EP3475470A1 - Process for treating a solid carbonaceous material containing aluminum, fluorides and sodium ions - Google Patents
Process for treating a solid carbonaceous material containing aluminum, fluorides and sodium ionsInfo
- Publication number
- EP3475470A1 EP3475470A1 EP17751126.8A EP17751126A EP3475470A1 EP 3475470 A1 EP3475470 A1 EP 3475470A1 EP 17751126 A EP17751126 A EP 17751126A EP 3475470 A1 EP3475470 A1 EP 3475470A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- solution
- aluminum
- compartment
- extraction solution
- process according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 90
- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 90
- 238000000034 method Methods 0.000 title claims abstract description 83
- 230000008569 process Effects 0.000 title claims abstract description 80
- 239000007787 solid Substances 0.000 title claims abstract description 38
- 229910001415 sodium ion Inorganic materials 0.000 title claims abstract description 35
- 150000002222 fluorine compounds Chemical class 0.000 title claims abstract description 28
- 239000003575 carbonaceous material Substances 0.000 title claims abstract description 20
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 159
- 239000000243 solution Substances 0.000 claims abstract description 159
- 238000000605 extraction Methods 0.000 claims abstract description 93
- 239000012528 membrane Substances 0.000 claims abstract description 72
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 60
- 238000002386 leaching Methods 0.000 claims abstract description 52
- 239000002244 precipitate Substances 0.000 claims abstract description 47
- 239000007864 aqueous solution Substances 0.000 claims abstract description 34
- 230000009467 reduction Effects 0.000 claims abstract description 16
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000012670 alkaline solution Substances 0.000 claims abstract description 7
- -1 fluoride ions Chemical class 0.000 claims description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 23
- 150000002500 ions Chemical class 0.000 claims description 22
- 125000002091 cationic group Chemical group 0.000 claims description 18
- 239000000203 mixture Substances 0.000 claims description 17
- 229910001610 cryolite Inorganic materials 0.000 claims description 16
- 230000015572 biosynthetic process Effects 0.000 claims description 14
- 125000000129 anionic group Chemical group 0.000 claims description 10
- 150000001450 anions Chemical class 0.000 claims description 7
- 150000001768 cations Chemical class 0.000 claims description 7
- 150000001875 compounds Chemical class 0.000 claims description 7
- 238000000909 electrodialysis Methods 0.000 claims description 7
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 6
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 6
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 6
- 150000003839 salts Chemical class 0.000 claims description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 4
- 229910021502 aluminium hydroxide Inorganic materials 0.000 claims description 4
- 229910001679 gibbsite Inorganic materials 0.000 claims description 4
- 230000003647 oxidation Effects 0.000 claims description 4
- 238000007254 oxidation reaction Methods 0.000 claims description 4
- 229910002651 NO3 Inorganic materials 0.000 claims description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 3
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Inorganic materials [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 claims description 3
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims description 3
- 229910021653 sulphate ion Inorganic materials 0.000 claims description 3
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 2
- 229910019142 PO4 Inorganic materials 0.000 claims description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 2
- 239000010452 phosphate Substances 0.000 claims description 2
- 229910052783 alkali metal Inorganic materials 0.000 claims 1
- 150000001340 alkali metals Chemical class 0.000 claims 1
- 238000011282 treatment Methods 0.000 abstract description 20
- 238000011084 recovery Methods 0.000 abstract description 7
- 235000011121 sodium hydroxide Nutrition 0.000 description 49
- 101710097688 Probable sphingosine-1-phosphate lyase Proteins 0.000 description 39
- 101710105985 Sphingosine-1-phosphate lyase Proteins 0.000 description 39
- 101710122496 Sphingosine-1-phosphate lyase 1 Proteins 0.000 description 39
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 37
- 238000000263 scanning probe lithography Methods 0.000 description 24
- 239000011775 sodium fluoride Substances 0.000 description 18
- 235000013024 sodium fluoride Nutrition 0.000 description 18
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminum fluoride Inorganic materials F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 description 16
- 238000006722 reduction reaction Methods 0.000 description 15
- IRPGOXJVTQTAAN-UHFFFAOYSA-N 2,2,3,3,3-pentafluoropropanal Chemical compound FC(F)(F)C(F)(F)C=O IRPGOXJVTQTAAN-UHFFFAOYSA-N 0.000 description 13
- 239000008151 electrolyte solution Substances 0.000 description 12
- 238000000926 separation method Methods 0.000 description 12
- 238000004519 manufacturing process Methods 0.000 description 11
- 239000000126 substance Substances 0.000 description 11
- 238000001556 precipitation Methods 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 150000004645 aluminates Chemical class 0.000 description 7
- 239000003518 caustics Substances 0.000 description 7
- 239000000463 material Substances 0.000 description 7
- 238000009825 accumulation Methods 0.000 description 6
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 description 6
- 229910001388 sodium aluminate Inorganic materials 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 5
- 238000005265 energy consumption Methods 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 238000007792 addition Methods 0.000 description 4
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 230000005684 electric field Effects 0.000 description 4
- 230000036571 hydration Effects 0.000 description 4
- 238000006703 hydration reaction Methods 0.000 description 4
- 238000005304 joining Methods 0.000 description 4
