Removal of crystal violet from wastewater using resorcinol-formaldehyde carbon xerogels

Resorcinol-formaldehyde activated carbon xerogels (RF-ACXs) were prepared at different conditions. RF-ACXs were characterized by Fourier transform infrared spectroscopy, surface area and porosity analyzer, X-rays diffraction, energy dispersive X-ray diffraction, and scanning electron microscopy. Batch adsorption was used to evaluate the ability of RF-ACXs to remove crystal violet (CV) from wastewater. CV adsorption capacities of RF-ACXs ranged from 66.47 to 121.53 mg·g^?1 for CV initial concentration ranged from 0 to 120 mg/L at 60°C. Kinetic and equilibrium adsorption data were analyzed using collection of models. The best results were achieved with the pseudo-second order kinetic model and Langmuir’s equilibrium model. Regenerability and reusability of RF-ACXs were investigated.     

Shape-controlled synthesis of submicro-sized cuprous oxide octahedra

Monodisperse submicro-sized cuprous oxide (Cu₂O) octahedra are successfully prepared in large quantities assisted by the capping reagent poly(vinyl pyrrolidone) (PVP-K30, MW=58 000) and the formation mechanism of Cu₂O octahedra is analyzed.     

Collagen–chitosan biocomposites produced using nanocarbons derived from goatskin waste

We report a simple method for the preparation of multifunctional biocomposite films by using collagen-containing waste material trimmed from goatskins. The waste was cleaned and carbonized to synthesize conducting and magnetic graphitic nanocarbon (GrC). Collagen was extracted from the trimmed waste and combined with chitosan and GrC to form flexible, semi-transparent, conductive and magnetic biocomposite films (GrC/Col–Ch) of micron-thickness. Electrical conductivity of the biocomposite films was shown to increase gradually with an increase in the concentration of chitosan and GrC. The tensile strength of the GrC/Col–Ch films increases up to 10 wt.% of GrC loading, above which it decreases due to the high carbon loading, as also shown from fracture surfaces examined by scanning electron microscopy. The small ferromagnetic property of the synthesized biocomposite films has been potentially used for magnetic tracking and actuation.     

Fabrication of low-density foam shells from resorcinol-formaldehyde aerogel

Resorcinol-formaldehyde (RF) aerogel chemistry has been used with encapsulation techniques to fabricate low-density, transparent, foam shells. To accomplish this, the gelation time was reduced from several hours to several minutes by the addition of acid following base-catalyzed RF particle growth. However, additional “annealing” of the gel for at least 20 h was needed to maximize crosslinking and minimize swelling in exchange solvents. Increasing the molar ratio of formaldehyde to resorcinol from 2 to 3 also helped to increase crosslinking. Densification of the foam shells due to dehydration during curing was greatly reduced by judicious choice of immiscible oil phases and by saturating the exterior oil phase during the annealing stage. Shells have been produced with diameters of about 2 mm, wall thicknesses ranging from 100 to 200 μm and foam densities approaching 50 mg/cc. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2111–2122, 1997     

形貌可控的Pt纳米催化剂的制备及其应用进展

铂纳米催化剂由于其高效的还原和氧化作用,在催化和电催化领域的应用非常的广泛.在反应中除了尺寸外,Pt纳米晶体的形貌对催化和电催化的活性和选择性也起到了关键的作用.调变合成单一形貌催化剂的条件,如稳定剂、还原剂和表面活性剂等,对于调控纳米粒子的形貌至关重要.目前形貌可控的铂纳米催化剂已被应用到加氢、氧化和Suzuiki偶...     

Shape-controlled synthesis of monodispersed beta-gallium oxide crystals by a simple precipitation technique

Uniformly sized and monodispersed β-Ga₂O₃ crystalline micro-rods and ellipsoids have been successfully synthesized through a facile direct precipitation technique, respectively, using Ga(NO₃)₃ and NH₄OH solution as starting materials. The as-prepared particles were characterized by XRD, FESEM equipped with EDS, TEM equipped with SAED, TG-DSC and Laser diffraction particle size analyzer, respectively. The results showed that the obtained β-Ga₂O₃ particles with a narrow particle size distribution were assembled with single crystalline β-Ga₂O₃ nano-sheets with the thickness of 100 nm. Furthermore, the reaction parameters including aging temperature, the molar concentration of Ga³⁺ and pH value had an essential effect on the morphology and size of the particles. Ostwald ripening and oriented attachment growth mechanism of the uniformly hierarchical β-Ga₂O₃ crystals were proposed. Finally, the target fabricated by using the as-prepared β-Ga₂O₃ particles as the raw materials exhibited a density as high as 6.01 g/cm³, showing potential applications in the high-quality thin film formed by magnetron sputtering for optoelectronic devices.     

