AU2004237790B2 - Processes for synthesis of layered double hydroxides using brine from saltworks - Google Patents
Processes for synthesis of layered double hydroxides using brine from saltworks Download PDFInfo
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- AU2004237790B2 AU2004237790B2 AU2004237790A AU2004237790A AU2004237790B2 AU 2004237790 B2 AU2004237790 B2 AU 2004237790B2 AU 2004237790 A AU2004237790 A AU 2004237790A AU 2004237790 A AU2004237790 A AU 2004237790A AU 2004237790 B2 AU2004237790 B2 AU 2004237790B2
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- bauxite
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- hydrotalcites
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- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 title claims description 57
- 239000012267 brine Substances 0.000 title claims description 54
- 238000000034 method Methods 0.000 title claims description 28
- 150000004679 hydroxides Chemical class 0.000 title claims description 20
- 230000015572 biosynthetic process Effects 0.000 title description 4
- 238000003786 synthesis reaction Methods 0.000 title description 4
- 239000000243 solution Substances 0.000 claims description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 37
- 229910001570 bauxite Inorganic materials 0.000 claims description 35
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 33
- 239000000203 mixture Substances 0.000 claims description 33
- 239000002994 raw material Substances 0.000 claims description 25
- 230000002194 synthesizing effect Effects 0.000 claims description 17
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical class OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 claims description 14
- 239000011734 sodium Substances 0.000 claims description 12
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 11
- 238000004131 Bayer process Methods 0.000 claims description 10
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 9
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 8
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 7
- 239000011780 sodium chloride Substances 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 5
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000001099 ammonium carbonate Substances 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 239000007787 solid Chemical group 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 229910001679 gibbsite Inorganic materials 0.000 claims description 3
- 229910052708 sodium Inorganic materials 0.000 claims description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 3
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 claims description 2
- 239000002253 acid Substances 0.000 claims description 2
- 150000007513 acids Chemical group 0.000 claims description 2
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 claims description 2
- 235000012538 ammonium bicarbonate Nutrition 0.000 claims description 2
- 235000012501 ammonium carbonate Nutrition 0.000 claims description 2
- 150000004677 hydrates Chemical class 0.000 claims description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 2
- 235000010755 mineral Nutrition 0.000 claims description 2
- 239000011707 mineral Substances 0.000 claims description 2
- 239000002245 particle Substances 0.000 claims description 2
- 229910001388 sodium aluminate Inorganic materials 0.000 claims description 2
- 229910004298 SiO 2 Inorganic materials 0.000 claims 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims 2
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 claims 1
- 229910010413 TiO 2 Inorganic materials 0.000 claims 1
- 229910001593 boehmite Inorganic materials 0.000 claims 1
- 229910001648 diaspore Inorganic materials 0.000 claims 1
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 claims 1
- 235000017550 sodium carbonate Nutrition 0.000 claims 1
- 239000002002 slurry Substances 0.000 description 47
- 239000011777 magnesium Substances 0.000 description 20
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 17
- 239000000047 product Substances 0.000 description 16
- 238000001914 filtration Methods 0.000 description 14
- 229910021645 metal ion Inorganic materials 0.000 description 14
- 235000002639 sodium chloride Nutrition 0.000 description 12
- PWZFXELTLAQOKC-UHFFFAOYSA-A dialuminum;hexamagnesium;carbonate;hexadecahydroxide;tetrahydrate Chemical group O.O.O.O.[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-]C([O-])=O PWZFXELTLAQOKC-UHFFFAOYSA-A 0.000 description 11
- 229910001701 hydrotalcite Inorganic materials 0.000 description 11
- 229960001545 hydrotalcite Drugs 0.000 description 11
- 239000012467 final product Substances 0.000 description 10
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- 238000003756 stirring Methods 0.000 description 7
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 6
- 230000032683 aging Effects 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 6
- 108091006629 SLC13A2 Proteins 0.000 description 5
- 150000001450 anions Chemical class 0.000 description 5
- 238000007796 conventional method Methods 0.000 description 5
- 239000010440 gypsum Substances 0.000 description 5
- 229910052602 gypsum Inorganic materials 0.000 description 5
