As(V) removal from aqueous media using α-MnO2 nanorods-impregnated laterite composite adsorbents

We present a novel way of enhancing the utility of low cost readily available laterite by impregnating it with the α-MnO₂ nanorods, thus making a composite material suitable for the removal of As(V) from aqueous media. The composites were synthesized by two methods: (i) ball-milling of a physical blend of laterite with pre-synthesized MnO₂; and (ii) in situ formation of MnO₂ in the presence of laterite. The BET surface area of composites prepared by both methods was markedly higher compared to un-modified laterite, and the presence of MnO₂ in the composite was also confirmed by XRD analysis and TEM microscopy. The adsorption capacity for As(V) was found to be highly pH dependent and the adsorption kinetics followed a pseudo second-order kinetic model. The Langmuir adsorption isotherm was found to be the best model to describe the adsorption equilibrium of As(V) onto un-modified laterite as well both ball-milled and in situ formed composite. The adsorption capacities at room temperature and pH 7.0 were found to be 1.50 mg g^?1, 8.93 mg g^?1 and 9.70 mg g^?1, for un-modified laterite, ball-milled and in situ formed composite, respectively.     

Removal of nickel from electroplating rinse waters using electrostatic shielding electrodialysis/electrodeionization

Electrostatic shielding zones made of electrode graphite powder were used as a new type of ionic and electronic current sinks. Because of the local elimination of the applied electric field, voltage and current within the zones, ions are led inside them and accumulate there. The current sinks were implemented in electrostatic shielding electrodialysis of a simulated nickel plating rinse water containing 100 mg L^?1 nickel and electrodeionization of a 0.001 M NiSO₄ solution with simultaneous electrochemical regeneration of the ion exchange resin beds. Pure water was obtained with a Ni²⁺ ion concentration of less than 0.1 mg L^?1 at a flow rate of 2.02 × 10^?4 dm³ s^?1 diluate stream and a current density of 30 A m^?2.     

Aluminum-free glass-ionomer bone cements with enhanced bioactivity and biodegradability

Al-free glasses of general composition 0.340SiO₂:0.300ZnO:(0.250-a-b)CaO:aSrO:bMgO:0.050Na₂O:0.060P₂O₅ (a, b = 0.000 or 0.125) were synthesized by melt quenching and their ability to form glass-ionomer cements was evaluated using poly(acrylic acid) and water. We evaluated the influence of the poly(acrylic acid) molecular weight and glass particle size in the cement mechanical performance. Higher compressive strength (25 ± 5 MPa) and higher compressive elastic modulus (492 ± 17 MPa) were achieved with a poly(acrylic acid) of 50 kDa and glass particle sizes between 63 and 125 μm. Cements prepared with glass formulation a = 0.125 and b = 0.000 were analyzed after immersion in simulated body fluid; they presented a surface morphology consistent with a calcium phosphate coating and a Ca/P ratio of 1.55 (similar to calcium-deficient hydroxyapatite). Addition of starch to the cement formulation induced partial degradability after 8 weeks of immersion in phosphate buffer saline containing α-amylase. Micro-computed tomography analysis revealed that the inclusion of starch increased the cement porosity from 35% to 42%. We were able to produce partially degradable Al-free glass-ionomer bone cements with mechanical performance, bioactivity and biodegradability suitable to be applied on non-load bearing sites and with the appropriate physical characteristics for osteointegration upon partial degradation. Zn release studies (concentrations between 413 μM and 887 μM) evidenced the necessity to tune the cement formulations to reduce the Zn concentration in the surrounding environment.     

Removal of fluoride from aqueous media by Fe3O4@Al(OH)3 magnetic nanoparticles

A novel magnetic nanosized adsorbent using hydrous aluminum oxide embedded with Fe₃O₄ nanoparticle (Fe₃O₄@Al(OH)₃ NPs), was prepared and applied to remove excessive fluoride from aqueous solution. This adsorbent combines the advantages of magnetic nanoparticle and hydrous aluminum oxide floc with magnetic separability and high affinity toward fluoride, which provides distinctive merits including easy preparation, high adsorption capacity, easy isolation from sample solutions by the application of an external magnetic field. The adsorption capacity calculated by Langmuir equation was 88.48 mg g^?1 at pH 6.5. Main factors affecting the removal of fluoride, such as solution pH, temperature, adsorption time, initial fluoride concentration and co-existing anions were investigated. The adsorption capacity increased with temperature and the kinetics followed a pseudo-second-order rate equation. The enthalpy change (ΔH⁰) and entropy change (ΔS⁰) was 6.836 kJ mol^?1 and 41.65 J mol^?1 K^?1, which substantiates the endothermic and spontaneous nature of the fluoride adsorption process. Furthermore, the residual concentration of fluoride using Fe₃O₄@Al(OH)₃ NPs as adsorbent could reach 0.3 mg L^?1 with an initial concentration of 20 mg L^?1, which met the standard of World Health Organization (WHO) norms for drinking water quality. All of the results suggested that the Fe₃O₄@Al(OH)₃ NPs with strong and specific affinity to fluoride could be excellent adsorbents for fluoride contaminated water treatment.     

