Uranium carbonate
Encyclopedia
Uranyl carbonate, UO2 is a carbonate
of uranium
that forms the backbone of several uranyl mineral species such as Andersonite
, McKelveyite
and Wyartite
and most importantly Rutherfordine
. It is also found in both the mineral and organic fractions of coal
and its fly ash and is the main component of uranium in mine tailing seepage water.
Uranium like other actinide
s readily forms a dioxide uranyl
core (UO2). In the environment, this uranyl core readily complexes with carbonate to form charged complexes. Although uranium forms insoluble solids or adsorbs to mineral surfaces at alkaline pH
it is these soluble carbonate complexes that increase its solubility, availability, and mobility with low affinities to soil. Uranium(VI) generally forms a pH-dependent suite of uranyl carbonate complexes in ground water solutions:
A common method for concentrating uranium from a solution uses solutions of uranyl carbonates which are passed through a resin bed where the complex ions are transferred to the resin by ion exchange
with a negative ion like chloride. After build-up of the uranium complex on the resin, the uranium is eluted with a salt solution
and the uranium is precipitated in another process.
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
that forms the backbone of several uranyl mineral species such as Andersonite
Andersonite
Andersonite, Andersonit or Andersonita , or hydrated sodium calcium uranyl carbonate is a rare uranium carbonate mineral that was only described in the last half century. Named for Charles Alfred Anderson of United States Geological Survey, who first described the mineral species, it is found in...
, McKelveyite
McKelveyite
Mckelveyite is a hydrated sodium, barium, yttrium, and uranium–containing carbonate, with the chemical formula 36. It was first described in 1965 from deposits in the Green River Formation, Sweetwater County, Wyoming, and is named after Vincent Ellis McKelvey , a former director of the United...
and Wyartite
Wyartite
Wyartite Ca3U6218 ·3-5 is a uranium bearing mineral named after Jean Wyart , mineralogist at the Sorbonne, Paris. Greenish black, black, black violet in color, translucent to opaque orthorhombic crystals presentantion. A hardness of 3 - 4 Mohs. Its other names are Ianthinite , Wyartit and Wyartita...
and most importantly Rutherfordine
Rutherfordine
Rutherfordine is a mineral containing almost pure uranyl carbonate. It crystallizes in the orthorhombic system in translucent lathlike, elongated, commonly radiating in fibrous, and in pulverulent, earthy to very fine-grained dense masses. It has a specific gravity of 5.7 and exhibits two...
. It is also found in both the mineral and organic fractions of coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
and its fly ash and is the main component of uranium in mine tailing seepage water.
Uranium like other actinide
Actinide
The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.The actinide series derives its name from the group 3 element actinium...
s readily forms a dioxide uranyl
Uranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
core (UO2). In the environment, this uranyl core readily complexes with carbonate to form charged complexes. Although uranium forms insoluble solids or adsorbs to mineral surfaces at alkaline pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
it is these soluble carbonate complexes that increase its solubility, availability, and mobility with low affinities to soil. Uranium(VI) generally forms a pH-dependent suite of uranyl carbonate complexes in ground water solutions:
- UO2(OH)2+
- UO2(CO3)22−
- UO2(CO3)34−
- UO2(CO3)(OH)3−
A common method for concentrating uranium from a solution uses solutions of uranyl carbonates which are passed through a resin bed where the complex ions are transferred to the resin by ion exchange
Ion exchange
Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion...
with a negative ion like chloride. After build-up of the uranium complex on the resin, the uranium is eluted with a salt solution
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
and the uranium is precipitated in another process.
The uranyl carbonate minerals
Uranyl carbonate complexes form a large class of mineral species. Several have been described in literature. These include:- AndersoniteAndersoniteAndersonite, Andersonit or Andersonita , or hydrated sodium calcium uranyl carbonate is a rare uranium carbonate mineral that was only described in the last half century. Named for Charles Alfred Anderson of United States Geological Survey, who first described the mineral species, it is found in...
(hydrated sodium calcium uranyl carbonate) - Astrocyanite-(Ce) (hydrated copper cerium neodymium lanthanum praseodymium samarium calcium yttrium uranyl carbonate hydroxide)
- Bayleyite (hydrated magnesium uranyl carbonate)
- Bijvoetite-(Y) (hydrated yttrium dysprosium uranyl carbonate hydroxide)
- Fontanite (hydrated calcium uranyl carbonate)
- Grimselite (hydrated potassium sodium uranyl carbonate)
- Joliotite (hydrated uranyl carbonate)
- Liebigite (hydrated calcium uranyl carbonate)
- McKelveyiteMcKelveyiteMckelveyite is a hydrated sodium, barium, yttrium, and uranium–containing carbonate, with the chemical formula 36. It was first described in 1965 from deposits in the Green River Formation, Sweetwater County, Wyoming, and is named after Vincent Ellis McKelvey , a former director of the United...
(hydrated barium sodium calcium uranium yttrium carbonate) - Metazellerite (hydrated calcium uranyl carbonate)
- Rabbittite (hydrated calcium magnesium uranyl carbonate hydroxide)
- Roubaultite (copper uranyl carbonate oxide hydroxide)
- RutherfordineRutherfordineRutherfordine is a mineral containing almost pure uranyl carbonate. It crystallizes in the orthorhombic system in translucent lathlike, elongated, commonly radiating in fibrous, and in pulverulent, earthy to very fine-grained dense masses. It has a specific gravity of 5.7 and exhibits two...
(uranyl carbonate) - Schrokingerite (hydrated sodium calcium uranyl sulfate carbonate fluoride)
- Shabaite (hydrated copper cerium neodymium lanthanum praseodymium samarium calcium yttrium uranyl carbonate hydroxide)
- Sharpite (hydrated calcium uranyl carbonate hydroxide)
- Swartzite (hydrated calcium magnesium uranyl carbonate)
- Voglite (hydrated calcium copper uranyl carbonate)
- WyartiteWyartiteWyartite Ca3U6218 ·3-5 is a uranium bearing mineral named after Jean Wyart , mineralogist at the Sorbonne, Paris. Greenish black, black, black violet in color, translucent to opaque orthorhombic crystals presentantion. A hardness of 3 - 4 Mohs. Its other names are Ianthinite , Wyartit and Wyartita...
(hydrated calcium uranyl carbonate hydroxide) - Widenmannite (lead uranyl carbonate)
- Zellerite (hydrated calcium uranyl carbonate)
- Znucalite (hydrated calcium zinc uranyl carbonate hydroxide)