硝酸氧化改性SBA-15 模板合成的中孔炭电容性能研究

采用有序中孔氧化硅SBA-15为模板，合成了具有高效能量存储的超级电容器电极材料——有序中孔炭材料；以硝酸为氧化剂，分别在26℃、50℃、70℃和100℃下对中孔炭进行了表面官能化处理。结合氮气等温吸附、X射线光电子能谱和热分析方法研究了氧化前后中孔炭孔结构和表面官能团的演化。结果表明：随着氧化温度的升高，比表面积和中孔含量减少，而表面官能团含量增加。电化学测试显示：原始中孔炭的能量密度为3．5Wh／kg，100℃氧化的中孔炭具有最高的能量密度（5．7Wh／kg）。表明硝酸官能化处理可将中孔炭材料应用范围拓展到高能量密度领域。同时初始中孔炭的功率密度为2015W／kg，70℃氧化的中孔炭具有最高的功率密度（3125W／kg）。研究表明能量密度的改善得益于表面官能化对双电层电荷密度的提高和引入了法拉第赝电容反应；而功率密度的提高来自亲水性的官能化炭表面所具有的低离子扩散阻力。     

Study on adsorption of Co(II) and Ni(II) onto mesoporous Ti-containing MCM-48

Ti-containing MCM-48 (Ti-MCM-48) material with mesoporous structure was synthesized and characterized, and the absorption processes of Co(II) and Ni(II) on the material were investigated in detail in the present study. The Ti- MCM-48 was synthesized by hydrothermal reaction and characterized by XRD, FT-IR and nitrogen sorption methods. Optimum pH value for maximum adsorption rate is 8.0, and the saturated adsorption capacities of Ti-MCM-48 for Co(II) and Ni(II) are 9.870 and 22.94 mg g(-1) respectively, which are greater than those of the reported materials Adsorption isotherms of Co(II) and Ni(II) on Ti-MCM-48 accord well with the Langmuir adsorption models. Kinetic data of adsorption reactions and the adsorption equilibrium parameters were also determined, and the obtained data correlated linearly with the pseudo-second order equation.     

Nitrogen adsorption method for determining the mesopore slit-like size distribution of expansive soils

One of the most important structural parameters involved in the characterization of the void space of soils is the pore size distribution. In this work, a nitrogen adsorption method is presented as an alternative to determine the mesopore contribution of slit-shaped pores to the abovementioned parameter in montmorillonite-containing soils. The mesopore size structural parameter obtained via this sorption method is related to montmorillonite d₀₀₁ interlayer distances proceeding from either X-ray or electron diffraction analysis, if only by assuming during sorption analysis that mesopores resident inside clay grains adopt slit-shaped geometries. Mineralogical analysis and determination of some important geotechnical properties of these montmorillonite-containing soils complement the preceding sorption and structural studies.     

Synthesis and characterization of TiO2-carbon nanocomposites with both micro- and mesopore size distributions

TiO₂-carbon nanocomposites were synthesized by simply mixing a TiO₂ sol with a semi-cured resorcinol and formaldehyde gel, followed by drying and pyrolysis at 1000 °C in an inert atmosphere. For comparison, the pure resorcinol and formaldehyde gel and the pure TiO₂ gel were also prepared, dried and pyrolysed in same conditions, respectively. The composites with a low TiO₂ content had the similar pore size distribution (PSD) and crystallographic structure to that of the blank sample (i.e., micropore size distribution), However the presence of high content TiO₂ in the composites effectively resulted in an increase in mesoporosity and a crystallographic structure of dominant rutile TiO₂ in the TiO₂-carbon nanocomposite.     

Bromine pretreated chitosan for adsorption of lead (II) from water

Pollution by heavy metals like lead (II) is responsible for health hazards and environmental degradation. Adsorption is a prevalent method applied for removal of heavy metal pollutants from water. This study explored adsorption performances of 30% bromine pretreated chitosan for lead (II) abatement from water. Bromine pretreatment alters porosity and specific surface area of chitosan by means of physicochemical interaction with cationic sites of chitosan skeleton, besides imparting anionic alteration at amino linkages of chitosan, to remove lead (II) by chemical interactions on superfluous active sites as characterized by FTIR, SEM, DTA and elemental analysis. Lead adsorptions were studied in batch mode by varying parameters viz. pH, bromine loading, sorbent dosage, initial lead concentration, contact time and temperature. The adsorption equilibrium data was well fitted to Freundlich isotherm and maximum sorption capacity of 30% bromine pretreated chitosan sorbent was 1·755 g/kg with 85–90% lead removal efficiency. Though cost and applicability of sorbent is unproven, yet contrast to raw chitosan derivatives, activated carbons and some resins, 30% bromine pretreated chitosan endow benign and efficient lead abatement technique.     

