Medium Specific Surface Area Research Articles

Size-Dependent Response of Hydrothermally Grown SnO2 for a High-Performance NO2 Sensor and the Impact of Oxygen.

A NO2 sensor with a detection limit down to the ppb level based on pristine SnO2 has been developed through a facile poly(acrylic acid)-mediated hydrothermal method. SnO2 particles of solid microsphere, hollow microsphere, and nanosphere morphologies were synthesized, with respective constitutional crystallite of size ∼2 μm in length and 10-20 nm and ∼7 nm in diameter. All sensors show great selectivity to NO2. The hollow microsphere sensor exhibits the best performance, with medium specific surface area (SSA), followed by the nanosphere sensor with the largest SSA. This is attributed to the superposition of two opposite effects on sensor response with increased SSA: more adsorption sites and fewer electrons to be taken out with overly small crystallite that may reach complete depletion. O2 is found to speed up the response and recovery times but reduce the response because O adsorbates facilitate the adsorption/desorption of NO2 thermodynamically, and the two oxidizing gases compete in harvesting electrons from SnO2. The adverse effect of humidity can be minimized by operating the sensor at 110 °C. The response of the hollow microsphere sensor to 50 ppb of NO2 is 8.8 (Rg/Ra) at room temperature, and it increases to 15.1 at 110 °C. These findings are useful for developing other oxidizing gas semiconductor sensors.

Direct evidence of pore structural effects on the compressive strength of lightweight cement slurry containing nano silica fume and hollow glass microspheres

This paper presents the results of an experimental study about the pore structure of 7 kinds of density-controlled lightweight cement slurry (LWCS) containing hollow glass microspheres and nano silica fume. X-ray micro-computed tomography (XCT) was used to characterize the microscopic pore structure of the LWCS specimens blended with nano silica fume (NSF) by 0–30% on the aspects of plane porosity, total porosity, pore size, sphericity, specific surface area, and fractal dimension. Meanwhile, the mineralogical and microstructural characterization of the NSF-affected pastes after the curing regime were tracked analyzed by thermogravimetric analysis (TGA), XCT, and scanning electron microscopy (SEM). Subsequently, the relationship between pore parameters and compressive strength of LWCS specimens was established. The optimum amount of nano silica fume was determined based on compressive strength, pore structure characterization parameters, and weight loss. The results show that the incorporation of NSF into LWCS matrix contributes to the improvement of the compressive strength. The optimal addition content for NSF is 20%, which can maximize the compressive strength at all curing ages. The filling of available space, the promotion of heterogeneous nucleation of cement hydrates and the pozzonlanic reaction of NSF itself, which densifies and homogenizes LWCS microstructures, account for the effects of NSF on the strength and pore characteristics of LWCS. The pore structure characterization parameters of LWCS, including total porosity, large pores (>100 µm) volume, large pores and medium pores (50–100 µm) volume, pore size, fractal dimension, and specific surface area, are all negatively linearly correlated with compressive strength. The harmful effect of large pores and medium pores on compressive strength is more pronounced than that of tiny pores (< 50 µm). There is a good negative ternary linear fitting relationship correlation between the fractal dimension, the large pores volume and the compressive strength (R2 =0.89). In order to prepare LWCS with excellent strength, the pores with size greater than 50 µm should be controlled or eliminated if possible. Fractal dimension is a more accurate quantitative parameter to characterize the compressive strength than the other pore parameters.

