Comparative study for the removal of methylene blue via adsorption and photocatalytic degradation

Physically and chemically activated carbons were prepared from date pits and olive stones. Titania and WO(x)-TiO(2)/MCM-41 were prepared as photoactive catalysts. Surface characterizations were investigated from ash content, pH, base neutralization capacities and FT-IR techniques. The textural characteristics, namely specific surface area (S(BET)) and pore texture, were determined from low temperature adsorption of N(2) at 77 K. The decolorization of aqueous solution of methylene blue was performed by means of two alternative methods. Steam-activated carbons own higher surface area compared with ZnCl(2)-activated carbons, and the micropore surface area represents the major contribution of the total area. Steam-activated carbons were the most efficient decolorizing adsorbents owing to its higher surface area, total pore volume and the basic nature of the surface. The calculated values of DeltaG(0), DeltaH(0) and DeltaS(0) indicate the spontaneous behavior of adsorption. The photocatalytic degradation is more convenient method in decolorizing of methylene blue compared with the adsorption process onto activated carbons.     

膜Zeta电位测试技术研究进展

分离膜荷电化显著地影响着膜的分离性能和耐污染能力。因此,定量化表征膜表面(包括孔表面)电性能具有重要的理论价值和实际意义。本文系统地综述了各种膜Zeta电位测定原理、特点及其不足,并展望了膜Zeta电位的未来研究方向。     

选择性萃取对沉积物非残渣态、粘土矿物结构及吸附特性的影响

用NH2OH·HCl, (NH4)2C2O4和H2O2对表层沉积物中非残渣态的Mn氧化物、Fe/Mn氧化物和有机质进行选择性化学萃取, 同时提取粘土矿物, 并对提取前后的表层沉积物样品进行了比表面积、FTIR、ESEM和XRD等分析. 结果表明, 萃取后沉积物的比表面积显著增大, 沉积物颗粒的分散度随之增大, 晶体边缘逐渐清晰, 棱角逐渐分明, 但沉积物的XRD和FTIR谱图变化不大, 原因在于XRD和FTIR谱图中的特征峰主要是由矿物组分产生的. 萃取后随着沉积物分散度的增大, 晶体颗粒表面粗糙度减弱, 沉积物的吸附能力降低, 表明颗粒表面特征对重金属的吸附起到一定作用; 而沉积物的比表面积与沉积物吸附能力之间的反比关系说明沉积物主要吸附组分对其吸附的贡献远远大于沉积物表面与孔隙结构的贡献.     

A study of the microstructure of dressed glass fibers

Photographs of the microstructures of PT300-100 and Ortex-560 glass fibers obtained on an electron microscope and three-dimensional patterns of their surfaces obtained on an atomic-force microscope are given. A procedure for the evaluation of the roughness characteristics of glass fibers using an atomic-force microscope of an NT-MDTNTEGRA Spectra model is given. Experimental parameters of the following roughness characteristics are given: surface average roughness, ten-point height of irregularities, and maximum and minimum profile heights. It is shown that the roughness characteristics depend to a considerable extent on the scanning surface area; the higher the area, the higher all measured characteristics.     

Impact of molecular surface characteristics on the reversed-phase retention behaviour of synthetic dyes

The lipophilicity and specific hydrophobic surface area of 42 synthetic dyes were determined on reversed-phase alumina layers using water-methanol mixtures as eluents, and their relationship with the molecular surface characteristics was elucidated by principal component analysis followed by a two-dimensional nonlinear map and cluster analysis. Four dyes remained on the origin in each eluent system. Except for two dyes, the majority showed regular retention behaviour with their retention decreasing steadily with increasing concentration of methanol in the mobile phase. Calculations indicated that both hydrophobicity parameters decrease with increasing polar surface area of the molecules.     

