CA1108375A - Recovery of magnesium from magnesium silicates - Google Patents
Recovery of magnesium from magnesium silicatesInfo
- Publication number
- CA1108375A CA1108375A CA310,288A CA310288A CA1108375A CA 1108375 A CA1108375 A CA 1108375A CA 310288 A CA310288 A CA 310288A CA 1108375 A CA1108375 A CA 1108375A
- Authority
- CA
- Canada
- Prior art keywords
- magnesium
- solution
- sulfate
- silicate
- naturally
- 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.)
- Expired
Links
- 239000000391 magnesium silicate Substances 0.000 title claims abstract description 12
- 239000011777 magnesium Substances 0.000 title claims description 40
- 229910052749 magnesium Inorganic materials 0.000 title claims description 31
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims description 30
- 238000011084 recovery Methods 0.000 title description 4
- 235000012243 magnesium silicates Nutrition 0.000 title description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 claims abstract description 25
- 235000010755 mineral Nutrition 0.000 claims abstract description 25
- 239000011707 mineral Substances 0.000 claims abstract description 25
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 claims abstract description 10
- HCWCAKKEBCNQJP-UHFFFAOYSA-N magnesium orthosilicate Chemical compound [Mg+2].[Mg+2].[O-][Si]([O-])([O-])[O-] HCWCAKKEBCNQJP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052919 magnesium silicate Inorganic materials 0.000 claims abstract description 10
- 235000019792 magnesium silicate Nutrition 0.000 claims abstract description 10
- 229910052943 magnesium sulfate Inorganic materials 0.000 claims abstract description 6
- LPHFLPKXBKBHRW-UHFFFAOYSA-L magnesium;hydrogen sulfite Chemical compound [Mg+2].OS([O-])=O.OS([O-])=O LPHFLPKXBKBHRW-UHFFFAOYSA-L 0.000 claims abstract description 6
- 235000019341 magnesium sulphate Nutrition 0.000 claims abstract description 5
- 230000001590 oxidative effect Effects 0.000 claims abstract description 5
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 claims description 42
- 239000000243 solution Substances 0.000 claims description 30
- 229940091250 magnesium supplement Drugs 0.000 claims description 29
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 28
- 229910052742 iron Inorganic materials 0.000 claims description 16
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 13
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 10
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 230000029087 digestion Effects 0.000 claims description 6
- 238000000605 extraction Methods 0.000 claims description 6
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 5
- 150000002681 magnesium compounds Chemical class 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- 239000010941 cobalt Substances 0.000 claims description 4
- 229910017052 cobalt Inorganic materials 0.000 claims description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 4
- 229960003390 magnesium sulfate Drugs 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- 239000003513 alkali Substances 0.000 claims description 3
- 239000012045 crude solution Substances 0.000 claims description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 2
- 239000000908 ammonium hydroxide Substances 0.000 claims description 2
- 239000007900 aqueous suspension Substances 0.000 claims description 2
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 abstract description 18
- 239000000347 magnesium hydroxide Substances 0.000 abstract description 18
- 229910001862 magnesium hydroxide Inorganic materials 0.000 abstract description 18
- 229910000021 magnesium carbonate Inorganic materials 0.000 abstract description 11
- 239000001095 magnesium carbonate Substances 0.000 abstract description 9
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 abstract description 6
- 235000001055 magnesium Nutrition 0.000 description 26
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 description 20
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 18
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 18
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 17
- 235000012254 magnesium hydroxide Nutrition 0.000 description 16
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 14
- 238000006243 chemical reaction Methods 0.000 description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 239000011575 calcium Substances 0.000 description 10
- 229910052791 calcium Inorganic materials 0.000 description 10
- 229960000816 magnesium hydroxide Drugs 0.000 description 10
- 239000000395 magnesium oxide Substances 0.000 description 10
- 235000012245 magnesium oxide Nutrition 0.000 description 10
- 239000011734 sodium Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 239000002585 base Substances 0.000 description 7
- 159000000003 magnesium salts Chemical class 0.000 description 7
- 229960002366 magnesium silicate Drugs 0.000 description 7
- 229910052708 sodium Inorganic materials 0.000 description 7
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 6
- 235000014380 magnesium carbonate Nutrition 0.000 description 6
- 229960000869 magnesium oxide Drugs 0.000 description 6
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 150000004760 silicates Chemical class 0.000 description 6
- CWBIFDGMOSWLRQ-UHFFFAOYSA-N trimagnesium;hydroxy(trioxido)silane;hydrate Chemical compound O.[Mg+2].[Mg+2].[Mg+2].O[Si]([O-])([O-])[O-].O[Si]([O-])([O-])[O-] CWBIFDGMOSWLRQ-UHFFFAOYSA-N 0.000 description 6
- 239000010425 asbestos Substances 0.000 description 5
- 229910052620 chrysotile Inorganic materials 0.000 description 5
- 229960001708 magnesium carbonate Drugs 0.000 description 5
- 229910052895 riebeckite Inorganic materials 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 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 4
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- WYTGDNHDOZPMIW-RCBQFDQVSA-N alstonine Natural products C1=CC2=C3C=CC=CC3=NC2=C2N1C[C@H]1[C@H](C)OC=C(C(=O)OC)[C@H]1C2 WYTGDNHDOZPMIW-RCBQFDQVSA-N 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000005755 formation reaction Methods 0.000 description 4
- 229910001385 heavy metal Inorganic materials 0.000 description 4
- 229910052700 potassium Inorganic materials 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000011435 rock Substances 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 3
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 229910000288 alkali metal carbonate Inorganic materials 0.000 description 3
- 150000008041 alkali metal carbonates Chemical class 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 239000000292 calcium oxide Substances 0.000 description 3
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 3
- 239000000356 contaminant Substances 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 238000002386 leaching Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 150000002739 metals Chemical group 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000005273 aeration Methods 0.000 description 2
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 2
- 229910052626 biotite Inorganic materials 0.000 description 2
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 229910001629 magnesium chloride Inorganic materials 0.000 description 2
- JESHZQPNPCJVNG-UHFFFAOYSA-L magnesium;sulfite Chemical compound [Mg+2].[O-]S([O-])=O JESHZQPNPCJVNG-UHFFFAOYSA-L 0.000 description 2
- 238000010979 pH adjustment Methods 0.000 description 2
- 229910052628 phlogopite Inorganic materials 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 239000000454 talc Substances 0.000 description 2
- 229910052623 talc Inorganic materials 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 230000001131 transforming effect Effects 0.000 description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052936 alkali metal sulfate Inorganic materials 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 229910052612 amphibole Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 229910052885 anthophyllite Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- NWXHSRDXUJENGJ-UHFFFAOYSA-N calcium;magnesium;dioxido(oxo)silane Chemical compound [Mg+2].[Ca+2].[O-][Si]([O-])=O.[O-][Si]([O-])=O NWXHSRDXUJENGJ-UHFFFAOYSA-N 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 229910001919 chlorite Inorganic materials 0.000 description 1
- 229910052619 chlorite group Inorganic materials 0.000 description 1
- QBWCMBCROVPCKQ-UHFFFAOYSA-N chlorous acid Chemical compound OCl=O QBWCMBCROVPCKQ-UHFFFAOYSA-N 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- FDKCTEWMJWRPDS-UHFFFAOYSA-N dialuminum;trimagnesium;trisilicate Chemical compound [Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-][Si]([O-])([O-])[O-].[O-][Si]([O-])([O-])[O-].[O-][Si]([O-])([O-])[O-] FDKCTEWMJWRPDS-UHFFFAOYSA-N 0.000 description 1
- 229910052637 diopside Inorganic materials 0.000 description 1
- TXKMVPPZCYKFAC-UHFFFAOYSA-N disulfur monoxide Inorganic materials O=S=S TXKMVPPZCYKFAC-UHFFFAOYSA-N 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 229910052634 enstatite Inorganic materials 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000002657 fibrous material Substances 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 239000002223 garnet Substances 0.000 description 1
- 238000001033 granulometry Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- 235000013980 iron oxide Nutrition 0.000 description 1
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 150000002680 magnesium Chemical class 0.000 description 1
- BBCCCLINBSELLX-UHFFFAOYSA-N magnesium;dihydroxy(oxo)silane Chemical compound [Mg+2].O[Si](O)=O BBCCCLINBSELLX-UHFFFAOYSA-N 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 229910052832 pyrope Inorganic materials 0.000 description 1
- 229910052611 pyroxene Inorganic materials 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical class [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 229910052889 tremolite Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/40—Magnesium sulfates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/14—Magnesium hydroxide
- C01F5/22—Magnesium hydroxide from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/24—Magnesium carbonates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
Abstract
A B S T R A C T
Substantially pure magnesium hydroxide or carbonate is obtained from naturally-occurring minerals containing at least 10% magnesium silicate by adjusting the pH a magnesium bisulfite solution obtained therefrom to between 8.0 and 8.9 under an oxidizing atmosphere thereby to produce a magnesium sulfate solution from which the magnesium hydroxide or carbon-ate can be readily obtained.
