Synthesis of high surface area nanocrystalline MgO by pluronic P123 triblock copolymer surfactant

Nanocrystalline magnesium oxide with high surface area was prepared by a simple precipitation method using pluronic P123 triblock copolymer (Poly(ethylene glycol)-block, Poly(propylene glycol)-block, Poly(ethylene glycol)) as surfactant. The prepared samples were characterized by X-ray Diffraction (XRD), N₂ adsorption (BET), Fourier transform infrared spectroscopy (FTIR), Thermal, differential thermal gravimetric and differential thermal analyses (TG/DTG/DTA) and Scanning electron microscopy (SEM). The obtained results revealed that the addition of surfactant is effective to prepare magnesium oxide with high surface area and affects the morphology of the prepared samples. The results showed that the magnesium oxide calcined at different temperatures ranging from 600 to 800 °C possessed a high surface area in the range of 133.9–78.1 m² g^?1. In addition, the magnesium oxide prepared with the addition of surfactant showed a narrower pore size distribution compared to the sample prepared without the addition of a surfactant.     

Delignification of intact biomass and cellulosic coproduct of acid‐catalyzed hydrolysis

The kinetics of acid‐catalyzed hemicellulose removal and also alkaline delignification of oat hull biomass were investigated. All three operational parameters namely, catalyst concentration (0.10–0.55 N H₂SO₄), temperature (110–130°C), and residence time (up to 150 min) affected the efficiency of hemicellulose removal, with 100% of hemicellulose removed by appropriate selection of process parameters. Analysis of delignification kinetics (in the temperature range of 30–100°C) indicated that it can be expressed very well by a two‐phase model for the crude biomass and also for the hemicellulose‐prehydrolyzed material. The application of acid‐catalyzed prehydrolysis improved the capacity of lignin dissolution especially at lower temperatures (30 and 65°C) and accelerated the dissolution of lignin. This acceleration of delignification by prehydrolysis was possible at all levels of temperature in the bulk phase; however, results were more significant at the lower temperatures in the terminal phase. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1783–1791, 2015     

Ghezeljeh nanoclay as a new natural adsorbent for the removal of copper and mercury ions:Equilibrium,kinetics and thermodynamics studies

Heavy metal determination was carried out by applying the solid phase extraction (SPE) method in batch mode followed by atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectrosco-py (ICP-AES) from aqueous solutions using Ghezeljeh montmoril onite nanoclay as a new natural adsorbent. The Ghezeljeh clay is characterized by using Fourier Transform Infrared (FT-IR) Spectroscopy, Scanning Electron Mi-croscopy–Energy Dispersive Spectrometry (SEM–EDS) and X-ray Diffractometry (XRD) and X-ray Fluorescence (XRF). The results of XRD and FT-IR of nanoclay confirm that montmoril onite is the dominant mineral phase. Based on SEM images of Ghezeljeh clay, it can be seen that the distance between the plates is Nano. The effects of varying parameters such as initial concentration of metal ions, pH and type of buffer solutions, amount of ad-sorbent, contact time, and temperature on the adsorption process were examined. The effect of various interfer-ing ions was studied. The adsorption data correlated with Freundlich, Langmuir, Dubinin–Radushkevich (D–R), and Temkin isotherms. The Langmuir and Freundlich isotherms showed the best fit to the equilibrium data for Hg(I ), but the equilibrium nature of Cu(II) adsorption has been described by the Langmuir isotherm. The kinetic data were described with pseudo-first-order, pseudo-second-order and double-exponential models. The adsorp-tion process follows a pseudo-second-order reaction scheme. Calculation ofΔG0,ΔH0 andΔS0 showed that the nature of Hg(II) ion sorption onto the Ghezeljeh nanoclay was endothermic and was favored at higher temper-ature, and the nature of Cu(II) ion sorption was exothermic and was favored at lower temperature.     

Synthesis,Characterization, and Bioactivity Evaluation of Amorphous and Crystallized 58S Bioglass Nanopowders

The aim of this work was synthesis and characterization of amorphous and crystallized 58S nanopowders produced via sol‐gel method. According to the thermal analysis, the nanopowders were heat‐treated at 600°C and 1100°C. X‐ray diffraction results revealed that the phases of Wollastonite and tricalcium phosphate were formed at 1100°C. The in vitro tests showed that hydroxyl carbonate apatite was precipitated on both crystallized and amorphous nanopowders, while amorphous nanopowder showed a higher bioactivity than that of crystallized nanopowder. In contrast, mechanical properties of crystallized specimen were higher than those of amorphous specimen.     