Competitive adsorption of copper(II), cadmium(II), lead(II) and zinc(II) onto basic oxygen furnace slag

Polluted and contaminated water can often contain more than one heavy metal species. It is possible that the behavior of a particular metal species in a solution system will be affected by the presence of other metals. In this study, we have investigated the adsorption of Cd(II), Cu(II), Pb(II), and Zn(II) onto basic oxygen furnace slag (BOF slag) in single- and multi-element solution systems as a function of pH and concentration, in a background solution of 0.01M NaNO(3). In adsorption edge experiments, the pH was varied from 2.0 to 13.0 with total metal concentration 0.84mM in the single element system and 0.21mM each of Cd(II), Cu(II), Pb(II), and Zn(II) in the multi-element system. The value of pH(50) (the pH at which 50% adsorption occurs) was found to follow the sequence Zn>Cu>Pb>Cd in single-element systems, but Pb>Cu>Zn>Cd in the multi-element system. Adsorption isotherms at pH 6.0 in the multi-element systems showed that there is competition among various metals for adsorption sites on BOF slag. The adsorption and potentiometric titrations data for various slag-metal systems were modeled using an extended constant-capacitance surface complexation model that assumed an ion-exchange process below pH 6.5 and the formation of inner-sphere surface complexes at higher pH. Inner-sphere complexation was more dominant for the Cu(II), Pb(II) and Zn(II) systems.     

Kinetics of neptunium(V) reduction with iron(II) sulfamate in nitric acid solutions

The kinetics of chemical reduction of Np(V) with iron(II) sulfamate in HNO₃ solutions was studied by spectrophotometry. The reduction process can be described by the equation NpO ₂ ⁺ + Fe²⁺ + 4H⁺ ? Np⁴⁺ + Fe³⁺ + 2H₂O and follows the first- and zero-order rate law with respect to the Np(V) concentration. The reaction rate constants were determined in relation to the HNO₃ concentration (1–3 M), iron(II) sulfamate concentration [(0.59–2.94) × 10^?3 M], and temperature (298.2–319.2 K). The activation energy (E _a) and the thermodynamic functions of formation of the activated complex (activation free energy ΔG ^≠, enthalpy ΔH ^≠, entropy ΔS ^≠) were calculated.     

Surface modification of carbon fibers with nitric acid solutions

We have studied the surface modification of carbonized carbon fibers with nitric acid solutions, compared the effects of 60 and 98% HNO₃, and examined the influence of the anodic polarization of the fiber for surface functionalization. Unmodified and surface-modified carbon fibers have been characterized by a variety of physicochemical techniques.     

Selective adsorption behavior of Pb(II) by mesoporous silica SBA-15-supported Pb(II)-imprinted polymer based on surface molecularly imprinting technique

In this study, a new Pb(II) ion-imprinted polymer (Pb(II)-IIP), which can be used for selective adsorption of Pb(II) from aqueous solutions, was successfully prepared based on the supported material of ordered mesoporous silica SBA-15 with the help of surface molecular imprinting technology. The prepared polymer was characterized by Fourier transmission infrared spectrometry, X-ray diffraction, transmission electron microscope and nitrogen adsorption-desorption isotherm. The results showed that the synthesized polymer possessed high ordered mesoporous structure. The adsorption behavior of the adsorbents for Pb(II) was investigated using batch experiments. The Pb(II)-IIP showed fast kinetics, high selectivity and satisfied adsorption capacity for adsorption of Pb(II). Under the optimum experimental condition, Pb(II) adsorption process over Pb(II)-IIP follows pseudo-second-order reaction kinetics and follows the Langmuir adsorption isotherm. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of Pb(II) onto Pb(II)-IIP was a spontaneous and exothermic nature of the process.     

Simulation of granular packing of particles with different size distributions

The study of granular matter composed of spherical particles is of interest in manufacturing, material, and metallurgy. The viscoelastic and frictional contacts between the particles are the cause of forming the agglomeration. We present a numerical simulation for particles packing with three different kinds of size distributions: monosize, bimodal, and Gaussian, using distinct element method (DEM). The particles are initially put randomly but without any overlap, and then fall down due to the gravity force and collide with neighbor particles. Because of the dissipative factors of viscoelastic collision and frictional force, all the particles finally come together to form an agglomeration. Coordination number, porosity, radial distribution function, and force distribution are calculated for different size distributions. It is demonstrated that particle size distribution does affect the granular packing structure.     