- 150000002825 nitriles Chemical class 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M potassium hydroxide Substances [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000004131 Bayer process Methods 0.000 description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 3
- 229910001634 calcium fluoride Inorganic materials 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 3
- 150000004679 hydroxides Chemical class 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 239000011734 sodium Substances 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 2
- 241000282414 Homo sapiens Species 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 229910020814 NaAl(OH)4 Inorganic materials 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 230000036541 health Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 235000010755 mineral Nutrition 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 230000003134 recirculating effect Effects 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 230000003381 solubilizing effect Effects 0.000 description 2
- 241000894007 species Species 0.000 description 2
- 239000006228 supernatant Substances 0.000 description 2
- 229910018626 Al(OH) Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- MXRIRQGCELJRSN-UHFFFAOYSA-N O.O.O.[Al] Chemical compound O.O.O.[Al] MXRIRQGCELJRSN-UHFFFAOYSA-N 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 208000034188 Stiff person spectrum disease Diseases 0.000 description 1
- 229920010524 Syndiotactic polystyrene Polymers 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910001618 alkaline earth metal fluoride Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 239000012223 aqueous fraction Substances 0.000 description 1
- 229910001570 bauxite Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000000292 calcium oxide Substances 0.000 description 1
- 235000012255 calcium oxide Nutrition 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000010349 cathodic reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005202 decontamination Methods 0.000 description 1
- 230000003588 decontaminative effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 208000012112 ischiocoxopodopatellar syndrome Diseases 0.000 description 1
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 229910001512 metal fluoride Inorganic materials 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000000935 solvent evaporation Methods 0.000 description 1
- 238000002490 spark plasma sintering Methods 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 239000012134 supernatant fraction Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
Definitions
- the present invention relates to a process for treating a solid carbonaceous material containing aluminum, fluorides and sodium ions.
- the process according to the present invention is particularly suitable for the treatment of spent potlinings deriving from production processes of primary aluminum.
- Aluminum is generally produced by the reduction of aluminum-based minerals, mainly bauxite.
- the reduction reaction is carried out in a electrolytic reduction cell (pot) containing molten cryolite (NasAlFe) and other salts, such as aluminum fluoride (A1F 3 ) , alkaline metal fluorides (e.g. NaF, LiF) and alkaline-earth metal fluorides (e.g. CaF 2 , MgF 2 ) .
- A1F 3 molten cryolite
- AlFe aluminum fluoride
- alkaline metal fluorides e.g. NaF, LiF
- alkaline-earth metal fluorides e.g. CaF 2 , MgF 2
- the walls and bottom of the electrolytic reduction cell are internally coated with a lining based on a carbonaceous material. When the cell is operating, the coating gradually deteriorates allowing various materials to penetrate into its interior.
- the deterioration of the lining continues with time until the functioning of the cell must be interrupted to replace the deteriorated lining ⁇ spent potlining) with a new lining.
- the spent potlining also indicated hereafter as SPL, generally also comprises a part of the wall of the refractory material located outside the cell which is removed together with the internal lining.
- SPLs Due to the operating conditions of the cell, SPLs contain significant quantities of aluminum, fluorides, alkaline metals - in particular sodium - and alkaline- earth metals, and other substances such as, for example, nitrides and cyanides.
- alkaline metals in particular sodium - and alkaline- earth metals
- other substances such as, for example, nitrides and cyanides.
- SPLs be suitably treated in order to reduce the content of dangerous substances to acceptable levels, before being definitely disposed of in landfills.
- SPLs Various treatment processes of SPLs are known in the state of the art, aimed at recovering at least a part of the substances contained therein, in particular aluminum and fluorides, and possibly recycling them in the production process of primary aluminum.
- Known treatment processes comprise, for example, combustion, roasting, or the reaction of SPLs with quicklime.
- Hydrometallurgical treatment processes of SPLs are also known, based on the extraction of the substances of interest from the carbonaceous material by means of acid or caustic solutions.
- the treatment processes of the known art generally involve high energy consumptions and/or considerable costs linked to the high quantities of reagents used for treating the SPLs. Furthermore, in many cases, the processes of the known art only allow an effective recovery of some of the substances of interest, generating further residues containing contaminating substances which in turn require specific treatments before allowing them to be safely disposed of.
- the process described in US 4,816,122 provides the extraction of SPLs with a concentrated solution of caustic soda to form an extraction solution containing sodium fluoride (NaF) and sodium aluminate (NaAl(OH) 4 ) . Due to the lower solubility of fluorides in concentrated solutions of caustic soda, part of the fluorides, if not all, remain in the solid insoluble residue in the form of NaF. After separating the extraction solution, the NaF is extracted from the solid insoluble residue with water or with a diluted aqueous solution of NaF.
- NaF sodium fluoride
- NaAl(OH) 4 sodium aluminate
- 4,816,122 provides the extraction of SPLs with a solution of diluted caustic soda for dissolving a greater quantity of sodium fluoride and forming an insoluble solid residue.