NiCo/SiO2 nanospheres for efficient synergetic decarboxylation of fatty acids and upgrading of municipal sludge HTL bio-crude to biofuels

Municipal sludge (MS) and derived HTL (hydrothermal liquefaction) bio-crude contains a large quantity of organics, including fatty acids, which may be a potential resource for producing biofuels via catalytic treatment. Herein, decarboxylation of fatty acids is chosen as the model reaction to screen a series of nickel-based bimetallic catalysts supported on homemade SiO2 nanospheres to investigate the synergetic effect. NiCo/SiO2 turned out with the best performance compared to NiCu-, NiZn-, NiMo- and NiFe/SiO2. An 83% conversion of stearic acid and an 84% selectivity of heptadecane via hydrothermal decarboxylation were achieved at 280 °C under 1 MPa H2. XPS results revealed the electron transfer from Co to Ni, leading to the formation of Niδ-, which is more accessible to bond with Cδ+ in the carboxyl group of fatty acids, thus facilitating the decarboxylation reaction. Compared to commercial SiO2, our homemade SiO2 showed a stronger carbon accumulation resistance, indicating a medium specific surface area was essential. Both the synergetic effect of NiCo bimetal and the carbon accumulation resistance of homemade SiO2 nanospheres contributed to the efficient hydrothermal decarboxylation. The NiCo/SiO2 catalyst was further applied for upgrading of MS HTL bio-crude to biofuels, and the theoretical higher heating value (HHV) was significantly improved from 34.4 to 37.2 MJ/kg, suggesting the potential application of converting MS bio-crude to biofuels.

O, N-doping high specific surface area microporous carbon materials derived from gram-positive bacteria and its outstanding performance for supercapacitors

To develop special structure nanomaterials from nature with large specific surface areas and conduct appropriate doping may be effective ways to improve the performance of carbon-basing energy storage devices and mobile power supplies. Pure Gram-positive bacteria carbon material with dense microporous structure and properly self O, N-doping was developed towards highly performance supercapacitors for the first time. The structural characterization and electrochemial survey show that carbon derived from Gram-positive bacteria can bring unexpected material properties for its layered and nitrogen, oxygen containing peptidoglycan cell wall structure. Specifically, bifidobacterium yogurt starter powder as a representative of Gram-positive bacteria was employed and pre-carbonized at 450 °C, then re-carbonized at 700, 800 and 900 °C with KOH activated, respectively. The as-prepared Gram-positive bacteria carbons (GpBCs) have inherited the bacteria's cell wall structure to some extent, which makes the specific surface area as high as 2877 m2/g. When the mess ratio of the precursor to KOH was 1: 2 and re-carbonized at 800 °C, the sample named GpBC-800-2 exhibited a medium specific surface area (2436 m2/g), and possessed proper oxygen(11.20%) and nitrogen(0.56%) doping. For further electrochemial measurement, GpBC-800-2 delivered a specific capacitance of 220 F/g and a 94.5% retention after 10000 cycles in 6 M KOH at the current density of 1 A/g in three-electrode system. For further assessment on symmetry devices, 30 F/g specific capacitance was obtained and 97.8% retention after 10000 cycles were achieved in 6 M KOH at the current density of 1 A/g for symmetry devices. The constructed devices presented an energy density of 4.2 Wh/kg at the power density of 0.5 kW/kg, and still remained 3.19 Wh/kg at the power density of 5 kW/kg. Results of this work have given a first glance for pure Garm-positive bacteria carbon materials in supercapacitor application.

Analysis of very-high surface area 3D-printed media in a moving bed biofilm reactor for wastewater treatment.