Insight into kinetics and thermodynamics properties of multicomponent lead(II), cadmium(II) and manganese(II) adsorption onto Dijah-Monkin bentonite clay

Multicomponent adsorption of lead(II), cadmium(II) and manganese(II) by Nigerian Dijah-Monkin bentonite clay was investigated. The clay samples were characterized for elemental composition, cation exchange capacity and textural properties. Natural bentonite exhibits cation exchange capacity of 47.7?meq/100?g and specific surface area of 23.5?m²/g. Manganese(II) displays higher values of rate constant than lead(II) in multimetals adsorption. However, lead(II) is favorably adsorbed onto bentonite adsorbents at different concentrations studied. The multimetals adsorption onto bentonite clay samples is site selective and site specific. The pseudo-second-order kinetics model gave a better fit to the adsorption data, suggesting ion exchange and/or complex formation. The adsorption mechanism could be described by intraparticle diffusion with some restriction of metals diffusion due to film or boundary layer. Also, the multicomponent adsorption is endothermic and becomes more spontaneous as temperature increased from 303 to 338?K. Nigerian bentonite clay in its natural form is a promising adsorbent for multimetals removal in aqueous solution.     

Magnetic characterization of nanocrystalline iron samples with different size distributions

Nanocrystalline iron was obtained by fusing magnetite and promoters. The oxidized form was reduced with hydrogen and passivated (sample P0). The average nanocrystallite size in sample P0 was d(P0) =16 nm and the width of size distribution was σ(P0) = 18 nm. Samples of nanocrystalline iron with narrower diameter ranges and larger and smaller average crystallite sizes were also synthesized. They were: sample P1 (d(P1) = 28 nm, σ(P1) = 5 nm), sample P2 (d(P2) = 22 nm, σ(P1) = 5 nm), sample P3 (d(P3) = 12 nm, σ(P1) = 9 nm). These four samples were studied at room temperature by dc magnetization measurements and ferromagnetic resonance at microwave frequency. Correlations between samples sizes distributions (average size and width of the sizes) and magnetic parameters (effective magnetization, anisotropy field, anisotropy constant, FMR linewidth) were investigated. It was found that the anisotropy field and effective magnetization determined from FMR spectra scale linearly with nanoparticle sizes, while the effective magnetic anisotropy constant determined from the hysteresis loops decreases with nanoparticle size increase.     

Removal of heavy metal lead(II) using nanoscale zero-valent iron with different preservation methods

In this study, different nanoscale zero-valent irons (nZVI) were prepared in order to improve their stability and reactivity to heavy metal lead (Pb (II)). The composition, particle size and morphology of obtained nZVI were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM). The effects of nZVI dosage, pH, initial Pb (II) concentration and reaction time on the removal efficacy of Pb (II) were investigated. The results show that undried nZVI has more active sites due to its weaker oxidation, and thus the removal efficiency of Pb(II) by undried nZVI was higher than that by dried nZVI. As a result, the same removal efficiency could be achieved with the use of less undried nZVI for the identical concentration of Pb(II). Furthermore, the experimental procedure could be apparently simplified, which eliminates the steps of washing, separation and dehydration compared with the traditional preparation method. The experimental data could be well fitted by the Langmuir adsorption isotherm model, and the maximum adsorption capacity of dried and undried nZVI is 671.14 and 807.23?mg·g^?1 at pH 6, respectively. The experimental data followed the pseudo second-order kinetic model with a kinetic constant of 7.65?×?10^?4 and 1.39?×?10^?3 for undried and dried nZVI, respectively. In conclusion, undried nZVI had high adsorption capacity and adsorption rate for Pb(II) in the solution.     

Removal of copper(II) and lead(II) from aqueous solution by manganese oxide coated sand II. Equilibrium study and competitive adsorption

The adsorption equilibrium of MOCS and the Cu(II) and Pb(II) ions removal capacity by MOCS in single-(non-competitive) and binary-(competitive) component sorption systems from aqueous solutions were investigated. The equilibrium data were analyzed using the Langmuir, Freundlich, Temkin and Redlich-Peterson isotherms. The characteristic parameters for each isotherm were determined. The Langmuir and Redlich-Peterson isotherms provided the best correlation for both Cu(II) and Pb(II) onto MOCS. From the Langmuir isotherms, maximum adsorption capacities of MOCS towards Cu(II) and Pb(II) are determined at different temperature. The maximum adsorption capacity of Cu(II) and Pb(II) per gram MOCS in single component sorption systems were from 5.91 and 7.71 micromol to 7.56 and 9.22 micromol for the temperature range of 288-318 K, respectively. The order of affinity based on a weight uptake by MOCS was as follows: Pb(II)>Cu(II). The same behavior was observed during competitive adsorption that is in the case of adsorption from their binary solution. The thermodynamic parameters (DeltaG degrees , DeltaH degrees , and DeltaS degrees) for Cu(II) and Pb(II) sorption on MOCS were also determined from the temperature dependence. This competitive adsorption showed that the uptake of each metal was considerably reduced with an increasing concentration of the other, the adsorption of Cu(II) being more strongly influenced by Pb(II) than vice versa due to the higher affinity of MOCS for the latter.     