Substantially pure magnesium hydroxide or carbonate is obtained from naturally-occurring minerals containing at least 10% magnesium silicate by adjusting the pH a magnesium bisulfite solution obtained therefrom to between 8.0 and 8.9 under an oxidizing atmosphere thereby to produce a magnesium sulfate solution from which the magnesium hydroxide or carbon-ate can be readily obtained.
Description
~ 3~^~S
The present invention relates to a process for recoverjng substantially pure magnesium hydroxide or carbonate from naturally occurring minerals containing magnesium sili-cate.
PRIOR ART
The possibility of a reaction of naturally occurring silicates of magnesium with sulfur dioxide in the presence of water is known, reference to such a reaction being made in early patents, such as U.S. Pat. no. 690,513, Jan. 7, 1902.
This reaction is possible because S02 in water is a much stronger acid than silicic acid. Depending on the relative amount of sulfur dioxide and magnesium silicate, the sulfite or - the bisulfite can be obtained. With an excess of S02, the bisulfite is formed. Thus, with chrysotile, the following reaction is observed:
MgO-2SiO2.2H~0 + 502/H20(excess~ 3Mg(HS03~2 + 2SiO2 ~
Mg bisulfite insoluble silica On the other hand, if the magnesium silicate is in 2D excess~ then the sulfite rather than the bisulfite is the final - product:
3MgO.2SiO2.2H20(excess) ~ 3S02/H20---~ 3MgS03 ~ 2SiO2 ~
In fact, a solution of bisulfite in water has the tendency to be transformed into a solution of sulfite by loss --of sulfur dioxide, if the solution is aerated~ in order to remove the free S02. Also the treatment of a solution of sulfite by S02 will allow the formation of the corresponding bisulfite, thus showing clear by the equilibrium which exists between these species, as shown by the following equation:
Mg(HSO3~2~ M9s03 ~ S2 ~ H2 Sulfur dioxide is a most interesting material for the - extractlon of magnesium from mineral sources of this metal because it can be prepared on site by the combustion of sulfur, a very abundant and cheap material or recovered from the roasting operations of sulfides which are very common in the mining industry. The processing of crude petroleum and the treatment of flue gas from the combustion of coal are also important sources of sulfur or sulfur dioxide.
The silica,es which contain magnesium are numerous and of frequent occurrence. The common mineral species con-taining significant amounts af magnesium bounded to silica are listed in the Following Table I:
TABLE I
SILICATES OF MAGNESIUM
Name Formula % Mg Serpentine M96(si4olo)(oH)8 26 Talc Mg3(Si4olo)(oH)2 19 Phlogopite KM93(Alsi3olo)(oH)2 17 Biotite K(Mg,Fe)3 (AlSi301o)(0H)2 13 Chrysolite (olivine) (Mg,Fe)2SiO4 23 Pyrope (garnet) M93Al2~sio4)3 15 Enstatite (pyroxene) Mg2(Si206) 24 ?
20 Diopside CaMg(Si2)6) 11 Chlorite Mg3(Si40lo)(o~l)2M93(oH)6 32 Tremolite Ca2Mgs(si8o22)(oH)2 15 Anthophyllite (Mg,Fe)7(si8o22)(oH)220 In the case of serpentine, large amounts of the incorporated fibrous chrysotile ~3MgO.2SiO2.2H20) are mined for the obtention of the fibrous material, asbestos. Also, the amphibole variety of silicates have led to the extraction _ of fibers mainly of crodicolite and amosite ~5.5FeO, 1.5MgO, 8SiO2.H20) varieties.
In most if not all of the mineral operations where the above silicates are involved, large amounts of rocks rich in magnesium have to be crushed in order to obtain the desired product, such as asbestos -Fiber, talc or simply aggregate for concrete. For example, in the case of chrysotile asbestos, the annuàl production of this material in Canada is of the order of 1.5 million tons per year. Since the fiber represents about 5%
of the weight o-f the rocks involved in the extraction, the total mass of mineral which is grounded in the course of the extraction is in the range of 30 million tons per year. The granulometry of the waste rocks or tailings~ varies greatly but a significant portion,between one and five percent,is already very finely grounded. Even if only one tenth of one percent is in the appropriate form for diges~ion by S02 for the extrac-tion of magnesium the amount of silicate thus made available, 30,000 tons, appears very important. At the present time, there is no use for such tai~ings. In fact, specially with the finely divided material, there is an environmental problem created by dust and an expeditures to carry these tailings on top of huge piles of wastes. Consequently, the cost of finely divided serpentine at the outlet of an asbestos mine is minimal, if not negative.
