Dissolution and recovery of at least one element nb or ta and of at least one other element u or rare earth elements from ores and concentrates

Abstract

The main subject-matter of the present invention is a process for the dissolution of at least one element chosen from niobium and tantalum and at least one other element chosen from uranium and the rare earth elements, advantageously for the dissolution of niobium, tantalum, uranium and rare earth elements, present in an ore or an ore concentrate. Said process comprises: the roasting of a material, comprising said elements, which material is mixed, dry or/in the presence of water, with an acid roasting agent in order to obtain a calcine; said material consisting of said ore or concentrate or having been obtained from said ore or said concentrate and said acid roasting agent providing for roasting in a sulphate medium; and the dissolution in an aqueous solution of the calcine obtained in order to obtain a slurry, the liquid fraction of which includes iron, in the ferric state, at a concentration of at least 50 g/l, advantageously of at least 70 g/l and very advantageously of at least 120 g/l.

1 . A process for the dissolution of at least one element chosen from niobium and tantalum and of at least one other element chosen from uranium and rare earth elements, advantageously for the dissolution of niobium, tantalum, uranium and rare earth elements, present in an ore or an ore concentrate, which comprises:
 the roasting of a material, comprising said elements, which material is mixed, dry or in the presence of water, with an acidic roasting agent in order to obtain a calcine; said material consisting of said ore or concentrate or having been obtained from said ore or said concentrate and said acidic roasting agent providing for roasting in a sulphate medium; and   the dissolution in an aqueous solution of the calcine obtained in order to obtain a slurry, the liquid fraction of which includes iron, in the ferric state, at a concentration of at least 50 g/l, advantageously of at least 70 g/l and very advantageously of at least 120 g/l.   
     
     
         2 . The process according to  claim 1 , wherein the iron present in said slurry was present in said calcine and/or was added, at least in part, in the liquid and/or solid form, to said calcine. 
     
     
         3 . The process according to  claim 1 , wherein the dissolution of the calcine is carried out without any addition of sulphuric acid. 
     
     
         4 . The process according to  claim 1 , wherein the dissolution of the calcine is carried out with addition of a reducing agent, such as SO 2 . 
     
     
         5 . The process according to  claim 1 , wherein the roasting, a solid/liquid reaction, is an acid roasting. 
     
     
         6 . The process according to  claim 1 , wherein the roasting, a gas/solid reaction, is a sulphation roasting. 
     
     
         7 . The process according to  claim 1 , wherein said roasting is carried out in the presence of iron, in the ferric form, advantageously present at an Fe/(Nb+Ta) molar ratio of greater than 2, very advantageously of greater than 3.5 and preferably of greater than 6; said iron being already present in the material to be roasted and/or having been added, at least in part, in the liquid and/or solid form, to said material to be roasted. 
     
     
         8 . The process according to  claim 1 , wherein the roasting is carried out in the presence of phosphate, advantageously present at a PO 4 /(Nb+Ta) molar ratio of greater than 2 and very advantageously of greater than 6; said phosphate being already present in the material to be roasted and/or having been added, at least in part, in the liquid and/or solid form, to said material to be roasted. 
     
     
         9 . The process according to  claim 1 , which additionally comprises, upstream of said roasting:
 a physical enrichment and/or a chemical treatment of the ore or concentrate.   
     
     
         10 . The process according to  claim 1 , which additionally comprises, upstream of said roasting:
 an acid leaching, advantageously a sulphuric acid atmospheric leaching; said leaching being carried out on an ore or concentrate, optionally physically enriched.   
     
     
         11 . The process according to  claim 10 , which comprises, upstream of the roasting:
 A) a leaching, in a single stage, cocurrentwise, in the presence of sulphuric acid, followed by a solid/liquid separation which produces a leachate and a leaching residue to be roasted; or   B) a leaching, in two stages, countercurrentwise, comprising a first leaching stage, followed by a solid/liquid separation which produces a leachate and a first leaching residue, and a second leaching stage carried out on said first leaching residue, in the presence of sulphuric acid, followed by a solid/liquid separation which produces a second leaching residue to be roasted and a liquid to be advantageously recycled to said first leaching stage.   
     
