Novel modified pectin for heavy metal adsorption

Modified pectin cross-linked with adipic acid, was synthesized and used for heavy metal removal from wastewater. SEM and FTIR were used to investigate its structure and morphology. The modified pectin had a rough, porous phase covered with carboxy groups, resulting a high adsorption capacity. And at the room temperature, the saturated loading capacity for Pb^2＋, Cu^2＋ and Zn^2＋ reached 1.82 retool/g, 1.794 mmol/g and 0.964 retool/g, respectively. The results proved its potential application to remove of the heavy metal.     

Silicas with thiourea grafted groups for the concentration of heavy metal ions

Two methods for the chemical bonding of thiourea and its derivatives on dispersed silica have been developed as a result of a detailed study of the process of the thiourea chemisorption on silica surface. Obtained S-containing silicas possess a high extraction efficiency for heavy metal ions.     

石英砂滤料表面改性及其在含Pb2+废水处理中的应用

石英砂是一种在废水处理中常用的滤料,但是由于石英砂自身对废水的净化能力有限,因此常常仅作为众多水处理环节中的一环.本文采用纳米二氧化硅对石英砂进行表面改性,研究了表面处理方式、二氧化硅负载方式、官能团类型、官能团负载方式等因素对改性石英砂去除重金属效果的影响.通过一系列实验,确定盐酸清洗表面、二氧化硅直接吸附、胺基修饰的石英砂改性最佳工艺.改性后石英砂表面粗糙,呈现多孔结构.在最佳工艺条件下,石英砂的重金属去除能力由改性前的0.8%提高至100%,改性后石英砂对重金属的去除能力提升超100倍.     

Microporous polycarbazole with high specific surface area for gas storage and separation

Microporous polycarbazole via straightforward carbazole-based oxidative coupling polymerization is reported. The synthesis route exhibits cost-effective advantages, which are essential for scale-up preparation. The Brunauer-Emmett-Teller specific surface area for obtained polymer is up to 2220 m(2) g(-1). Gas (H(2) and CO(2)) adsorption isotherms show that its hydrogen storage can reach to 2.80 wt % (1.0 bar and 77 K) and the uptake capacity for carbon dioxide is up to 21.2 wt % (1.0 bar and 273 K), which show a promising potential for clean energy application and environmental field. Furthermore, the high selectivity toward CO(2) over N(2) and CH(4) makes the obtained polymer possess potential application in gas separation.     

Preparation of mesoporous silicon dioxide with high specific surface area

The influence of the reactant ratio on the specific surface area, total pore volume, and mean pore diameter of mesoporous silicon dioxide prepared by the sol-gel method was examined. The optimal reactant ratio for preparing the material with a high specific surface area was determimed.     

Comprehensive study of nanostructured supports with high surface area for Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch synthesis on nanostructure supports with high surface area such as nanostructure γ-alumina, single wall carbon nanotubes (SWNTs), and the hybrid of SWNTs/nanostructure γ-alumina has been investigated. The nanostructure γ-alumina was promoted with lanthanum to obtain better performance of catalyst and 15 wt% cobalt loading was the basis of our investigation. Fischer-Tropsch synthesis was performed in a fixed bed reactor under different reaction conditions (220–240 °C, 15–25 bar, H₂/CO ratio of 2, GHSV of 900–1400) in order to study the effects of temperature, pressure and gas hourly space velocity (GHSV) changes on hydrocarbon selectivity and catalyst activity. The catalysts were extensively characterized by different methods including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma (ICP), hydrogen (H₂) chemisorption and temperature-programmed reduction (TPR). The results showed that the yield of hybrid supported catalyst (55.4%) is higher than that of nanostructure γ-alumina supported catalyst (55.0%) and lower than that of SWNTs supported cobalt catalyst (71.0%). The hybrid supported catalyst showed higher reduction degree and dispersion of cobalt particles. The temperature, pressure and GHSV effects on hybrid supported catalyst were studied and results showed that higher pressure favors the chain growth and temperature increase leads to the increases in methane selectivity and CO conversion. Higher hydrocarbon selectivity and CO conversion showed positive relationship with increasing GHSV while lower hydrocarbon selectivity diminishes.     

Recent developments in the preparation of high surface area metal fluorides

An overview of the main procedures for the preparation of fluorides with very high surface areas is given. Three processes are outlined: (i) plasma fluorination, (ii) sol–gel route and (iii) oxidative decomposition of inorganic precursors. From all three processes nanostructured metal fluorides with 100–400 m² g⁻¹ can be obtained. Prevention of the local overheating during fluorination seems to be the key factor to obtain the high surface area fluorides. TEM investigations of AlF₃ and CrF₃ obtained by oxidative decomposition revealed considerable differences in their morphologies and crystallinity. CrF₃ is completely amorphous and unstable under beam. AlF₃ contains an amorphous phase and nanocrystalline phases of α-AlF₃ and β-AlF₃. Nanocrystals are uniformly distributed within the amorphous phase. Also present are the rod-like nanostructures that consist of β-AlF₃ and are 5–10 nm wide.     