- 229910019440 Mg(OH) Inorganic materials 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 239000011575 calcium Substances 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 239000000706 filtrate Substances 0.000 description 4
- 239000010442 halite Substances 0.000 description 4
- 229910052749 magnesium Inorganic materials 0.000 description 4
- 239000011259 mixed solution Substances 0.000 description 4
- 150000001768 cations Chemical class 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 239000003063 flame retardant Substances 0.000 description 3
- 238000006460 hydrolysis reaction Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000004033 plastic Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000013535 sea water Substances 0.000 description 3
- 238000004065 wastewater treatment Methods 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical group [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 239000011810 insulating material Substances 0.000 description 2
- 239000013067 intermediate product Substances 0.000 description 2
- 239000010446 mirabilite Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 239000003381 stabilizer Substances 0.000 description 2
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- 229910020101 MgC2 Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- -1 aluminum ions Chemical class 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000005452 food preservative Substances 0.000 description 1
- 235000019249 food preservative Nutrition 0.000 description 1
- 229910052598 goethite Inorganic materials 0.000 description 1
- 229910052595 hematite Inorganic materials 0.000 description 1
- 239000011019 hematite Substances 0.000 description 1
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 239000000391 magnesium silicate Substances 0.000 description 1
- 235000012243 magnesium silicates Nutrition 0.000 description 1
- 239000011738 major mineral Substances 0.000 description 1
- 235000011963 major mineral Nutrition 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910017604 nitric acid 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
- 238000005245 sintering Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 229910021653 sulphate ion Inorganic materials 0.000 description 1
- 239000001117 sulphuric acid Substances 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Description
TITLE OF THE INVENTION CN Processes for synthesis of layered double hydroxides using brine from saltworks FIELD OF THE INVENTION This invention relates to processes for synthesis of layered double hydroxides (LDH), also known as hydrotalcites, using brine which is the concentrated residue from saltworks of seawater or salt lakes or underground saline deposits after halite and/or mirabilite have been removed with either acid-digested lateritic bauxite or alkaline-digested bauxite or red mud from the Bayer process of producing alumina.
-1N CN BACKGROUND OF THE INVENTION Brine is the concentrated residue from saltworks of seawater or salt lakes or underground saline deposits after halite and/or mirabilite have been removed. The major component of brine is MgC12, with lesser amounts of MgSO 4 NaC1, KC1 and trace amounts of MgBr 2 etc.
After halite has been removed from seawater and other saline solutions, the concentrated residue becomes very viscous and hydroscopic. It thus becomes very difficult to be further concentrated by solar energy for salt production. Regarding the utilization of brine, most inventions are in the area of recovering extra halite (NaC1) from brine, such as in Canadian patent number CA2464642, British patent numbers GB626641, GB617137, GB 1130182 and GB 189919834, European patent numbers EP1440036 and US patent number US2003080066.
There are some inventions for utilizing brine as an industrial raw material; such as production of caustic soda (NaOH) or magnesium silicates in US patent numbers US2004238373 and US6761865 respectively, or production of iodine in Japanese patent number JP2184504, or production of Mg(OH) 2 in British patent number GB547526. Many other inventions have suggested using brine as a food preservative, such as in Canadian patent numbers CA2455193 and CA1323799, Chinese patent number CN1347663, French patent numbers FR2840510 and FR2827122, British patent numbers GB190423616 and GB144368, Korean patent number KR2001090329, New Zealand patent number NZ514545 and Russian patent number RU2165147. However, despite so many inventions, there is still a great amount of brine being discharged as the waste by-product from saltworks.
Layered double hydroxides (LDH) are also known as hydrotalcites which have layered structures. The basic layers are composed of divalent and trivalent metal ions hydroxides with anions and water molecules filling the spaces between layers. They are therefore also called anion clays. Once heated, hydrotalcites can lose those inter-layered water and hydroxyl groups and become layered double oxides (LDO). These LDOs retain their original layered structure. After absorbing water, hydroxyl groups and anions from aqueous solution, they can revert back to their original LDH structures.