- the caustic solution containing sodium fluoride is concentrated by evaporation to precipitate solid NaF which, after being separated from the concentrated solution, is re- dissolved in water.
- Both of the above embodiments lead to the separation and recovery of solid NaF, which is then re- dissolved to form an aqueous solution to be subjected to electrodialysis for producing an aqueous solution of HF and an aqueous solution of NaOH.
- the aqueous solution of HF can be reacted with alumina (AI 2 O3) to produce A1F 3 , so as to obtain a reusable product in the bath of the electrolytic reduction cell to produce primary aluminum.
- the solution of NaOH produced by electrodialysis can be recycled to the purification process of the aluminum mineral (Bayer process) to produce alumina to be fed to the electrolytic reduction cell.
- the extraction is carried out with a concentrated caustic solution, most of the aluminum contained in the SPLs is solubilized in the form of sodium aluminate. Also in this case, the sodium aluminate can be recycled to the Bayer process, possibly after being dried by means of spray-drying.
- the extraction is effected with a diluted caustic solution, a significant part of the aluminate remains in the caustic solution which has been concentrated by evaporation; this fraction of aluminum is destined for disposal.
- the aluminum originally present in the SPLs is not separated and recovered from the caustic extraction solution in which it is dissolved in the form of aluminate and it can therefore only be usefully recycled to the Bayer process.
- a further drawback of this process lies in the fact that the separation of the aluminate from NaF is not sufficiently forced (part of the aluminate remains in the solutions of NaF and part of the NaF remains in the solutions containing the aluminate) for allowing the final production of reusable materials having a high degree of purity.
- the Applicant has therefore established the primary objective of providing a process for the treatment of carbonaceous materials containing aluminum, fluorides and sodium ions, in particular SPLs, in a simple and effective way, at least partially avoiding the drawbacks of the known art.
- an objective of the present invention is to provide a process for the treatment of the above-mentioned carbonaceous materials, in particular SPLs, which allows the content of substances potentially dangerous for the health of human beings and the environment to be almost completely eliminated therefrom, or at least reduced.
- a second objective of the present invention is to provide a process which allows substances to be recovered from the above carbonaceous materials, in particular SPLs, which can be re-used in the production process of primary aluminum, in particular in the electrolytic reduction cell of alumina, in an effective and economically convenient way.
- a further objective of the present invention is to provide a process which, starting from the above- mentioned carbonaceous materials, in particular SPLs, allows the selective production of the most desired compounds containing aluminum, in relation, for example, to the specific requirements of the plant in which the production cycle of primary aluminum is carried out.
- the precipitated aluminum compounds for example cryolite, aluminum fluoride, aluminum hydroxide or a mixture of the same
- these products can be re-used by feeding them, also directly, into a cell for the electrolytic reduction of alumina.
- the process of the invention is particularly versatile and adaptable to the requirements of a specific production plant in which it is implemented.
- the membrane electrolysis treatment also generates an aqueous solution of NaOH which can be recovered and re-used for leaching additional SPL, with a consequent saving of reagents.
- the process of the invention can be carried out in a continuous mode, in a simple and effective way, with a reduced consumption of chemical reagents and electric energy with respect to the processes of the known art.
- the insoluble solid residue resulting from the leaching step can be safely disposed of in landfills. Depending on the content of impurities still present, this solid residue can also be used as auxiliary fuel in combustion processes or, if particularly pure, as material for constructing the lining of the electrolytic reduction cell of alumina.
- the present invention relates to a process for treating a solid carbonaceous material containing aluminum, fluorides and Na + ions which comprises the steps:
- carbonaceous material containing aluminum, fluorides and sodium ions is used for indicating various solid materials that contain aluminum, fluorides and sodium ions, including SPSs deriving from electrolytic reduction processes of alumina, carbon dust coming from aluminum melting processes and wastes of spent baths used in electrolytic reduction cells (aluminum dross) .
- SPSs deriving from electrolytic reduction processes of alumina
- carbon dust coming from aluminum melting processes and wastes of spent baths used in electrolytic reduction cells (aluminum dross) .
- SPLs sulfuraceous material containing aluminum, fluorides and sodium ions that can be treated with the process of the present invention.
- membrane electrolysis indicates an electrochemical process implemented in a electrolytic cell in which at least one ion-selective membrane is present, which separates at least two compartments; the ion-selective membrane can only be crossed by positively charged ionic species (cationic permselective membrane) or only by negatively charged ionic species (cationic permselective membrane) , that migrate from one compartment to the other of the cell under the influence of an electric field generated by a difference in electric potential applied to the electrodes of the cell; membrane electrolysis allows the separate recovery of at least one precipitate comprising aluminum and a solution of NaOH.
- membrane electrolysis also comprises electrodialysis processes.
- the leaching step is carried out with an alkaline aqueous solution (leaching solution), preferably an aqueous solution of NaOH, KOH or mixtures thereof.