A kinetic study of xylose recovery from a hemicellulose-rich biomass for xylitol fermentative production

Hemicellulose in the complex structure of lignocellulosic substances is mainly composed of xylan which is a polymer based on monosaccharide xylose. Using acidic or enzymatic hydrolysis, hemicellulose can be depolymerized into its constituent monomer. The kinetics of hemicellulose depolymerization and decomposition in oat hull was investigated under moderate pressures with catalyst (H₂SO₄) concentration up to 0.55?N and temperatures of up to 130?°C for a total residence time of 150?min. Different trends of recovery or generation and kinetic mechanisms obtained for the components in the hydrolysate which could be described by different kinetic models, that is, a single-phase kinetic mechanism with product decomposition (two-step sequential reaction) could describe xylose generation. However, generation of arabinose, furfural, and acetic acid followed a single-phase mechanism with no decomposition (one-step reaction). Generation of glucose in the hydrolysate followed a biphasic mechanism due to the fast- and slow-releasing fractions into the liquid phase which was apparently with no decomposition. A pentose recovery of almost 80% was achieved under optimal conditions. Parameters of xylitol bioproduction indicated that a xylitol/xylose conversion yield of 0.80?g/g is achievable from the concentrated hydrolysate with no complementary treatment proving its low toxicity compared to other hemicellulose resources.     

A comparative study on optimised and non‐optimised axial flow,spherical reactors in naphtha reforming process

In this study, the operating conditions of an axial flow spherical reactor have been optimised using a reliable optimisation technique and the results are compared with the results of non‐optimised conditions. The dynamic behaviour of the reactor has been considered in the optimisation process and orthogonal collocation method has been used in order to solve the obtained equations from mathematical modelling of the process. The goal of this study is to maximise the aromatics and hydrogen production rate. Therefore, the objective function is the combination of two terms which include the production rate of the mentioned components. The catalyst distribution for each reactor, the inlet pressure of the system, Length per radius for each reactor, the naphtha feed molar flow rate and the hydrogen mole fraction in the recycle stream as well as the inlet temperature of each reactor have been optimised in this study. © 2011 Canadian Society for Chemical Engineering     

Textile with immobilised nano titanium dioxide for repeated discoloration of CI Reactive Black 5 under UV‐A

A commercially available catalyst with high photocatalytic activity (Degussa p‐25) was immobilised on a comparatively inexpensive substrate that included cotton/polyester knitted fabric by citric acid under sonication. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy analysis revealed the presence of nano titanium dioxide on the surface of the fabric. Discoloration of CI Reactive Black 5 in aqueous solution was successfully carried out by adding a piece of nano titanium dioxide‐treated fabric into the dye solution under UV‐A irradiation. The ultraviolet–visible spectra indicated complete discoloration of CI Reactive Black 5 dye solutions. CI Reactive Black 5 solution, along with electrolytes including sodium sulphate and calcium carbonate, was also successfully discoloured with lower efficiency. Further, the photocatalytic properties of the nano titanium dioxide‐immobilised fabric did not change after dye solution discoloration and it was used several times for discoloration of the same solutions. The proposed system can be developed on a large scale.     

Synthesis and characterization of PVA/PES thin film composite nanofiltration membrane modified with TiO2 nanoparticles for better performance and surface properties

Novel polyethersulfone (PES)/poly (vinyl alcohol) (PVA)/titanium dioxide (TiO₂) composite nanofiltration membranes were prepared by dip-coating of PES membrane in PVA and TiO₂ nanoparticles aqueous solution. Glutaraldehyde (GA) was used as a cross-linker for the composite polymer membrane in order to enhance the chemical, thermal as well as mechanical stabilities. TiO₂ nanoparticles with different concentrations (0, 0.05, 0.1, 0.5 wt.%) were coated on the surface of PVA/PES composite membrane. The morphological study was investigated by atomic force microscopy (AFM), scanning surface microscopy (SEM) and along with X-ray diffraction (XRD). In addition, the membranes performances, in terms of permeate flux, ion rejection and swelling factor were also investigated. It was found that the increase in TiO₂ solution concentration can highly affect the surface morphology and filtration performance of coated membranes. The contact angle measurement and XRD studies indicated that the TiO₂ nanoparticles successfully were coated on the surface of PVA/PES composite membranes. However, rougher surface was obtained for membranes by TiO₂ coating. The filtration performance data showed that the 0.1 wt.% TiO₂-modified membrane presents higher performance in terms of flux and NaCl salt rejection. Finally, TiO₂ modified membranes demonstrated the lower degree of swelling.     

Photoluminescence emission of nanoporous anodic aluminum oxide films prepared in phosphoric acid

The photoluminescence emission of nanoporous anodic aluminum oxide films formed in phosphoric acid is studied in order to explore their defect-based subband electronic structure. Different excitation wavelengths are used to identify most of the details of the subband states. The films are produced under different anodizing conditions to optimize their emission in the visible range. Scanning electron microscopy investigations confirm pore formation in the produced layers. Gaussian analysis of the emission data indicates that subband states change with anodizing parameters, and various point defects can be formed both in the bulk and on the surface of these nanoporous layers during anodizing.