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This article gives a historical overview of a number of chemical practices carried out by the Ancient Egyptians and shows that beyond being purely empirical, in more than one instance their methods suggest an understanding of the rudiments of modern day chemistry. A close analysis of some of their preparations indicates that Ancient Egyptians were familiar with the principles of oxidation and reduction, could control the pH of a solution and were successful in preparing novel compounds through a controlled technology of chemical synthesis. In the latter endeavor it is shown that these Ancient people embraced the scientific method, preceding Aristotle’s rejection in Ancient Greece of a purely deductive approach to scientific enquiry. Egyptian Blue, the only pigment synthesized by the Ancient Egyptians is also discussed, and attention is drawn to its potential future contributions to modern high-tech applications.

The photocatalytic behaviour of TiO 2 prepared from titanium (IV) ethoxide was determined with regard to the decomposition of methyl orange (MO) and methylene blue (MB) dyes, respectively. In addition, we compared the behaviour of TiO 2 photocatalysts prepared in a similar fashion but which were (1) doped with different amounts of zirconium, (2) mixed with active carbon and (3) doped with different amounts of zirconium and mixed with active carbon. All of the TiO 2 samples were found to be mesoporous with some microporosity having an average particle size between 200 and 500 nm and with anatase crystallographic modification. The kinetics of the MO and MB dyes' photocatalytic degradation fitted well with the Langmuir–Hinshelwood model and were found to follow pseudo-first-order kinetics. The rates were highest for the TiO 2 samples doped with both Zr and mixed with the activated carbon. Characterization of these TiO 2 photocatalysts was carried out by X-ray diffraction, scanning electron microscopy and adsorption studies.

Cobalt aluminate spinels were prepared from cobalt and aluminium nitrate solutions using sol–gel synthesis route by ammonium hydroxide precipitation. The gels were dried at 75°C, doped with different amounts of magnesium nitrate, and then calcined for 3 h at 650°C. Sample characterization was carried out by infrared spectroscopy, X-ray diffraction, scanning electron microscopy, nitrogen adsorption studies, thermogravimetry and by determining acid–base properties. This was carried out with the objective of elucidating the effect, if any, of the presence of the dopant on the spinel structure and properties. The spinel structure was clearly exhibited in all of the prepared samples which were predominantly mesoporous. None of the samples showed any acidic properties, i.e. they exhibited only basic properties. We found that doping with Mg resulted in a slightly increased disorder of cation distribution for those samples doped with higher amounts of Mg. Doping also led to a general increase in surface areas and the development of larger pores, as well as larger content of chemisorbed water.

Pore-size distribution studies were carried out employing nitrogen adsorption, mercury porosimetry and thermoporometry techniques on two titania gels prepared from titanous chloride and ammonia using oxygen gas as the oxidizing agent. These gels were also characterized by scanning electron microscopy and X-ray diffraction. After heat-treatment at 340 °C and 520 °C, the gels were found to possess the anatase structure, being predominantly mesoporous in nature as indicated by nitrogen adsorption studies and α S -plots. Very good agreement was observed between the BJH pore-size distribution analysis data and the thermoporometry pore-size determinations. Comparable results were also obtained by mercury porosimetry. The validity of thermoporometry as a viable and reliable technique for pore structure analysis was ascertained.

Titanium oxides, with moderately high surface areas exhibiting a mixed mesoporous/microporous texture, were prepared from titanium ethoxide. The porosity seemed to stem from the loss of volatile components from the inner coordination sphere of the titanium ions. After impregnation with sulphate groups, a general decrease in surface area was observed. This decrease was more drastic at higher temperatures when the sulphate ions are in a bidentate state of ligation. A high sulphate concentration led to a distinctive decrease in the total pore volume and to the loss of the microporous texture. Micropore blocking appeared to be due to the presence of the bidentate sulphate groups. The latter are responsible for the higher surface acidities displayed by the sulphated oxides.

A study was carried out of the uptake of Cu 2+ , Ni 2+ , Co 2+ and Ca 2+ cations by hydrous titanium oxides prepared at different pH values using titanous chloride as the starting material and hydrogen peroxide as the oxidizing agent. Characterization of the oxides was carried out by nitrogen adsorption and infrared studies. The oxides were found to be amphoteric in nature and exhibited an isoelectric point of 6.6. An attempt was made to elucidate the mechanism of cation uptake which does not entail a simple ion-exchange mechanism.

A series of zirconia gels has been prepared at different pH values by the addition of aqueous ammonia to aqueous solutions of zirconyl chloride. The gels were air dried at 110°C and their surface characteristics and structure studied with the aid of infrared spectroscopy, nitrogen adsorption and simultaneous DTA, TGA and DTG methods. Infrared studies suggest the formation of compounds of the type ZrO 2 · xH 2 O · yNH 3 . Preparation pH values of 8.02 and 10.01 produced high area gels with considerable pore volumes, whereas pH values of 4.50 and 7.01 led to unpredictable areas with ill-defined textures reflecting the metastability of the systems. Differential thermal analysis curves revealed two distinctive endotherms allowing the separate identification of interstitial and cordinatively bound water. As the pH of precipitation increased, the amount of coordinated water decreased.

Abstract   The surface characteristics of mixed zirconium and titanium oxides prepared from different starting materials are investigated. One mode of preparation entailed the use of zirconium sulfate and titanium oxysulfate as starting materials and ammonium hydroxide as precipitating agent. The produced oxides were washed to different extents to obtain samples with different sulfate content. A second preparative mode used zirconium oxychloride and titanous chloride as starting materials also with ammonium hydroxide as precipitating agent. The oxidation of the titanous to the titanic form for these oxides was carried out by means of oxygen gas. Resulting samples were heat treated at 400 �C and 600 �C, and textural characteristics determined from the adsorption of N2 at 77 K, complemented by infrared and thermal studies. The samples precipitated from the oxychloride and chloride salts of zirconium and titanium, as well as those precipitated from the sulfate and oxysulfate salts and washed free of the sulfate ions displayed quite similar textural characteristics. The unheated samples and those heat-treated at 400 �C were mesoporous, with some microporosity, and relatively large surface areas in the order of 200–300 m2/g. Heat treatment to 600 �C led to a relative decrease in surface area, in the order of 100 m2/g, and to the disappearance of microporosity. The mixed zirconium and titanium oxides with a sulfate content of ≈17% displayed significantly lower surface areas, smaller than 10 m2/g, with a prevalence of micro and mesoporosity. Infrared and thermal studies indicated the presence of differently bounded sulfato groups, which seem to have a blocking effect on the pores, resulting in the observed smaller surface areas. [ABSTRACT FROM AUTHOR]