- an alkaline aqueous solution preferably an aqueous solution of NaOH, KOH or mixtures thereof.
- the leaching solution is preferably an aqueous solution of NaOH.
- the leaching solution preferably has a pH within the range of 10-14, more preferably within the range of 12-14.
- the leaching can be effected with diluted or concentrated leaching solutions (e.g. aqueous solutions of NaOH or KOH) .
- diluted or concentrated leaching solutions e.g. aqueous solutions of NaOH or KOH.
- the diluted leaching solution preferably has a concentration of hydroxide equal to or higher than 1% by weight and lower than 10% by weight, more preferably within the range of 5% - 8%, said percentages referring to the weight of the diluted leaching solution.
- the concentrated leaching solution preferably has a concentration of hydroxide equal to or higher than 10% by weight and lower than 40% by weight, preferably within the range of 15% - 25%, said percentages referring to the weight of the concentrated leaching solution.
- the leaching step comprises at least a first leaching operation carried out with a concentrated leaching solution and a subsequent washing operation of the resulting insoluble residue with water or with a very diluted leaching solution, preferably having a concentration of hydroxide equal to or lower than 3% by weight with respect to the weight of the solution. In this way, in fact, the extraction of both aluminum and fluorides from the SPL is maximized.
- the extraction solutions deriving from leaching with diluted or concentrated leaching solutions together with the washing solutions, can be joined to form a single extraction solution to be subjected to the subsequent membrane electrolysis step.
- the leaching can be effected with a leaching solution having room temperature (25°C) or higher than 25°C, more preferably within the range of 70°C - 95°C.
- the duration of the leaching is generally selected in relation to the quantity of SPL to be treated, the temperature and concentration of the leaching solution. Preferably, the duration of the contact between SPL and solution ranges from 15 to 300 minutes.
- the ratio between the quantity of SPL and leaching solution is within the range of 20 - 400 g SPL/1 leaching solution, more preferably within the range of 70 - 150 g/1.
- the extraction solution can be treated with one or more oxidizing agents, before subjecting said extraction solution to electrolysis.
- the extraction solution for example, can be subjected to treatment with ozone (O 3 ) to chemically decompose the possible cyanides dissolved.
- the SPL can be subjected to leaching after being calcined to thermally decompose the possible cyanides present.
- the aluminum is mainly present in SPLs in the form of alumina (AI 2 O 3 ) , cryolite (Na 3 AlF 6 ) and aluminium fluoride (AIF 3 ) , the main dissolution reactions that involve these compounds during leaching are the following (1) - (3) :
- the insoluble solid residue can be separated from the extraction solution by means of filtration and/or decanting, for example, or with other techniques known to skilled person in the art.
- the insoluble solid residue can also be washed in order to reduce the quantity of fluorides remaining after the leaching with a diluted aqueous solution of NaF.
- the washing solution containing the fluorides extracted from the insoluble solid residue can then be joined with the extraction solution obtained from the leaching step or it can be treated according to known techniques for producing, for example, an aqueous solution of NaOH and A1F 3 , as described for example in US 4,816,122.
- the extraction solution comprising the leaching products, namely at least fluoride ions, sodium ions and aluminum in the form of sodium aluminate, is subjected to electrolysis in a membrane cell to recover the electrolysis products separately, i.e. a precipitate containing aluminum and a solution containing NaOH.
- the present invention exploits the electrolytic process for causing, through the H + ions produced in the anodic reaction, the precipitation of an insoluble compound of aluminum in a first compartment of the membrane cell.
- the OH ⁇ ions produced in the cathodic reaction simultaneously form NaOH in a second compartment of the cell, together with the Na + ions present in the extraction solution.
- the membrane electrolysis process comprises the following steps:
- At least one anode compartment comprising at least one anode immersed in an anolyte
- At least one cathode compartment comprising at least one cathode immersed in a catholyte
- said anode compartment being separated from said cathode compartment by at least one permselective cationic membrane;
- H + ions are formed in the anode compartment which, by locally lowering the pH of the anolyte, cause the formation of a solid precipitate containing aluminum.
- An aqueous dispersion of a substantially insoluble compound of aluminum is therefore formed in the anode compartment, which can be easily separated from the aqueous fraction.
- the Na + cations of the extraction solution present in the anode compartment migrate towards the cathode compartment through the permselective cationic membrane.
- the permselective cationic membrane allows the Na + cations present in the anode compartment to migrate into the cathode compartment and prevents, instead, the anions present in the cathode compartment (OH-) from migrating into the anode compartment.
- OtT ions which, together with the Na + cations that have selectively migrated from the anode compartment to the cathode compartment, form NaOH.
- OtT ions also form the corresponding hydroxides .
- the catholyte supplied to the cathode compartment is preferably an aqueous solution of NaOH.
- a solution of NaOH can be recovered, having a higher concentration with respect to that of the starting catholyte.
- the solution of NaOH which is formed in the cathode compartment can be at least partially used as leaching solution for leaching further SPL.