Structure-Function Analysis of the Emulsifying and Interfacial Properties of Apomyoglobin and Derived Peptides

Apomyoglobin was chosen as a model to study the emulsifying properties of proteins. It was cleaved into three peptides using cyanogen bromide and these peptides were purified and tested for emulsifying and interfacial properties. Two of the peptides had improved emulsifying activity compared to the whole protein. The peptide (residues 1-55) with the highest emulsifying activity and whole apomyoglobin were studied further. The amount of protein or peptide adsorbed at the oil-water interface of an emulsion was measured and the surface area occupied per molecule was calculated. For apomyoglobin, at maximal surface coverage each molecule occupied a surface area of approximately 8 nm2. This is consistent with a packed monolayer, based on the approximate dimensions of apomyoglobin. For peptide (1-55), at maximal surface coverage each molecule occupied a surface area of approximately 3 nm2. This is consistent with the area that the two amphipathic alpha-helices which are potentially present in this molecule would cover, if they were aligned along the oil-water interface. The different structural characteristics of these molecules responsible for their emulsifying properties are discussed. Copyright 1999 Academic Press.     

Memory effects on the interfacial characteristics of dioctadecyldimethylammonium bromide monolayers at the air-water interface

The structural and dynamic characteristics of dioctadecyldimethylammonium bromide (DODAB) monolayers on a pure water subphase were investigated by surface film balance, Brewster angle microscopy, and relaxation in area and surface pressure at constant surface pressure and area, respectively. The first compression-expansion cycle of the monolayer is not reversible and the second pi-A compression isotherm deviates to larger molecular areas relative to the first one. At a microscopic level this hysteresis may be assigned to an irreversible hydration of the ammonium groups of DODAB. The morphology and reflectivity of DODAB monolayers during compression and expansion on the monolayer depend on the monolayer history. Bright domains randomly dispersed were observed during compression before collapse. Surprisingly, this random distribution of domains changes into a fractal-like structure during the monolayer expansion in a narrow range of surface pressures. This morphology does not form when the monolayer is previously compressed above the collapse surface pressure. 2D foam-like structure is often observed when the film is expanded at maximum area. Relaxation phenomena in DODAB monolayers are attributed to monolayer reorganization and nucleation of liquid-condensed domains from the liquid-expanded phase. These time-dependent processes are irreversible.     

Influence of surface properties of the titanium dioxide porous films on the characteristics of solar cells

Porous films formed by cylindrical geometrically anisotropic fragments of TiO₂ have been produced by electrochemical anodization of titanium. The specific surface area and pore volume of the samples were determined by the BET method. It is shown that the samples have a bimodal pore-size distribution with maxima depending on the anodization voltage: by increase in voltage the inner diameter of the cylindrical pores grows, which leads to a decrease in the specific surface area. Dye sensitized solar cells were assembled on the basis of the obtained materials to study the effect of certain characteristics on the efficiency of solar energy conversion. The electrical transport properties of the films were studied by impedance spectroscopy.     

Effects of exchanged surfactant cations on the pore structure and adsorption characteristics of montmorillonite

Ca-montmorillonite (Ca-Mont) was exchanged with two quaternary amines, tetramethylammonium (TMA) chloride and hexadecyltrimethylammonium (HDTMA) bromide, to study the surfactant ion exchange effect on the pore structure, surface characteristics, and adsorption properties of montmorillonite. The revolution of both the surface area and pore structure of montmorillonite was characterized based on classical and fractal analyses of the nitrogen isotherms as well as the XRD patterns. The change of surface characteristics was identified from FTIR patterns and zeta-potential plots. The adsorption isotherms of acid dye, Amido Naphthol Red G (AR1), were then measured to identify the effects of the ion-exchange process on the adsorption properties of montmorillonite. It was found that the exchange processes might induce an increase or decrease in the surface area, pore size, pore volume, and surface fractal dimension D of montmorillonite, depending on the size, the molecular arrangement, and the degree of hydration of the exchanged ion in the clay. On the other hand, it was also found that the hydrophobic bonding by conglomeration of large C(16) alkyl groups associated with HDTMA could cause positive charge development on the surface of montmorillonite, which was not observed for TMA-modified montmorillonite (TMM). The effects of the alteration of the surface characteristics of montmorillonites on their adsorption selectivity for acid dye were discussed.     