Moving Bed Biofilm Reactors (MBBRs) can efficiently treat wastewater by incorporating suspended biocarriers that provide attachment surfaces for active microorganisms. The performance of MBBRs for wastewater treatment is, among other factors, contingent upon the characteristics of the surface area of the biocarriers. Thus, novel biocarrier topology designs can potentially increase MBBR performance in a significant manner. The goal of this work is to assess the performance of 3-D-printed biofilter media biocarriers with varying surface area designs for use in nitrifying MBBRs for wastewater treatment. Mathematical models, rendering, and 3D printing were used to design and fabricate gyroid-shaped biocarriers with a high degree of complexity at three different levels of specific surface area (SSA), generally providing greater specific surface areas than currently available commercial designs. The biocarriers were inoculated with a nitrifying bacteria community, and tested in a series of batch reactors for ammonia conversion to nitrate, in three different experimental configurations: constant fill ratio, constant total surface area, and constant biocarrier media count. Results showed that large and medium SSA gyroid biocarriers delivered the best ammonia conversion performance of all designs, and significantly better than that of a standard commercial design. The percentage of ammonia nitrogen conversion at 8 hours for the best performing biocarrier design was: 99.33% (large SSA gyroid, constant fill ratio), 94.74% (medium SSA gyroid, constant total surface area), and 92.73% (large SSA gyroid, constant biocarrier media count). Additionally, it is shown that the ammonia conversion performance was correlated to the specific surface area of the biocarrier, with the greatest rates of ammonia conversion (99.33%) and nitrate production (2.7 mg/L) for manufactured gyroid biocarriers with a specific surface area greater than 1980.5 m2/m3. The results suggest that the performance of commercial MBBRs for wastewater treatment can be greatly improved by manipulation of media design through topology optimization.

LIGHTWEIGHT ELASTOMER COMPOUNDS REINFORCED WITH CELLULOSE NANOFIBRILS AND A CARBON BLACK HYBRID FILLER SYSTEM

ABSTRACT Cellulose is found in the walls of plant cells, making it the most common biopolymer in the world. It is mechanically stable, resistant to hydrolysis, and boasts—especially in its nanoscopic state—a large reactive surface area and low density. To realize reinforcement in rubbers, the large and polar cellulose surface must interact with the nonpolar elastomer matrix. The dispersion of hydrophilic fillers is, however, still a major challenge in rubber technology. In this work, commercially available nanofibrillated cellulose (NFC) was incorporated into a nonpolar BIIR via latex mixing. Transmission electron microscopy, tensile testing, swelling, and rheometry were used to characterize the compound properties and the reinforcing potential of NFC. The compounds were compared with the established and highly dispersible standard carbon black N550 with a medium specific surface area. In addition, hybrid filler systems with both particle types were prepared. This yielded well-dispersed nanocomposites of a new kind exhibiting high stiffness, good tensile properties, and reduced material weight.

Synergistic Supercritical Water ‘Wet’ Activated Biomass Carbon as High Performances Electrode Materials for Supercapacitor

The ‘dry’ activation by mixing precursor and activation agent, is considered as a traditional method to prepare porous carbon. Herein, we develop a distinct ‘wet’ activation approach, that is, synergistic supercritical water and KOH activation to prepare porous carbon from pistachio shell. The activation process is less activation agent-consuming and time-costing, highly efficient and free of harmful products, in accord with the principles of green chemistry. The sample presents a microporous structure and medium specific surface area (200–900 m2 g−1) with a partial graphitization confirmed by X-ray Difffraction and Raman. The sample also exhibits stable surface groups. The samples are evaluated as the potential electrode material for supercapacitor. The sample S1 shows excellent electrochemical performance, delivering a high capacitance of 232 F g−1 (260 F cm−3) at 0.5 A g−1, and an impressive 144 F g−1 (161 F cm−3) at 100 A g−1, as well as long cyclic capability (>10000 cycles). Remarkably, it also possesses a surface area normalized capacitance as high as 65.5 μF cm−2 .The two-electrode symmetric cell also demonstrates its potential practical performance. This method provides a promising route to achieve the green, cost-effective, and large-scale preparation of porous carbon from biomass for energy storage.