- the precipitate containing aluminum which is formed in the anode compartment can, for example, be an aluminum salt (e.g. NasAlFe) , an aluminum hydroxide (Al(OH) 3 ) or a mixture of the above compounds depending on the composition of the anolyte.
- an aluminum salt e.g. NasAlFe
- Al(OH) 3 aluminum hydroxide
- composition of the precipitate containing aluminum which is formed in the anode compartment during the membrane electrolysis can be advantageously determined by suitably varying the composition of the extraction solution before the electrolysis.
- a precipitate substantially composed of Na 3 AlF 6 By adding, for example, further fluoride ions to the extraction solution before the electrolysis, a precipitate substantially composed of Na 3 AlF 6 can be obtained.
- the formation of a precipitate substantially composed of Al(OH) 3 can be obtained, which, after drying, can be converted into AI 2 O 3 (alumina) .
- the precipitation of the fluoride ions can be obtained, for example, by adding ions of at least one alkaline-earth metal, preferably Ca 2+ ions, to the extraction solution.
- the process according to the present invention can therefore be easily adapted to the requirements of the user, based, for example, on the need for obtaining cryolite or alumina to be fed to the bath of the electrolytic cell to produce primary aluminum.
- the recovery of a precipitate containing aluminum and the separate recovery of an aqueous solution of NaOH can be advantageously obtained by effecting the membrane electrolysis in a cell comprising at least one permselective cationic membrane and at least one permselective anionic membrane.
- the membrane electrolysis process comprises the following steps :
- At least one anode compartment comprising at least one anode immersed in an anolyte;
- at least one cathode compartment comprising at least one cathode immersed in a catholyte;
- At least one supply compartment interposed between said anode compartment and said cathode compartment ;
- said supply compartment being separated from said anode compartment by at least one permselective cationic membrane;
- said supply compartment being separated from said cathode compartment by at least one permselective anionic membrane
- the aluminate and fluoride ions present in the extraction solution migrate from the central supply compartment towards the positively charged anode, passing through the permselective anionic membrane.
- the Na + cations migrate in the opposite direction, towards the negatively charged cathode, passing through the permselective cationic membrane.
- H + ions that are generated in the anode compartment cannot migrate towards the cathode compartment due to the permselective anionic membrane, they combine, in the anode compartment, with the aluminate and fluoride ions that have migrated from the supply compartment, causing the precipitation of aluminum as A1F 3 , cryolite or as a mixture thereof.
- fluoride ions can be added in the anode compartment, for example by feeding an aqueous solution of HF during the electrolytic process.
- the catholyte supplied to the cathode compartment is preferably an aqueous solution of NaOH.
- the solution of NaOH which is formed in the cathode compartment can be at least partially used as leaching solution for leaching further SPL.
- the anolyte supplied to the anode compartment is preferably an acid electrolytic solution.
- the pH of the anolyte is preferably within the range of 0-5, more preferably within the range of 0-3.
- the anolyte for example, can be selected from halogen acids, in particular HF, sulfuric acid, phosphoric acid and the like .
- the membrane electrolysis process can be carried out in an electrodialysis apparatus.
- the electrodialysis technique using one or more cells comprising a cationic membrane and an anionic membrane, allows a precipitate containing aluminum to be obtained and, separately, a solution of NaOH, substantially exploiting the same separation principle described above for the cell comprising a cationic membrane and an anionic membrane.
- the membrane electrolysis process according to the present invention can be carried out either batchwise or in continuous. Said process is preferably carried out in continuous, i.e. by continuously feeding the extraction solution to the membrane cell (for example, in the anode compartment or in the supply compartment) and continuously extracting from the same, an equal volume of treated solution containing precipitated aluminum.
- the electrolytic solution used as catholyte is also preferably fed in continuous to the membrane cell and continuously extracted from the same in an equal volume, so as to become progressively enriched with NaOH or another alkaline metal hydroxide that is formed during the electrolytic process.
- the catholyte is recirculated in continuous to the cathode compartment and water is simultaneously fed to the same compartment in such a quantity as to keep the concentration of NaOH constant in the catholyte extracted from the same compartment.
- the additions of material in the compartments of the electrolytic cell and the withdrawals of material from the same can be effected through one or more ducts positioned directly in the compartments or along the recirculation circuits of the electrolytic solutions to the same compartments.
- the additions and withdrawals are preferably effected along the recirculation circuits, as this helps to keep the electrolysis conditions stable in the cell.
- the extraction solution is supplied to the cell in a compartment in which an electrolytic solution having a desired pH is present, for example a pH value equal to or close to that at which the electrolytic precipitation of the aluminum can start (pH about 8- 10.5) .
- the extraction solution to be treated is preferably fed to the cell in such a quantity as to not substantially alter the pH of the electrolytic solution.
- the electrolytic solution having a desired pH is preferably an aqueous solution comprising at least one salt composed of at least one cation of an alkaline or alkaline-earth metal and at least one anion having an oxidation potential higher than the oxidation potential of water under the conditions in which the membrane electrolysis step is carried out.
- the anion is preferably soluble in water within the pH range of the leaching solution.