Determination of sulfamethoxazole in foods based on CeO2/chitosan nanocomposite-modified electrodes

An electrochemical immunosensor based on nanocomposite-modified glass carbon (GC) electrode has been developed. The biospecific surface was a CeO₂-chitosan (CHIT)-modified nanocomposite to which anti-sulfamethoxazole (SMX) polyclonal antibody (Ab) was immobilized. The assay was based on competition of SMX and horseradish peroxidase (HRP)–SMX to the antibody immobilized. Electrochemical voltammetry and impedance spectroscopy studies revealed that the presence of CeO₂-CHIT nanocomposite significantly enhanced conductivity of the electrode. The large electro-active surface area of nanoCeO₂-CHIT/GC electrode resulted in the high loading of anti-SMX polyclonal antibody. The electrochemical signals of the immunosensor mainly resulted from the HRP catalyzed hydrogen peroxide reduction in the presence of thionine. The immunosensor showed high sensitivity for the detection of SMX. The electrochemical response signals of the immunosensor were found to be linearly proportional to SMX concentration in the range from 5 × 10^? 7 to 5 × 10^? 4 mg mL^? 1 with a regression coefficient of 0.9935 and a detection limit of 3.25 × 10^? 7 mg mL^? 1. No cross-reactivity of antibodies with other antibiotics of sulfonamide family was found. Under optimal conditions, the immunosensor was successfully applied to the electrochemical determination of SMX in milk, honey and egg samples, showing excellent stability and anti-interference ability.     

Photodegradation of bisphenol-A in a batch TiO2 suspension reactor

In this work, the photocatalytic behaviors of bisphenol-A (BPA), which has been listed as one of endocrine disrupting chemicals, were carried out in a batch TiO₂ suspension reactor. The photodegradation efficiency has been investigated under the controlled process parameters including initial BPA concentration (i.e., 1–50 mg L^?1), TiO₂ dosage (i.e., 5–600 mg/200 cm³), initial pH (i.e., 3–11), and temperature (i.e., 10–70 °C). It was found that the optimal conditions in the photoreaction process could be coped with at initial BPA concentration = 20 mg L^?1, TiO₂ dosage = 0.5 g L^?1 (100 mg/200 cm³), initial pH = 7.0, and temperature = 25 °C. According to the Langmuir–Hinshelwood model, the results showed that the photodegradation kinetics for the destruction of BPA in water also followed the first-order model well. The apparent first-order reaction constants (k_obs), thus obtained from the fittings of the model, were in line with the destruction-removal efficiencies of BPA in all the photocatalytic experiments. Based on the intermediate products identified in the study, the possible mechanisms for the photodegradation of BPA in water were also proposed in the present study.     

Gold nanoparticle/single-walled carbon nanotube film on the surface of glassy carbon electrode and its application

A sensor based on gold nanoparticle/single-walled carbon nanotube film on the surface of glassy carbon electrode is prepared. Electrochemical behavior of adrenaline hydrochloride (AH) on the surface of gold nanoparticle/single-walled carbon nanotube modified glassy carbon electrode is investigated. A simple, sensitive, and inexpensive method for determination of AH is proposed. The oxidation peak currents is proportional to adrenaline hydrochloride concentrations in the range of 0.20 mg L^? 1 to 1.80 mg L^? 1 in 0.1 M phosphate buffer solution of pH 7.3, the detection limit for AH is 0.06 mg L^? 1, and the recoveries are in the range from 100.0 to 110.0% with RSD of 1.2–1.9% (n = 6).     

