Activated lignin‒chitosan extruded blends for efficient adsorption of methylene blue

This work investigates the production of activated lignin-chitosan extruded (ALiCE) pellets with controlled particle size distribution (almost spherical: dp ~500‒1000µm) for efficient methylene blue adsorption. The novel preparation method employed in this study successfully produced activated lignin-chitosan pellets. Structural and morphological characterizations were performed using BET, FTIR and SEM-EDX analyses. The influence of contact time, solution pH, ionic strength, initial adsorbate concentration and desorption studies was investigated. The experimental data fitted well with the Langmuir isotherm (R2 = 0.997), yielding a maximum adsorption capacity of 36.25mg/g. The kinetic data indicated that methylene blue (MB) adsorption onto ALiCE can be represented by the pseudo second-order-model with intraparticle processes initially controlling the process of MB adsorption. Overall, these results indicate that the novel ALiCE offers great potential for removing cationic organic pollutants from rivers and streams.

Application of chitosan loaded with metal oxide nano particles to remove lead present from sea water

Chitosan is a natural polymer obtained by deacetylation of chitin. After cellulose chitin is the second most abundant polysaccharide in nature. It is biologically safe, non-toxic, biocompatible and biodegradable polysaccharide. Chitosan loaded with zinc oxide nanoparticles have gained more attention bio sorbent because of their better stability, low toxicity, simple and mild preparation method and high sorption capacity. Chitosan loaded with zinc oxide nanoparticles have been prepared of chitosan. The physicochemical properties of nanoparticles were characterized by Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM) Analysis. Its sorption capacity for lead and cadmium ions studied. Factors such as initial concentration of lead ions, cadmium ions sorbent amount, contact time, pH and temperature were investigated. It is found that chitosan loaded with zinc oxide nanoparticles could sorb lead and cadmium ions effectively, this sorption rate was affected significantly by initial concentration of lead and cadmium ions, sorbent amount, contact time, pH of solution. The maximum of percentage of lead sorption was 98 % with initial concentration 3 mg/l and sorbent amount 0.05 g, pH 11 in 45 min and cadmiumwas90 %with initial concentration 3mg/l and sorbent amount 0.05 g, pH 11 in45 min. Consequently chitosan loaded with zinc oxide nanoparticles demonstrated greater fixation ability for lead ions than cadmium ions.

Platinum–tin/carbon catalysts for ethanol oxidation: Influence of Sn content on the electroactivity and structural characteristics

Carbon-supported Pt–Sn catalysts commonly contain Pt–Sn alloy and/or Pt–Sn bimetallic systems (Sn oxides). Nevertheless, the origin of the promotion effect due to the presence of Sn in the Pt–Sn/C catalyst towards ethanol oxidation in acid media is still under debate and some contradictions. Herein, a series of Ptx–Sny/C catalysts with different atomic ratios are synthesized by a deposition process using formic acid as the reducing agent. Catalysts structure and chemical compositions are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) and their relationship with catalytic behavior towards ethanol electro-oxidation was established. Geometric structural changes are producing by highest Sn content (Pt1–Sn1/C) promoted the interaction of Pt and Sn forming a solid solution of Pt–Sn alloy phase, whereas, the intermediate and lowest Sn content (Pt2–Sn1/C and Pt3–Sn1/C, respectively) promoted the electronic structure modifications of Pt by Sn addition without the formation of a solid solution. The amount of Sn added affects the physical and chemical characteristics of the bimetallic catalysts as well as reducing the amount of Pt in the catalyst composition and maintaining the electrocatalytic activities at the anode. However, the influence of the Sn oxidation state in Pt–Sn/C catalysts surfaces and the alloy formation between Pt and Sn as well as with the atomic ratio on their catalytic activity towards ethanol oxidation appears minimal. Similar methodologies applied for synthesis of Ptx–Sny/C catalysts with a small change show differences with the results obtained, thus highlighting the importance of the conditions of the preparation method.

Photochemistry of 4-chlorophenol on cellulose and silica

The photochemistry of 4-chlorophenol (4-CP) was studied on silica and cellulose, using time-resolved diffuse reflectance techniques and product degradation analysis. The results have shown that the photochemistry of 4-CP depends on the support, on the concentration, and also on the sample preparation method. Transient absorption and photoproduct results can be understood by assuming the formation of the carbene 4-oxocyclohexa-2,5-dienylidene in both supports. On cellulose, at concentrations lower than 10 mumol g(-1), the carbene leads to the unsubstituted phenoxyl radical, and phenol is the main degradation product. At higher concentrations a new transient resulting from phenoxyl radicals coupling was also observed, and dihydroxybiphenyls are also formed. The reaction of the carbene with ground-state 4-CP was also detected through the formation of 5-chloro-2,4'-dihydroxybiphenyl. 4-Chlorophenoxyl radical and degradations products resulting from its coupling were also detected. Oxygen has little effect on the photochemistry of 4-CP on cellulose. On silica the transient benzoquinone O-oxide was formed in the presence of oxygen. Benzoquinone and hydroquinone are the main degradation products. In well-dried samples the formation of hydroquinone is reduced. At higher concentrations the same products as detected on cellulose were observed. 4-CP undergoes slow photochemical decomposition under solar radiation in both supports. The same main degradation products were observed in these conditions.