     
         12 . The process according to  claim 10 , which additionally comprises, upstream of the roasting:
 A1) a leaching, in a single stage, cocurrentwise, at a potential of greater than 500 mV Ag/AgCl and advantageously of greater than or equal to 600 mV Ag/AgCl, in the presence of H 2 SO 4  and optionally of a make-up of at least one reducing agent, followed by a solid/liquid separation which produces a ferric leachate and a leaching residue to be roasted;   A2) a leaching, in a single stage, cocurrentwise, at a potential of less than 500 mV Ag/AgCl and advantageously of less than or equal to 450 mV Ag/AgCl, in the presence of H 2 SO 4  and of at least one reducing agent, followed by a solid/liquid separation which produces a ferrous leachate and a leaching residue enriched in niobium and/or tantalum to be roasted;   B1) a leaching, in two stages, countercurrentwise, comprising a first leaching stage, at a potential of greater than 500 mV Ag/AgCl and advantageously of greater than or equal to 600 mV Ag/AgCl, in the presence of H 2 SO 4  and optionally of a make-up of at least one reducing agent, followed by a solid/liquid separation which produces a ferric leachate and a first leaching residue, and a second leaching stage carried out on said first leaching residue, either at a potential of greater than 500 mV Ag/AgCl and advantageously of greater than or equal to 600 mV Ag/AgCl, in the presence of H 2 SO 4  and optionally of a make-up of at least one reducing agent, or at a potential of less than 500 mV Ag/AgCl and advantageously of less than or equal to 450 mV Ag/AgCl, in the presence of H 2 SO 4  and of at least one reducing agent, followed by a solid/liquid separation which produces a second leaching residue to be roasted and a liquid with residual acidity to be advantageously recycled to said first leaching stage;   B2) a leaching, in two stages, countercurrentwise, comprising a first leaching stage, at a potential of less than 500 mV Ag/AgCl and advantageously of less than 450 mV Ag/AgCl, in the presence of H 2 SO 4  and of at least one reducing agent, followed by a solid/liquid separation which produces a ferrous leachate and a first leaching residue, and a second leaching stage carried out on said first leaching residue, either at a potential of greater than 500 mV Ag/AgCl and advantageously of greater than or equal to 600 mV Ag/AgCl, in the presence of H 2 SO 4  and optionally of a make-up of at least one reducing agent, or at a potential of less than 500 mV Ag/AgCl and advantageously of less than or equal to 450 mV Ag/AgCl, in the presence of H 2 SO 4  and of at least one reducing agent, followed by a solid/liquid separation which produces a second leaching residue enriched in niobium and/or tantalum to be roasted and a liquid to be advantageously recycled to said first leaching stage; said advantageously recycled liquid being recycled as it is or after separation, at least partial, from the niobium and/or tantalum present therein.   
     
     
         13 . The process according to  claim 12 , wherein said leaching is of A2) or B2) type, advantageously of B2) type. 
     
     
         14 . The process according to  claim 1 , which additionally comprises, upstream of said roasting:
 an ultrafine grinding of the material to be roasted, for the production of said material at a particle size ≦30 μm, advantageously ≦15 μm and very advantageously ≦10 μm.   
     
     
         15 . The process according to  claim 1 , which additionally comprises, downstream of said dissolution:
 a solid/liquid separation carried out directly on the slurry or after an additional stage of dilution of said slurry by a limited factor, advantageously ≦5, in order to prevent the precipitation of the dissolved elements; said solid/liquid separation producing a solid attack residue and a roasting leachate including said dissolved elements.   
     
     
         16 . The process according to  claim 15 , which additionally comprises, downstream of said dissolution:
 the separation of the niobium and/or tantalum from said roasting leachate and the recycling of said leachate, from which said niobium and/or tantalum was/were separated, optionally diluted, for the implementation of a sulphuric acid atmospheric leaching carried out on an ore or concentrate upstream of the roasting.   
     
     
         17 . The process according to  claim 11 , which comprises:
 a leaching of A1, A2, B1 or B2 type according to  claim 12  and the recovery of a leachate and of a leaching residue;   an optional ultrafine grinding of said leaching residue;   the roasting of said optionally ground leaching residue;   the dissolution of the calcine obtained on conclusion of said roasting, in order to obtain a slurry;   a liquid/solid separation, carried out directly on said slurry or on said slurry diluted by a limited factor, which produces a solid attack residue and a roasting leachate including the desired elements;   the separation of the niobium and/or tantalum from said roasting leachate and the recycling of the leachate, from which said niobium and/or tantalum was/were previously separated, which is optionally diluted, for the implementation of said leaching.   
     
     
         18 . The process according to  claim 11 , which comprises:
 a desliming of an ore or ore concentrate, which is optionally physically enriched, for the recovery, on the one hand, of slimes including iron and, on the other hand, of the deslimed ore or concentrate;   a leaching of A1, A2, B1 or B2 type according to  claim 12  carried out on said deslimed ore or concentrate, optionally with addition of a portion of the slimes recovered in step 1 above, and the recovery of a leachate and of a leaching residue;   an optional ultrafine grinding of the leaching residue;   the roasting of said optionally ground leaching residue, carried out with addition of iron via another portion of the slimes recovered in step 1 above;   the dissolution of the calcine obtained on conclusion of said roasting, in order to obtain a slurry;   a liquid/solid separation, carried directly on said slurry or on said slurry diluted by a limited factor, which produces an attack residue and a roasting leachate including the desired elements;   the separation of the niobium and/or tantalum from said roasting leachate and the recycling of said roasting leachate, from which said niobium and tantalum was/were previously separated, which is optionally diluted, for the implementation of said leaching.   
     
     
         19 . The process according to  claim 1 , which is carried out with an ore or ore concentrate; the ore concerned being chosen from the minerals of the pyrochlore, euxenite, samarskite, perovskite and fergusonite groups and their mixtures. 
     
     
         20 . A process for the recovery of at least one element chosen from niobium and tantalum and of at least one other element chosen from uranium and the rare earth elements, advantageously for the recovery of niobium, tantalum, uranium and rare earth elements, present in an ore or an ore concentrate, which comprises:
 the dissolution of said elements according to the process of  claim 1 ; and   the separation of said elements.