Preparation,crystal structure and characterization of α-NaSbP2S6 and β-NaSbP2S6 phases

The new phases α-NaSbP₂S₆ and β-NaSbP₂S₆ were synthesized by ceramic and reactive flux methods at 773 K. The structures of α-NaSbP₂S₆ and β-NaSbP₂S₆ were determined by the single-crystal X-ray diffraction technique. α-NaSbP₂S₆ crystallizes in the monoclinic space group P2₁/c with a = 11.231(2) Å, b = 7.2807(15) Å, c = 11.640(2) Å, β = 108.99(3)°, V = 900.0(3) Å³ and z = 4. β-NaSbP₂S₆ crystallizes in the monoclinic space group P2₁ with a = 6.6167(13) Å, b = 7.3993(15) Å, c = 9.895(2) Å, β = 92.12(3) °, V = 484.10(17) Å³ and z = 2.The α- and β-phases of NaSbP₂S₆ are closely related, the main difference lies in the stacking of the [Sb[P₂S₆]]_nⁿ⁻ layers. The structure of α-NaSbP₂S₆ consists of two condensed layers (MPS₃ type) to give an ABAB… sequence with Na⁺ cations located in the interlayer space. The packing of β-NaSbP₂S₆ is formed by monolayers of [Sb[P₂S₆]]_nⁿ⁻ stacked in an AA… fashion separated by a layer of Na⁺ cations. Both phases are derivates of the M¹⁺M³⁺P₂Q₆ family.The optical band gaps of α-NaSbP₂S₆ and β-NaSbP₂S₆ were determined by UV–vis diffuse reflectance measurements to be 2.17 and 2.25 eV, respectively.     

Enzymatic degradation behavior and cytocompatibility of silk fibroin–starch–chitosan conjugate membranes

The objective of this study was to investigate the influence of silk fibroin and oxidized starch conjugation on the enzymatic degradation behavior and the cytocompatability of chitosan based biomaterials. The tensile stress of conjugate membranes, which was at 50 Megapascal (MPa) for the lowest fibroin and starch composition (10 weight percent (wt.%)), was decreased significantly with the increased content of fibroin and starch. The weight loss of conjugates in α-amylase was more notable when the starch concentration was the highest at 30 wt.%. The conjugates were resistant to the degradation by protease and lysozyme except for the conjugates with the lowest starch concentration. After 10 days of cell culture, the proliferation of osteoblast-like cells (SaOS-2) was stimulated significantly by higher fibroin compositions and the DNA synthesis on the conjugate with the highest fibroin (30 wt.%) was about two times more compared to the native chitosan. The light microscopy and the image analysis results showed that the cell area and the lengths were decreased significantly with higher fibroin/chitosan ratio. The study proved that the conjugation of fibroin and starch with the chitosan based biomaterials by the use of non-toxic reductive alkylation crosslinking significantly improved the cytocompatibility and modulated the biodegradation, respectively.     

Molten-salt decomposition synthesis of SnO2 nanoparticles as anode materials for lithium ion batteries

SnO₂ nanoparticles were synthesized by a simple, easily scaled-up molten-salt decomposition method with SnSO₄ as the molten salt and the reactive phase. During the synthesis process, the undecomposed molten SnSO₄ makes it possible to obtain SnO₂ nanoparticles by serving as the dispersion medium and keeping the particles from aggregation. The as-prepared SnO₂ had a tetragonal rutile structure with an average particle size of 50 nm. When used as anode materials for lithium ion battery, SnO₂ nanoparticles retained the charge capacity still as high as 402 mAh g^? 1 at a current density of 156 mA g^? 1 after 40 cycles. Moreover, cyclic voltammograms tests showed the formation/deformation of Li₂O was partially reversible.     

Size-controlled synthesis of Rod-like α-FeOOH nanostructure

One-dimensional goethite (α-FeOOH) nanorods were successfully fabricated by a hydrothermal route without any template. Experimental results reveal that concentrations of Fe^3 + and ethylenediaminetetraacetic disodium salt (Na₂EDTA) affect the phase composition and size of the as-synthesized products. The size of the rod-like α-FeOOH increased when the concentration of Na₂EDTA was increased, where Na₂EDTA acts as a nucleation inhibitor. α-Fe₂O₃ nanoparticles were produced when the concentration of Fe^3 + was increased from 0.02 to 0.08 and 0.40 M. A possible formation mechanism was proposed based on the results of the time dependent experiments. Different electrolytes and surfactants can affect the size and the aspect ratio of the as-prepared nanorod-like α-FeOOH. Na₂SO₄ induced the decreasing of the size of the as-prepared sample. KCl and PVP affected the aspect ratio of the nanorods.     