The chemistry of the sulfite or bisulfite of mag-nesium shows that this material can be transformed into several magnesium derivatives having useful properties. By thermal decomposition, the sulfite can lead to the formation of mag-nesium oxide with evolution of S02. In the course of this process however, some sulfite is transformed into sulfate:
MgS03 ~ MgO ~ S0 ~ 3 By exchange with calcium chloride, the sulfite can give magnesium chloride:
MgS03 + CaC12~ CaS03 ~ ~ M9C12 The magnesium hydroxide can be formed by treatment of the sulfite with a strong base, such as NaOH. Further heat treatment of Mg(OH)2 leads to magnesium oxide:
MgS03 ~ 2NaOH-----~ Mg(OH)2 ~ ~ Na2S03 Mg(OH)2 ~> MgO ~ H20 The carbonate can be obtained through a similar exchange reaction:
MgS03 ~ Na2C~3---~3 MgC03 ~ t Na2S03 All these reactions are wel1 known and do not repre-sent a novelty in the area of extraction and transformation of magnesium salts but show the interest of magnesium sulfite or even sulfate as a starting material for the formation of magnesium salts.
Many uses for the magnesium salts, MgO,Mg(OH)2, MgC12, MgC03, MgS04, require a product of very high degree of purity. For example' a very important use of magnesium oxide ; 20 is in the manufacture of refractory material. The presence of a few percent of impurities in the oxide modiFies the re-sistance of MgO to high temperature in a very adverse way and renders the material useless as reFractory. The usual impuri-ties are calcium oxide, aluminum oxide and iron oxides (either ~
ferrous or ferric). In TRAITE DE CHIMIE MINERALE, Paul BAUU, ~ ;
TOMEI, p. 115, 1951 it is shown that the presence of small amounts of contaminants decreases the melting temperature of the magnesium oxide by several hundred degrees. Another area where the purity of the magnesium salt is critical is the for-mation of the metal by the electrolysis of magnesium chloride~
, ~ ~ 3~3~ ~
These two examples from areas representing major uses for magnesium illustrate the need for very pure magnesium salts.
The naturally occurring magnesium silicates are very seldom in the pure state when found in nature. The secondary metals can be either part of the stoichiometry of the silicate of magnesium or simply mixed with the silicate. For example, chrysotile wastes 3MgO.2SiO2.2H20, are contaminated by 6% by weight of iron, plus traces of nickel and chnome. Also, up to one percent of calcium can be Found in many samples. In the case of chrysotile, the iron is mixed with crystal, in a very intimate manner, but not chemically combined to the main structure of the silicate. In other instances, for example with amosite~ another variety of asbes-tos, (5.5FeO, l.SMgO, 8SiO2.H20) the iron is part of the crystal structure. In ; practice, many of the silicates containing magnesium are meta-morphic rocks, which implies that there is always a certain amount of substitution of magnesium by another metal such as iron, calcium or aluminum. A good illustration of this situ-ation is given by the formula of biotite K(Mg,Fe) (AlSi301o) (OH)2 or phlogopite KMg3 (AlSi301o) (~)2 When sulfur dioxide is used in combination with water, to leach magnesium from a silicate, all the other metals present, either combined or mixed, such as calcium and iron are dissolved at the same time. And the crude sulfite solution, thus obtained, contains such impurities as calcium and iron which render the crude sulfite improper to be used as a source of pure magnesium compound.
The problem of obtaining a pure magnesium compound from S02 leaching is well illustrated by the patent of Trubey, et al, U.S. patent 3,085,858, April 16, 1963. In the case of this patent, the leaching was done by S02 on dolomite, a d ~
natural mixture of calcium oxide and magnesium oxide rather than on a silicate. This patent reports thak even with this simple source of magnesium, 3% of CaO was contaminating the magnesium oxide after processing, in spite of careful pre-cautions not to leach calcium in the course oF the digestion of the mineral. lhe approach of Trubey which controls the presence of calcium by using a stream of C02 cannot be applied to eliminate iron, heavy metals and aluminum from a solution of crude sulfite of magnesium as obtained from naturally-occurring silicates.
SUMMARY OF T~IE IN\IENTION
The object of the pr~sent invention is related to the treatment of the crude solution of the S02-leached magnesium obtained from a silicate and contaminated by all the minor components of a natural silicate namely sodium, potassium~ .
calcium, iron, aluminum traces of heavy metals such as chrome and nickel 9 in order to remove these impurities and to obtain a magnesium compound oF very high purity.
In accordance with the present invention, there is now provided an improved process for recovering substantially pure magnesium hydroxide or magnesium carbonate from naturally-occurring minerals containing magnesium silicate. The improved process of the present invention comprises digesting an aqueous suspension of a naturally~occurring mineral containing mag-; nesium silicate with sulfur dioxide to produce a crude solution of magnesium bisulfite, adjusting the pH of said magnesium bisulfite solution to between 8.0 and 8.9 under an oxidizing atmosphere thereby to precipitate the impurities contained therein and causing the magnesium bisulfite to be converted to magnesium sulfate and precipitating the magnesium as magnesiumhydroxide or carbonate by adjusting the pH of the magnesium ~ 3~
bisulfite solution to between 9.5 and 10.5 with an alkali metal hydroxide or by treatment with an alkali metal carbonate, and recovering the substantially pure magnesium hydroxide or carbonate thus produced.
A main feature of the present invention is tha~ the metallic contaminants found in naturally-occurriny minerals containing magnesium silicate can be selectively precipitated from a bisulfite solution obtained by leaching the naturally-occurring minerals by the adjustment of the pH in the range of 8.0 to 8.9 under an oxidizing atmosphere in opposition to prior art procedure where each contaminant has to be eliminated sepa-rately and where mixtures of magnesium sulfite and sulfate were found in the end product.
Another advantage of the present invention is that beside obtaining the desired salt of magnesium a good pro-portion of the starting sulfur dioxide can be recovered in the form of ammonium or alkali metal sulfate, the latter having well known commercial utilities.
A further advantage of the present invention is that since the process oxidizes the bisulFite formed to sulfate, the pollution problems generated by the handling of sulfites and recovery of sulfur dioxide are eliminated. It is generally known that release of sulfur dioxide is highly undesirable in industrial processes because of the adverse effect of sulfur dioxide on the environment.
The naturally-occurring mineral containing magnesium silicate which can be used in accordance is preferably one which contains at least 10% magnesium, and ~here the specific impurities such as calcium is not more than 20%~ iron 15%, aluminum 10%, agglomerated chrome, nickel and cobalt 2%, while the total agglomerated alkali (Na and K) do not exceed 15%.
~ 3~ ~
Another feature o~ the starting mineral is that its mesh size should be smaller than 60 with a mesh size of at least 200 to 325 being preferred. It is possible to use a mineral contain-ing less than 10% magnesium or having a mesh size greater than 60, but it should be appreciated that yield and purity of the magnesium compound obtained being of commercial importance, the exercise of the improved process of the present invention will be carried out under the preferred conditions which give the superior results.
The adjustment of the pH to from 8.0 to 8.9 is carried out with ammonium or alkali metal hydroxide such as sodium or potassium hydroxide. The preferred pH adjustment is about 8.5 and is carried out under an oxldizing atmosphere which is obtained by bubbling air or oxygen in the solution and in the presence of a strong base such as an alkali metal ~-~ hydroxide whereby magnesium hydroxide is precipitated or an alkali metal carbonate whereby magnesium carbonate is precipi-tated. The cobalt or nickel present in the starting mineral will accelerate the oxidation of the bisulfite to sulfate.
