Structural characterization of dodecyltrimethylammonium (DTMA) bromide modified sepiolite and its adsorption isotherm studies

In this study, dodecyltrimethylammonium (DTMA) bromide was used to modify natural sepiolite via an ion exchange reaction to form DTMA-sepiolite. Sepiolite and DTMA-sepiolite were then characterized by using Brunauer–Emmett–Teller (BET), elemental analysis, XRD, FT-IR, thermogravimetric (TG) and zeta potential analysis techniques. The BET surface area of sepiolite significantly decreased from 152.14 m² g^–1 to 88.63 m² g^–1, after the modification, due to the coverage of the pores of sepiolite. DTMA was located onto sepiolite according to the differential thermogravimetric (dTG) peaks of DTMA-sepiolite. XRD results confirmed the interaction between DTMA⁺ cations and sepiolite. FT-IR spectra indicated the existence of DTMA functional groups on sepiolite surface. After the characterization was accomplished, adsorption isotherm studies of naphthalene, which is the first member of the polycyclic aromatic hydrocarbons (PAHs), were carried out. The maximum adsorption capacity of DTMA-sepiolite for naphthalene was determined from Langmuir isotherm equation at pH 6 and 20 °C as 1.88 × 10^–4 mol g^?1 or 24.09 mg g^?1.     

Effects of H3PO4 and KOH in carbonization of lignocellulosic material

Samples of lignocellulosic material, stem of date palm (Phoenix dactylifera), were carbonized at different temperatures (400–600 °C) to investigate the effects of their impregnation with aqueous solution of either phosphoric acid (85 wt%) or potassium hydroxide (3 wt%). The products were characterized using BET nitrogen adsorption, helium pycnometry, Scanning Electron Microscopy (SEM) and oil adsorption from oil–water emulsion (oil viscosity, 60 mPa s at 25 °C). True densities of the products generally increased with increase in carbonization temperature. Impregnated samples (acid/base) showed wider differences in densities at 400 (1.978/1.375 g/cm³) than at 600 °C (1.955/2.010 g/cm³). Without impregnation, the sample carbonized at 600 °C showed higher density of 2.190 g/cm³. This sample has impervious surface with BET surface area of 124 m²/g. Acid-impregnated sample carbonized at 500 °C has the highest surface area of 1100 m²/g and most regular pores as evidenced by SEM micrographs. The amounts of oil adsorbed decreased with increase in carbonization temperature. Without impregnation, sample carbonized at 400 °C exhibited equilibrium adsorption of 4 g/g which decreases to about a half for sample carbonized at 600 °C. Impregnation led to different adsorptive capacities. There are respective increase (48 wt%) and decrease (5 wt%) by the acid- or base-impregnated samples carbonized at 600 °C. This suggests higher occurrence of oil adsorption-enhancing surface functional groups such as carbonyl, carboxyl and phenolic in the former sample.     

Effects of potassium distributions in carbonizations of bituminous coal

The carbonization of coal/KOH mixtures were investigated to identify the influence of potassium distributions on characteristics of the final products. The products were characterized using TGA, BET, TEM and adsorption of lead from its aqueous solutions with initial concentrations of 10–100 ppm. For the activated carbon obtained at 600 °C, the potassium distribution affected both the BET surface areas (661–1994 m²/g) and the meso- and micro-pore volumes ratios (0.48–0.91). There were also evolutions of nanostructures of both straight and curved tubular morphologies as evidenced by TEM micrograph. The samples exhibited different adsorptive capacities when tested in adsorption of lead from aqueous solutions. The adsorption followed second order kinetics and the equilibrium data were better described by empirical Freudlich isotherm model. The amount of lead adsorbed ranges from 4.3 to 47.3 mg/g. Thus, different degrees of potassium effects led to activated carbons with different surface and adsorptive properties.     

In situ study of nitrobenzene grafting on Si(1 1 1)-H surfaces by infrared spectroscopic ellipsometry

The binding of nitrobenzene (NB) molecules from a solution of 4-nitrobenzene-diazonium-tetrafluoroborate on a Si(1 1 1)-H surface was investigated during the electrochemical processing in diluted sulphuric acid by means of infrared spectroscopic ellipsometry (IR-SE). The grafting was monitored by an increase in specific IR absorption bands due to symmetric and anti-symmetric NO₂ stretching vibrations in the 1400–1700 cm^?1 regime. The p- and s-polarized reflectances were recorded within 20 s for each spectrum only. NB molecules were detected when bonded to the Si(1 1 1) surface but not in the 2 mM solution itself. Oxide formation on the NB grafted Si surface was observed after drying in inert atmosphere and not during the grafting process in the aqueous solution.     