球磨方式对锂离子正极材料LiFePO4性能的影响

采用高温固相合成法制备橄榄石型的LiFePO₄正极材料，在合成过程中分别采用湿法球磨和干法球磨两种球磨方式。用X-射线衍射，扫描电镜，激光粒度测试等对合成材料进行表征，并对以LiFePO₄为正极的电池进行电化学性能测试。结果表明，相对于干法球磨，湿法球磨制备的LiFePO₄样品具有更好的电化学性能，0.2C放电的首次放电比容量为134.9 mAh·g^-1，并有优良的大电流放电性能及循环性能。这主要是因为采用湿法球磨制备的LiFePO₄材料物相较纯、粒径均匀，与导电添加剂的接触更加紧密，从而提高了LiFePO₄材料电化学性能。     

两性霉素B与鞘磷脂单分子层的相互作用

选取哺乳动物生物膜中的重要脂质分子鞘磷脂(SM)作为单分子膜的基本组分, 采用Langmuir-Blodgett(LB)膜技术研究了不同比例的两性霉素B/鞘磷脂单层膜的表面压力-平均分子面积(π-A)曲线以及基于π-A曲线的混合性分析, 同时通过原子力显微镜(AFM)研究了其表面形态的变化. 结果表明, 组分间的摩尔比和表面压力对混合单层膜稳定性、混合性以及分子间相互作用具有重要影响.     

Regional characteristics of naturally occurring radionuclides in surface sediments of Chinese deserts and the Keum River area of Korea

Naturally occurring radionuclides (NORN) such as ⁴⁰K, ²²⁶Ra and ²³²Th from 44 surface sediment samples collected from four desert regions of Chinese were determined to investigate the regional characteristics of the source areas of Asian dust. The radionuclides for 41 surface sediment samples collected from seven sites of the Keum River area in Korea were also determined to compare the regional characteristics with the Chinese desert area. The specific activities (SA) and the specific activity ratios (SAR) of the radionuclides were investigated for distinguishing the source region of Asian dust. The SA of ²²⁶Ra and ²³²Th as well as the SAR of ²²⁶Ra/⁴⁰K and ²³²Th/⁴⁰K were found to be useful to characterize source area and tracing Asian dust.     

Peculiarities of the vibratioanl spectra of molecules adsorbed on the surface of heterogeneous catalysts: theoretical analysis

The vibrational spectra of adsorption complexes resulting from the adsorption of ammonia on the surface of heterogeneous catalysts are interpreted by computation of frequencies and forms of normal vibrations. The characteristics of normal vibrations are computed from the state of separate fragments of adsorption complexes. It is shown that an interaction of internal coordinates, associated with the adsorption bond, with internal coordinates of the adsorbed molecule leads to a decrease of characteristics of vibrations sensitive to the surface area. A correlation is established between the characteristics of such vibrations and the changes in their frequencies in comparison with the free molecule.     

Influence of the intercalated cations on the surface energy of montmorillonites: consequences for the morphology and gas barrier properties of polyethylene/montmorillonites nanocomposites

Organically modified montmorillonites obtained by cation exchange from the same natural layered silicate were studied. The surface properties of the pristine and a series of organically modified clays were determined by inverse gas chromatography and the water adsorption mechanisms were studied by a gravimetric technique coupled with a microcalorimeter. A significant increase of the specific surface area, a decrease of the water adsorption, and a decrease of the dispersive component of the surface energy were observed when the sodium cations of the natural montmorillonite were exchanged for a quaternary ammonium. Slighter differences in surface properties were observed, on the other hand, between the different types of organically modified montmorillonites. Indeed, similar dispersive components of the surface energy were determined on the organoclays. Nevertheless, the specific surface area increased in the range 48-80 m(2)/g with increasing d-spacing values and the presence of specific groups attached to the quaternary ammonium, such as phenyl rings or hydroxyl groups, led to some specific behaviors, i.e., a more pronounced base character and a higher water adsorption at high activity, respectively. Differences in interlayer cation chain organization, denoted as crystallinity, were also observed as a function of the nature of the chains borne by the quaternary ammonium. In a later step, polyethylene-based nanocomposites were prepared with those organically modified montmorillonites. The clay dispersion and the barrier properties of the nanocomposites were discussed as a function of the montmorillonite characteristics and of the matrix/montmorillonite interactions expected from surface energy characterization.     

