生物质多孔炭特征构建及对N_(2)O吸附可行性分析

针对N_(2)O的排放现状和原因,在生物炭对农业土壤中N_(2)O的排放控制的应用研究进行了总结.分析了多孔炭的物理化学性质对N_(2)O吸附的关键作用,重点论述不同制备条件对生物质多孔炭理化性质的影响.其中含木质素较高的生物质原料在高温热解后更容易形成微孔结构,在不同温度(400℃~1000℃)和生物质前驱体的条件下,多孔炭的比表面积和微孔容积最高分别可达2979m^(2)/g和1.130cm^(3)/g.此外,使用活化剂及杂原子掺杂剂的方式可以改变生物质多孔炭的表面极性、酸碱性、亲疏水性等的化学性质,并增加表面官能团种类,从而通过增强化学吸附作用进一步提高生物质多孔炭的吸附容量.最后,根据生物质多孔炭的特点,从吸附容量、可再生性和选择性等三个方面分析了生物质多孔炭吸附富集N_(2)O的可行性.最后,根据生物质多孔炭的特点,从吸附容量、可再生性和选择性等三个方面分析了生物质多孔炭吸附富集N_(2)O的可行性,为生物质多孔炭对N_(2)O气体吸附控制应用提供了科学依据.

Insights into SO_2 and H_2O co-adsorption on Cu(100) surface with calculations of density functional theory

The co-adsorption behaviors of SO2 and H2 O on face-centered cubic Cu（100） ideal surface were studied using the GGA-r PBE method of density functional theory（DFT） with slab models. The optimized structures of single H2 O and SO2 on Cu（100） surface were calculated at the coverage of 0.25 ML（molecular layer） and 0.5 ML. The results show that there was no obvious chemical adsorption of them on Cu（100） surface. The adsorbed structures, adsorption energy and electronic properties including difference charge density, valence charge density, Bader charge analysis and partial density of states（PDOS） of co-adsorbed structures of H2 O and SO2 were investigated to illustrate the interaction between adsorbates and surface. H2 O and SO2 can adsorb on surface of Cu atoms chemically via molecule form at the coverage of 0.25 ML, while H2 O dissociated into OH adsorbed on surface and H bonded with SO2 which keeps away from surface at the coverage of 0.5 ML.

H_(2)O分子在五边形BCN上的吸附与解离特性研究

基于密度泛函理论的第一性原理计算方法,研究了H_(2)O分子在五边形BCN上的吸附与解离过程.研究结果表明,五边形BCN结构的B原子是H_(2)O分子的最稳定的活性吸附位点.H_(2)O分子在该活性位点极易解离,其初步解离过程为放热反应且分解势垒仅为0.191 eV,并形成稳定的OH/H产物.深入研究发现,H_(2)O分子初步解离后的五边形BCN表面,可直接分解后续吸附的H_(2)O分子.该研究结果为五边形BCN对H_(2)O分子的吸附解离机制提供理论借鉴.

Enhancement of catalytic activity by homo-dispersing S_2O_8^(2–)-Fe_2O_3 nanoparticles on SBA-15 through ultrasonic adsorption

Mesoporous superacids S2O82–-Fe2O3/SBA-15(SFS)with active nanoparticles are prepared by ultrasonic adsorption method.This method is adopted to ensure a homo-dispersed nanoparticle active phase,large specific surface area and many acidic sites.Compared with bulk S2O82–-Fe2O3,Br?nsted acid catalysts and other reported catalysts,SFS with an Fe2O3 loading of 30%(SFS-30)exhibits an outstanding activity in the probe reaction of alcoholysis of styrene oxide by methanol with 100%yield.Moreover,SFS-30 also shows a more excellent catalytic performance than bulk S2O82–-Fe2O3 towards the alcoholysis of other ROHs(R=C2H5-C4H9).Lewis and Bronsted acid sites on the SFS-30 surfaces are confirmed by pyridine adsorbed infrared spectra.The highly efficient catalytic activity of SFS-30 may be attributed to the synergistic effect from the nano-effect of S2O82–-Fe2O3 nanoparticles and the mesostructure of SBA-15.Finally,SFS-30 shows a good catalytic reusability,providing an 84.1%yield after seven catalytic cycles.