Preparation and characterization of LTA-type zeolite framework dispersed ruthenium nanoparticles and their catalytic application in the hydrolytic dehydrogenation of ammonia–borane for efficient hydrogen generation

The safe and efficient hydrogen storage and production are major obstacles to use hydrogen as an energy carrier. Therefore, significant efforts have been focused on the development of new materials for the chemical hydrogen storage and production. Of particular importance, ammonia–borane (NH₃BH₃) is emerging as one of the most promising solid hydrogen carrier due to its high gravimetric hydrogen storage capacity (19.6 wt.%) and low molecular weight (30.8 g/mol). ammonia–borane can release hydrogen gas upon catalytic hydrolysis under mild conditions. Herein, the discovery of a new catalytic material, ruthenium nanoparticles stabilized by ZK-4 zeolite framework, for this important reaction has been reported. This new catalyst system was prepared by borohydride reduction of ruthenium(III)-exchanged ZK-4 zeolite in water at room temperature. The characterization of the resulting material by advanced analytical tools shows the formation of ZK-4 zeolite dispersed ruthenium nanoparticles (2.9 ± 0.9 nm). The catalytic performance of the resulting supported ruthenium nanoparticles depending on activity, lifetime and reusability was demonstrated in the hydrolytic dehydrogenation of ammonia–borane. They were found to be highly active (initial TOF = 5410 h^?1), long-lived (TTO = 36,700) and reusable catalyst (retaining of >85% of initial activity in the 5th reuse) in this important catalytic reaction at room temperature under air.     

Preparation of rodlike t-ZrO2 nanoparticles by two-step calcination of 1,12-diaminododecane–zirconia mesostructured composites

Rodlike t-ZrO₂ nanoparticles with aspect ratio of 1.3–8.0 and large surface area (152 m²/g) have been produced by two-step calcination of 1,12-diaminododecane–hydrous zirconia mesostructured composites. The two-step calcination consists of first calcination at 300 °C for 24 h and then at 400 °C for another 24 h. The resulting t-ZrO₂ nanoparticles can be stored under ambient conditions for at least 2 months without discernible transformation to the monoclinic phase. Compared to one-step calcination at 400 °C, the two-step calcination increases the amount of hydrocarbon fragments (3.6 wt% versus 2.9 wt%) adsorbed onto the resulting t-ZrO₂ nanoparticles. This increase may account for the improved phase stability of the rodlike t-ZrO₂ nanoparticles.     

Synthesis of SnO2 nanoparticles inside mesoporous carbon via a sonochemical method for highly reversible lithium batteries

A sonochemical method was introduced to synthesize SnO₂ nanoparticles in the pores of mesoporous carbon without any other agents. The nitrogen adsorption measurement and transmission electron microscopy results revealed that the SnO₂ nanoparticles with the average particle size of around 10 nm were homogeneous distribution in the matrix. The aggregation of SnO₂ was hindered by the three-dimensioned porous frameworks, resulting in a relatively large surface area of 362 m² g^? 1, which is beneficial for lithium-ion storage in batteries. The resultant composites with 43% SnO₂ exhibited a high reversible capacity of 200 mAh g^? 1 even after 300 cycles, which is 186% higher than that of the initial mesoporous carbon matrix. This strategy is expected to incorporate other functional nanoparticles inside mesoporous carbon for many applications.     

Studies on mechanical properties of wood fiber reinforced cross-linked starch composites made from enzymatically degraded allylglycidyl ether-modified starch

In a previous work we introduced a new family of thermoset composites of softwood fiber and allylglycidyl ether modified potato starch (AGE-starch with a degree of substitution of 1.3 and 2.3) prepared by hot pressing. To improve the processability of AGE-starch with a DS = 1.3 (LDS-3) and to increase hygromechanical properties, the LDS-3 matrix has now been partially degraded by α-amylase at 45 °C (pH 6) for 0.5, 6 and 18 h. The study shows that already a 30 min enzymatic hydrolysis has a marked effect on the modified starch molecular weight and its thermal properties. The new composites with enzyme hydrolyzed AGE-starch, generically named D-LDS-3, showed good fiber dispersion and excellent interface between the fiber and matrix as studied by SEM. Premixes of D-LDS-3 matrix and fiber showed improved processability. The water vapor absorption was evaluated at 43.2% and 82.2% RH and the stiffness and strength properties were measured. The water uptake was shown to be reduced. The strength of neat matrix D-LDS-3-6 at ambient 68% RH reached 63 MPa and Young’s modulus 3200 MPa and with 40 wt.% wood fiber reinforcement impressive 128 MPa and 4500 MPa, respectively.     

