Process for the selective removal of arsenic in the course of the oxidizing attack by means of a carbonated liquor on a uraniferous ore containing same

A process for the selective removal of arsenical materials, in the course of a continuous hot oxidizing attack process, comprises attacking a uraniferous ore containing arsenical materials as impurities in the presence of an oxidizing agent in the reaction medium by means of an aqueous liquor formed by a recycling solution containing alkali metal carbonate and bicarbonate, and uranium close to the limit of solubility thereof, under concentration, temperature and pressure conditions which causes solubilization of the uranium present in the ore, and re-precipitation thereof in the attack medium. A suspension of a solid phase in a liquid phase is collected which, after cooling, is subjected to a separation operation. The liquid phase is recycled to the attack operation, and the separated solid phase is treated by means of an aqueous liquor to re-dissolve the precipitated uranium which is characterized in that the arsenic which is solubilized in the attack operation is extracted by means of a magnesium compound which is introduced in an amount that is at least equal to the stoichiometric amount required to cause precipitation of magnesium arsenate