H_2-induced CO adsorption and dissociation over Co/Al_2O_3 catalyst

The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H＊ over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^＊, which reacted with adsorbed CO subsequently via CO^＊＋OH^＊ → CO2^＊＋H^＊; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^＊＋2H^＊ → CH^＊＋OH^＊. The formation of the surface species （CH） from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis.

Thermogravimetric Study on Oxygen Adsorption/Desorption Properties of Double Perovskite Structure Oxides REBaCo_2O_(5+δ)(RE= Pr,Gd,Y)

The oxygen adsorption/desorption properties of double perovskite structure oxides PrBaCo2O5＋δ,GdBaCo2O5＋δ,and YBaCo2O5＋δ were investigated by the thermogravimetry（TG）method in the temperature range of 400~900 ℃.The calculated oxygen adsorption/desorption surface reaction rate constants ka and kd of these double perovskite structure oxides were larger than the commonly used cubic perovskite oxides,such as Ba0.95Ca0.05Co0.8Fe0.2O3-δ and Ba0.5Sr0.5Co0.8Fe0.2O3-δ,whereas,the oxygen permeation flux was comparable to that of the latter,which was attributed to the smaller difference of oxygen vacancy in oxygen and nitrogen atmosphere（Δδ/Vmol）in these double perovskite structure oxides.The large oxygen adsorption/desorption rate constants of GdBaCo2O5＋δ and PrBaCo2O5＋δ made them nice catalyst coating materials,on other membrane surfaces,to improve the oxygen permeability.

DFT Investigation of O_2 Adsorption on Si(001)-(2×2×1):H

A novel model was developed to theoretically evaluate the 02 adsorption on H-terminated Si（001）-（2×2×1） surface. The periodic boundary condition, the ultrasoft pseudopotentials technique based on density functional theory （DFT） with generalized gradient approxi,natior, （GGA） functional were applied in our ab initio calculations. By analyzing bonding energy oil site, the favourable adsorption site was determined. The calculations also predicted that the adsorption products should be Si=O and H2O. This theoretical study snpported the reaction mechanism provided by Kovalev et al, The results were also a base for further investigation of some more complex systems such as the oxida.tion on porous silicon surface.

Growth of Carbon Nanocoils by Porous α-Fe2O3/SnO2 Catalyst and Its Buckypaper for High Efficient Adsorption

High-purity(99%)carbon nanocoils(CNCs)have been synthesized by using porousα-Fe2O3/SnO2 catalyst.The yield of CNCs reaches 9,098%after a 6 h growth.This value is much higher than the previously reported data,indicating that this method is promising to synthesize high-purity CNCs on a large scale.It is considered that an appropriate proportion of Fe and Sn,proper particle size distribution,and a loose-porous aggregate structure of the catalyst are the key points to the high-purity growth of CNCs.Benefiting from the high-purity preparation,a CNC Buckypaper was successfully prepared and the electrical,mechanical,and electrochemical properties were investigated comprehensively.Furthermore,as one of the practical applications,the CNC Buckypaper was successfully utilized as an efficient adsorbent for the removal of methylene blue dye from wastewater with an adsorption efficiency of 90.9%.This study provides a facile and economical route for preparing high-purity CNCs,which is suitable for large-quantity production.Furthermore,the fabrication of macroscopic CNC Buckypaper provides promising alternative of adsorbent or other practical applications.

First-principles Calculations of H_2O Adsorption Reaction on the GaN(0001) Surface

The adsorption and decomposition of H2O on GaN（0001） surface have been explored employing density functional theory （DFT）. Two distinct adsorption features of H2O on GaN（0001） corresponding to molecular adsorption and H-OH dissociative adsorption are revealed by our calculations. The activities of the surface reactions of H2O on GaN（0001） surface are investigated. For the stepwise processes of H2O decomposition into H2 in gas phase and adsorbed O atom （H2O（g）→H2O（chem）→OH（chem） ＋ H（chem）→2H（chem） ＋ O（chem）→H2（g） ＋ O（chem））, the first and second steps are facile and can even occur at room temperature; while the last two have high barriers and thus are difficult to proceed, especially the fourth step is endothermic. In short, H2O adsorption and decomposition into H2 in gas phase and adsorbed O atom on GaN（0001） surface are exothermic by -43.98 kcal/mol.