In chemistry and chemical industries, LDH and LDO can be used as catalysts or carriers for catalysts. As a functional material, they can absorb infrared and ultraviolet radiations and C1 have also been used as an insulating material. They can be used as a fire retardant and PVC U stabilizer in the plastic industry. They have very strong absorption capability for many Sharmful anions and thus have many applications in the field of waste water treatment, pollution prevention and environmental rehabilitation etc.
Due to the fact that the major cation in brine is magnesium which is the most common divalent cation found in natural hydrotalcites; therefore, it is possible to use brine as one of the raw materials for synthesizing hydrotalcites.
(N
SDETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS C1 The objective of this invention is to provide three methods of synthesizing layered double hydroxides, also known as hydrotalcites, using brine from saltworks as one of the raw materials.
The typical compositions of brine by weight are MgCl 2 11.0 45.0%, MgSO 4 4.0 NaCl 2.0 KC1 0.2 2.0% and MgBr 2 0.2 0.8%.
Details of these three synthesis processes are described as follows: METHOD A: Synthesizing layered double hydroxides (LDH), also known as hydrotalcites, using brine and acid-digested lateritic bauxite as raw materials.
1. Mix the brine and solution of acid-digested lateritic bauxite so that the molar ratios of Mg (Al+Fe 3 are 1 1 to 1 5 as Solution A. The total concentration ofMg 2 in this solution should be 1 mol/L or less.
2. Prepare Solution B with NaOH and water soluble carbonates or bicarbonates, the total concentrations of cations should be less than 3 mol/L. Molar ratios of NaOH to carbonates or bicarbonates should be 2 1. The molar weights of CO 3 2 or HCO3- in Solution B should be 35% to 50% that of Mg 2 in Solution A.
3. Pour Solution B into Solution A while stirring vigorously and continuously stir for 10 minutes. Slurry will be formed due to the precipitation.
4. Age the slurry at 50 80 0 C for 6 48 hours, de-water the slurry using conventional methods, such as filtration or centrifuge etc. and then wash it several times with clean water.
Dry the slurry at temperatures below 90°C and pulverize it to less than 200 mesh.
The product is a hydrotalcite, with the general formula of [Mglx(A1,Fe )x(OH)2 [(CO3)x/2 nH20] where x 0.5 0.17 and Mg/(Al+Fe 3 1 METHOD B: Synthesizing layered double hydroxides (LDH), also known as hydrotalcites, using brine C1 and alkaline-digested bauxite as raw materials.
S1. Mix the brine and solution of alkaline-digested bauxite so that the molar ratios of Mg:Al are 1 1 to 5 1 as Solution A, with the maximum concentration of Mg 2 to be less than 1 mol/L.
2. Prepare Solution B with 0.5 2 mol/L of water soluble carbonates or bicarbonates.
3. Measure and mix the above two solutions so that the weight ratios of carbonates or bicarbonates to (Mg+Al) in the mixed solution are between 1 1 and 1 1.5. Slurry will be formed due to the precipitation.
4. Age the slurry at 50 80oC for 6 48 hours, de-water the slurry using conventional methods, such as filtration or centrifuge etc. and then wash it several times with clean water.
C1 5. Dry the slurry at temperatures below 90°C and pulverize it to less than 200 mesh.
The product is a hydrotalcite, with the general formula of [Mglx.(A1,Fe )x(OH)2 +[(CO3)x/2 nH20] where x 0.5 0.17 and Mg/Al 1 METHOD C: Synthesizing layered double hydroxides (LDH), also known as hydrotalcites, using red mud from the Bayer process of producing alumina as raw materials.
1. Measure the red mud and the de-sulphated brine, so that molar ratios of Mg:(Al+Fe 3 are 1 1 to 5 1. Charge them into a mixer. Water can be added, to make the solid to liquid ratios between 1 3 and 1 2. Mix the slurry thoroughly and age it at 50 80 0 C for 6 48 hours.
3. Dry the slurry at temperatures below 90°C and then sinter it between 450 750 C for 2 5 hours. The sintered product is then pulverized to less than 200 mesh.