- the anion is preferably selected from sulphate, nitrate, perchlorate, phosphate, borate and mixtures thereof, more preferably from sulphate, nitrate, perchlorate and mixtures thereof.
- the above cation is preferably Na + .
- the formation of the aluminum precipitate leads to a progressive reduction in the conductivity of the anolyte with a consequent increase in the cell voltage and, therefore, energy consumptions of the process.
- the presence of the support electrolyte ensures a sufficiently high conductivity of the anolyte, reducing the energy consumptions.
- the support electrolyte can be added to the extraction solution or, more preferably, introduced into the recirculation line of the anolyte in the anode compartment.
- the electrolysis can be started using an aqueous solution comprising the support electrolyte as anolyte, to which the extraction solution to be treated is subsequently added.
- the support electrolyte is preferably present in the anolyte in a quantity within the range of 0.1-3 moles/1 of monovalent cations.
- the precipitate containing aluminum can be separated from the anolyte by means of conventional solid/liquid separation systems known in the art.
- the precipitate can be separated, for example, by decanting.
- the decanted precipitate can then be filtered, washed and dried.
- the supernatant fraction that is recovered from the precipitate during the decanting or filtration can be advantageously partially recycled to the electrolytic treatment step, joining it with the alkaline extraction solution to be treated, so as to recirculate in the cell, the aluminum still present in the same in hydrosoluble form.
- the process of the invention can be carried out in electrochemical cells of the type known in the state of the art.
- the density of current applied to the electrodes is preferably selected within the range of 100-5, 000 A/m 2 .
- Figure 1 which schematically represents the process of the invention wherein the membrane electrolysis is effected in a single-membrane cell
- FIG. 2 which schematically represents the process of the invention wherein the membrane electrolysis is carried out in a two-membrane cell.
- an aliquot of SPL 18 is treated in a leaching unit L with an alkaline aqueous solution 19 under the conditions previously described, in order to obtain an extraction solution 21 comprising at least aluminum in hydrosoluble form, fluorides and sodium ions.
- the extraction solution 21 is fed, through lines 11 and 1, to the anode compartment 2 of an electrolytic cell 3.
- the cell 3 comprises a cathode compartment 4.
- the anode compartment 2 and the cathode compartment 4 respectively comprise an anode 5 and a cathode 6.
- the anode 5 and cathode 6 are separated in the respective compartments 2 and 4 by means of a permselective cationic membrane 7.
- An electrolytic solution (catholyte) is fed in continuous to the cathode compartment 4, which, after being subjected to electrolysis, is extracted from the cathode compartment 4 and recirculated to the head of the same compartment by means of the recirculation line 8; said electrolytic solution is preferably a solution of NaOH.
- the water present in the cell is electrolyzed with the formation of H + ions and gaseous O2 in the anode compartment 2, and OH ⁇ ions and gaseous 3 ⁇ 4 in the cathode compartment 4. Due to the effect of the difference in electric potential applied, the alkaline ions present in the anode compartment 2 (mainly Na + ) migrate towards the cathode compartment 4.
- the oxygen formed at the anode 5 is recovered through line 12.
- the hydrogen formed at the cathode 6 is also recovered through line 14.
- the H + ions produced cause a lowering of the pH with the consequent formation of a precipitate containing aluminum.
- reaction (4) leads to the formation of a precipitate of aluminum hydroxide.
- reaction (5) can also take place in the anode compartment, which leads to the formation of a cryolite precipitate NaAl(OH) + 6 NaF + 4 H + ⁇ 2 Na 3 AlF 6
- the anolyte containing aluminum in the form of a precipitate is collected from the anode compartment 2 through line 9 and fed to a solid/liquid separation system 10.
- the precipitate is separated, by means of line 15, from the aqueous dispersion generated by the electrolysis.
- the precipitate comprising aluminum is fed to an electrolytic reduction cell C of alumina to produce primary aluminium.
- the liquid fraction (supernatant) separated in the solid/liquid separation system 10 and containing aluminum remaining in hydrosoluble form, is fed, through line 20, to an accumulation tank A. At least a fraction of the solution present in the accumulation tank A is recirculated to the leaching unit L through line 17. A second fraction of the solution present in the accumulation tank A is recirculated to the head of the anode compartment 2 through the recirculation line 1.
- the chemical composition of the extraction solution fed to the electrolysis cell can be modified to favour the formation of a precipitate containing aluminum having a pre-determined composition.
- Ca 2+ ions can be added, in the leaching unit L, to the extraction solution in order to precipitate the fluorides in the extraction solution 21 in the form of CaF 2 .
- the CaF 2 can then be separated in a liquid/solid separation system 25, by removing it from the extraction solution 21 through line 22.
- the extraction solution free from fluoride ions 23 leaving the separation system 25, is fed to the cell 3, joining it with the recirculation line 1.
- the OH ⁇ ions generated by the electrolysis combine with the Na + cations that have migrated from the anode compartment, also conveying the hydration water with them, forming a solution of NaOH.
- water is also fed to the cathode compartment 4, so as to allow the electrolytic process to take place in the presence of a catholyte having a constant concentration.