In the final precipitation step the pH of the a~justment to form 9.5 to 10.5 with 9.8 to 10.2 being preferred is also carried with a strGng base such as an alkali metal hydroxide whereby magnesium hydroxide is precipitated or an alkali metal carbonate whereby magnesium carbonate is precipi-tated.
,~
' .
3 ~ ~
DETAILED DESCRIPTION
Step 1- DIGESTION OF THE MAGNESIUM-BEARING MINERAL BY SULFUR
DIOXIDE IN T~IE PRESENCE OF WATER
The naturally-occurring mineral containing magnesium silicate is a divided material with a mesh size smaller than 60 mesh. With a product larger than mesh 60, the reaction ; proceeds but in order to have a faster and more complete reaction, it is preferable to have a material finer than mesh 200. The volume of water present is also related to the ease of reaction. A ratio of mineral weight to volume of water that allows for the solubility of magnesium bisulfite is important.
The reaction of digestion can be performed at atmospheric pressure or at a higher pressure. At atmospheric pressure, it is advisable to avoid too high temperatures, above 50C, in order not to decrease the solubility of S02 in water. At 25C, with a water ratio of 20 g of mineral (for example, serpentine) per liter of water the reaction is complete after, about, three hours. It is indicated, when the reaction nears completion, to ~; stop the addition of S02. In that manner, all the remaining S02 present in solution reacts with the magnesium-bearing mineral to give a solution of bisulfite free of S02. This simplifies the environmental considerations related with the presence of S02.
When the digestion is completed, the reaction mixture is filtered to remove the silica and any unreacted solid material present. In that manner, a sGlution of bisulfite, -~ sulfite and sulfate of magnesium and other metals present, such as calcium and iron is obtained. The digestion is done under very acidic conditions, the pH of the solution being kept in 30 the range of 0.10 to 2.0 at this stage.
Step 2- SELE~TIVE PRECIPITATION OF METALLLC IMPURITIES FROM
THE CRUDE SOLUTION_ ____ The precipitation of the impurities from the bisulfite solution is done by transforming the sulfite or bisulfite into sulfate in an oxidizing atmosphere while in-creasing the pH of the solution in the range of 8.5 by addition of a strong base. The advantage of transforming the sulfite into sulfate is to fall upon a stable and uniform type of anion at this stage. The solution of bisulf;te is easily oxidi~ed by air and this oxidation is much accelerated by the presence of traces of heavy metals, such as cobalt. Since the presence of some sulfate is unavoidable, it is simpler to proceed to full oxidation at this stage and thus avoid having a mixture of salts as the end products. In practice, it has been found that aeration of the solution of crude bisulFite for about one hour at room temperature allows the transformation of bisulfite to sulfate to be complete.
While this aeration is proceeding, the pH of the solution is raised to a value of 8.5 by addition of a basic reagent. Ammonia or an alkali metal hydroxide for example sodium hy~roxide have proved to be appropriate base for this pH
adjustment. Iron, calcium, aluminum and other heavy metals are thus precipitated at that pH. By filtration, they are elimi-nated and the clear solution which contains magnesium sulfate is obtained.
Step 3- RECOVERY OF MAGNESIUM SALTS
The precipitation of magnesium hydroxide is obtained by further increase of the pH to 9.S - 10.5 by a strong base such as an alkali metal or ammonium hydroxide. By filtration, very pure magnesium hydroxide is recovered, indicating a purity of over 99%. If magnesium carbonate is the desired product, this second raise of pH is replaced by addit;on of sodium carbonate.
Step 4- RECOVERY OF SULFATES
When the magnesium salts have been recovered, there remains a solution of the sulfate of the base which has been used (sodium or ammonium) and the sulfate of the small amount of alkali metals present in the starting silicate. By evapo-ration of the filtrated, ammonium sulfate (or sodium sulFate) can be obtained.
The sequential operations are represented by the following Flowsheet I.
`3~
F WSHEET I
Silicate of Mg Bisulfite of Mg~ Silica :
~ + SO2/-H10 ~ Sulfite of ~ enreacted : impurities Ca,Fe,Al,Na........ silicate ___ _~
(discarded~
Bisulfite of Mg STEP 2 Precipitate Solution Sulfite of O ~OH-~pH 8.5)> of Fe,Ca, ~ of sulfate Ca,Fe,Al,Na.... 2 Al,................ Mg,Na,K
(discarded) Solution Mg(OH)2~ Su1fate of sulfate OH (pH 10) or + solution of Mg,Na,K..... or MgCO3~ Na~ or NH
: . Na2C3 4 :-Sulfate SulFate of Solution of : solution STEP 4~ Na or NH~ + sulFate of Na~ or NH4 . . alkali (discarded) The present inven-tion will be more fully understood by referring to the following Examples which are given to illustrate the invention rather than limit its scope.
In a 2 liter flask, a 40 9 sample of chrysotile mesh ~ 200 - 325 is suspended in 1,500 ml of water. The atmosphere over the suspension is kept saturated with S02 and the liquid phase is strongly agitated at room temperature. After a contact of 3.5 hours, the suspension is filtered over asbestos.
The filtrate is then treated with sodium hydroxide (44 ml NaOH 10%) in order to bring the pH to 8.6. The solution is aerated as it is neutralized by a stream of air (150 ml/
min), for 1.5 hour, in order to oxidize the sulfite to sulfate.
After filtration, the pH of the sulfate solution of magnesium is raised to 9.9 by addition of 204.5 ml NaOH 10%.
Magnesium hydroxide (15.6 9) is thus precipitated with a yield of 68% related to the amount of magnesium available in the starting material. The analysis of the precipitate gives 99.1%
Mg(OH)2.
By evaporation9 71.5 g of Na2S04.7H20 is recovered, a yield of 82% .
A similar procedure is used for the other examples.
.
By proceeding in the same manner and using the con-ditions set forth in Table Il, the results shown in Table II
are obtained. It is noted that Example 8 is given to illustrate the decreased yield obtained with the process of the present invention when using a mineral wherein the mag-nesium conten~ is less than 10% by weight.
3~
_ _ _ ._ _ _ _ _ - ,`,t. _ CJ
.~1 ~ N ~ ~0 ':t 1~ N O N ~ 1 ~ ~ ~e _ _ _ _ _ _ _ _ _ ~~ ~ K
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O O T ~_ O ~_ ~ ~ Ln O N O O N
E ~_ o~ a~ t~ ~ O~ CJ~ c~ I~ O'- ~:1 ci~
o.~ a~ o o~ ~ a~ ~n o~ o- a- o~ ol ~> ~ . _ _ _ _ _ _ _ _ _ CL T .. O Cl~ ~_ O O a~ al ~_ O Cl~ O
LLI Q ~ _ a~ O O a'~ CJ~ O O C~l O O
` j' ~I oO~i . _ ,__ ___ '__ _ _ ~' . _ r ~ , ~ ~ s Ln ~ ~ o ~ r~ Ln o o Ln Ln .i C,'X~ ,_ r- . ~ . . l C~J ~' r~ .
