Uranium Pechiney

Elf Atochem S.a.

Atochem

Atofina

Elf Exploration Production

Comurhex

Philippe Joubert

Roland Bachelard

Jean-Pierre Disson

Pierre Ravenel

Fran&ccedil;oise Andolfatto

A cathode comprising an electrically conductive substrate made of titanium, nickel, tantalum, zirconium, niobium, iron or alloys thereof, coated with an intermediate layer of oxides of titanium and of a precious metal, and with an outer layer comprising metal oxides of titanium, zirconium and a precious metal, can be used for the electrolysis of solutions, in particular for the electrolysis of aqueous solutions of alkali metal chlorides.

Cathode for electrolyzing aqueous solutions

Method for making lithium hexafluorophosphate

Process for destroying a rigid thermal insulator obtained in particular by a process of the sol-gel type and positioned in a confined space, the process comprising the stage of introducing a dissolving liquid into the confined space in order to convert the insulator into a liquid phase. The process applies in particular to destroying an insulating jacket positioned in the annular space of an oil well.

Process for destroying a rigid thermal insulator positioned in a confined space

The invention relates to a continuous process for the preparation of aluminum nitride by the carbonitriding of alumina. According to this process, a reaction that uses alumina, carbon, and a resin that generates carbon by pyrolysis is performed in a methodical reactor. The invention relates to a continuous process for the preparation of aluminum nitride by the carbonitriding of alumina.

Continuous process for the preparation of aluminum nitride by the

Contaminating amounts of sulfate ions are removed from aqueous saline solutions comprised thereof by (i) contacting such saline solution with a zirconium compound, at an acidic pH, (ii) separating the resulting medium into (a) a saline solution depleted in sulfate ions and (b) a zirconium compound onto which said sulfate ions are sorbed, (iii) desorbing the sulfate ions from the stage (ii) zirconium compound at a basic pH, and (iv) separating the medium of desorption into (1) a basic aqueous solution enriched in sulfate ions and (2) a zirconium compound substantially devoid of sulfate ions, with the proviso that the zirconium compound is a novel hydrated zirconium hydroxide having the formula Zr(OH).sub.4 .multidot.xH.sub.2 O, in which x ranges from 4 to 200, and such zirconium compound comprising an undried gelatinous precipitate thereof.

Removal of sulfate ions from saline solutions comprised thereof

Metal carbide and metal nitride powders produced by the carbothermal reduction of one or more metal oxides reacted with a binder material and a carbonaceous additive or optionally, a binder capable of supplying carbon to the reaction. The metal oxides are selected from among SiO.sub.2, Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.2, HfO.sub.2 and B.sub.2 O.sub.3 and are combined with the binder in the presence of carbon to form granules having a controlled pore volume. The granules are then subjected to a carbothermal reduction reaction, in the presence of a nitrogen or a neutral atmosphere, to produce metal nitrides or metal carbides respectively, having an excess of carbon incorporated therein. The product is subsequently heated to react the excess carbon within the compound with oxygen from the atmosphere to form carbon monoxide gas, which may be removed by an optional exhaust system. The remaining metal carbide or metal nitride powder may then be collected and used in various applications such as the production of ceramic objects.

Metal carbide and nitride powders

Method of making metal carbide and nitride powders

Process for the preparation of pulverulent metallic oxides with predetermined reactivity which is adjusted by the specific surface area, which are intended to be subjected to subsequent conversions, by thermal treatment of corresponding nitrates in the form of an aqueous solution or of a solids material, consisting of hydrated uranyl nitrate, on its own or in admixture with at least one of thorium nitrate, cerium nitrate and plutonium nitrate, which process is characterized in that it consists of two treatment stages:

Process for the preparation of pulverulent metallic oxides from metallic

Process for the selective separation of uranium in carbonated aqueous solution from soluble impurities including in particular at least one of the elements zirconium and/or hafnium and/or molybdenum, thereby making it possible to produce a uraniferous liquor in a greatly improved state of purity, comprising precipitation of the zirconium and/or hafnium by introducing an alkali metal hydroxide, then separation of the zirconiferous precipitate which possibly contains hafnium and/or molybdenum from the resulting uraniferous solution with its reduced impurities content, which still possibly contains molybdenum, which is characterized in that in order to increase the removal of zirconium and/or hafnium and/or molybdenum, the uraniferous carbonated aqueous solution is treated by means of a dilute alkaline aqueous solution containing at most 17 g/l of at least one alkali metal hydroxide expressed in respect of OH.sup.-, in an amount such that the resulting pH-value is imperatively higher than 11 but is generally between 11.8 and 12.5.

Process for the selective separation of uranium, zirconium and/or

A process for the purification by selective separation of uranium and/or molybdenum from zirconium and/or hafnium among other impurities contained in an amino organic phase by bringing them together with an aqueous sulphuric re-extraction solution, characterized in that, with a view to increasing the separation factor of the zirconium and/or hafnium on the one hand and the uranium and/or molbydenum on the other hand, the aqueous sulphuric re-extraction solution contains at least one alkali or equivalent sulphate.

Process for the purification of uraniferous and/or molybendiferous amino

A method of purifying uraniferous aqueous solutions containing impurities, particularly at least one of the elements zirconium and/or hafnium, and also containing at least one of the anions SO.sub.4.sup.=, NO.sub.3.sup.-, Cl.sup.- or F.sup.- acting as complexing agents for the uranium and impurities, by precipitation of said impurities by means of an alkaline agent, characterized in that the following stages are carried out for the purpose of selectively and quantitatively separating the impurities from the uranium:

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Lyons, France

Philippe Joubert