- the water can be introduced, for example, into the recirculation line 8 of the catholyte, through line 16.
- the electrolysis process is preferably started by applying a potential difference to the electrodes of the membrane cell and recirculating the respective electrolytic solutions (anolyte and catholyte) in the anode and cathode compartments until a pH value is reached in the anolyte, which is close to the starting value of the precipitation of aluminum.
- the desired pH value can also be reached by adding suitable acid or base compounds.
- the extraction solution is then fed to the anode compartment preferably with a volumetric flow-rate which is such as to not substantially alter the pH of the solution recirculated in the same compartment. In this way, the substantially instantaneous precipitation of the aluminum is obtained, which is then removed from the flow leaving the compartment, preventing it from accumulating inside the anode compartment where it could damage the ion-selective membrane.
- the extraction solution is fed to the anodic solution leaving the anode compartment, before the introduction of said anodic solution to the separation system 10.
- the formation of the aluminum precipitate occurs outside the cell, preventing possible damage to the ion-selective membrane.
- the membrane can be protected, for example by positioning a diaphragm of polymeric material, e.g. polyester, close to the ion-selective membrane so as to mechanically protect the membrane from the possible abrasive action of the aluminum precipitate.
- the electrolytic cell 3 used for the membrane electrolysis of the extraction solution comprises: an anode compartment 6 in which an anode 7 immersed in an anolyte is present; a cathode compartment 4 in which a cathode 5 immersed in a catholyte is present.
- the anode compartment 6 and cathode compartment 4 are separated by a central supply compartment 2, which is separated from the anode compartment 6 by a permselective anionic membrane 9 and from the cathode compartment 4 by a permselective cationic membrane 8.
- aqueous alkaline solution (catholyte) is fed in continuous into the cathode compartment 4, which, after being subjected to electrolysis, is extracted from the cathode compartment 4 and recirculated to the head of the same compartment through the recirculation line 12; said electrolytic solution is preferably a solution of NaOH.
- An acidic electrolytic aqueous solution is fed as anolyte to the anode compartment 6, for example a solution of HF.
- the anolyte is extracted from the anode compartment 6 and recirculated to the head of the same compartment 6 through the recirculation line 16.
- the oxygen formed at the anode 7 is recovered through line 21.
- the hydrogen formed at the cathode 5 is recovered through line 22.
- An aliquot of SPL 23 is treated in the leaching unit L with an alkaline aqueous solution 19 under the conditions previously described, so as to obtain an extraction solution 1 comprising at least aluminum in hydrosoluble form, fluorides and sodium ions.
- the extraction solution 1 is fed to the supply compartment 2.
- the supply of extraction solution 1 is preferably effected with a flow-rate which is such that the electric conductivity in the cell during the electrolysis is kept substantially constant and consequently the cell voltage is also kept constant.
- the Na + ions of the extraction solution circulating in the central supply compartment 2 migrate towards the cathode compartment 4 through the permselective cationic membrane 8 whereas the anions present in the extraction solution (OH-, Al(OH)4 ⁇ and F ⁇ ) migrate towards the anode compartment 6 through the permselective anionic membrane 9.
- the H + ions produced by the anodic reaction cause a lowering of the pH with the consequent formation of a precipitate containing for example A1F 3 .
- Diluted hydrofluoric acid can optionally be fed to the anode compartment 6, for favouring the precipitation of A1F 3 , for example on the recirculation line of the anolyte 16 through line 15.
- the precipitate containing aluminum is extracted from the anode compartment 6 through line 17 and fed to a solid/liquid separation section 20 (e.g. decanter) .
- the decanted precipitate leaves the separator through line 18.
- the precipitate containing aluminum can be filtered, washed and dried before being re-used.
- the precipitate of A1F 3 is fed to an electrolytic reduction cell C of alumina for the production of primary aluminum.
- the liquid fraction (supernatant) which is separated in the separation system 20 can be partially recirculated through line 16 to the head of the electrolytic anode compartment, so as to recover, by precipitation, the aluminum still present in the same in hydrosoluble form.
- the OH ⁇ ions generated by the electrolysis combine with the Na + cations that have migrated from the anode compartment, which also carry the hydration water, forming a solution of NaOH.
- water is also fed to the cathode compartment 4, so as to allow the electrolytic process to be carried out in the presence of a catholyte having a constant concentration of NaOH.
- the water can be introduced, for example, into the recirculation line 12 of the catholyte, through line 11.
- the addition of the extraction solution 1 in the recirculation line 10 of the central supply compartment 2 causes an increase in the overall volume of solution to be treated.
- a fraction of the extraction solution treated leaving the supply compartment 2 is fed to an accumulation tank A, through line 14.
- a second fraction of the above- mentioned treated extraction solution is recirculated to the head of the supply compartment 2 through line 10 to recover the residual aluminum present in hydrosoluble form.
- An electrolytic cell was used for the electrolysis, with electrodes having surfaces equal to 1 dm 2 and equipped with a permselective cationic membrane.