. __ _. _ _ _ _ _ _ __ L~ . ._ . N ~ C~J ~ ~ c .. , . N X S la (~ IU O ~ O 1~ 115 I~J la 1~ .
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I~ I ~O IX) Ln ~O d' ~n ~t ~o ~t CL ~ . CO CO ~ O~C~ I 00 __ CO T T
~ ~ Io~ Io O C To o To o T O O
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.~ _ _ . _ _ __ _ _ _ _ .' '. 0 N~ L~ ~LO O ~'1 cn L~i N O O N Ln ~ ~ Os ~-) ~ 1~ t~> ~ IY~ ':t e~ ~ d ~
C:l~ .
L~ ,0 _ _ _ __ , _ ~:. l ~_ I v~ . O oo O cn c~ cn co ~n o cn +
m o. QJ ,_ O _ O O O o O o _ . s. ~.
_ _ _ _ _ ~n o o o o Ln o Ln cn ~' S CD N n NO N Ln LN ON N N ON N ., N O N O O ~ t~ O O O O O S_ .
- 1~) N l LD ~0 U~ ~0 N ~0 N . J~ Vl . , _ . _ _ _ _ _ _ _ +
l ~_ : ~ _ a)l l LD .-- N ~ '' S ~J
CZ: ,_ O O O ~O O O ~O O C D
C~ ;~51 . _ _ _ _ _ _ __ _ _ ~ ~ 40-:E . cq~ ~ o N al ~
.~ ~ 0~ . _~ ; OO O O O ~ ~ L,l_~
~ ., Lr~ Ln Ln . ~n C~l N CJ- O cn s 8 C-c~ EQ--~ ~D L~ Ln O O .- N . ~ _ Ln . ~ O N N N ~1 cn ~n ~o ~ o ~ c~ >
. N N N N .-- _ CYI r-- _- N _ 2:
. ~S ~ . T L
CJI E O Ln N O O O Ln O Ln O Ln _ O
= ~_ : _ _ _ ~ _ _ _ _ _ _ N L ._ ;~
aJ cJ a~ ^ CD ^ +~ +~ I
C~ CLJ C~ r- C~ ~ _ CL C '_ ~ C~ C C CU
C ~ ~ ~o ~ o '~ ~o '' '1~ ~o ~ ~ t~ '-1 CL' ~ C~ CL V ~
c~ ~: L') c cn ~ L~ o c L~ o ~ ~ o ~ ._ ~ .~ ~ _ n~ ;- cu L~ V CLI ~n Q ~ _ ~ I_ o L/~ L ~ o L~ ~ LQ
s ~ c ' s ~ c~ L~ c s E o o c *
_.LQ _ Lf) ~_ ~ LQ _ ~ . Q. ~5 cl c~ c~ * ~
. . . . . _ __ _ _ _ _ _X O ~ N C~> ~ Ln ID t~ Cl~ C~ O r--__ Ll . _ _ _ __ _ ,_ r--- .
By proceeding in the same manner as in Ex. 1-11 and substituting the appropriate amount of sodium carbonate for the sodium hydroxide in Step 2 there is obtained magnesium carbon-ate in substantially quantitative yields.
.
The present invention relates to a process for recoverjng substantially pure magnesium hydroxide or carbonate from naturally occurring minerals containing magnesium sili-cate.
PRIOR ART
The possibility of a reaction of naturally occurring silicates of magnesium with sulfur dioxide in the presence of water is known, reference to such a reaction being made in early patents, such as U.S. Pat. no. 690,513, Jan. 7, 1902.
This reaction is possible because S02 in water is a much stronger acid than silicic acid. Depending on the relative amount of sulfur dioxide and magnesium silicate, the sulfite or - the bisulfite can be obtained. With an excess of S02, the bisulfite is formed. Thus, with chrysotile, the following reaction is observed:
MgO-2SiO2.2H~0 + 502/H20(excess~ 3Mg(HS03~2 + 2SiO2 ~
Mg bisulfite insoluble silica On the other hand, if the magnesium silicate is in 2D excess~ then the sulfite rather than the bisulfite is the final - product:
3MgO.2SiO2.2H20(excess) ~ 3S02/H20---~ 3MgS03 ~ 2SiO2 ~
In fact, a solution of bisulfite in water has the tendency to be transformed into a solution of sulfite by loss --of sulfur dioxide, if the solution is aerated~ in order to remove the free S02. Also the treatment of a solution of sulfite by S02 will allow the formation of the corresponding bisulfite, thus showing clear by the equilibrium which exists between these species, as shown by the following equation:
Mg(HSO3~2~ M9s03 ~ S2 ~ H2 Sulfur dioxide is a most interesting material for the - extractlon of magnesium from mineral sources of this metal because it can be prepared on site by the combustion of sulfur, a very abundant and cheap material or recovered from the roasting operations of sulfides which are very common in the mining industry. The processing of crude petroleum and the treatment of flue gas from the combustion of coal are also important sources of sulfur or sulfur dioxide.
The silica,es which contain magnesium are numerous and of frequent occurrence. The common mineral species con-taining significant amounts af magnesium bounded to silica are listed in the Following Table I:
TABLE I
SILICATES OF MAGNESIUM
Name Formula % Mg Serpentine M96(si4olo)(oH)8 26 Talc Mg3(Si4olo)(oH)2 19 Phlogopite KM93(Alsi3olo)(oH)2 17 Biotite K(Mg,Fe)3 (AlSi301o)(0H)2 13 Chrysolite (olivine) (Mg,Fe)2SiO4 23 Pyrope (garnet) M93Al2~sio4)3 15 Enstatite (pyroxene) Mg2(Si206) 24 ?
20 Diopside CaMg(Si2)6) 11 Chlorite Mg3(Si40lo)(o~l)2M93(oH)6 32 Tremolite Ca2Mgs(si8o22)(oH)2 15 Anthophyllite (Mg,Fe)7(si8o22)(oH)220 In the case of serpentine, large amounts of the incorporated fibrous chrysotile ~3MgO.2SiO2.2H20) are mined for the obtention of the fibrous material, asbestos. Also, the amphibole variety of silicates have led to the extraction _ of fibers mainly of crodicolite and amosite ~5.5FeO, 1.5MgO, 8SiO2.H20) varieties.
In most if not all of the mineral operations where the above silicates are involved, large amounts of rocks rich in magnesium have to be crushed in order to obtain the desired product, such as asbestos -Fiber, talc or simply aggregate for concrete. For example, in the case of chrysotile asbestos, the annuàl production of this material in Canada is of the order of 1.5 million tons per year. Since the fiber represents about 5%
of the weight o-f the rocks involved in the extraction, the total mass of mineral which is grounded in the course of the extraction is in the range of 30 million tons per year. The granulometry of the waste rocks or tailings~ varies greatly but a significant portion,between one and five percent,is already very finely grounded. Even if only one tenth of one percent is in the appropriate form for diges~ion by S02 for the extrac-tion of magnesium the amount of silicate thus made available, 30,000 tons, appears very important. At the present time, there is no use for such tai~ings. In fact, specially with the finely divided material, there is an environmental problem created by dust and an expeditures to carry these tailings on top of huge piles of wastes. Consequently, the cost of finely divided serpentine at the outlet of an asbestos mine is minimal, if not negative.