Quality variations of poultry litter biochar generated at different pyrolysis temperatures

Producing biochar and biofuels from poultry litter (PL) through slow pyrolysis is a farm-based, value-added approach to recycle the organic waste. Experiments were conducted to examine the effect of pyrolysis temperature on the quality PL biochar and to identify the optimal pyrolysis temperature for converting PL to agricultural-use biochar. As peak pyrolysis temperature increased incrementally from 300 to 600 °C, biochar yield, total N content, organic carbon (OC) content, and cation exchange capacity (CEC) decreased while pH, ash content, OC stability, and BET surface area increased. The generated biochars showed yields 45.7–60.1% of feed mass, OC 325–380 g kg⁻¹, pH 9.5–11.5, BET surface area 2.0–3.2 m² g⁻¹, and CEC 21.6–36.3 cmol_c kg⁻¹. The maximal transformation of feed OC into biochar recalcitrant OC occurred at 500 °C, yet 81.2% of the feed N was lost in volatiles at this temperature. To produce agricultural-use PL biochar, 300 °C should be selected in pyrolysis; for carbon sequestration and other environmental applications, 500 °C is recommended.     

Synthesis and characterization of hierarchically structured mesoporous MnO2 and Mn2O3

Hierarchically structured mesoporous MnO₂ with high surface area was prepared by a facile precursor route. Well-defined morphological manganese oxalate, synthesized by adding l-lysine via a hydrothermal method, was used as precursor. Mesoporous amorphous MnO₂ with high Brunauer–Emmett–Teller (BET) surface area (340 m²/g) and mesoporous Mn₂O₃ composed of nano-crystals (BET surface area 188 m²/g) were obtained by selective calcination of the oxalate precursor at 330 °C and 400 °C, respectively. Thermogravimetric and differential thermal analyses (TG–DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂-sorption analysis and X-ray photoelectron spectroscopy (XPS) were used to characterize the structure and property of products. Cyclic voltammetry (CV) and charge–discharge measurements were used to preliminarily study the electrochemical performance of the products. The range of pH value (about 5.0–7.0) in the synthesis process is apt to prepare the hierarchical structured manganese dioxide. Other types of amino acids were also employed as the crystallization modifiers and different morphologies of manganese dioxides were obtained.     

A facile synthetic strategy for mesoporous crystalline copper–polyaniline composite

A facile and novel strategy for preparing mesoporous crystalline copper–polyaniline composite is reported wherein the reaction is carried out at room temperature using copper nitrate as the oxidizing agent and methanol as the solvent. The composite obtained as a precipitate has been characterized using UV–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption–desorption method, Barrett–Joyner–Halenda (BJH) method, Brunauer–Emmett–Teller method (BET) and thermogravimetric analysis (TGA). The XRD studies in conjunction with the BJH method reveals that the composite has crystalline nature with a mesoporous structure and has a diameter of 3.5 nm. The specific surface area of copper–polyaniline composite is estimated to be as high as 63.2 m² g^?1 using the BET surface area plot. The characterization of the filtrate indicates the presence of pernigraniline with a very small weight percent of copper.     

Structure and oxygen storage capacity of Pr/Nd doped CeO2–ZrO2 mixed oxides

Binary Ce–Zr (CZ), trinary Ce–Zr–Pr (CZP), Ce–Zr–Nd (CZN) mixed oxides were prepared by coprecipitation. The structural and textural properties were characterized by the X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) method, Raman and X-ray absorption near-edge spectra (XANES) techniques, while the oxygen storage capacity (OSC) was evaluated under both dynamic and static conditions at 500 °C. The doping of Pr or Nd cations causes the lattice deformation of the tetragonal Zr-rich mixed oxides to form a pseudocubic structure and prevents the phase demixing after calcination in flowing steam/air at 1050 °C for 5 h. After the hydrothermal ageing treatment, the doped samples show higher BET surface areas and better oxygen mobility. Pr exists mainly in the form of trivalent cations in the aged CZP and functions primarily as the doping element with large ionic radius instead of redox couple Pr³⁺/Pr⁴⁺, which may introduce more Ce³⁺ species and hereby more lattice defects. Among the aged samples, CZP shows the best oxygen storage capacity and the fastest oxygen release rate.     