Reactive adsorption desulfurization coupling aromatization on Ni/ZnO-Zn_6Al_2O_9 prepared by Zn_xAl_y(OH)_2(CO_3)_z·x H_2O precursor for FCC gasoline

Aiming to improve the reactive adsorption desulfurization（RADS） performances of Ni/Zn O adsorbents,ZnxAly（OH）2（CO3）z·x H2 O precursor is synthesized by coprecipitation of Zn2＋,AlO-2,and CO2-3; the Zn OZn6Al2O9 composite oxides are obtained by the calcination of ZnxAly（OH）2（CO3）z·x H2 O precursor,and the Ni/Zn O-Zn6Al2O9（6.0 wt% Ni O） adsorbents are prepared by wetness impregnation method. The phase,acid strength,acid type and quantity,morphology,and thermal properties were characterized by X-ray diffraction,temperature-programmed desorption of ammonia,pyridine-adsorbed infrared spectrum,high-resolution transmission electron microscopy,and Thermo Gravimetry-Derivative Thermo Gravimetry（TG-DTG）,respectively. The breakthrough sulfur capacities of six adsorbents are between 34.2 and 47.9 mg/gcat. The kinetic studies indicated that the active energy of RADS（49.4 k J/mol） could reach nano-sized Zn O,the particle size of is about 12.0 nm. All the excellent RADS performances can be due to the high SBET. Also,there are some extents of aromatization reactions that occur,which can be contributed to the B？nsted acid rooted in Zn6Al2O9 composite oxide,and the octane number of products can be preserved well.

Kinetic and Thermodynamic Studies on Raney Ni/Al2O3 Adsorption for Deep Desulfurization of Benzene Stream

How to remove trace amount of sulfur in benzene is of significance,and deep desulfurization by Ni-containing absorbents is an efficient and promising method.In this paper,The Raney Ni/Al2 O3 adsorbent was prepared and its kinetic and thermodynamic characteristics on adsorptive desulfurization of benzene were studied.The results showed that Raney Ni/Al2 O3 adsorbent exhibited good adsorption performance.The equilibrium isotherms indicated that the adsorption of thiophene over the Raney Ni/Al2 O3 adsorbent complied with the Freundlich model.The results of adsorption kinetics studies showed that the pseudo-second-order kinetics equation was more advantageous than the pseudo-first-order kinetics equation in describing the adsorption kinetics of thiophene on Raney Ni/Al2 O3.The rate constant value(kp)was positively correlated with the temperature whereas the adsorption mass transfer process was mainly determined by the intraparticle and film diffusion.The adsorption thermodynamic analysis proved that△G^0<0,△H^0>0,and△S^0>0,implying that the adsorption was a spontaneous,entropy-increasing and endothermic process.

Adsorption of NO and NH_3 over CuO/γ-Al_2O_3 catalyst

The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH3 and NO on CuO/γ-Al2O3 catalysts plays an important role in the reaction. Performance of the CuO/γ-Al2O3 catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350℃. Comprehensive tests were carried out to study the adsorption behavior of NH3 and NO over the catalysts. The desorption experiments prove that NH3 and NO are adsorbed on CuO/γ-Al2O3 catalysts. The adsorption behaviors of NH3 and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results show that NH3 could be strongly adsorbed on the catalysts, resulting in coordinated NH3 and NH4＋. NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The interaction of NH3 and NO molecules with the Cu2＋ present on the CAl2O3 （100） surface was investigated by using a periodic density functional theory. The results show that the adsorption of all the molecules on the Cu2＋ site is energetically favorable, whereas NO bound is stronger than that of NH3 with the adsorption site, and key information about the structural and energetic properties was also addressed.