The chemistry of the sulfite or bisulfite of mag-nesium shows that this material can be transformed into several magnesium derivatives having useful properties. By thermal decomposition, the sulfite can lead to the formation of mag-nesium oxide with evolution of S02. In the course of this process however, some sulfite is transformed into sulfate:
MgS03 ~ MgO ~ S0 ~ 3 By exchange with calcium chloride, the sulfite can give magnesium chloride:
MgS03 + CaC12~ CaS03 ~ ~ M9C12 The magnesium hydroxide can be formed by treatment of the sulfite with a strong base, such as NaOH. Further heat treatment of Mg(OH)2 leads to magnesium oxide:
MgS03 ~ 2NaOH-----~ Mg(OH)2 ~ ~ Na2S03 Mg(OH)2 ~> MgO ~ H20 The carbonate can be obtained through a similar exchange reaction:
MgS03 ~ Na2C~3---~3 MgC03 ~ t Na2S03 All these reactions are wel1 known and do not repre-sent a novelty in the area of extraction and transformation of magnesium salts but show the interest of magnesium sulfite or even sulfate as a starting material for the formation of magnesium salts.
Many uses for the magnesium salts, MgO,Mg(OH)2, MgC12, MgC03, MgS04, require a product of very high degree of purity. For example' a very important use of magnesium oxide ; 20 is in the manufacture of refractory material. The presence of a few percent of impurities in the oxide modiFies the re-sistance of MgO to high temperature in a very adverse way and renders the material useless as reFractory. The usual impuri-ties are calcium oxide, aluminum oxide and iron oxides (either ~
ferrous or ferric). In TRAITE DE CHIMIE MINERALE, Paul BAUU, ~ ;
TOMEI, p. 115, 1951 it is shown that the presence of small amounts of contaminants decreases the melting temperature of the magnesium oxide by several hundred degrees. Another area where the purity of the magnesium salt is critical is the for-mation of the metal by the electrolysis of magnesium chloride~
, ~ ~ 3~3~ ~
These two examples from areas representing major uses for magnesium illustrate the need for very pure magnesium salts.
The naturally occurring magnesium silicates are very seldom in the pure state when found in nature. The secondary metals can be either part of the stoichiometry of the silicate of magnesium or simply mixed with the silicate. For example, chrysotile wastes 3MgO.2SiO2.2H20, are contaminated by 6% by weight of iron, plus traces of nickel and chnome. Also, up to one percent of calcium can be Found in many samples. In the case of chrysotile, the iron is mixed with crystal, in a very intimate manner, but not chemically combined to the main structure of the silicate. In other instances, for example with amosite~ another variety of asbes-tos, (5.5FeO, l.SMgO, 8SiO2.H20) the iron is part of the crystal structure. In ; practice, many of the silicates containing magnesium are meta-morphic rocks, which implies that there is always a certain amount of substitution of magnesium by another metal such as iron, calcium or aluminum. A good illustration of this situ-ation is given by the formula of biotite K(Mg,Fe) (AlSi301o) (OH)2 or phlogopite KMg3 (AlSi301o) (~)2 When sulfur dioxide is used in combination with water, to leach magnesium from a silicate, all the other metals present, either combined or mixed, such as calcium and iron are dissolved at the same time. And the crude sulfite solution, thus obtained, contains such impurities as calcium and iron which render the crude sulfite improper to be used as a source of pure magnesium compound.
The problem of obtaining a pure magnesium compound from S02 leaching is well illustrated by the patent of Trubey, et al, U.S. patent 3,085,858, April 16, 1963. In the case of this patent, the leaching was done by S02 on dolomite, a d ~
natural mixture of calcium oxide and magnesium oxide rather than on a silicate. This patent reports thak even with this simple source of magnesium, 3% of CaO was contaminating the magnesium oxide after processing, in spite of careful pre-cautions not to leach calcium in the course oF the digestion of the mineral. lhe approach of Trubey which controls the presence of calcium by using a stream of C02 cannot be applied to eliminate iron, heavy metals and aluminum from a solution of crude sulfite of magnesium as obtained from naturally-occurring silicates.
SUMMARY OF T~IE IN\IENTION
The object of the pr~sent invention is related to the treatment of the crude solution of the S02-leached magnesium obtained from a silicate and contaminated by all the minor components of a natural silicate namely sodium, potassium~ .
calcium, iron, aluminum traces of heavy metals such as chrome and nickel 9 in order to remove these impurities and to obtain a magnesium compound oF very high purity.
In accordance with the present invention, there is now provided an improved process for recovering substantially pure magnesium hydroxide or magnesium carbonate from naturally-occurring minerals containing magnesium silicate. The improved process of the present invention comprises digesting an aqueous suspension of a naturally~occurring mineral containing mag-; nesium silicate with sulfur dioxide to produce a crude solution of magnesium bisulfite, adjusting the pH of said magnesium bisulfite solution to between 8.0 and 8.9 under an oxidizing atmosphere thereby to precipitate the impurities contained therein and causing the magnesium bisulfite to be converted to magnesium sulfate and precipitating the magnesium as magnesiumhydroxide or carbonate by adjusting the pH of the magnesium ~ 3~
bisulfite solution to between 9.5 and 10.5 with an alkali metal hydroxide or by treatment with an alkali metal carbonate, and recovering the substantially pure magnesium hydroxide or carbonate thus produced.
A main feature of the present invention is tha~ the metallic contaminants found in naturally-occurriny minerals containing magnesium silicate can be selectively precipitated from a bisulfite solution obtained by leaching the naturally-occurring minerals by the adjustment of the pH in the range of 8.0 to 8.9 under an oxidizing atmosphere in opposition to prior art procedure where each contaminant has to be eliminated sepa-rately and where mixtures of magnesium sulfite and sulfate were found in the end product.
Another advantage of the present invention is that beside obtaining the desired salt of magnesium a good pro-portion of the starting sulfur dioxide can be recovered in the form of ammonium or alkali metal sulfate, the latter having well known commercial utilities.
A further advantage of the present invention is that since the process oxidizes the bisulFite formed to sulfate, the pollution problems generated by the handling of sulfites and recovery of sulfur dioxide are eliminated. It is generally known that release of sulfur dioxide is highly undesirable in industrial processes because of the adverse effect of sulfur dioxide on the environment.
The naturally-occurring mineral containing magnesium silicate which can be used in accordance is preferably one which contains at least 10% magnesium, and ~here the specific impurities such as calcium is not more than 20%~ iron 15%, aluminum 10%, agglomerated chrome, nickel and cobalt 2%, while the total agglomerated alkali (Na and K) do not exceed 15%.
~ 3~ ~
Another feature o~ the starting mineral is that its mesh size should be smaller than 60 with a mesh size of at least 200 to 325 being preferred. It is possible to use a mineral contain-ing less than 10% magnesium or having a mesh size greater than 60, but it should be appreciated that yield and purity of the magnesium compound obtained being of commercial importance, the exercise of the improved process of the present invention will be carried out under the preferred conditions which give the superior results.