The product is a layered double oxide (LDO) with the general formula of Mgm(A1,Fe 3 )n Ox where x m+3n/2.
4. The LDO is charged into a soluble carbonates or bicarbonates solution with concentrations of 0.5 2 mole/L and at a ratio of one mole of carbonate or bicarbonate to 200 300g of the LDO.
The mixture is stirred continuously for 5 10 minutes and then aged at 50 for 6 48 hours.
6. De-water the slurry using conventional methods, such as filtration or centrifuge etc.
and then wash it several times with clean water.
7. Dry the slurry at temperatures below 90°C and pulverize it to less than 200 mesh.
The product is a hydrotalcite, with the general formula of [Mglx(A1,Fe )x(OH)2 [(CO3)x/2 nH20] where x 0.5 0.17 and Mg/(Al+Fe 3 The red mud mentioned above is the solid residue after removal of aluminum ions from the solution during the Bayer process. It has particle sizes between micron and sub-micron, and the typical chemical compositions by weight are Fe 2 0 3 30 60%, A1 2 0 3 10 25%, Si0 2 3 50%, Na 2 0 2 15%, CaO 0 8% and TiO2 0 0 The soluble carbonate and bicarbonate mentioned above can be either sodium carbonate or Ssodium bicarbonate or ammonium carbonate or ammonium bicarbonate or their hydrates or the combination of them.
Advantages of these methods are that the process is simple, and the outlay of equipment is low; while the raw main materials required are cheap and easily obtainable. If red mud is used as the raw material, then it will solve the storage and environmental pollution problems of red mud. The final product of hydrotalcites, have applications in many areas. For example, in chemistry and chemical industries, they can be used as catalysts or carriers for catalysts. As a functional material, they can absorb infrared and ultraviolet radiations and have also been used as an insulating material. They can be used as a fire retardant and PVC r,1 stabilizer in the plastic industry. They have very strong absorption capabilities for many harmful anions and thus have many applications in the field of waste water treatment, pollution prevention and environmental rehabilitation etc.
EXAMPLES
In the Method A, Mg 2 in the brine is used as the source of divalent metal ions and A13+ and Fe 3 from the acid-digested lateritic bauxite are used as the sources of trivalent metal ions.
Hydrotalcites are formed after the chemical reactions and aging process. The major minerals in the lateritic bauxite are gibbsite, then goethite and hematite. This type of bauxite is usually structurally loose and chemically active. It can be easily dissolved by mineral acids such as hydrochloric acid, nitric acid and sulphuric acid etc. However, hydrochloric acid is the preferred choice because of the environmental and cost concerns. Due to the existence of iron, the final product of hydrotalcite produced using this method will be red in colour. If lighter colour products are desired, then the Method B should be employed.
The ratios of the divalent metal ions to the trivalent metal ions in the final product will affect its properties. Generally speaking, if the amount of the former is higher, then the final products will be structurally more stable; whereas the converse will produce better absorption capability products. It is preferred to limit the molar ratios of the divalent metal ions to trivalent metal ions between 1 1 and 5 1. In practice, the weight ratios between magnesium ions in the brine and bauxite should be restricted between 0.5 and 2.5 times.
The molar ratio of NaOH to carbonate or bicarbonate in Solution B should be 2 1. The molar weights of C0 3 2 or HC03 in Solution B should be 35% to 50% that of Mg 2 in Solution A, whereas the molar weight of NaOH should be 60% to 100% that of Mg 2 The total concentration in the solution should be less than 3 mol/L. Both Solutions should be stirred vigorously before and during the mixing. To ensure the homogeneity, the mixture should be continuously stirred for 5 10 minutes after two Solutions have been added J together. The best aging conditions are at temperatures between 60 to 70 0 C and durations of to 16 hours. After aging, the slurry can be de-watered by either filtration or centrifuge.
C1 The slurry is best dried naturally at room temperature or dried at temperatures less than U or spray dried.