Size control and characterization of spherical carbon aerogel particles from resorcinol-formaldehyde resin

Spherical resorcinol-formaldehyde (RF) aerogel particles were synthesized by emulsion polymerization of resorcinol with formaldehyde in a slightly basic aqueous solution, followed by supercritical drying with carbon dioxide. RF carbon aerogel particles were prepared by carbonizing of the RF aerogel particles at a high temperature under a nitrogen atmosphere. By changing the viscosity of the RF sol added to the cyclohexane containing a surface-active agent for preparation of the spherical RF hydrogels, we investigated the influence of the apparent viscosity of the RF sol on the size of the generated RF carbon aerogel particles. We could successfully prepare the RF carbon aerogel particles with a truly spherical shape and control their size in the range from about 10 to 500 μm by changing the apparent viscosity of the RF sol. The spherical RF carbon aerogel particles with an average diameter of 20 μm have a BET surface area of about 800 m²/g and a uniform mesopore radius of 1.78 nm.     

微米级海胆状钙霞石三维组装体的水热制备

以九水硝酸铝[Al(NO3)3.9H2O]和硅酸钠(Na2SiO3)为主要原料,在200℃下通过水热合成的方法,制备了微米级海胆状钙霞石的三维组装体,并考察了山梨(糖)醇和氢氧化钠的添加对产物形貌的影响。借助X射线衍射仪(XRD)和扫描电子显微镜(SEM)对产物的结构和形貌进行了表征。结果表明:在研究范围内,所得产物都为钙霞石,是亚微米短棒形成的海胆状三维组装体;组装体的形貌主要受所加氢氧化钠的影响,山梨(糖)醇的加入不会改变产物的结构,但会影响体系的pH,从而对组装单元短棒的大小有所影响。     

Spherical porous carbon particles derived from suspensions and sediments of resorcinol-formaldehyde particles

The goal of this study is the completion of the parameter field of resorcinol-formaldehyde solutions towards the regime of non-monolithic phases. For low sodium carbonate concentration and low mass content of resorcinol and formaldehyde in the starting solution the formation of spherical particles rather than monolithic gels is observed. The organic precursors were converted into carbon powders by pyrolysis. The resulting carbon particles were characterized by scanning electron microscopy (SEM), nitrogen sorption and small-angle X-ray scattering (SAXS). The study shows that carbonization of the organic particles results in spherical carbon particles with a micropore volume of about 0.28 cm³/g. The composition of the starting solution, however, strongly affects the external surface area as determined from sorption data for the organic as well as for the corresponding carbon particles; the values derived can be converted into average diameters of spherical particles ranging from 30 nm to 5 μm. Complementary SEM and SAXS measurements confirm these findings. A diameter of 5 μm appears to be the upper size limit in particle size forming, while 30 nm spheres develop near the formation of a continuous gel at relatively high sodium carbonate concentrations.     

Development of highly oriented polymer crystals from row assemblies

The development of organized structures from sheared isotactic polypropylene melts with different amounts of dibenzylidene sorbitol (DBS) as a nucleating agent has been followed in real time using small angle X-ray scattering in conjunction with synchrotron radiation. The results show that, above a certain DBS concentration threshold, the lamellar crystals are highly oriented perpendicular to the direction of the prior applied shear field. The role of the directing agent in nucleating the crystallization and templating the crystal anisotropy is discussed.     

Production of synthesis gas from methane using compression ignition reformer

A new form for a partial oxidation compression ignition reformer, which is different from existing methods of reformation, is suggested to which the concept of super-adiabatic combustion is applied. In addition, experiments are conducted on variables such as the oxygen/methane ratio, the total flow rate, the intake preheating temperature, and the oxygen enrichment ratio, all of which affect the production of hydrogen, in order to understand the optimal features of the movement of the reformer. Results showed that the concentration of hydrogen and carbon monoxide was 20.84% and 13.36%, respectively, under the optimal standard conditions of an oxygen/methane ratio of 0.26, a total flow rate of 106.5 L/min, and an intake preheating temperature of 355 oC. Under the same conditions, the concentration of hydrogen decreased to 20.31% when the oxygen enrichment ratio was 55.6%, while that of carbon monoxide increased to 20.85% when the oxygen enrichment ratio was 50.33%.     