Density Functional Study of the C Atom Adsorption on the α-Fe_2O_3 (001) Surface

The adsorption of C atoms on the α-Fe2O3（001） surface was studied based on density function theory（DFT） ,in which the exchange-correlation potential was chosen as the PBE（Perdew,Burke and Ernzerhof） generalized gradient approximation（GGA） with a plane wave basis set. Upon the optimization on different adsorption sites with coverage of 1/20 and 1/5 ML,it was found that the adsorption of C atoms on the α-Fe2O3（001） surface was chemical adsorption. The coverage can affect the adsorption behavior greatly. Under low coverage,the most stable adsorption geometry lied on the bridged site with the adsorption energy of about 3.22 eV; however,under high coverage,it located at the top site with the energy change of 8.79 eV. Strong chemical reaction has occurred between the C and O atoms at this site. The density of states and population analysis showed that the s,p orbitals of C and p orbital of O give the most contribution to the adsorption bonding. During the adsorption process,O atom shares the electrons with C,and C can only affect the outermost and subsurface layers of α-Fe2O3; the third layer can not be affected obviously.

Kinetic Adsorption of Cd onto Nanometer Al_2O_3/Carbon Fibre

A new nanometer material, nano-Al2O3 with carbon fibre as the carrier, was employed for the removal of Cd with low concentrations from polluted water. The characterization of the material was carried out by means of SEM and TEM. Batch adsorption and elution experiments were carried out to determine the adsorption properties of Cd on the new adsorbent. The classical Thomas model was applied to estimating the equilibrium coefficients of Cd adsorption and the saturated adsorption ability. The results show that the Thomas model is fit for describing the kinetic adsorption process, and the maximum adsorption capacity of the nanometer Al2O3/carbon is 69.29 mg/g. The resulting information also indicates that the desorption of Cd eluted with de-ionized water at a rate of 9.8 mL/min can be neglected. With the advantage of a high adsorption capacity for removing low concentration Cd, the Al2O3/carbon fibre possesses the potentiality to be an effective adsorbent for the removal of Cd from polluted water.

Kinetics and Thermodynamics of Adsorption Methylene Blue onto Tea Waste/CuFe₂O₄Composite

Tea waste/CuFe2O4 (TW/C) composite was prepared by co-precipitation method. The TW and TW/C samples are characterized by FTIR, XRD, SEM and N2 physical adsorption. The results showed that specific surface area of 350 and 570 m2·g?1 for TW and TW/C, respectively. The average pore size of TW/C is ca. 100 nm. Adsorption of methylen blue onto TW/C composite has been studied. Measurements are performed at various contact time, pH and adsorbent dosage. The adsorption kinetics of methylen blue (MB) could be described by the pseudo-second order kinetic model. The adsorption isotherms are described by means of Langmuir and Freundlich isotherms. It was found that the Freundlich model fit better than the Langmuir model. The thermodynamic constants of the adsorption were calculated to predict the nature of adsorption. The values of thermodynamic parameters indicate that a spontaneous and endothermic process was occurred.

Theoretical studies of adsorption property on Ir_4/MgO and Ir_4/γ-Al_2O_3

The adsorption properties of atomic and molecular species on Ir4/MgO and Ir4/γ-Al2O3 have been systematically studied by means of planewave density functional theory（DFT）calculations using the periodic boundary conditions.The binding energies of these species were ordered as follows：H2O〈C2H4〈H〈OH〈S〈N〈O〈C.The adsorption energies of adatoms on Ir4/MgO were larger than those on Ir4/γ-Al2O3 except hydrogen atom,but were in reverse for the molecules calculated.In addition,the difference of adsorption energies on MgO and γ-Al2O3 supports has been elucidated by analyzing the electronic properties.A detailed investigation on state density clarifies the nature of the magnitude of adsorption energy.These calculated results are consistent well with the available experimental and theoretical results.

