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The formation of submicron TiO2 smoke (a gas‐phase suspension) from titanium tetrachloride in a low‐pressure hydrolysis reaction in a simple reactor configuration has been studied. Particle size distribution, particle morphology and degree of crystallinity have been characterized as a function of reaction conditions. Highly crystalline anatase TiO2 particles with narrow size distribution and smaller particle size were formed at high reactor temperature, while larger, amorphous particles were found at lower reactor temperatures. These results are consistent with literature studies. At 817 °C, small (450 nm), spherical, unagglomerated particles could be produced. A gas‐phase dispersion of these particles is intended for use as seeds in subsequent kinetic studies of titanium dioxide formation reactions involving a rapid compression methodology.

Locally available tar sands were used for the removal of phenol and cadmium ions from their aqueous solutions. Batch sorption experiments showed that tar sands did not remove phenol from aqueous solutions, but they were effective in cadmium adsorption. Cadmium uptake was found to increase with an increase in initial concentration of the metal ions, temperature, pH and sorbent amount. On the other hand, the presence of ions such as sodium, Na + , suppressed the uptake of cadmium ions. Physical activation of the tar sands influenced the adsorption process negatively. The sorption process was relatively fast and the equilibrium isotherm data were well represented by the Langmuir model.

Jordanian tar sands were used as an adsorbent for the removal of copper ions from aqueous solutions. Experimental results showed that the adsorption of Cu 2+ ions onto tar sands was pH-and temperature-dependent. Copper ion uptake increased with increasing pH, temperature and initial adsorbate concentration, but decreased with adsorbent concentration. An increase of ca. 40% in the uptake was noted when the tar sands were activated physically with CO 2 . The presence of NaCl salt in the adsorption process influenced the uptake of Cu 2+ ions by the adsorbent studied. The adsorption process was very fast with equilibrium being achieved in about 2 min. The experimental data were well represented by both the Langmuir and Freundlich isotherm models.

ABSTRACT:In this work, the response of single-wall carbon nanotube as a resistive NO 2 sensor was investigated. A model was developed based on the Freundlich adsorption isotherm and a multi-exponential function was used to describe the relationship between the sensor response and the gas concentration. The model predicts both static and dynamic responses in a closed sampling system. In addition, the model considers the effect of different variables such as the operating temperature, NO 2 concentration in air and the two phases (adsorption and desorption) of response. The developed model is in good accordance with the experimental data. This model could be used to design new environmental detection devices and interpret experimental data by providing some insight into the sensor behaviour during the transient phase.