Ambient pressure dried tetrapropoxysilane-based silica aerogels with high specific surface area

In the present paper, we report the synthesis of tetrapropoxysilane (TPOS)-based silica aerogels with high surface area and large pore volume. The silica aerogels were prepared by a two-step sol-gel process followed by surface modification via a simple ambient pressure drying approach. In order to minimize drying shrinkage and obtain hydrophobic aerogels, the surface of the alcogels was modified using trichloromethylsilane as a silylating agent. The effect of the sol-gel compositional parameters on the polymerization of aerogels prepared by TPOS, one of the precursors belonging to the Si(OR)₄ family, was reported for the first time. The oxalic acid and NH₄OH concentrations were adjusted to achieve good-quality aerogels with high surface area, low density, and high transparency. Controlling the hydrolysis and condensation reactions of the TPOS precursor turned out to be the most important factor to determine the pore characteristics of the aerogel. Highly transparent aerogels with high specific surface area (938 m²/g) and low density (0.047 g/cm³) could be obtained using an optimized TPOS/MeOH molar ratio with appropriate concentrations of oxalic acid and NH₄OH.     

Determination of specific surface area for uranium compounds

A new method of thermal desorption chromatography, in which hydrogen is used as carrier instead of helium, and a water bath instead of an air bath, is presented for determining the specific surface area of uranium compounds. The method proposed has a higher accuracy and a better applicability.     

One-step synthesis of hierarchical porous γ-alumina with high surface area

Hierarchical porous γ-alumina is successfully fabricated from a precursor solution consisting of surfactants, polystyrene (PS) spheres, inorganic salts and solvents. After calcinations, uniform macropores are closely packed. The macropore size coincides with the original PS sphere size. These macropores are connected by small windows. In addition, the macropore walls have mesoporous structures, as confirmed by SAXS measurement and TEM observation. After calcination at 900 °C, the amorphous alumina frameworks are converted to the crystallized γ-alumina phase. Even after crystallization, the existence of uniform mesopores and high surface are well retained, though the mesoporous ordering is lower.     

Porous silicon oxycarbide glasses from organically modified silica gels of high surface area

High surface area alkyl-substituted silica aerogels and xerogels were successfully prepared by sol-gel processing and supercritical drying. The gels were further heat treated in inert atmosphere to temperatures as high as 1000°C. Surface areas and pore structure of the gels and gels pyrolyzed at high temperatures were determined by multipoint BET surface area measurement. The aerogels and xerogels exhibited surface areas of about 1100 m²/g. No significant effect of pH was found on the surface areas of gels in the two step sol-gel process, but gels of low pH showed smaller pore diameter and higher density. Xerogels showed smaller surface area, pore size, and pore volume compared to aerogels. Upon pyrolyzing in inert atmosphere, the surface areas of all the gels decreased with temperature as a result of collapse of micropores and shrinkage of mesopores. Unlike pure silica gel, which loses almost all surface area and densifies at 1000°C, the advantage of the alkyl-substituted gels is that they maintained a high surface area of 400 m²/g at 1000°C.Also with the Department of Agronomy.     

Thermogravimetric determination of specific surface area for soil colloids

A simple and easy method based on differential drying of samples at different temperatures has been proposed for quantitative determination of the specific surface areas of colloidal disperse systems. The following fundamental dependence of moisture thermodynamic potential [ψ] on absolute drying temperature T is used in the method: ψ = Q–aT, where Q is the specific heat of evaporation and a is a parameter related to the initial temperature and relative air humidity in an external thermodynamic reservoir (laboratory apartment). Gravimetric data on moisture mass fraction W and the value of ψ have been used to plot Polanyi potential curves W(ψ) for the studied samples. The curves have been employed to calculate the isotherms of moisture sorption. The capacity of a monolayer and the effective specific surface area have been determined from these isotherms in terms of the BET theory. The surface area estimated from the published results of classical experiments is about 1000 m²/g. The problem of the “absolute zero of humidity,” which is of great importance for determining the properties of colloidal disperse bodies normalized with respect to the solid phase mass, has been discussed.     

Enhancing adsorption of heavy metal ions onto biobased nanofibers from waste pulp residues for application in wastewater treatment