Sustainable pyrolytic sludge-char preparation on improvement of closed-loop sewage sludge treatment: Characterization and combined in-situ application

Aiming at closed-loop sustainable sewage sludge treatment, an optimal and economical pyrolytic temperature was found at 400–450 °C considering its pyrolysis efficiency of 65%, fast cracking of hydrocarbons, proteins and lipids and development of aromatized porous structure. Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) tests demonstrated the development of adsorptive functional groups and crystallographic phases of adsorptive minerals. The optimal sludge-char, with a medium specific surface area of 39.6 m2 g−1 and an iodine number of 327 mgI2 g−1, performed low heavy metals lixiviation. The application of sludge-char in raw sewage could remove 30% of soluble chemical oxygen demand (SCOD), along with an acetic acid adsorption capacity of 18.0 mg g−1. The developed mesopore and/or macropore structures, containing rich acidic and basic functional groups, led to good biofilm matrices for enhanced microbial activities and improved autotrophic nitrification in anoxic stage of an A/O reactor through adsorbed extra carbon source, and hence achieved the total nitrogen (TN) removal up to 50.3%. It is demonstrated that the closed-loop sewage sludge treatment that incorporates pyrolytic sludge-char into in-situ biological sewage treatment can be a promising sustainable strategy by further optimization.

Optimized Assembly of Micro-/Meso-/Macroporous Carbon for Li–S Batteries

In order to explore the effect of hierarchical porous carbon on the performances of Li–S batteries, we synthesized three kinds of micro-/meso-/macroporous carbon materials with different pore properties by facile hard-template method. Different from the majority of reports on porous carbon ensuing large specific surface area (SSA) and total pore volume, it was found that in the case of identically high sulfur content, the pore size distribution substantially influences the performances of Li–S batteries rather than the SSA and total pore volume. Furthermore, in the assembly of micro-/meso-/macropores, the micropore volume ratio to the total pore volume is dominant to the capabilities of batteries. Among the samples, the porous carbon carbonized with the precursor of sucrose at 950[Formula: see text]C presents the highest initial discharge specific capacity of 1327[Formula: see text]mAh/g and retention of 630[Formula: see text]mAh/g over 100 cycles at 0.2C rate along with the best rate capability. This sample possesses the largest micropore volume ratio of 47.54% but a medium SSA of 1217[Formula: see text]m2/g and inferior total pore volume of 0.54[Formula: see text]cm3/g. The abundant micropores effectively improve the conductivity of dispersed sulfur particles, inhibit the loss of sulfur series and enable the cathode to exhibit superior electrochemical performances.

A biochar-based medium in the biofiltration system: Removal efficiency, microorganism propagation, and the medium penetration modeling

ABSTRACTBiofiltration is a method of biological treatment belonging to cleaner technologies because it does not produce secondary air pollutants, but helps to integrate natural processes in microorganisms for decomposing volatile air pollutants and solving odor problems. The birch wood biochar has been chosen as a principal material for biofilter bed medium. The experiments were conducted at the temperatures of 24, 28, and 32 °C, while the concentration of acetone, xylene, and ammonium reached 300 mg/m3 and the flow rate was 100 m3/hr. Before passing through the stage of the experimental research into the packing material inside biofilters, microorganisms were introduced. Four strains of microorganisms (including micromycetes Aspergillus versicolor BF-4 and Cladosporium herbarum 7KA, as well as yeast Exophiala sp. BF1 and bacterium Bacillus subtilis B20) were selected. At the inlet loading rate of 120 g/m3/hr, the highest elimination capacity of xylene in the biochar-based biofilter with the inoculated medium was 103 g/m3/hr, whereas that of ammonia was 102 g/m3/hr and that of acetone was 97 g/m3/hr, respectively. The maximum removal efficiency reached 86%, 85%, and 81%, respectively. The temperature condition (though characterized by some rapid changes) can hardly have a considerable influence on the biological effect (i.e., microbiological activity) of biofiltration; however, it can cause the changes in physical properties (e.g., solubility) of the investigated compounds.Implications: The birch biochar can be successfully used in the biofiltration system for propagation of inoculated microorganisms, biodegrading acetone, xylene, and ammonia. At the inlet loading rate of 120 g/m3/hr, the highest elimination capacity of xylene was 103 g/m3/hr, that of ammonia was 102 g/m3/hr, and that of acetone was 97 g/m3/hr, respectively. The morphological structure of biochar can be affected by the aggressive air contaminants, causing the change in the medium specific surface area, which is one of the factors controlling the biofilter performance. Although biological effects in biofiltration are typically considered to be more important than physical effects, the former may be more important for compounds with high Henry’s Law coefficient values, and the biofilter design should thus provide conditions for better compound absorption.