In the Method B, Mg 2 in the brine is used as the source of divalent metal ions and A13+ in the alkaline-digested bauxite is used as the source of trivalent metal ions. The alkaline-digested bauxite slurry is the intermediate product from the Bayer process of manufacturing aluminum oxide or hydroxide. It is a mixture of caustic soda (commonly expressed as Na20), sodium aluminate (commonly expressed as A1 2 0 3 and soda (commonly expressed as Na 2
CO
3 It has a typical composition of Na20 250 300 g/L, A1 2 0 3 350 g/L and Na 2
CO
3 10 g/L. Since there is no iron in the raw materials, therefore the final products of hydrotalcites are white in colour.
C The amount of brine used in this process should be adjusted so that the mole ratios of divalent to trivalent metal ions in the mixed solution are between 1 1 and 5 1. Procedures of mixing, aging, de-watering and drying are identical to Method A.
In the Method C, Mg 2 in the brine is used as the source of divalent metal ions and A13+ in the red mud from the Bayer process of producing alumina is used as the source of trivalent metal ions. Hydrotalcite is produced after chemical reactions, aging, de-watering and drying processes. Because of impurities in the red mud, the final products are only suitable for applications requiring less purity or no colour restrictions; such as in waste water treatments or as a fire retardant in dark-coloured plastic products etc.
Using this Method, the SO42- in the brine should be removed prior to the process. This is because of the existence of certain amounts of Ca 2 in red mud, which can easily react with SO42- in brine and form a precipitate of gypsum (CaSO 4 .2H 2 This gypsum will reduce the content of hydrotalcites in the final product. It is well known that to remove SO42- in brine, CaCl 2 can be added into brine and gypsum will be formed and precipitated out, as shown in the following reaction: S042 CaC12 2H 2 0 CaSO 4 .2H 2 01 2CF- This precipitated gypsum can be easily separated from brine using conventional methods, such as filtration or centrifuge etc.
Once this sulphate-free brine is mixed with red mud, calcium ions from red mud will react with MgCl 2 in brine and the following reaction will occur: Ca(OH) 2 MgC2 Mg(OH) 2 2 CaC12 Therefore, the Ca 2 from the red mud will assist the precipitation of Mg(OH) 2 whereas the CaCl 2 will be removed during the washing and de-watering stages. This CaC12 can be 17 re-claimed from the solution and used again in the de-sulphating stage. The large amount of NaOH in red mud will also assist the precipitation of Mg 2 l in brine, as seen in the following equation: C)2NaOH MgC1 2 Mg(OH) 2 2NaC1 Therefore, after those chemical reactions, Mg 2 will be transferred into the solid phase, whereas Na and Ca 2 remain in the solution and can be washed off in the next stages.
Ratios between the divalent metal ions from the additives and trivalent metal ions from the red mud will affect the properties of the final products. Generally speaking, if the amount of the former is higher, then the final products will be structurally more stable; whereas the converse will produce products with better absorption capability. The amount of brine required can be calculated from the amount of red mud used, so that the calculated mass of magnesium in brine should be 0.5 3 times of dry mass of red mud.
Water can be added into the mixture, so that the mixture will become an easily flowing but sticky slurry. If there is not enough water in the mixture, then the mixture will be difficult to homogenize. However, too much water will waste energy and wear out equipments for the follow-up processes.
The slurry can be de-watered using conventional methods, such as filtration or centrifuge etc.
The slurry is best dried naturally at room temperature or dried at temperatures less than 90 0
C,
so that further aging can be achieved.
The purpose of sintering the intermediate product is to transfer the divalent and trivalent metal oxides or hydroxides into solid solution. The sintered products are layered double oxides (LDO) which can be either sold as a commodity or processed further into hydrotalcites.
Layered double oxides can be hydrolyzed into hydrotalcites in carbonates or bicarbonates solution. A typical reaction can be expressed as: Mg 6 (A1,Fe) 2 0 9 13H 2 0 C03 2 [Mg 3 (A1,Fe)(OH)8 2
CO
3 4H 2 0 2(OH) In this equation, the theoretical molar ratio of carbonate or bicarbonate to LDO is 1 1.