Mueller matrix measurements of algae with different shape and size distributions

The full Mueller matrix was measured to obtain the polarization state of the scattered light for a variety of algae with different shapes, wall compositions, sizes, and refractive indices. The experimental setup was a multiple laser Mueller matrix ellipsometer, by which measurements were performed for scattering angles from 16° to 160° sampled at every second degree for wavelengths of 473?nm and 532?nm. Previously, the polarization of light scattered from microalgae was investigated only for a few species, and the Mueller matrix was found to have little variation between the species. In our work a total of 11 algal species were investigated, representing diatoms, dinoflagellates, coccolithophorids, green algae, and a cryptophyte. The selection of species was made to obtain high variability in shape, size, cell wall, and refractive index. As in previous investigations, very small variations were found between species for most of the Mueller matrix elements, but noticeable variations were found for M(11), (M(12)+M(21))/2 and (M(33)+M(44))/2.     

Equilibrium studies of sorption of lead(II) ions by different pectin compounds

The adsorption of Pb(II) ions from aqueous solution by different pectin compounds was studied in a batch sorption system. Water-soluble low- and high-esterified pectins and insoluble calcium pectate beads were investigated. The lead-binding capacity of all pectin compounds was highest within the pH range from 7 to 8. The binding capacities and rates of Pb(II) ions by pectin compounds were evaluated. The Langmuir, Freundlich and BET sorption models were applied to describe the isotherms and isotherm constants. Sorption isothermal data could be well interpreted by the Langmuir model. These results obtained through the study suggest that pectin compounds are favorable sorbers. The largest amount of Pb(II) ions were bound by pectin with the low degree of esterfication. Therefore, pectin substances may be considered as perspective for sorption and removal of Pb(II) ions from wastewaters.     

Isotherm studies of lead(II), manganese(II), and cadmium(II) adsorption by Nigerian bentonite clay in single and multimetal solutions

This study was aimed at evaluating the isotherm of lead(II), manganese(II), and cadmium(II) adsorption in single and multimetal solutions using Nigerian bentonite. The natural and calcined clays were characterized for specific surface area, surface morphology, elemental composition, and cation exchange capacity (CEC). The adsorption data were analyzed and interpreted using isotherm models. The natural bentonite exhibits a specific surface area of 23.5?m²/g and a CEC value of 47.7 mEq/100?g and displays a higher adsorption capacity of all heavy metals in both single and multimetal solutions than the calcined bentonite. The removal of lead(II) by natural bentonite in single-component system is 0.0448?mmol/g. The order of selectivity is lead(II)?>?cadmium(II)?>?manganese(II). Result also shows that both clays demonstrate a preferable adsorption toward lead(II). Lead(II) adsorption is less affected by the presence of counter cations in multimetal solution. The adsorption of heavy metals onto Dijah-Monkin bentonite is site selective and site specific, and the adsorption data are well presented by the Langmuir model. The CEC could be the primary mechanism for the uptake of heavy metals, and the removal capacity was shown to depend on the ionic radius of metal ions.     

Synthesis of ordered large-pore mesoporous carbon for Cr(VI) adsorption

Highly ordered mesoporous carbon with large accessible pores (OMC-P) was prepared by using laboratory-made poly(ethylene oxide)-b-polystyrene diblock copolymer as template via the evaporation-induced self-assembly method. The OMC-P was first used as adsorbent for removal of Cr(VI) ion from aqueous solution. Adsorption behavior was studied as a function of time, concentration of adsorbate, temperature, and pH. The kinetics of adsorption of Cr(VI) ion onto OMC-P is well fit to the pseudo-second order model. The Cr(VI) ion adsorption is favored at lower temperatures and at initial acid pH values in the equilibrium. The Freundlich and the Langmuir isotherm fit the equilibrium data satisfactorily. The influence of porosity on equilibrium adsorption capacity was investigated on three types of carbon materials, namely, OMC-P, ordered mesoporous carbon templated from amphiphilic triblock copolymer F127 (OMC-F) and commercial activated carbon (AC). The prepared OMC-P exhibits much higher adsorption performance than the other two carbons.     

硝酸氧化对沥青烯基有序介孔炭电化学性能的影响

采用硝酸对沥青烯基有序介孔炭(Ordered mesoporous carbon,OMC)进行氧化处理,在硝酸浓度为5mol/L、40℃～100℃下,考察了氧化温度对沥青烯基OMC的孔结构和电化学性能的影响,讨论了不同表面化学氛围的OMC孔道内电解液离子的传输过程.OMC的结构表征和性能测试采用XRD、物理吸附仪和电化...