Microwave assisted growth of SAPO-34 on β-SiC foams for methanol dehydration to dimethyl ether

SAPO-34 layers were successfully grown on β-SiC foam with medium specific surface-area, using microwave-assisted hydrothermal synthesis method (MAHyS) for applications as a structured catalyst. Preliminary investigations on SAPO-34 phase purity were conducted to select the appropriate concentrations and protocol to grow pure SAPO-34 on SiC foams. SAPO-34/SiC foam composite was obtained via microwave-assisted synthesis route. X-ray diffraction (XRD) was used to confirm the formation of the composite. Microwave irradiation time, number of coating cycles and pretreatment of the SiC support with zeolite precursor and the template solution were studied to optimize the growth and coverage of SAPO-34 crystals on the SiC foam surface. SAPO-34 crystals with cubic morphologies having 7μm average size were obtained after 6h microwave irradiation at 180°C. However, multi coating steps were required to obtain full coverage of SAPO-34 crystals. Template pretreatments of the host material (SiC foams) significantly improved the loading of crystals on the support surface. Full coverage of SAPO-34 on SiC foams was obtained after 3 times of coatings, which is mostly attributed to the template layer formed on the foam surface that induced the heterogeneous nucleation on the support. The SAPO-34/SiC foam structured catalyst exhibited excellent selectivity and stability in methanol dehydration to dimethyl ether, which was carried out in a fixed bed reactor.

β-SiC alveolar foams as a structured photocatalytic support for the gas phase photocatalytic degradation of methylethylketone

Alveolar open-cell self-bonded β-SiC foams with medium specific surface area and large mean cell size were used as high open porosity structured support for TiO2 in the gas phase photocatalytic degradation of methylethylketone. The influence of parameters such as the TiO2 weight content and the foam mean cell size, as well as both methylethylketone concentration and air flow rate was investigated. The structured TiO2/β-SiC foam photocatalytic material takes advantage of the static mixer role played by the β-SiC foam support and of its ability to increase the amount of TiO2 per unit reactor volume. The value of using TiO2/β-SiC foams for structuring flow-through reactors was highlighted in comparison to the commercial Quartzel photocatalytic felt standard and thin film coated wall reactor, the gain in performances being all the more pronounced that the pollutant concentration and the air flow rate were low.

Potentiality of Clay Raw Materials from Northern Morocco in Ceramic Industry: Tetouan and Meknes Areas

This study aims at evaluating the potential suitability of Tetouan and Meknes (central Morocco) clay material as raw materials in various ceramic applications by investigating their textural, chemical, thermal and firing characteristics. Textural properties were identified by specific surface area, cation exchange capacity (CEC) and bulk density (ρs). Chemical and thermal properties were assessed using XRF and TG/DTA techniques, respectively. Firing characteristics at temperatures from 800℃ to 1100℃ were determined by linear firing shrinkage, loss on weight and water absorption capacity. The Meknes clays are characterised by medium cation exchange capacity (CEC) and specific surface area (SSA) values due to their moderate smectite content. The Tetouan clays have medium to low CEC and medium SSA values. The main oxides in the clayey samples are SiO2 (35 - 54.3 wt%), Al2O3 (20.6 - 43.9 wt%), and Fe2O3 (9.7 - 22.4 wt%). The amount of CaO in Meknes clays ranges from 8 to 12 wt%, whereas CaO is only present in some Tetouan clay (TE4, TE7, TN4 and TN5). A significant densification of ceramic behaviour could be noticed for most of Tetouan clays at firing temperatures above 1000℃. Meknes clays show earlier densification from 800℃. The chemical, textural and ceramic properties of Tetouan and Meknes clays indicate their suitability as raw materials for the production of structural ceramics. The high amount of Fe2O3 in all clays makes them inappropriate in fine ceramics.