However, in practice, to ensure the complete hydrolysis reaction, the molar ratio of carbonate or bicarbonate to LDO should be higher, that is, between 1.1 1 and 1.5 1. Types of carbonates or bicarbonates have little effect on the results of hydrolysis. However, sodium carbonate (Na 2
CO
3 is preferred for economical reasons. The hydrolysis product should be de-watered and washed several times to remove carbonate and other impurities.
Examples of the process of this invention are described as follows: EXAMPLE 1: Synthesizing layered double hydroxides using brine and acid-digested bauxite 0 Cl Raw material No. 1 is the brine from a saltwork with the following compositions: MgS0 4 o 70 g/L, MgC1 2 165 g/L, NaC1 90 g/L and KC1 20 g/L.
0 Raw material No. 2 is the lateritic bauxite with the following compositions: A1203 48%, SFe 2 0 3 16%, Si0 2 Ti0 2
H
2 0 24% and other impurities 2%.
1. Measure 175g of lateritic bauxite and pulverize it to <200 mesh.
S2. Charge the pulverized bauxite powder into 6.5L of IN hydrochloric acid. Continuously Sstir for 10 minutes until most of the powder has been digested.
3. Filter the solution and retain the filtrate.
4. Add 1.3L of brine into the filtrate and mark it as Solution A.
Measure 90g of NaOH and 120g of Na 2
CO
3 Dissolve them in 2L of water and mark it Sas Solution B.
Cl 6. Add Solution B into vigorously stirred Solution A and continuously stir for 5 minutes.
Precipitation will occur and the mixed solution will turn into a slurry.
7. Age the slurry at 60 0 C for 12 hours. De-water the slurry by filtration and wash it twice with clean water. Dry the cleaned slurry at 80 0 C. Cool it to room temperature and pulverize it to <200 mesh for future use. The final product is a hydrotalcite.
EXAMPLE 2: Synthesizing layered double hydroxides using brine and acid-digested bauxite Raw material No. 1 is the brine from a saltwork with the following compositions: MgS0 4 116 g/L, MgC1 2 311 g/L, NaC1 52 g/L and KC1 5 g/L.
Raw material No. 2 is the lateritic bauxite with the same compositions as in Example 1.
1. Measure 175g of lateritic bauxite and pulverize it to <200 mesh.
2. Charge the pulverized bauxite powder into 1.5L of 4N hydrochloric acid. Continuously stir for 10 minutes until most of the powder has been digested.
3. Filter the solution and retain the filtrate.
4. Add 0.7L of brine and 3L of water into the filtrate and mark it as Solution A.
Measure 100g of NaOH and 100g of NaHCO 3 and dissolve them in 4L of water and mark it as Solution B.
6. Add Solution B into vigorously stirred Solution A and continuously stir for 5 minutes.
Precipitation will occur and the mixed solution will turn into a slurry.
7. Age the slurry at 80 0 C for 10 hours. De-water the slurry by filtration and wash it twice with clean water. Dry the cleaned slurry at 60 0 C. Cool it to room temperature and pulverize it to <200 mesh for future use. The final product is a hydrotalcite.
EXAMPLE 3: Synthesizing layered double hydroxides using brine and alkaline-digested bauxite Raw material No. 1 is the brine from a saltwork with the following compositions: MgS0 4 72 g/L, MgCl 2 570 g/L, NaC1 3.5 g/L and KC1 2.0 g/L.
Raw material No. 2 is the solution of alkaline-digested bauxite with the following C1 compositions: Na20 260 g/L, A1 2 0 3 310 g/L and Na 2
CO
3 30 g/L..
S1. Measure 1L of alkaline-digested bauxite solution, 2L of brine and 10L of water and mix them thoroughly.
2. Prepare 25L ofNa 2
CO
3 solution at the concentration of 1 mol/L.
3. Add the Na 2
CO
3 solution into the above slurry and mix well.
4. Age the slurry at 60 0 C for 12 hours. De-water the slurry by filtration and wash it twice with clean water. Dry the cleaned slurry at 70 0 C. Cool it to room temperature and grind to <200 mesh for future use. The final product is a hydrotalcite.
