Effects of pH, zeta potential and initial contaminant concentration were studied in detail. Four background cations (Na + , K + , Ca 2+ and Mg 2+ ) with a concentration of 0.01 M showed little influence on the TC adsorption at the studied pH range while the divalent heavy metal cation Cu(II) could significantly enhance the adsorption. The results indicated that the highest adsorption capacity of TC were 183.47 mmol/kg and 67.57 mmol/kg on MSCG with and without Cu(II), respectively. According to mechanism investigation for the adsorption of TC by pH impact study and XPS analysis, besides electrostatic interaction and π–π interactions, the Cu(II) also acts as a bridge between TC and MSCG, which significantly improve the adsorption of TC. This study provided valuable guidance and effective method for the removal of TC from aquatic environments. [ABSTRACT FROM AUTHOR]

Ditch-buried straw return (DBSR) is a novel farming system that not only efficiently eliminates the need to burn straw, but also shows positive effects on soil carbon sequestration and crop yields. Implementation of DBSR, however, may penetrate the tillage pan, increasing the risk of N leaching losses. We therefore determined whether N retention could be increased by DBSR in order to reduce the risk of N loss to the environment. A four-year field experiment and a complementary greenhouse experiment were conducted to test the effects of DBSR on N retention in a rice-wheat rotation system. We found that DBSR altered the spatial distribution of fertilizer N. N content was significantly increased above but reduced below the straw layer in the field experiment. The greenhouse experiment further confirmed the N retention effects by the straw layer. In theory, a maximum of 9.09 mg urea-N could be adsorbed by one gram dry wheat straw. Our results suggest that DBSR has the potential to increase N retention in the soil, thus increasing crop uptake and minimizing leaching N loss in the rice-wheat rotation system. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption equilibrium of hydrogen on graphene sheets (GS) was studied based on a sample of GS with SBET = 300 m2/g at the temperatures of 77.15 K–293.15 K and the pressures of 0 MPa–6 MPa. In the meantime, the adsorptions (Excess adsorption measurements) of hydrogen on granular coconut shell SAC-02 activated carbon (SBET = 2074 m2/g) and carbon nanofiber (CNFs, SBET = 205 m2/g) were investigated at the pressures of 0–8 MPa and the temperature of 77.15 K. The outcomes from experiments were used to determine the parameters in Toth equation by way of Non-linear fit. The absolute adsorption amounts of hydrogen on the GS, which were calculated from the equation, were used to calculate the isosteric heat of hydrogen adsorption by use of adsorption isosteres. It shows that, under the experimental conditions, the excess adsorption amount of hydrogen on the GS increases monotonically and correlatively as pressure increases, and the mean relative deviation between the experimental data and those predicted from Toth equation is less than 1%. The result also shows that the storage density of hydrogen on the GS is 1.75 wt% and 0.168 gH2/L at pressure 5.4 MPa and temperature 77.15 K, which is lower than that of hydrogen on the activated carbon but is higher than that of hydrogen on the CNFs. The isosteric heat of hydrogen adsorption on the GS falls within 5.14 kJ/mol–6.37 kJ/mol, which is comparable to that of hydrogen adsorption on the activated carbon. It suggests that interaction between hydrogen molecules and the graphene layer is stronger than that between hydrogen and carbon surface, and the hydrogen storage capacity of GS is closely related to its physical properties. [Copyright &y& Elsevier]

• High selectivity and sensitivity of GeP monolayer to nitrogen oxides. • The variation of work function change can be used to distinguish NO 2 and NO. • Compressive strain improve sensitivity of GeP to NO 2 without raising recovery time. • Applied negative electric field can greatly enhance response of GeP monolayer to NO 2. The sensing properties of GeP monolayer to small gas molecule (CO, CO 2 , O 2 , H 2 O, NH 3 , NO and NO 2) have been investigated by performing first-principle calculations. Based on calculated adsorption distance, adsorption energy and charge transfer, we find that GeP monolayer is the most sensitive to NO 2 and NO molecules, and all gas molecules act as acceptors to gain electrons from GeP monolayer. The adsorption energy of NO 2 is smaller than that of NO molecule, which implies that NO 2 is more easily desorbed from GeP. And different work function changes also indicate the possibility to identify NO 2 and NO in an oxygen-free environment. Moreover, we apply uniaxial and biaxial strains to GeP monolayer and find that a small biaxial compressive strain can effectively enhance the sensitivity of work function type sensor based GeP to NO 2 molecule without increasing recovery time. We also discuss the effect of external vertical electric field on the adsorption performance of NO 2 molecule. The negative electric field can significantly increase the adsorption strength, charge transfer and work function change of NO 2 -GeP system. Our results indicate that GeP monolayer is a potential candidate for NO 2 gas sensor. [ABSTRACT FROM AUTHOR]

• Adsorption properties of SF6 decomposition components on ceria surface were compared based on DFT calculations. • Adsorption of H 2 S, SO 2 and SOF 2 cause conspicuous charge redistribution on CeO 2 (110) surface. • CeO 2 (110) shows higher sensitivity to H 2 S, SO 2 and SOF 2 in comparison with SF 6. The detection of sulfur hexafluoride (SF 6) decomposition components is significant for monitoring the conditions of SF 6 -gas-insulated equipment. In present study, the adsorption of SF 6 and its decomposition components (H 2 S, SO 2 , SOF 2 , and SO 2 F 2) on ceria (110) was investigated by performing calculations based on density functional theory (DFT). Adsorption energy, adsorption configuration, charge transfer, density of states, potential energy and work function for molecular adsorption were adopted to evaluate the performance of ceria (110) on sensing SF 6 decomposition components. Among all the gas molecules, H 2 S, SO 2 and SOF 2 were chemically adsorbed on ceria surface with the adsorption energy following the order: SOF 2 > SO 2 > H 2 S, while SO 2 F 2 and SF 6 were physically adsorbed on the substrate. Besides, the amount of charge transfer and work function modification of H 2 S, SO 2 and SOF 2 molecule's adsorption were larger than those of SO 2 F 2 and SF 6. These calculation results demonstrated ceria (110) showed prominent sensitivity to H 2 S, SO 2 and SOF 2 while less activity to SF 6 , which means sensor based on ceria is promising for detecting H 2 S, SO 2 and SOF 2 in SF 6 gas background, and thus has the potential to online monitor the working condition of SF 6 -gas-insulated equipment. [ABSTRACT FROM AUTHOR]