Nitric acid activation of graphite granules to increase the performance of the non-catalyzed oxygen reduction reaction (ORR) for MFC applications

Nitric acid and thermal activation of graphite granules were explored to increase the electrocatalytic performance of dissolved oxygen reduction at neutral pH for microbial fuel cell (MFC) applications. Electrochemical experiments showed an improvement of +400 mV in open circuit potential for graphite granules when they were activated. The improvement of ORR performance observed with activated granules was correlated to the increase of Brunauer–Emmett–Teller (BET) surface of the activated material and the emergence of nitrogen superficial groups revealed by X-ray photoelectron spectroscopy (XPS) analysis on its surface.The use of activated graphite granules in the cathodic compartment of a dual-chamber MFC led to a high open circuit voltage of 1050 mV, which is among one of the highest reported so far. The stable performance of this cathode material (current density of 96 A m^?3 at +200 mV/Ag–AgCl) over a period of 10 days demonstrated its applicability as a cathode material without any costly noble metal.     

Fabrication and electrochemical performance of nickel ferrite nanoparticles as anode material in lithium ion batteries

Nano-sized nickel ferrite (NiFe₂O₄) was prepared by hydrothermal method at low temperature. The crystalline phase, morphology and specific surface area (BET) of the resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and nitrogen physical adsorption, respectively. The particle sizes of the resulting NiFe₂O₄ samples were in the range of 5–15 nm. The electrochemical performance of NiFe₂O₄ nanoparticles as the anodic material in lithium ion batteries was tested. It was found that the first discharge capacity of the anode made from NiFe₂O₄ nanoparticles could reach a very high value of 1314 mAh g⁻¹, while the discharge capacity decreased to 790.8 mAh g⁻¹ and 709.0 mAh g⁻¹ at a current density of 0.2 mA cm⁻² after 2 and 3 cycles, respectively. The BET surface area is up to 111.4 m² g⁻¹. The reaction mechanism between lithium and nickel ferrite was also discussed based on the results of cycle voltammetry (CV) experiments.     

Study on the gas evolution and char structural change during pyrolysis of cotton stalk

The gas release properties and char structural evolution during the pyrolysis of cotton stalk were investigated. The evolution characteristics of volatile products were examined by pyrolysis–Fourier transform infrared spectroscopy (FTIR)/thermal conductivity detection (TCD) analysis (Py–FTIR/TCD). The char chemical structure and physical characteristics were investigated by means of FTIR and N₂ physisorption techniques. Evolution characteristics of the main volatile products were given. The evolution of CO₂ was approximately 26 °C earlier than that of CO. CH₄ evolution covered over a wider temperature range of 300–600 °C, with a maximum at 394 °C. The amount of hydroxyl, aliphatic CH and olefinic CC bonds in the char decreased significantly above 250 °C. The aromatization process started at ≈350 °C and continued to higher temperatures, leaving the char enriched with condensed aromatic ring systems. The BET surface area increased continually with increasing temperature to reach a maximum value of 4.68 m²/g at 500 °C and decreased at higher temperatures. The micropore volume showed a similar behavior to the surface area, while the mesopore volume and total pore volume always increased.     

Mesoporous germanium as anode material of high capacity and good cycling prepared by a mechanochemical reaction

Mesoporous Ge was prepared by mechanochemical reaction of GeO₂ and Mg powders followed by an etching process with HCl solution. It was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and charge–discharge measurement. With a pore-distribution concentrated around 10 nm, the product presents a BET surface area of 49.98 m²/g. When using as an anode material for lithium ion battery, the mesoporous Ge exhibits a reversible capacity of 950 mA h/g and retains a capacity of 789 mA h/g after 20 cycles at a current density of 150 mA/g. The cycleability is significantly improved compared with non-porous Ge.     