INVESTIGATION OF THE SOLID- SOLID SURFACE ADSORPTION OF Eu_2O_3 ON AMORPHOUS Al_2O_3

Solid-solid surface adsorption of Eu2O3 on amorphous Al2O3 have been investigated by Mossbauer spectroscopy, X- ray diffraction analysis and laser Raman spectra (LRS). No X-ray diffraction peak of crystalline Eu2O3 can be found for all samples studied. The LRS show that two peaks at 998 and 1051 cm-1 assigned to two-dimensional surface europium-oxygen species appear at Eu2O3 content of 18.7 wt%. The peak at 1068 cm-1 due to the surface species and another peak at 342cm-1 due to crystalline Eu2O3 content start to appear for the sample with an Eu2O3 content of 36.5 wt%. The dispersity of Eu2O3 on the surface of amorphous Al2O3 were compared with that of α-Al2O3,η-Al2O3 and SiO2 gel. The results of these studies indicate that the structure of Eu2O3 dispersed onto the support surface depend on the structure of support and that there is an inductive effect of support on the structure of the Eu2O3.

Adsorption of H2O, OH, and O on CUCl（111） Surface： A Density Functional Theory Study

The adsorption of H2O molecule and its dissociation products, O and OH, on CuCl（111） surface was studied with periodic slab model by PW91 approach of GGA within the framework of density functional theory. The results of geometry optimization indicate that the top site is stable energetically for H2O adsorbed over the CuCl（111） surface. The threefold hollow site is found to be the most stable adsorption site for OH and O, and the calculated adsorption energies are 309.5 and 416.5 kJ/mol, respectively. Adsorption of H20 on oxygen-precovered CuCl（111） surface to form surface hydroxyl groups is predicted to be exothermic by 180.1 kJ/mol. The stretching vibrational frequencies, Mulliken population analysis and density of states analysis are employed to interpret the possible mechanism for the computed results.

Comparable Studies of Adsorption and Magnetic Properties of Ferrite MnFe_2O_4 Nanoparticles,Porous Bulks and Nanowires

The spinel ferrites MnFe2O4 nanowires were synthesized by hydrothermal route,porous MnFe2O4 and nanoparticles morphologies were synthesized by sol-gel method with egg white.The structures,morphologies,magnetic properties and adsorption properties of these obtained ferrites with different morphologies were studied contrastively.Results show that the obtained samples exhibit ferromagnetic properties.This realizes convenient magnetic separation from solution when they are used in the treatment of organic dyes wastewater.However,the contrastive studies show that the saturation magnetizations（Ms） of MnFe2O4 with different morphologies are different and the Ms follows the order：Ms（porous）〈Ms（nanoparticles）〈Ms（nanowires）.In addition,the adsorptions of methylene blue（MB） onto these ferrites depend on ferrites＇ morphologies seriously.The adsorption rate of MB on the porous MnFe2O4 is much higher than those onto the other two samples because the porous structure can provide high efficient mass transport through the pores.

Combination Effect of Cation Vacancies and O2 Adsorption on Ferromagnetism of Na0.5Bi0.5TiO3（100） Surface:ab initio Study

The combination effect of cation vacancies and O2 adsorption on ferromagnetism of Na0.5Bi0.5TiO3（100） surface is studied by using density functional theory. An ideal Na0.5Bi0.5TiO3（100） surface is non-magnetic and the cation vacancy could induce the magnetism. By comparing the formation energies for Na, Bi and Ti vacancy, the Na vacancy is more stable than the others. Therefore, we focus on the configuration and electric structure for the system of O2 molecule adsorption on the Na0.5Bi0.5TiO3（100） surface with a Na vacancy. Among the five physisorption configurations we considered, the most likely adsorption position is Na vacancy. The O2 adsorption enhances the magnetism of the system. The contribution of spin polarization is mainly from the O 2p orbitals. The characteristics of exchange coupling are also calculated, which show that the ferromagnetic coupling is favorable. Compared with the previous calculation results, our calculations could explain the room-temperature ferromagnetism of Na0.5Bi0.5TiO3 nanocrytalline powders more reasonably, because of taking into account adsorbed oxygen and cation vacancies. Moreover, our results also show that adsorption of O2 molecule as well as introduction of cation vacancies may be a promising approach to improve multiferroic materials.