Raney metal type catalysts are prepared by leaching the reactive material out from alloys of catalytically active transition metals such as nickel, cobalt, iron, copper and a reactive material such as aluminum with
Authors:G. Ramadevi, T. Sreenivas, A. Navale, and N. Padmanabhan
This paper describes the solvent extraction studies carried out on an acidic low assay uranium bearing leach liquor generated
during sulfuric acid leaching of a refractory uranium ore using alamine 336–isodecenol–kerosene reagent combine. The leach
liquor has a U3O8 content of about 270 mg/L, free acidity 2.4 N H2SO4 and total dissolved solids concentration of 260 g/L. Process parameteric variation studies indicated strong influence of
free acidity of the leach liquor, alamine 336 concentration and aqueous to organic phase ratio on the extraction efficiency
of uranium. An extraction efficiency of about 95% was achieved when the free acidity of leach liquor was 1 N H2SO4 or lower, using 2% (v/v) alamine 336 at ambient temperature with an aqueous to organic phase ratio of 1:1. The loading capacity
under these conditions was 1.2 g/L of U3O8. About 98% of the uranium values could be stripped from the loaded organic using 1 N NaCl in 0.2 N H2SO4. The solvent extraction studies aided in developing a suitable process flowsheet for treating refractory uranium ores which
need high acidity during leaching and relatively lower acidity for purification by solvent extraction.
The tetravalent and hexavalent uranium content of three Egyptian phosphate type ore samples namely; Sebayia, Abu Tartur and
Qatrani have been studied through selective leaching by hydrochloric acid at normal, oxidized and reduced conditions at an
amount of hydrochloric acid less than the stoichiometric value i.e. before phosphoric acid production. Oxidizing condition
is attained by incorporating 2% of manganese dioxide in the leaching cycle, whereas reducing condition is attained by adding
2% iron powder. The achieved results show that the amount of tetravalent uranium varies between 5 and 95%. As soon as the
achieved stoichiometric value of hydrochloric acid is sufficient to produce phosphoric acid both tetravalent and hexavalent
uranium dissolve by virtue of phosphoric acid complexing power for uranium. The chemical form of uranium in the ore determines
the type of solvent needed to recover it.
Authors:H. Pant, V. Sharma, S. Naik, Gursharan Singh, D. Kalgutkar, S. Patil, N. Jayachandran, and V. Unni
A radiotracer technique was used to investigate the leaching of an antifouling agent from different marine paint formulations
with an objective to select the best paint formulation for bulk production. The antifouling agent (Diuron) itself was labeled
with carbon-14 (half-life: 5,730 years, β-energy: 156 keV) and used as a radiotracer. The different paint formulations added
with radiolabeled Diuron were applied onto suitably selected substrates and measured for initial intensity of β-radiation
using a Geiger-Muller detector connected to a ratemeter. The painted substrates were subjected to shower tests for a pre-decided
time and subsequently measured for β-radiations. The comparison of intensity of β-radiations in substrates prior and post
shower tests provides information about leaching of antifouling agent Diuron from the paint formulation. The high leaching
percentage of antifouling agent Diuron post shower tests indicates non-suitability of paint formulation for marine and civil
structures. However, low leaching rate of Diuron will make a paint formulation more efficient and suitable. Based on the results
of investigation, a paint formulation with minimum leaching rate was identified and selected for bulk production by a paint
Authors:L. A. Perez-Maqueda, C. Maqueda, J. L. Perez-Rodriguez, J. Subrt, Z. Cerny, and V. Balek
amorphization, accompanied with the formation of hard agglomerates by cold-welding [ 11 ].
Selective leaching by acid has been used to prepare porous silica from various clay minerals, including vermiculite [ 12 – 15 ]. The presence of iron in the
Kádár, I., T. Németh, G.J. Kovács 1987: Nitrogen efficiency and nitrate leaching on a calcareous chernozem soil. - In: 5 th International Symposium of CIEC. 2. Sec. 1, Balatonfüred, Hungary, pp. 130–137.