The adjustment of the pH to from 8.0 to 8.9 is carried out with ammonium or alkali metal hydroxide such as sodium or potassium hydroxide. The preferred pH adjustment is about 8.5 and is carried out under an oxldizing atmosphere which is obtained by bubbling air or oxygen in the solution and in the presence of a strong base such as an alkali metal ~-~ hydroxide whereby magnesium hydroxide is precipitated or an alkali metal carbonate whereby magnesium carbonate is precipi-tated. The cobalt or nickel present in the starting mineral will accelerate the oxidation of the bisulfite to sulfate.
In the final precipitation step the pH of the a~justment to form 9.5 to 10.5 with 9.8 to 10.2 being preferred is also carried with a strGng base such as an alkali metal hydroxide whereby magnesium hydroxide is precipitated or an alkali metal carbonate whereby magnesium carbonate is precipi-tated.
,~
' .
3 ~ ~
DETAILED DESCRIPTION
Step 1- DIGESTION OF THE MAGNESIUM-BEARING MINERAL BY SULFUR
DIOXIDE IN T~IE PRESENCE OF WATER
The naturally-occurring mineral containing magnesium silicate is a divided material with a mesh size smaller than 60 mesh. With a product larger than mesh 60, the reaction ; proceeds but in order to have a faster and more complete reaction, it is preferable to have a material finer than mesh 200. The volume of water present is also related to the ease of reaction. A ratio of mineral weight to volume of water that allows for the solubility of magnesium bisulfite is important.
The reaction of digestion can be performed at atmospheric pressure or at a higher pressure. At atmospheric pressure, it is advisable to avoid too high temperatures, above 50C, in order not to decrease the solubility of S02 in water. At 25C, with a water ratio of 20 g of mineral (for example, serpentine) per liter of water the reaction is complete after, about, three hours. It is indicated, when the reaction nears completion, to ~; stop the addition of S02. In that manner, all the remaining S02 present in solution reacts with the magnesium-bearing mineral to give a solution of bisulfite free of S02. This simplifies the environmental considerations related with the presence of S02.
When the digestion is completed, the reaction mixture is filtered to remove the silica and any unreacted solid material present. In that manner, a sGlution of bisulfite, -~ sulfite and sulfate of magnesium and other metals present, such as calcium and iron is obtained. The digestion is done under very acidic conditions, the pH of the solution being kept in 30 the range of 0.10 to 2.0 at this stage.
Step 2- SELE~TIVE PRECIPITATION OF METALLLC IMPURITIES FROM
THE CRUDE SOLUTION_ ____ The precipitation of the impurities from the bisulfite solution is done by transforming the sulfite or bisulfite into sulfate in an oxidizing atmosphere while in-creasing the pH of the solution in the range of 8.5 by addition of a strong base. The advantage of transforming the sulfite into sulfate is to fall upon a stable and uniform type of anion at this stage. The solution of bisulf;te is easily oxidi~ed by air and this oxidation is much accelerated by the presence of traces of heavy metals, such as cobalt. Since the presence of some sulfate is unavoidable, it is simpler to proceed to full oxidation at this stage and thus avoid having a mixture of salts as the end products. In practice, it has been found that aeration of the solution of crude bisulFite for about one hour at room temperature allows the transformation of bisulfite to sulfate to be complete.
While this aeration is proceeding, the pH of the solution is raised to a value of 8.5 by addition of a basic reagent. Ammonia or an alkali metal hydroxide for example sodium hy~roxide have proved to be appropriate base for this pH
adjustment. Iron, calcium, aluminum and other heavy metals are thus precipitated at that pH. By filtration, they are elimi-nated and the clear solution which contains magnesium sulfate is obtained.
Step 3- RECOVERY OF MAGNESIUM SALTS
The precipitation of magnesium hydroxide is obtained by further increase of the pH to 9.S - 10.5 by a strong base such as an alkali metal or ammonium hydroxide. By filtration, very pure magnesium hydroxide is recovered, indicating a purity of over 99%. If magnesium carbonate is the desired product, this second raise of pH is replaced by addit;on of sodium carbonate.
Step 4- RECOVERY OF SULFATES
When the magnesium salts have been recovered, there remains a solution of the sulfate of the base which has been used (sodium or ammonium) and the sulfate of the small amount of alkali metals present in the starting silicate. By evapo-ration of the filtrated, ammonium sulfate (or sodium sulFate) can be obtained.
The sequential operations are represented by the following Flowsheet I.
`3~
F WSHEET I
Silicate of Mg Bisulfite of Mg~ Silica :
~ + SO2/-H10 ~ Sulfite of ~ enreacted : impurities Ca,Fe,Al,Na........ silicate ___ _~
(discarded~
Bisulfite of Mg STEP 2 Precipitate Solution Sulfite of O ~OH-~pH 8.5)> of Fe,Ca, ~ of sulfate Ca,Fe,Al,Na.... 2 Al,................ Mg,Na,K
(discarded) Solution Mg(OH)2~ Su1fate of sulfate OH (pH 10) or + solution of Mg,Na,K..... or MgCO3~ Na~ or NH
: . Na2C3 4 :-Sulfate SulFate of Solution of : solution STEP 4~ Na or NH~ + sulFate of Na~ or NH4 . . alkali (discarded) The present inven-tion will be more fully understood by referring to the following Examples which are given to illustrate the invention rather than limit its scope.
In a 2 liter flask, a 40 9 sample of chrysotile mesh ~ 200 - 325 is suspended in 1,500 ml of water. The atmosphere over the suspension is kept saturated with S02 and the liquid phase is strongly agitated at room temperature. After a contact of 3.5 hours, the suspension is filtered over asbestos.
The filtrate is then treated with sodium hydroxide (44 ml NaOH 10%) in order to bring the pH to 8.6. The solution is aerated as it is neutralized by a stream of air (150 ml/
min), for 1.5 hour, in order to oxidize the sulfite to sulfate.
After filtration, the pH of the sulfate solution of magnesium is raised to 9.9 by addition of 204.5 ml NaOH 10%.
Magnesium hydroxide (15.6 9) is thus precipitated with a yield of 68% related to the amount of magnesium available in the starting material. The analysis of the precipitate gives 99.1%
Mg(OH)2.
By evaporation9 71.5 g of Na2S04.7H20 is recovered, a yield of 82% .
A similar procedure is used for the other examples.
.
By proceeding in the same manner and using the con-ditions set forth in Table Il, the results shown in Table II
are obtained. It is noted that Example 8 is given to illustrate the decreased yield obtained with the process of the present invention when using a mineral wherein the mag-nesium conten~ is less than 10% by weight.