Analysis of shear strength of cylindrical assemblies with anaerobic adhesives using Weibull statistics

A statistical method to study the reliability of cylindrical anaerobic adhesively-bonded assemblies is presented in this work. An anaerobic adhesive was used to manufacture four groups of bonds with different gaps, but with the same surface pre-treatment and curing position. Shear strength values were obtained and used to determine reliability of all adhesive bonds using the Weibull statistical distribution. Although the Weibull analysis has been widely used in the study of composite materials, its application in adhesive bonds is being explored now. A two-parameter Weibull distribution was employed to execute the Weibull analysis, using an estimator that renders a more realistic Weibull modulus value, as other estimators were found to subestimate or overestimate this value. Weibull modulus values were obtained for adhesive bonds with different gaps to study their reliability, and these results have been compared with the shear strength results.     

A robust chemo-enzymatic lactone synthesis using acyltransferase from Mycobacterium smegmatis

The new application of acyltransferase, isolated from Mycobacterium smegmatis for the chemo-enzymatic Baeyer-Villiger oxidation of cyclic ketones to lactones was demonstrated. Acyltransferase exhibited high activity, and high stability under harsh reaction conditions, like oxidation with 60% aq. H₂O₂ at 45 °C. This paves the way to a novel robust chemo-enzymatic method for lactone synthesis with high yields.     

Au-catalyzed synthesis of benzofurans from phenols and alkynes using molecular oxygen

An efficient Au-catalyzed transformation for the synthesis of benzofurans from phenols and alkynes using molecular oxygen has been developed. The reaction proceeds smoothly with commercially available, eco-friendly oxidant and affords the products in moderate to good yields. This reaction is a facile approach for the formation of C − C and C–O bonds.     

Photocatalytic synthesis of aniline from nitrobenzene using Ag-reduced graphene oxide nanocomposite

We used a UV-irradiation reduction method to prepare Ag-reduced graphene oxide (RGO) composite by reducing graphite oxide and silver ion in ethanol. Transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), UV–vis absorption spectrophotometry (UV–vis), and X-ray photoelectron spectroscopy (XPS) characterized the prepared samples. Ag–RGO nanocomposite was tested for reduction of nitrobenzene to aniline under visible light. The Ag–RGO nanocomposites have a high efficiency to convert nitrobenzene to aniline under visible-light irradiation. Therefore, Ag-reduced graphene oxide nanocomposite can be used as a photocatalyst for organic synthesis.     

One-step synthesis of t-ZrO2 from Zircon using magnesium-calcium minerals as stabilizers

Stabling crystal structure at room temperature is a classic problem in the study of Zirconium dioxide (ZrO₂). However, there are few investigations on making tetragonal zirconia (t-ZrO₂) in one step at a low cost. In this research, t-ZrO₂ is synthesized using a one-step high-temperature solid-state sintering technique with magnesite, dolomite, and limestone as stabilizers and zircon as the raw material. The most suitable stabilizers and reaction conditions are determined, and the mechanism of zirconia structure stabilization is explored. The findings suggest that magnesite has the lowest effect as a crystal structure stabilizer, whereas dolomite and limestone are pretty close, but dolomite introduces more impurities. The ideal reaction conditions were 60% mol limestone at 1500 °C. The stabilization mechanism is zirconia gap correction, according to XRD and EPR data. The characterization of the SEM demonstrates that the heat treatment temperature and stabilizer had little effect on the morphology of t-ZrO₂. When limestone was introduced throughout the process, EDS data revealed that some amorphous silicon-calcium compounds occurred in the product. The focus of follow-up work will be on how to lessen the impact in this area. This research offers vital reference value for reducing the cost of the synthetic t-ZrO₂ process.     

Evaluation of an improved epichlorohydrin synthesis from dichloropropanol using a microchemical system

Synthesizing epichlorohydrin (ECH) from dichloropropanol (DCP) is a complicated reaction due to the partial decomposition of ECH under harsh conditions. A microchemical system can provide a feasible platform for improving this process by conducting a separation once full conversion has been achieved. In this work, referring to a common DCP feed used in industry, the reaction performance of mixed DCP isomers with NaOH in the microchemical system on various time scales was investigated. The operating window for achieving high conver-sion and selectivity was on a time scale of seconds, while the side reactions normal y occurred on a time scale of minutes. Plenty of Cl?ions together with a high temperature were proved to be critical factors for ECH hydrolysis. A kinetic study of alkaline mediated ECH hydrolysis was performed and the requirements for an improved ECH synthesis were proposed by combining quantitative analysis using a simplified reaction model with experimen-tal results on the time scale of minutes. Compared with the conventional distillation process, this new strategy for ECH synthesis exploited microchemical system and decoupled the reaction and separation with potentials of higher productivity and better reliability in scaling up.