Preparation,microstructure and electrochemical performance of nanoparticles LiMn2O3.9Br0.1

LiMn₂O_3.9Br_0.1 nanoparticles were prepared by a room-temperature solid-state coordination method. The structure and morphology of the as-prepared materials were analyzed by X-ray diffractometry and transmission electron microscopy. The results show that the LiMn₂O_3.9Br_0.1 is well-crystallized and consists of monodispersed nanoparticles 80–100 nm in size. Results of electrochemical testing show that the samples prepared at different temperatures have similar electrochemical performance. The initial discharge capacities of LiMn₂O_3.9Br_0.1 prepared at 800 °C and 700 °C are 121 mAh g^? 1 and 118.9 mAh g^? 1, respectively, higher than for LiMn₂O₄ prepared using the same method.     

Polyaniline nanowire electrodes with high capacitance synthesized by a simple approach

Polyaniline (PANI) nanowire electrodes were successfully synthesized by electrodeposition using starch as template. The electrodes were characterized with scanning electron microscope (SEM) and X-ray diffraction technique. SEM images showed that the electrodes electrodeposited using the starch template had nanowire morphology, but the PANI electrodeposited in absent solution had agglomerate block morphology. Cyclic voltammograms at different scan rates and charge–discharge tests were performed in 0.5 M H₂SO₄ aqueous solution. The PANI nanowire electrodes had a high capacitance (882 F g^? 1) and a high stability (5% capacity loss after 500 cycles).     

Experimental study on synthesizing TiO2 nanotube/polyaniline (PANI) nanocomposites and their thermoelectric and photosensitive property characterization

In this paper, TiO₂ nanotube/polyaniline (PANI) nanocomposites were made. The thermoelectric and photosensitive properties of the nanocomposites were studied. The effects of processing time, voltage, concentration of F^? ions and H₃PO₄ on the formation of TiO₂ nanotubes were investigated. The morphologies of the synthesized nanocomposites were revealed by scanning electron microscopy (SEM). The formation of polyaniline was confirmed by both Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The optimum conditions for the formation of well-organized TiO₂ nanotubes are at 20 V for 60 min in the electrolyte containing 0.2 M fluorine ions. The highest absolute value of the Seebeck coefficient for the TiO₂ nanotube/polyaniline nanocomposites is 124 μV/K at 30 °C. Pure Ti foil does not show photosensitive property, while the TiO₂ nanotubes have strong photosensitivity.     

Synthesis of hydroxyapatite crystals using carboxymethyl inulin for use as a delivery of ibuprofen

In the present study biodegradable, environmentally friendly polysaccharide-based polycarboxylate, carboxymethyl inulin (CMI), was used to produce hydroxyapatite (HAP) particles by wet chemical synthesis under controlled temperature, pH, and atmospheric conditions. The morphology and microstructure of the HAP nanoparticles were investigated by XRD, SEM, DTA–TGA and FTIR. CMI affects morphology, surface area, dimension and particle size distribution of the crystals. The reduction in size is greater in the direction of the c-axis. The increase in the polymer concentration to 7.5 g/L resulted in the mixture of nanoparticles with particle sizes of less than 100 nm. The SEM micrograph shows the formation of well-crystallized, agglomerated small particles of HAP. X-ray analysis has shown that the resulting particles have high thermal stability.The obtained crystals were used to produce tablets by direct compression of HAP. The influence of sample's CMI concentration on drug release profiles was investigated by using ibuprofen (C₁₃H₁₈O₂) as a model drug. The model was used to determine the effective diffusion coefficient of the drug from the tablets. A good agreement between experimental data and model predictions was obtained as calculated in the present work. The values of the diffusion coefficients range from 1.62 × 10^? 7 to 4.72 × 10^? 7 m² h^? 1.     

Effect of processing methods on physicochemical properties of titania nanoparticles produced from natural rutile sand

Titania (TiO₂) nanoparticles were produced from natural rutile sand using different approaches such as sol–gel, sonication and spray pyrolysis. The inexpensive titanium sulphate precursor was extracted from rutile sand by employing simple chemical method and used for the production of TiO₂ nanoparticles. Particle size, crystalline structure, surface area, morphology and band gap of the produced nanoparticles are discussed and compared with the different production methods such as sol–gel, sonication and spray pyrolysis. Mean size distribution (d₅₀) of obtained particles is 76 ± 3, 68 ± 3 and 38 ± 3 nm, respectively, for sol–gel, sonication and spray pyrolysis techniques. The band gap (3.168 < 3.215 < 3.240 eV) and surface area (36 < 60 < 103 m² g^?1) of particles are increased with decreasing particle size (76 > 68 > 38 nm), when the process methodology is changed from sol–gel to sonication and sonication to the spray pyrolysis. Among the three methods, spray pyrolysis yields high-surface particles with active semiconductor bandgap energy. The effects of concentration of the precursor, pressure and working temperature are less significant for large-scale production of TiO₂ nanoparticles from natural minerals.