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- Author or Editor: S. Khalil x
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Abstract
Fast neutron activation analysis has been applied to the direct determination of oxygen in coal conversion liquids. The detection system consists of two solid 7.6 cm×7.6 cm NaI(T1) detectors connected to a summing amplifier and mounted at 180° with respect to a uniaxially rotated sample container. Differences have been observed in the gamma-ray self-absorption for the low average atomic number organic matrix in coal liquids as compared to the higher average atomic number standards such as USGS Standard Rock BCR-1 and NBS Standard Reference Mateiral 136b, K2Cr2O7, which have commonly been used for oxygen determinations in silicate rocks. In order to minimize problems associated with self-absorption and variable irradiation and counting geometries, a set of organic liquids was selected and evaluated for use as oxygen standards in the analysis of coal-derived liquids. The standard liquids were selected using criteria of high boiling point, well-defined stoichiometry, high purity, non-hygroscopic nature and simple C−H−O elemental composition. The final set of liquid standards is shown to yield an experimental oxygen—stoichiometric oxygen correlation coefficient of 0.9995 with an intercept at the origin, for liquids with oxygen contents from 3.55 to 49.94%. Dilutions of standards from the set with n-hexane permit extension of the range to lower oxygen contents.
Abstract
Fast neutron activation analysis has been used for the direct determination of nitrogen in coal conversion liquids. In our previous work on coals, solid standards such as N-1-naphthylacetamide. NBS SRM 912 urea and NBS SRM 148 nicotinic acid were used for nitrogen determinations. In this work, a set of organic liquids was selected and evaluated for use as nitrogen standards in the analysis of coal-derived liquids. The use of the liquid standards minimizes problems associated with maintaining uniform irradiation and counting geometries and self absorption differences related to varying matrix densities. The standard liquids were selected using criteria of high boiling point, well-defined stoichiometry, high-purity, non-hygroscopic nature and simple C−H−N elemental compositions. Excellent agreement between the 14 MeV INAA data and calculated stoichiometric values has been demonstrated for liquids with nitrogen contents from 1.89 to 39.95%. The liquid standards have been used to determine nitrogen in a set of typical coal conversion liquids and several international standards.
Abstract
Mixed crystalline zirconium-titanium arsenates ZrxTi(1–x) (HAsO4)2·H2O and harnium-titanium arsenates HfxTi(1–x) (HAsO4)2 H2O (where x=0–1) of various compositions with different Zr/Ti or Hf/Ti ratios have been prepared. The compounds have been characterized by X-ray, thermal analysis, chemical analysis, and pH-titrations. For powder X-rays, the compounds appear to be homogeneous crystalline materials with structures similar to 
-ZrP, -TiP or -ZrTiP. The thermograms show a loss of approximately two moles of H2O, followed by a small loss of O2 with probable formation of ZrO2, As2O3, HfO2, As2O3, ZrO2, As2O5, HfO2, As2O5 from which As2O3 and As2O5 are practically sublimed in two steps. The exchange capacities at r.t. are generally similar to -ZrP and -TiP but are found to be much lower in value.
Abstract
Solid amorphous mixed zirconium-titanium phosphates, with general formula ZrxTi/1–x//HPO4/2.n H2O/ where x=0.1–1, and n=3–5/, are mixed with an excess of solid oxalic acid dihydrate and digested in molten oxalic acid. Then oxalic acid is removed by extraction and the residue washed with dilute /O.OlM/ HCl solution and bidistilled water. As a result of this method, crystalline mixed zirconium-titanium phosphate is formed.
Mixed insoluble acidic salts of tetravalent metals
VII. Conversion of sodium form amorphous pure and mixed zirconium-titanium phosphates into crystalline form via molten oxalic acid
Abstract
Solid amorphous Zr-, Ti- and ZrxTi(1–x) phosphates (where x=0.10, 0.33, 0.66, and 0.90) in various sodium forms were contacted with an excess of solid oxalic acid dihydrate to its molten state for a given time. The oxalic acid was removed by extraction and the residue was washed with redistilled water. As a result of this, crystalline forms of Zr-, Ti-, and ZrxTi(1–x) phosphates were obtained. Using various sodium forms of the initial samples, higher rate of crystallisation resulted than that found in case of hydrogen forms of initial samples.
Thermal behaviour of acidic salts of mixed tetravalent metals
IV. Thermal decomposition of crystalline zirconium-titanium phosphate prepared through the fluorine complex (HF method)
In this study, two green microalgae, Dunaliella bardawil and Chlorella ellipsoidea , are exposed to different pH values. The two tested microalgae could grow in a wide range of pH (4–9 for D. bardawil and 4–10 for C. ellipsoidea ). The dry weight gain and the biochemical components of D. bardawil were greatly enhanced at pH 7.5. On the contrary, dry weight and carbohydrate content of C. ellipsoidea attained their maximum values at the alkaline pH. On the other hand, the protein content of C. ellipsoidea recorded its highest value at pH 4, while the pigment content of the same alga highly accumulated at pH 4, 6 and 7.5 and decreased as pH directed to the alkaline side. Both pH 6 and pH 9 stimulated the accumulation of vitamin E and vitamin C in D. bardawil , with the highest values of the three compounds recorded at pH 9. In case of C. ellipsoidea , β-carotene content increased at pH 6 and 10 as compared with control, but the amount of β-carotene was much higher at pH 6 than at pH 10. Contrarily, vitamin E was highly accumulated in C. ellipsoidea cells at pH 10 than at pH6. BothpH6 andpH10 caused a significant decline in vitaminCcontent in C. ellipsoidea .
Abstract
Mixed crystalline alpha zirconium — titanium phosphates with variable zirconium to titanium ratios have been prepared both by the well known gel reflux method and a modified HF method. Chemical analysis, X-ray, i.r. and thermal analysis were used to characterize the materials. Exchange capacities for these ion-exchangers have been evaluated by pH-titration combined with radioisotope tract technique for Na+, K+, Rb+ and Cs+.
The thermal behaviour of the entitled nickel(II) and copper(II) complexes of ¯4-acetylamino-2-hydroxy-5-methyl azobenzene has been studied by means of differential thermal analysis (DTA), thermogravimetry (TG), X-ray powder diffraction, IR and electrical conductivity. A light has been thrown on the nature of interaction of the solvents of crystallization with the host complex. Some of the kinetic parameters are calculated and discussed.
Rice husk ash fired at different temperatures, 450, 700 and 1000°C, was mixed with different concentrations of lime (molar lime/silica ash ratio of 0.2, 0.5 and 1.0). Each dry mixture was first ground and hydrated in the suspension form (water/solid ratio = 10) for various time intervals within the range of 1 to 365 days. The surface properties of the unhydrated and hydrated samples were studied by means of nitrogen adsorption measurements. The results indicated that the surface areas and total pore volumes of unhydrated solid mixtures and hydrated lime-rice husk ash samples, prepared with lime/silica ash ratio of 1.0, decrease with increasing firing temperature of rice husk ash. The effect of varying the lime/silica ash ratio of the solid mixture on the surface area and pore structure was fully discussed. The results of surface area and pore volume measurements could also be related to the crystal structure of silica produced from rice husk ash.