3~
_ _ _ ._ _ _ _ _ - ,`,t. _ CJ
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_~ ~e . _ _ __ _ _ _ _ _ N
O O T ~_ O ~_ ~ ~ Ln O N O O N
E ~_ o~ a~ t~ ~ O~ CJ~ c~ I~ O'- ~:1 ci~
o.~ a~ o o~ ~ a~ ~n o~ o- a- o~ ol ~> ~ . _ _ _ _ _ _ _ _ _ CL T .. O Cl~ ~_ O O a~ al ~_ O Cl~ O
LLI Q ~ _ a~ O O a'~ CJ~ O O C~l O O
` j' ~I oO~i . _ ,__ ___ '__ _ _ ~' . _ r ~ , ~ ~ s Ln ~ ~ o ~ r~ Ln o o Ln Ln .i C,'X~ ,_ r- . ~ . . l C~J ~' r~ .
. __ _. _ _ _ _ _ _ __ L~ . ._ . N ~ C~J ~ ~ c .. , . N X S la (~ IU O ~ O 1~ 115 I~J la 1~ .
I_ _. _ ._ _ __ _ _ __ O'~ :
I~ I ~O IX) Ln ~O d' ~n ~t ~o ~t CL ~ . CO CO ~ O~C~ I 00 __ CO T T
~ ~ Io~ Io O C To o To o T O O
11:1 L'l a a T I 111 I la ICI /~:1 I I
a~ ~:1 Z z z z z a: z z ~ Z :Z~
.~ _ _ . _ _ __ _ _ _ _ .' '. 0 N~ L~ ~LO O ~'1 cn L~i N O O N Ln ~ ~ Os ~-) ~ 1~ t~> ~ IY~ ':t e~ ~ d ~
C:l~ .
L~ ,0 _ _ _ __ , _ ~:. l ~_ I v~ . O oo O cn c~ cn co ~n o cn +
m o. QJ ,_ O _ O O O o O o _ . s. ~.
_ _ _ _ _ ~n o o o o Ln o Ln cn ~' S CD N n NO N Ln LN ON N N ON N ., N O N O O ~ t~ O O O O O S_ .
- 1~) N l LD ~0 U~ ~0 N ~0 N . J~ Vl . , _ . _ _ _ _ _ _ _ +
l ~_ : ~ _ a)l l LD .-- N ~ '' S ~J
CZ: ,_ O O O ~O O O ~O O C D
C~ ;~51 . _ _ _ _ _ _ __ _ _ ~ ~ 40-:E . cq~ ~ o N al ~
.~ ~ 0~ . _~ ; OO O O O ~ ~ L,l_~
~ ., Lr~ Ln Ln . ~n C~l N CJ- O cn s 8 C-c~ EQ--~ ~D L~ Ln O O .- N . ~ _ Ln . ~ O N N N ~1 cn ~n ~o ~ o ~ c~ >
. N N N N .-- _ CYI r-- _- N _ 2:
. ~S ~ . T L
CJI E O Ln N O O O Ln O Ln O Ln _ O
= ~_ : _ _ _ ~ _ _ _ _ _ _ N L ._ ;~
aJ cJ a~ ^ CD ^ +~ +~ I
C~ CLJ C~ r- C~ ~ _ CL C '_ ~ C~ C C CU
C ~ ~ ~o ~ o '~ ~o '' '1~ ~o ~ ~ t~ '-1 CL' ~ C~ CL V ~
c~ ~: L') c cn ~ L~ o c L~ o ~ ~ o ~ ._ ~ .~ ~ _ n~ ;- cu L~ V CLI ~n Q ~ _ ~ I_ o L/~ L ~ o L~ ~ LQ
s ~ c ' s ~ c~ L~ c s E o o c *
_.LQ _ Lf) ~_ ~ LQ _ ~ . Q. ~5 cl c~ c~ * ~
. . . . . _ __ _ _ _ _ _X O ~ N C~> ~ Ln ID t~ Cl~ C~ O r--__ Ll . _ _ _ __ _ ,_ r--- .
By proceeding in the same manner as in Ex. 1-11 and substituting the appropriate amount of sodium carbonate for the sodium hydroxide in Step 2 there is obtained magnesium carbon-ate in substantially quantitative yields.
.
Claims (4)
1. In a process for the extraction of a magnesium compound from a naturally-occurring mineral containing at least 10% magnesium silicate, the improvement which comprises digesting an aqueous suspension of a naturally-occurring mineral containing at least 10% magnesium silicate with sulfur dioxide and recovering the crude solution of magnesium bi-sulfite thus obtained, and adjusting the pH of said magnesium bisulfite solution under an oxidizing atmosphere with ammonium hydroxide or an alkali metal hydroxide to a pH between 8 and 8.9 thereby to precipitate the impurities contained in the starting mineral and to obtain a substantially pure magnesium sulfate - containing solution, and recovering the magnesium-sulfate-containing-solution.
2. The process of Claim 1, wherein the starting naturally-occurring mineral containing magnesium has a mesh size smaller than 60 mesh.
3. The process of Claim 1, wherein the starting silicate contains at least 10% by weight of magnesium and not more than 15% iron, 10% aluminum, 15% agglomerated alkali and 2% agglomerated chrome, nickel and cobalt.
4. The process of Claim 1, wherein the digestion is carried out at a pH of 0.10 to 2Ø
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US838,220 | 1977-09-30 | ||
US05/838,220 US4124683A (en) | 1977-09-30 | 1977-09-30 | Recovery of magnesium from magnesium silicates |
Publications (1)
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CA1108375A true CA1108375A (en) | 1981-09-08 |
Family
ID=25276576
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CA310,288A Expired CA1108375A (en) | 1977-09-30 | 1978-08-30 | Recovery of magnesium from magnesium silicates |
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CA (1) | CA1108375A (en) |
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US8152895B2 (en) * | 2003-04-23 | 2012-04-10 | Ut-Battelle, Llc | Production of magnesium metal |
US7666250B1 (en) | 2003-11-12 | 2010-02-23 | Ut-Battelle, Llc | Production of magnesium metal |
US20040213705A1 (en) | 2003-04-23 | 2004-10-28 | Blencoe James G. | Carbonation of metal silicates for long-term CO2 sequestration |
US20060171869A1 (en) * | 2003-11-12 | 2006-08-03 | Anovitz Lawrence M | Method of extracting lithium |
WO2007060149A1 (en) * | 2005-11-23 | 2007-05-31 | Shell Internationale Research Maatschappij B.V. | A process for sequestration of carbon dioxide by mineral carbonation |
CN104891537B (en) * | 2015-05-20 | 2017-05-17 | 南阳东方应用化工研究所 | Comprehensive utilization method of silicate minerals |
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US1865224A (en) * | 1929-03-05 | 1932-06-28 | Dow Chemical Co | Method of making magnesium sulphate |
US2112903A (en) * | 1936-07-06 | 1938-04-05 | Booth Harold Simmons | Production of alkaline earth carbonate |
BE467339A (en) * | 1943-06-08 | |||
US4058587A (en) * | 1973-05-24 | 1977-11-15 | Ernest William Nelson | Process for removing impurities from acidic fluid solutions |
ZA741871B (en) | 1974-03-22 | 1975-11-26 | Ver Refractories Ltd | The beneficiation of magnesite |
-
1977
- 1977-09-30 US US05/838,220 patent/US4124683A/en not_active Expired - Lifetime
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