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hydrogenation reactions. Leaching is usually carried out using sodium hydroxide (NaOH), or sometimes potassium hydroxide solution [ 8 , 10 , 11 ]. The kinetics of the leaching process have been investigated by measuring the amount of hydrogen evolved

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Phosphogypsum (PG) is a residue of the phosphate fertilizer industry that has relatively high concentrations of harmful radioactive materials. The reduction in concentration of the radionuclides from PG was investigated. The removal process is based on leaching of radionuclides using suitable organic extractants. The studied radionuclides were 226Ra, 210Pb, 238U and 40K. The factors affect the leaching process such as type of leaching materials, contact time, concentration of the desired solvent, liquid to solid ratio, and temperature were studied. Based on the experimental results, about 71.1, 76.4, 62.4, and 75.7% of 226Ra, 210Pb, 238U and 40K respectively were successfully removed from the PG. The reduction in the concentration of radionuclides was accompanied by reduction in the concentration of rare earth elements (∑REE) equals to 69.8%. Using the desired organic extractant under optimum conditions for treatment of the PG waste leads to obtain a decontaminated product that can be safely used in many industrial applications.

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The oxidation of Fe2+ in uranium leaching solutions with gaseous mixture of SO2 and air has been studied. The variables studied include H2SO4 concentration, temperature, SO2 concentration and time. The oxidation rate was founded to increase greatly with an increase in the solution temperature. The almost total oxidation of Fe2+ is readily achieved at 95 °C. By appropriately adjusting the temperature of solution and SO2/O2 in the gas, oxidation of ferrous ion and generation of sulphuric acid can be carried out. It was founded that solutions produced by such oxidation processing are very suitable for the uranium ore leaching.

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A process of ferrous ion oxidation by sodium nitrite in sulfate uranium in situ leaching solutions was investigated. Kinetic, spectrophotometric, and heat effect studies have been made in order to investigate the chemistry of the oxidation process. As a result the method of ferrous ion oxidation in uranium in situ leaching solution was developed that makes possible to decrease sodium nitrite consumption by 20–30 times comparing with traditional oxidation technique. It was founded also that process of ferrous ion oxidation can be conducted with partial sodium nitrite recirculation.

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about it so far. Therefore, the aim of this paper is to investigate the effect of acidity and diffusibility on the coking deactivation of ZSM-5 zeolite catalyst by using different steaming and HNO 3 leaching processes. Experimental

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The minor and trace element content in coal is of great interest due to the potential impact on the environment from the release of these elements during combustion. Reducing the concentrations of potentially hazardous elements in coal prior to combustion is one way of dealing with this issue. In this research particle induced X-ray emission (PIXE) was used to investigate a hydrothermal leaching process for the removal of trace elements from a bituminous coal. The leaching agents HNO3 and NaOH were evaluated along with the effects of process parameters (temperature, pressure, and time) on the method's effectiveness. The variable with the greatest influence was the leaching agent itself. HNO3 was determined to be more effective than NaOH in reducing elemental concentrations for nearly all the elements determined. Increasing the temperature did result in greater reductions for some elements (Cl, Br, Zn) whereas increasing the pressure and duration of the leaching process had minimal impact on reductions, in elemental concentrations.

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Leaching of micro-constituents from a granular silicate can be described by a specific mass transfer function. This quantity may be determined for column leaching experiments by radioanalysis of the eluate for about 15 elements. Concurrently, the internal diffusion and the isotopically exchangeable mass of the various micro-components may be determined by radiotracer experiments. This text summarizes the quantitative formulation of the leaching process and the use of radiotracers in it.

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The electrogenerative-leaching of galena activated mechanically in planetary centrifugal mill were studied. A dual cell system was introduced to investigate the leaching process. The experimental results indicated that the mechanical activation improved the galena’s lattice constant, the lattice distortion and the degree of crystal defect, which resulted a decreasing of initial potential of galena electrode and an increasing of output voltage of the leaching cell.

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The leaching of137Cs and90Sr from Surrey Earth montmorillonite and Silver Hill illite has been studied. Three forms of the clays, calcined and uncalcined and their composites with cement, were leached with four leachants, deionized water, and simulated sea ground and storage pond waters. Results were expressed as the cumulative fraction of activity leached against the square root of time, and used to compute diffusion coefficients. These suggested that all the leaching processes studied were slow (10−22 to 10−18 m2.s−1).

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In this second part, examples of glass pieces submitted to a leaching process are analyzed. A discussion is undertaken to show how to prevent secondary effects. It is pointed out how the near-surface region of the glass sample interacts with the surrounding aqueous solution, by testing three different glass compositions and various leaching solutions, and different leaching time and temperature. An increasing rate of the heaviest components of the glassy matrix, which is observed in almost all cases, is connected with the glass composition as well as with the solution composition. The strong leaching solution's pH value depends on ion-exchange and redox equilibria as main phenomena.

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