Solvent extraction behaviour of tracer zirconium in TTA-xylene system

The solvent extraction behaviour of tracer zirconium in the TTA-xylene system has been studied. By studying the effect of TTA concentration, extraction time, and acid concentration for HNO₃ and HCl, optimum conditions of zirconium extraction are determined. It is found that zirconium is 98% extracted in one minute of extraction with 0.5M TTA in xylene from an 8M HNO₃ solution. A plot of 1g D versus 1g [TTA] gives a straight line with a slope of 2. This suggests that the zirconium ion is hydrolyzed and is present as ZrO²⁺, zirconyl ion, in aqueous solutions. Based on work done while the author was at the Massachusetts Institute of Technology, Cambridge, Mass. 02139, USA.     

Uptake of Ba2+ ions by natural bentonite and CaCO3: A radiotracer, EDXRF and PXRD study

Ba²⁺ uptake by natural bentonite, CaCO₃ in addition to a number of bentonite-CaCO₃ mixtures with variable compositions as a function of pH and Ba²⁺ concentration was studied. Radiotracer method, EDXRF, and PXRD were used. The results of radiotracer experiments showed that the uptake of Ba²⁺ by CaCO₃ was larger than its uptake by natural bentonite samples, particularly at low initial concentrations of Ba²⁺ and higher pH values. This finding was supported by the EDXRF results. According to the sorption data, the apparent DG° values of sorption were in the range -9±1 to -13±3 kJ/mol. The PXRD studies revealed the formation of BaCO₃ upon sorption of Ba²⁺ on pure CaCO₃ and on some of the bentonite-CaCO₃ mixtures.     

Sorption behavior of Co2+, Zn2+ and Ba2+ ions on alumina,kaolinite and magnesite

The sorption behavior of Ba²⁺, Co²⁺ and Zn²⁺ ions on alumina, kaolinite and magnesite have been investigated using the batch method.⁶⁰Co,⁶⁵Zn and¹³³Ba were used as radiotracers. The mineral samples were separated into different particle size fractions using an Andreasen Pipette. The particle sizes used in the sorption experiments were all less than 38 m. Synthetic groundwaters were used which had compositions similar to those from the regions where the minerals were recovered. The samples were shaken with a lateral shaker at 190 rpm, the phases were separated by centrifuging and adioactivity counted using a NaI(Tl) detector. Kinetic studies indicated that sorption onto the minerals took place in two stages with the slower process dominating. The highest sorption was observed on alumina. Both Freundlich and Dubinin-Radushkevich type isotherms were found to describe the sorption process well. The distribution ratio,R _d was found to be a function of the liquid volume to solid mass ratio. TheR _d 's for sorption on binary mixtures of minerals were experimentally determined and compared with those predicted fromR _d values of each individual mineral.     

A Knapsack Model for Bandwidth Management of Prerecorded Multiple MPEG Video Sources

In this article we provide a framework for controlling the bit rate of multiple prerecorded MPEG video sequences by choosing the quantization factors assigned to individual sources in a way that the total mean square error at the output of the encoder is minimized. We propose and test a knapsack model for the selection of the quantization factors. Our computations based on a set of relatively diverse video sequences reveal that the proposed model achieves a high utilization of the available bandwidth and acceptable distortion levels without any data loss.