Particulate porous inorganic material based on a lead vanadate or phosphovanadate, useful for capturing and conditioning gaseous iodine
An inorganic material in a form of open-porosity particles, each of the particles comprising a lead vanadate or phosphovanadate of formula Pb 3-x X x (VO 4 ) 2-2y (PO 4 ) 2y , wherein x=0 or x>0 but ≤0.33; y=0 or y>0 but <1; X=Ba 2+ , Ca 2+ , Sr 2+ or Cd 2+ ; and metallic lead or a lead salt. A method for preparing the material, a method for capturing iodine present in a gaseous effluent as well as a method for conditioning iodine present in a gaseous effluent in a form of an iodoapatite.
1 . An inorganic material in a form of open-porosity particles, wherein each of the particles comprises:
a lead vanadate or phosphovanadate of formula (1):
Pb
3
-
x
X
x
(
VO
4
)
2
-
2
y
(
PO
4
)
2
y
(
1
)
where:
x is equal to 0 or x is greater than 0 but no more than 0.33;
y is equal to 0 or y is greater than 0 but less than 1;
X is Ba 2+ , Ca 2+ , Sr 2+ or Cd 2+ ; and
metallic lead or a lead salt, wherein the lead salt is selected from the group consisting of: lead(II) sulfide, lead(II) sulfate, lead(II) carbonate, lead(II) bromide, lead(II) chloride, lead(II) fluoride, lead(II) hydroxide, lead(II) selenide, lead(II) telluride, lead(II) nitrate, lead(II) chlorate and lead(II) perchlorate trihydrate.
2 . The material of claim 1 , wherein the metallic lead or the lead salt is intimately mixed with the lead vanadate or phosphovanadate.
3 . The material of claim 2 , wherein the lead salt is lead(II) sulfide.
4 . The material of claim 1 , wherein the lead salt is within the pores of the particles.
5 . The material of claim 4 , wherein the lead salt is lead(II) nitrate.
6 . The material of claim 1 , wherein the lead vanadate or phosphovanadate is of formula (2):
Pb
3
(
VO
4
)
2
-
2
y
(
PO
4
)
2
y
(
2
)
wherein y is equal to 0 or y is greater than 0 but less than 1.
7 . The material of claim 6 , wherein the particles comprise lead vanadate of formula Pb 3 (VO 4 ) 2 .
8 . The material of claim 1 , wherein the particles have dimensions between 300 μm and 3 mm.
9 . A method for preparing the material of claim 1 , comprising at least the steps of:
a) preparing a mixture M comprising at least one precursor of formula (3) or of formula (4):
Pb
2
-
x
X
x
V
2
-
2
y
P
2
y
O
7
(
3
)
Pb
3
-
x
X
x
(
VO
4
)
2
-
2
y
(
PO
4
)
2
y
(
4
)
where:
x is equal to 0 or x is greater than 0 but no more than 0.33;
y is equal to 0 or y is greater than 0 but less than 1;
X is Ba 2+ , Ca 2+ , Sr 2+ or Cd 2+ ; and
an alginate of an alkaline metal in water;
b) extruding in a divided form the mixture M in an aqueous solution A comprising a lead salt and optionally a barium salt, a calcium salt, a strontium salt or a cadmium salt, whereby beads formed by a hydrogel are obtained;
c) drying the beads; and
d) calcining the beads, whereby open-porosity particles are obtained;
and further comprising:
adding metallic lead or a lead salt that is insoluble or only slightly soluble in water to the precursor of formula (3) or (4) and to the alkaline metal alginate in the mixture M; or
depositing a lead salt in the pores of the particles obtained at step d).
10 . The method of claim 9 , which further comprises, between step b) and step c), a replacement of all or part of the water of the hydrogel by an organic solvent having a standard boiling point of less than 100° C.
11 . A method for capturing iodine present in a gaseous effluent, comprising putting the gaseous effluent in contact with the material of claim 1 .
12 . The method of claim 11 , wherein the iodine present in the gaseous effluent is a radioactive iodine.
13 . The method of claim 12 , wherein the radioactive iodine is iodine-129.
14 . A method for conditioning iodine present in a gaseous effluent in a form of an iodoapatite, comprising the steps of:
i) capturing the iodine by putting the gaseous effluent in contact with the material of claim 1 whereby a material comprising lead iodide is obtained; then
ii) heat treating the material comprising lead iodide, whereby the material comprising lead iodide is transformed into the iodoapatite.
15 . The method of claim 14 , wherein at step ii), the material comprising lead iodide is heated at a temperature from 400° C. to 650° C.
16 . The method of claim 14 , wherein the iodine present in the gaseous effluent is a radioactive iodine.
17 . The method of claim 16 , wherein the radioactive iodine is iodine-129.