茂县大骨节病病区水化学特征

茂县大骨节病区分布具有明显的地域特点,考察了当地地质环境概况,同时对该区地表水、地下水取样,对常量组分、腐殖酸、微量组分进行了分析,阐述了该区的水化学特征。     

Effects of organic micromolecules in coal on its wettability

Two types of bituminous coal were extracted with tetrahydrofuran solvent using microwave-assisted method at 50°C and atmospheric pressure. Pore structure parameters and wettability of raw coals and their residues were separately tested with nitrogen adsorption and capillary penetration method. Fourier transform infrared spectrometer was employed for analysis of surface functional groups of raw coals and their residues. Results showed remarkably degraded wettability of coal, especially gas coal, after extraction, whereas wetting height of raw coal reached more than twice that of residual coal within the same wetting time. Given the different storage characteristics of organic micromolecules in coal, pore volume of coal increased after extraction, and solvent extraction exerted different effects on pores. Pores of gas coal expanded with reduced specific surface area and improvement in hydrophobicity. Pores of coking coal increased with increasing specific surface area and degrading hydrophobicity. Organic micromolecules in coal and several side-chain groups in macromolecular skeleton structure were dissolved, reducing contents of functional groups in coal, decreasing quantities of groups, such as methyl and carbonyl, on coal surface, and modifying microcosmic surface characteristics of coal and improving hydrophobicity. Through comprehensive analysis, pore structure, and microcosmic surface characteristics of coal jointly determined its wettability.     

Sorption characteristics of nano manganese oxide: efficient sorbent for removal of metal ions from aqueous streams

Nanocrystalline manganese oxide was prepared and characterized using various techniques like XRD, surface area analyzer and zeta potential measurements. The sorption characteristics with respect to uptake of various ions including uranyl have been evaluated. Various experimental conditions which affect the sorption characteristics have been studied. Nanocrystalline manganese oxide was prepared by the hydrolysis of KMnO₄ and the nano oxide were found to have a size of 8 nm and surface area of 145 m²/g. Due to the high surface area, the sorption property of the nano oxide was good. It was found that the sorption was achieved at different pH values and with varying time of equilibration. Thus it is seen that the kinetics was an important aspect for the possible separation of metal ions.     

纳米TiO2-SiO2复合氧化物的制备与性质

采用溶胶-凝胶结合CO2超临界干燥方法制备了比表面积大、热稳定性好的纳米TiO2-SiO2复合氧化物.考察了原料组成和焙烧温度对复合氧化物比表面积、热稳定性和酸性的影响,通过加氢脱硫反应考察了该复合氧化物作为加氢精制催化剂载体的可行性.结果表明,采用该方法制备的复合氧化物为纳米颗粒,在n(Ti)/n(Si)=1时,其比表面积和孔容最大;与纯TiO2相比,引入SiO2明显提高了复合氧化物的热稳定性和晶型稳定性;以此复合氧化物为载体的加氢精制催化剂具有很好的低温脱硫活性,TiO2-SiO2复合氧化物载体的酸性特征影响了催化剂的加氢脱硫活性.     

Influence of copper content on NO removal of the activated carbon fibers produced by electroplating

In this study, the activated carbon fibers (ACFs) on which copper metal was deposited by electroplating were used to remove nitric oxide (NO). N(2)/77 K adsorption isotherm characteristics, including the specific surface area and micropore volume, were investigated by BET and T-plot methods. NO removal efficiency was confirmed by gas chromatographic technique. From the experimental results, the copper content supported on ACFs led to an increase in the NO conversion, in spite of the decrease of the specific surface area or the micropore volume of ACFs. Consequently, the presence of Cu on ACFs played an important role in improving the NO reduction into O(2) and N(2), which was mainly attributed to the catalytic reactions of Cz-NO-Cu.     

The physical and surface chemical characteristics of activated carbons and the adsorption of methylene blue from wastewater

Adsorption of a basic dye, methylene blue, from aqueous solutions onto as-received activated carbons and acid-treated carbons was investigated. The physical and surface chemical properties of the activated carbons were characterized using BET-N(2) adsorption, X-ray photoelectron spectroscopy (XPS), and mass titration. It was found that acid treatment had little effect on carbon textural characteristics but significantly changed the surface chemical properties, resulting in an adverse effect on dye adsorption. The physical properties of activated carbon, such as surface area and pore volume, have little effect on dye adsorption, while the pore size distribution and the surface chemical characteristics play important roles in dye adsorption. The pH value of the solution also influences the adsorption capacity significantly. For methylene blue, a higher pH of solution favors the adsorption capacity. The kinetic adsorption of methylene blue on all carbons follows a pseudo-second-order equation.