Preparation of CaTiO3 fine powders by the hydrothermal method

Fine powders consisting of 0.1–0.5 μm size crystallites of CaTiO3 are prepared at 150–200°C by the hydrothermal method starting from hydrated titania gel and reactive calcium oxide suspended as an aqueous slurry in an autoclave. The resulting high-purity CaTiO3 is characterised by TEM, X-ray powder diffraction, chemical analyses and sintering characteristics. The hydrothermally prepared CaTiO3 powders are sinterable to high-density ceramics below 1400°C. The dc conductivity behaviour of the chemically reduced ceramics is presented.

A simple biosynthetic method for the preparation of glycerol-labelled phosphatidylcholine

A convenient method is described for the preparation of glycerol-labelled phosphatidylcholine with very high specific activity. It involves germination of soybean seeds in the dark at 37°C for 48 h in the presence of labelled glycerol, followed by extraction and purification of the phospholipid.

A New Method for the Preparation of Sulphuryl Chloro Fluoride

It has been observed that a suspension of sodium fluoride in boiling acetonitrile could be used for the preparation of fluorine compounds such as silicon tetrafluoride [1], thiophosphoryl fluoride [2], sulphur tetrafluoride [3,4], and fluorocyclophosphazenes [5]. This method, when adopted for the fluorination of sulphuryl chloride [6], it is observed that a mixture of sulphuryl fluoride and sulphuryl chloro fluoride is obtained. On the other hand, when lead fluoride is substituted for sodium fluoride, pure sulphuryl chloro fluoride is evolved. Based on this observation, a new method has been standardised for the preparation of a pure sample of sulphuryl chlorofluoride by fluorinating sulphuryl chloride by lead fluoride in acetonitrile medium.

A simple method for large-scale preparation of chick embryo tRNA

A simple method for preparing bulk quantities of tRNA from chick embryo has been developed. In this method chick embryos were homogenized in a buffer of pH 4.5, followed by deproteinization with phenol. The aqueous layer was allowed to separate under gravity. The resulting aqueous layer, after two more phenol treatments, was directly passed through a DEAE-cellulose column and the tRNA eluted therefrom with 1 Image NaCl. The tRNA prepared by this method was as active as the one prepared at neutral pH.

Effect of the method of preparation and pretreatment on the texture of alumina and related catalysts

The effect of the method of preparation and pretreatment on catalyst texture was investigated in the case of alumina, silica-alumina, 10 × molecular sieve and thoria catalysts. All the catalysts were characterised with respect to their specific surface area, surface acidity, pore size distribution and pore volume. The above properties were found to reflect the textural changes that might have been undergone by the catalyst surface as a result of the method of preparation and pretreatment. The method of preparation was found to influence markedly the acidity of the surface and to a lesser extent the surface area and pore size distribution. Acid-treatment was found to increase selectively the acidity of the catalyst while heat-treatment was found to decrease proportionally the acidity as well as surface area of the catalyst.

A hybrid electrochemical-thermal method for the preparation of large ZnO nanoparticles

A simple and efficient two-step hybrid electrochemical-thermal route was developed for the synthesis of large quantity of ZnO nanoparticles using aqueous sodium bicarbonate electrolyte and sacrificial Zn anode and cathode in an undivided cell under galvanostatic mode at room temperature. The bath concentration and current density were varied from 30 to 120 mmol and 0.05 to 1.5 A/dm(2). The electrochemically generated precursor was calcined for an hour at different range of temperature from 140 to 600 A degrees C. The calcined samples were characterized by XRD, SEM/EDX, TEM, TG-DTA, FT-IR, and UV-Vis spectral methods. Rietveld refinement of X-ray data indicates that the calcined compound exhibits hexagonal (Wurtzite) structure with space group of P63mc (No. 186). The crystallite sizes were in the range of 22-75 nm based on Debye-Scherrer equation. The TEM results reveal that the particle sizes were in the order of 30-40 nm. The blue shift was noticed in UV-Vis absorption spectra, the band gaps were found to be 5.40-5.11 eV. Scanning electron micrographs suggest that all the samples were randomly oriented granular morphology.

Preparation and characterization of rubidium-beta-alumina by the gel-to-crystallite conversion method

Preparation of Rb-beta -alumina was realized by the gel-to-crystallite conversion method. Reaction of hydrated aluminum hydroxide gel with RbOH in ethanol medium gave rise to the Rb+-inserted pseudoboehmite precursor under wet chemical conditions. The thermal decomposition of the precursor yielded Rb-beta -alumina. The Rb2O:Al2O3 ratio of monophasic Rb-beta -alumina ranged from 1:10 to 1:22. The extended stability in the compositional range is due to the fact that the conduction planes containing Rb+ and O2- ions can have lower occupancy of Rb+ ions for larger sized alkali ions, permitting the steric separation of the adjoining spinel blocks. High-resolution electron microscopy revealed that the decreasing occupancy of alkali ions in the conduction plane is balanced by changing widths of spinel blocks arising from the shift of tetrahedral Al3+ ions to octahedral sites and an accompanying increase in stacking defects. (C) 2000 Elsevier Science Ltd. All rights reserved.