Phage Langmuir monolayers and Langmuir–Blodgett films

Stable, insoluble Langmuir monolayer films composed of Staphylococcus aureus-specific lytic bacteriophage were formed at an air–water interface and characterized. The phage monolayer was very strong, withstanding a surface pressure of ～40 mN/m at 20 °C. The surface pressure–area (Π–A) isotherm possessed a shoulder at ～7 × 10⁴ nm²/phage particle, attributed to a change in phage orientation at the air–water interface from horizontal to vertical capsid-down/tail-up orientation as surface pressure was increased. The Π–A-dependence was accurately described using the Volmer equation of state, assuming horizontal orientation to an air–water interface at low surface pressures with an excluded area per phage particle of 4.6 × 10⁴ nm². At high pressures phage particles followed the space-filling densely packed disks model with a specific area of 8.5 × 10³ nm²/phage particle. Lytic phage monolayers were transferred onto gold-coated silica substrates from the air–water interface at a constant surface pressure of 18 mN/m by Langmuir–Blodgett method, then dried and analyzed by scanning electron microscopy (SEM) and ellipsometry. Phage specific adsorption (Γ) in Langmuir–Blodgett (LB) films measured by SEM was consistent with that calculated independently from Π–A isotherms at the transfer surface pressure of 18 mN/m (Γ = 23 phage particles/μm²). The 50 nm-thickness of phage monolayer measured by ellipsometer agreed well with the horizontal phage average size estimated by SEM. Surface properties of phage Langmuir monolayer compare well with other monolayers formed from nano- and micro-particles at the air–water interface and similar to that of classic amphiphiles 1,2-diphytanoyl-sn-glycero-3-phosphocholine (phospholipid) and stearic acid.     

Effect of gamma radiation on the mechanical and barrier properties of HEMA grafted chitosan-based films

Chitosan films were prepared by dissolving 1% (w/v) chitosan powder in 2% (w/v) aqueous acetic acid solution. Chitosan films were prepared by solution casting. The values of puncture strength (PS), viscoelasticity coefficient and water vapor permeability (WVP) of the films were found to be 565 N/mm, 35%, and 3.30 g mm/m² day kPa, respectively. Chitosan solution was exposed to gamma irradiation (0.1–5 kGy) and it was revealed that PS values were reduced significantly (p≤0.05) after 1 kGy dose and it was not possible to form films after 5 kGy. Monomer, 2-hydroxyethyl methacrylate (HEMA) solution (0.1–1%, w/v) was incorporated into the chitosan solution and the formulation was exposed to gamma irradiation (0.3 kGy). A 0.1% (w/v) HEMA concentration at 0.3 kGy dose was found optimal-based on PS values for chitosan grafting. Then radiation dose (0.1–5 kGy) was optimized for HEMA grafting. The highest PS values (672 N/mm) were found at 0.7 kGy. The WVP of the grafted films improved significantly (p≤0.05) with the rise of radiation dose.     

Efficient stripping voltammetric detection of organophosphate pesticides using NanoPt intercalated Ni/Al layered double hydroxides as solid-phase extraction

We developed a simple strategy for designing a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs) based on solid-phase extraction (SPE) using nanosized Pt intercalated Ni/Al layered double hydroxides (labeled as NanoPt-LDHs). By assembling NanoPt with LDHs together, the resulting NanoPt-LDHs are highly efficient to capture OPs. It dramatically facilitates the enrichment of OPs onto their surface and realizes the sensitive stripping voltammetric detection of methyl parathion (MP) as a model of OPs. The stripping analysis shows highly linear over MP concentration ranges of 0.001–0.15 and 0.3–1.0 μg mL^? 1 with a detection limit of 0.6 ng mL^–1 (S/N = 3). The combination of NanoPt, LDHs, SPE, and square-wave voltammetry (SWV) provides a fast, simple, and sensitive electrochemical method for OPs.     

Doping level effect on visible-light irradiation W-doped TiO2–anatase photocatalysts for Congo red photodegradation

A series of W-modified TiO₂ (W–TiO₂) photocatalysts were synthesized by a simple sol–gel method. The new photocatalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis-diffuse reflectance spectroscopy (DRS), and Brunauer, Emmett and Teller (BET) surface area analyzer. The photoactivity of the W–TiO₂ photocatalysts was evaluated by the photocatalytic oxidation of Congo red (CR) dye. It was found that the average size of the prepared photocatalysts is 10 nm. Moreover, they have high surface areas (∼ 216 m² g⁻¹) and their light-absorption extends to the visible region compared to pure TiO₂. The effects of W-loading and of the calcination temperature of the prepared photocatalysts on their photocatalytic activity were also studied. The obtained results show that the W_0.5–TiO₂ photocatalyst calcined at 350 °C is much highly photoactive than non-doped or highly doped TiO₂. The enhanced photocatalytic activity of the weakly doped TiO₂ may be attributed to the increase in the charge separation efficiency and the presence of surface acidity on the W_0.5–TiO₂ photocatalyst.     

