Determination of the Uranium(VI) and ‐(IV) Species in Uranium Ores

Abstract

The determination of the two species of uranium(VI and IV) present in 6 uranium ores was studied in relation to the chemical and mineralogical composition, humidity, and pH of the samples taken over from the mine. X-ray diffraction studies, performed on the uranium ores in powder form allowed to establish their mineralogical composition. Thechemical analysis pointed out Quite numerous monographic studies and reviews have been devoted to the distribution of the U VI and U IV chemical species present in the composition of the minerals forming the uranium ores [1Ϫ3]. Up to the ratio between the two uranium species in several ores it is seen as varying with the conditions characterizing the mining sites from which the samples under analysis had been extracted. One of the remarks done was that the H и and HO и primary radiolysis products, resulted from the decomposition of the ground water under the influence of the α-rays emitted by uranium nuclei, as well as those associated to chain nuclear fission reactions for the Oklo-Gabon zone, induced major transformations in the ratio established between the two uranium species [4Ϫ6].Raman spectrometric measurements in gaseous phase performed on the samples of uranium ores with different mineralogical composition pointed out the presence of certain H 2 O-salt-H 2 -O 2 and H 2 O-salt-H 2 ± CH 4 inclusions of organic origin, resulted from micro organisms, in the holes microcraks.

Equilibrium and Kinetics of U(VI)aq Adsorption on in situ Generated Fe2O3. nH2O

“…The residual concentration of U(VI) was analyzed to calculate the equilibrium adsorption capacity according to the following equation [31]: (1) where Q e is the equilibrium adsorption capacity (mg . g -1 ); C i and C e are the initial and final/equilibrium concentrations of the ionic species (mg. L -1 ), respectively; V is solution volume (L) and m is the dried sorbent mass (g).…”

“…From the value of Dubinin -Radushkevich constant, K, the adsorption energy value, E (kJ.mol -1 ), may be determined according to the equation [31,33,35,37]: (7) Depending on its value the type of the adsorption process may be determined as follows: for E ∈ [1,16] is physical adsorption and for E > 16 is chemisorption, respectively.…”

“…Uranium mining activity continues to be a major source of radioactive environmental pollution by producing huge amounts of low radioactive wastes heaped around the mining galleries and large quantities of wastewaters [1]. It is also present in the sea-water and it can contaminate the fish [2].…”

“…The radioactive pollution is also faced by other countries such as Serbia in the spa waters [3], Greece in the Axios River's case [4] and Italy in the building materials [5]. This undesired phenomenon challenges the scientific community to discover the most effective solutions for ecological rehabilitation of polluted sites [1].…”

“…Uranium is nephrotoxic and accumulates in bones, liver and kidneys causing permanent damages to the affected organs [6]. Uranium contaminated mine water with low content of U(VI) (1-10 mg1.L -1 ) is a challenge for the classic treatment methods such as ion exchange, solvent extraction, adsorption on different supports due to their specific drawbacks [1]. The solution to this problem is sorption/precipitate flotation process [1].…”