Water flow exchange characteristics in coarse granular filter media

Elution of inhibitory metabolites is a key parameter controlling the efficiency of air cleaning bio- and biotrickling filters. To the authors knowledge no studies have yet considered the relationship between specific surface area related elution velocity and physical media characteristics, which constitutes a scientific gap. This study investigates the impact of particle size distribution (considering materials with multiple particle sizes) and irrigation rate on the overall specific surface area related elution velocity distribution in porous granular media. The elution measurements performed in this study are performed at a concurrent airflow of 0.3ms−1, water irrigation rates of 1–21cmh−1 in materials with particle diameters ranging from 2 to 14mm to represent media and operation conditions relevant for low flow biotrickling filter design. Specific surface area related elution velocity distribution was closely related to the filter water content, water irrigation rate, media specific surface area and particle size distribution. A predictive model linking the specific surface area related elution velocity distribution to irrigation rate, specific surface area and particle size distribution was developed and predicted the observed specific surface area related elution velocity distributions with a mean error of 9%.

Air–water mass transfer of sparingly soluble odorous compounds in granular biofilter media

Mass transfer from air to the liquid phase is a key parameter controlling the efficiency of air cleaning biofilters. Especially the removal of sparingly soluble organic compounds such as volatile odorous sulfur compounds is mass transfer limited. When determining mass transfer rates of sparingly soluble organic compounds the approach have been to either conduct measurements using highly soluble compounds or sparingly soluble compounds with chemical removal of the compounds in the water phase to maintain maximum mass transfer. These data may, therefore, not represent the correct mass transfer rates for sparingly soluble compounds. As a consequence existing mass transfer models may not be accurate for these compounds. In addition most studies of mass transfer in granular media are based on materials consisting of uniform particles. This study investigates the impact of particle size (considering materials with multiple particle sizes), gas velocity and contaminant chemical properties on the overall volumetric mass transfer coefficient based on direct measurements (without the use of chemical reactions) of volatile, sparingly soluble, odorous organic compounds in granular media. Mass transfer was found closely related to particle size, compound solubility, particle size range, specific surface area and gas velocity. Predictive models linking mass transfer, gas velocity, contaminant solubility, media specific surface area, particle size and medium CO2 mass transfer were developed.

Study on Modified Ceramic in Treatment of Micro-Polluted Source Water for Strengthening Filtration

As filter media sand, ceramic has the certain removal effect in treating turbidity, organic matter from water .but the removal rate is limited. Modied filter could change filter surface characteristics. in this article, modied ceramic with aluminum hydroxide 。the experimental resulta showe that the trentment effect of ceramics filter coated aluminum is higher than ordinary ceramic in turbidity, CODMn, UV254 in the water, the removal efficacy is 96.64%，38.14%,47.77%respectively,aftercoated aluminum ceramic getting through the filter candle ,the Zeta potential of filter water is more close to zeto point and helpful for adhering to particles and intercepted. Conventional filtering process of water plant adopting quard sand ,ceramic so on media has low treatment tate in low turbidy , contaninging organic micro-polluted source watet .the reason that those media specific surface area is limited ,under neutral condition surface carries negative charge,absorption capacity is little.which affect impurities adhesion on filter materials[1],to make outlet water quality improved ,.people begin to seek economic,good treatment effect filter media,modified media has become a kind of new workmamship in rencent 10 years[2-6]. .Modified media could make ordinary media surface properties improve, enhance intercepting capability and absoption.now much study regard sand as carrier .and ferric chloride,ferric nitrate,aluminum oxide as modifier. adopt study of modified ceramic little,although ceramic has more porosity , aperture and specific sueface area,which formed internal surface area is smaller respectively .accoding to sanitary standard for drinking water ,ameliorating ceramic performance and advancing effluent is urgently to be solve daboutsubject. this study used aluminum hydroxide as modifier ,investigated coater aluminum ceramic filtering effect.