Efficient immobilization of 9,10-anthraquinonyl moiety at solid interfaces through 2-(bromomethyl)anthraquinone one-electron cleavage

We report here a new and very efficient method for the coverage of different carbon materials with 9,10-anthraquinone attached via a methylene linker. The method is based on one-electron reduction of 2-(bromomethyl)anthraquinone (AQ-CH₂-Br) to a free radical AQ–CH₂ which was readily achieved using propylene carbonate (PC) as solvent containing tetrabutylammonium iodide. This way, the radical AQ–CH₂ adds to the abovementioned carbons forming very stable and dense covalently bound anhraquinonyl methane layers (Г ≈ 2 × 10^− 9 mol cm^− 2). The grafting could be performed by constant potential electrolyses (q < 0.5 × 10^− 3 C mm^− 2).     

A new composite electrode of Ni-Ferrite/TiOx/Si(111): Preparations and photoelectrochemical studies

A composite electrode of Ni-ferrite/TiO_x/Si(111) was synthesized by grafting Ni²⁺Fe²⁺Fe³⁺–LDH–TiCl₃ (LDH: Layered Double Hydroxides) on n-Si(111) surface and calcined under 1100 °C. Photoelectric research results indicated that the electrode had good photovoltaic effects in an electrolyte solution containing 7.6 M HI and 0.05 M I₂, while platinum plate was used as counter-electrode. The observed photo-voltages (U_pv) and photocurrent densities (j_pc) of the electrode were at ?0.75 V and 5.35 mA/cm², respectively. Compared with electrodes of oxidized n-Si(111) crystal and n-Si(111) wafer covered by Ni-ferrites, j_pc of the electrode Ni-ferrite/TiO_x/Si(111) was increased greatly.     

Solar active nano-TiO2 for mineralization of Reactive Red 120 and Trypan Blue: 1st Nano Update

Nano-TiO₂ was synthesized by sol–gel method. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) images, transmission electron microscope (TEM), BET surface area measurement and DRS analysis. The formation of anatase phase nano-TiO₂ was confirmed by XRD measurements and its crystalline size is found to be 15.2 nm. SEM images depict the crystalline nature of prepared TiO₂. The BET surface area of prepared TiO₂ is found to be 86.5 m² g^?1 which is higher than that of commercially available TiO₂–P25. The photocatalytic activity of prepared anatase phase TiO₂ has been tested for the degradation of two azo dyes: Reactive Red 120 (RR 120) and Trypan Blue (TB) using solar light. The photocatalytic activity of nano-TiO₂ is higher than TiO₂–P25 under solar light. The mineralization of dyes has been confirmed by chemical oxygen demand (COD) measurements.     

A microtubular all CNT gas diffusion electrode

We report a microtubular gas diffusion electrodes made of multi-walled carbon nanotubes (MWCNT). The electrodes were prepared by inside-out cake filtration of an aqueous MWCNT suspension onto a microfiltration hollow fiber (HF) membrane, followed by washing out the surfactant, drying and removal of the all CNT microtube from the HF membrane. Length, outer diameter, and wall thickness of the tubular electrodes are: up to 44 cm, ~ 1.7 mm and 275 μm, respectively. The BET surface area is 200 m²/g with a porosity of 48–67% and an electrical conductivity of ~ 20 S/cm. Application of this microtubular Gas Diffusion Electrodes (GDE) was studied for the oxygen reduction reaction (ORR) in divided and undivided electrochemical cells. Oxygen supply into the lumen of the tubular electrodes resulted in much higher current densities for ORR than in experiments where the electrolyte was saturated by bubbling with pure oxygen. Within the 0.25–1.0 bar pressure (gauge) region, higher ORR rates were achieved at lower pressure. We also show that H₂O₂ production is possible using the new GDE. We propose to use such novel electrodes for the fabrication of tubular electrochemical reactors, e.g. fuel cells, H₂O₂ generators, CO₂ reduction and other processes that involve GDE application.