Biobased nanofibers are increasingly considered in purification technologies due to their high mechanical properties, high specific surface area, versatile surface chemistry and natural abundance. In this work, cellulose and chitin nanofibers functionalized with carboxylate entities have been prepared from pulp residue (i.e., a waste product from the pulp and paper production) and crab shells, respectively, by chemically modifying the initial raw materials with the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) mediated oxidation reaction followed by mechanical disintegration. A thorough investigation has first been carried out in order to evaluate the copper(II) adsorption capacity of the oxidized nanofibers. UV spectrophotometry, X-ray photoelectron spectroscopy and wavelength dispersive X-rays analysis have been employed as characterization tools for this purpose. Pristine nanofibers presented a relatively low content of negative charges on their surface thus adsorbing a low amount of copper(II). The copper adsorption capacity of the nanofibers was enhanced due to the oxidation treatment since the carboxylate groups introduced on the nanofibers surface constituted negative sites for electrostatic attraction of copper ions (Cu²⁺). The increase in copper adsorption on the nanofibers correlated both with the pH and carboxylate content and reached maximum values of 135 and 55 mg g^?1 for highly oxidized cellulose and chitin nanofibers, respectively. Furthermore, the metal ions could be easily removed from the contaminated nanofibers through a washing procedure in acidic water. Finally, the adsorption capacity of oxidized cellulose nanofibers for other metal ions, such as nickel(II), chromium(III) and zinc(II), was also demonstrated. We conclude that TEMPO oxidized biobased nanofibers from waste resources represent an inexpensive and efficient alternative to classical sorbents for heavy metal ions removal from contaminated water.     

Design and synthesis of novel thiourea metal complexes with controllable antibacterial properties

A new bidentate O,S donor thiourea ligand (L¹), namely N‐(2‐hydroxyethyl)‐N′‐2‐chlorobenzoylthiourea, and its oxazolidine derivative (L²) were synthesized. Derivative L² was used for the preparation of Ni(L²)₂ and Cu(L²)₂ complexes. The compounds were investigated using X‐ray crystallography and Fourier transform infrared, ¹H NMR and UV–visible spectroscopies. Single‐crystal X‐ray analysis showed strong hydrogen bonding interactions between carbonyl oxygen and N(10) ─ H in the L¹ ligand. In addition, the antibacterial activities of these compounds were evaluated against Gram‐positive and Gram‐negative bacteria, measured using the colony count method. The Cu(L²)₂ complex exhibited a significant antibacterial activity while the activity of the other compounds was much lower. Finally, the relationship between the structure and antibacterial properties of these compounds was investigated using highest occupied and lowest unoccupied molecular orbital energies calculated by density functional theory method based on the 6‐31G*/LANL2DZ basis set.     

A powerful approach to fabricate nitrogen-doped graphene sheets with high specific surface area

This study develops a powerful strategy for fabricating the nitrogen-doped graphene sheets with good crystallinity, high specific surface area, and high percentages of pyridinic/graphitic-nitrogen structures. Due to the specified N-doping structures and high specific surface area of 719 m² g^− 1, our N-doped graphene sheets show an excellent electrocatalytic activity for the oxygen reduction reaction (ORR).     

A novel hydrazine electrochemical sensor based on the high specific surface area graphene

An ultrasensitive platform is presented for the determination of hydrazine by combining the high specific surface area and higher electrical conductivity of poly(sodium styrenesulfonate) (PSS) graphene nanocomposite film with amperometric detection. The PSS-graphene were synthesized by the Hummers method and used to modify a glassy carbon electrode. The material was characterized by scanning electron microscopy and is found to be suitable for sensing hydrazine. The overpotential of hydrazine on the modified electrode is 0.31 V which is lower than in many electrochemical sensors. The calibration curve for hydrazine is linear in the range from 3.0 to 300 µmol L^?1, and the detection limit is as low as 1 µmol L^?1. This is the first report in which such a high sensitivity and low limit of detection has been achieved. It is concluded that PSS graphene represents an efficient electron mediator for sensing hydrazine.     

Heat of adsorption of cysteine enzymes on mesoporous silica with high specific surface area

The adsorption of a cysteine enzyme, on mesoporous silica with high specific surface area synthesized by the sol-gel method, was studied in a heat flow calorimeter, to determine the energy involved in the adsorption process of the protein. The adsorption was carried out at a constant temperature of 30°C to avoid the denaturation of the enzyme. The observed results indicate that the obtained biomaterials (silica-enzyme) have possibilities for their application in several biotechnology processes. The heat of papain adsorption and the solid-enzyme (SiO₂-Papain) interactions at different pH are presented.     

新型重金属离子捕集剂的合成及其对废水中铜离子的捕集作用

以活化硅胶为载体,γ-氯丙基三甲氧基硅烷为偶联剂,由乙二胺和二硫化碳合成了新型的具有螫合功能的氨基硫代甲酸聚合物(EPCR).研究了EPCR用量、pH值、反应时间、温度等对乙二胺四乙酸(EDTA)配合Cu2+溶液中Cu2+去除率的影响,确定了最佳去除条件.结果表明,EPCR对Cu2+的最大吸附量为34.10mmol/g...     

Compounds of molybdenum and tungsten with high specific surface area: II. Carbides

Temperature-programmed carburization of W₂N and Mo₂N powders in CH₄H₂ mixtures up to 1150 and 970 K, respectively, leads to metastable face-centered cubic carbide phases. The reaction is topotactic in the sense that the face-centered cubic structure of the metal atoms remains unaltered, while the nitrogen and carbon atoms exchange their interstitial positions. Thus, the product retains the structure, crystallite size, and high specific surface area of its nitride parent, namely, 55 and 185 m² g^?1 for β-WC_1?x and α-MoC_0.45, respectively.