Analytical electron tomography mapping of the SiC pore oxidation at the nanoscale

Silicon carbide is a ceramic material that has been widely studied because of its potential applications, ranging from electronics to heterogeneous catalysis. Recently, a new type of SiC materials with a medium specific surface area and thermal conductivity, called β-SiC, has attracted overgrowing interest as a new class of catalyst support in several catalytic reactions. A primary electron tomography study, performed in usual mode, has revealed a dual surface structure defined by two types of porosities made of networks of connected channels with sizes larger than 50 nm and ink-bottled pores with sizes spanning from 4 to 50 nm. Depending on the solvent nature, metal nanoparticles could be selectively deposited inside one of the two porosities, a fact that illustrates a selective wetting titration of the two types of surfaces by different liquids. The explaining hypothesis that has been put forward was that this selectivity against solvents is related to the pore surface oxidation degree of the two types of pores. A new technique of analytical electron tomography, where the series of projections used to reconstruct the volume of an object is recorded in energy filtered mode (EFTEM), has been implemented to map the pore oxidation state and to correlate it with the morphology and the accessibility of the porous network. Applied, for the first time, at a nanoscale resolution, this technique allowed us to obtain 3D elemental maps of different elements present in the analysed porous grains, in particular oxygen; we found thus that the interconnected channel pores are more rapidly oxidized than the ink-bottled ones. Alternatively, our study highlights the great interest of this method that opens the way for obtaining precise information on the chemical composition of a 3D surface at a nanometer scale.

Growing Carbon Nanotube on Aluminum Oxides: An Inherently Safe Approach for Environmental Applications

Using micron-sized Al 2O 3 particles as carriers to grow carbon nanotubes (CNTs) under 700°C atmosphere of methane and hydrogen after pre-planted catalysts of Fe–Ni nanoparticles, those composite CNTs (CCNTs) have demonstrated several unique properties compared to CNTs—medium specific surface area and zeta potential, high adsorption capacity for metal ions, high recovery rate by acids, low decomposition heat for exothermal reaction, and so on. The adsorption behaviours of Pb 2+, Cu 2+ and Cd 2+ in aqueous solutions by CCNTs are in good agreement with the Langmuir adsorption isotherm and second order kinetic model with maximum individual adsorption capacities of 67.11, 26.59 and 8.89 mg g −1. The individual and competitive adsorption behaviours indicated that the preference order of adsorption were Pb 2+ > Cu 2+ > Cd 2+ for aluminum oxides, activated carbon, commercial CNTs, and CCNTs as well as other researchers’ CNTs. We suggest that future development of CNTs to combine with metals and/or other materials, such as TiO 2, should consider attached to carriers or surface in order to avoid concerns on environment, health and safety. Thus, growing CNTs on Al 2O 3 particles to form CCNTs is an inherently safe approach for many promising environmental applications.

A new one-dimensional tungsten carbide nanostructured material

A new medium specific surface area one-dimensional tungsten carbide nanostructure was obtained by the Shape Memory Synthesis method, in which the macrostructural features of a carbonaceous 1D-preformed template were maintained during the carburization of tungsten oxide and determined the resulting carbide morphology.

Biological iron(II) oxidation as pre-treatment to limestone neutralisation of acid water

Iron(II) should be oxidised to iron(III) before the neutralisation of acid water with limestone, otherwise the oxidation will occur downstream of the neutralisation plant with the formation of acid (reactions 1 and 2). This study aimed at investigating the effect of surface area of the medium that supports bacterial growth on the rate of biological iron(II) oxidation. The study showed that the biological iron(II) oxidation rate is directly proportional to the square root of the medium specific surface area.