- a 20 A current (current density: 200 A/m 2 ) was fed to the electrodes .
- Both the anolyte and catholyte were circulated in the respective anode and cathode compartments with a flow-rate equal to about 30 1/min and subjected to electrolysis until a whitish precipitate had started to form. Upon the appearance of the precipitate, the electrolysis was interrupted in order to characterize the catholyte. Upon the appearance of the precipitate, 3.05 1 of catholyte solution having a concentration of NaOH of 212.3 g/1, were present in the cell. The solution in the anode compartment reached a pH equal to about 9.8.
- the electrolysis process was then restarted, supplying further extraction solution to the anode compartment and extracting from the same, the dispersion containing the precipitate which was fed to a decanter.
- the extraction solution was fed to the anode compartment joining it with the recirculated anolyte in such a proportion, with respect to the latter, as to not substantially modify the pH of the solution in the anode compartment.
- the clarified solution at the outlet of the overflow of the decanter was sent to an accumulation tank from where it could be taken for being recirculated to the electrolytic cell.
- the decanted fraction containing the precipitate was collected in a beaker and filtered, obtaining a cake containing aluminum.
- the cake was washed with water and dried at a temperature of 120°C for 12 hours.
- the electrolytic process was carried out for 3 hours, feeding a total quantity of about 2.3 1 of a solution of NaAl(OH) 4 .
- the anolyte and catholyte were circulated in the cell and electrolyzed until a precipitate had started to form in the anode compartment.
- the electrolysis was then interrupted in order to characterize the catholyte.
- 3.16 1 of catholyte having a concentration of NaOH equal to 238.4 g/1, were present in the cathode compartment, whereas the solution in the anode compartment reached a pH of about 9.6.
- the electrolysis process was then restarted, supplying further extraction solution to the anode compartment and extracting from the same, with the same flow-rate, the dispersion containing the precipitate, which was fed to a decanter.
- the extraction solution was fed to the anode compartment joining it with the recirculated anolyte in such a proportion, with respect to the latter, as to not substantially modify the pH of the solution in the anode compartment .
- the decanted fraction containing the precipitate was collected in a beaker and filtered, obtaining a cake containing aluminum. The cake was then washed with water and dried at a temperature of 120°C for 12 hours.
- the electrolytic process was carried out for 5 hours and 30 minutes, feeding a total quantity of about 2.0 1 of alkaline extraction solution.
- the filtered, washed and dried solid obtained in the anode compartment weighed 161.1 g and was substantially composed of a mixture of Na 3 AlF 6 (88% by weight) and Al (OH) 3 (12% by weight) .
- EXAMPLE 3 Extraction solution containing NaAl (OH) 4
- the extraction solution was fed to the central compartment of a cell equipped with a cationic permselective membrane and an anionic permselective membrane as described above with reference to figure 2.
- the electrolysis process was carried out for about
- the final extraction solution circulating in the central compartment had a volume of 2.12 1 and the following composition: NaAL(OH)4 at a concentration of 20.53 g/l, NaF at a concentration of 7.07 g/l and free NaOH at a concentration of 1.50 g/l.
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CN113249578B (en) * | 2021-05-06 | 2022-07-12 | 中南大学 | Recycling treatment method of fluorine-containing waste generated by aluminum electrolysis and aluminum fluoride product |
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US4113831A (en) * | 1975-10-02 | 1978-09-12 | National Fluoride And Chemical Corporation | Recovery of sodium fluoride and other chemicals from spent carbon liners |
GB8301974D0 (en) * | 1983-01-25 | 1983-02-23 | Alcan Int Ltd | Aluminium fluoride from scrap |
US4889695A (en) * | 1985-02-20 | 1989-12-26 | Aluminum Company Of America | Reclaiming spent potlining |
US5141610A (en) * | 1988-04-19 | 1992-08-25 | Vaughan Daniel J | Electrodialytic process for restoring sodium hydroxide etchants for aluminum |
CA2118943C (en) * | 1992-07-24 | 2004-04-20 | Ian Lewis Kidd | Treatment of solid material |
RU2092439C1 (en) * | 1995-08-09 | 1997-10-10 | Акционерное общество открытого типа "Всероссийский алюминиево-магниевый институт" | Method of treatment of fluorine containing aluminium production waste by electrolysis |
US20120292200A1 (en) * | 2008-04-03 | 2012-11-22 | Shekar Balagopal | Electrolytic process to produce aluminum hydroxide |
CN101306798B (en) * | 2008-06-24 | 2010-08-25 | 中国铝业股份有限公司 | Process for treating waste liner of aluminium cell catalyzed by coal |
RU2462418C1 (en) * | 2011-06-07 | 2012-09-27 | Эдвард Петрович Ржечицкий | Method of producing aluminium fluoride |
RU2472865C1 (en) * | 2011-08-31 | 2013-01-20 | Государственное образовательное учреждение высшего профессионального образования "Иркутский государственный технический университет" (ГОУ ИрГТУ) | Method of processing fluorine-containing wastes from electrolytic production of aluminium |
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