(N
EXAMPLE 4: Synthesizing layered double hydroxides using brine and alkaline-digested bauxite Raw materials are the same as in Example 3.
1. Measure 1L of alkaline-digested bauxite slurry, 2L of brine and 10L of water and mix them thoroughly.
2. Prepare 28L ofNaHCO 3 solution at the concentration of 1 mol/L.
3. Add the NaHCO 3 solution into the above slurry and mix well.
4. Age the slurry at 70 0 C for 10 hours. De-water the slurry by filtration and wash it twice with clean water. Dry the cleaned slurry at 80 0 C. Cool it to room temperature and pulverize it to <200 mesh for future use. The final product is a hydrotalcite.
EXAMPLE 5: Synthesizing layered double hydroxide using brine and red mud from the Bayer process of alumina production Raw material No. 1 is the brine from a saltwork with the following compositions: MgSO 4 g/L, MgC12 430 g/L, NaCl 16.0/L and KC1 5.0g/L. Sulphate radicals in the brine have been removed by adding CaC12 into the solution and removing the precipitate of gypsum.
Raw material No. 2 is the red mud from a Bayer process alumina production plant. It has the following compositions: A1 2 0 3 24.6%, Fe 2 0 3 34.2%, Si0 2 16.5%, CaO Na20 9.8% and Ti0 2 6.8%.
1. Measure 1.5L of de-sulphated brine, 0.5Kg of dried red mud and 1L of water. Mix them well, so that a homogeneous slurry is formed, then age it at 60 0 C for 12 hours.
2. De-water the slurry by filtration and dry it at 80 0 C. Sinter the dried slurry at 500 0 C for 3 hours. Cool it to room temperature and pulverize it to <200 mesh.
3. Prepare 2L ofNa 2
CO
3 solution at the concentration of 1 mol/L.
4. Add the above pulverized powder into the Na 2
CO
3 solution and continuously stir for minutes.
Age the slurry at 60 0 C for 12 hours.
6. De-water the slurry by filtration and wash it twice with clean water. Dry the cleaned slurry at 80 0 C. Cool it to room temperature and pulverize it to <200 mesh for future use.
C1 The final product is a hydrotalcite.
EXAMPLE 6: Synthesizing layered double hydroxide using brine and red mud from the Bayer process of alumina production Raw materials are the same as those in Example 1. Measure 2L of de-sulphated brine, 0.8Kg of dried red mud and 1.5L of water. Mix them well, so that a homogeneous slurry is formed, then and age it at 80 0 C for 10 hours.
2. De-water the slurry by filtration and dry it at 70°C. Sinter the dried slurry at 600 0 C for 2 hours. Cool it to room temperature and pulverize it to <200 mesh.
3. Prepare 4L ofNaHCO 3 solution at the concentration of 1 mol/L.
C1 4. Add the above pulverized powder into the NaHCO 3 solution and continuously stir for minutes.
Age the slurry at 80 0 C for 8 hours.
6. De-water the slurry by filtration and wash it twice with clean water. Dry the cleaned slurry at 80 0 C. Cool it to room temperature and pulverize it to <200 mesh for future use.
The final product is a hydrotalcite.
Claims (2)
11.0
45.0%, MgSO 4 4.0 NaCl 2.0 KC1 0.2 2.0% and MgBr 2 0.2 0.8%. Claim A method of synthesizing layered double hydroxides (LDH), also known as hydrotalcites, using brine and acid-digested lateritic bauxite as raw materials as claimed in Claim 1, where one of the major components of the said lateritic bauxite is the gibbsite, the typical chemical compositions of the said lateritic bauxite are A1 2 0 3 40 50%, Fe 2 0 3 10 20%, SiO 2 3 TiO2 2 5% and H20 22 28%. Claim 6. A method of synthesizing layered double hydroxides (LDH), also known as hydrotalcites, using brine and acid-digested lateritic bauxite as raw materials as claimed in Claim 1, where the said acid-digested lateritic bauxite solution is the solution after lateritic bauxite has been digested with concentrated mineral acids and solid residues have been removed. Claim 7. A method of synthesizing layered double hydroxides (LDH), also known as hydrotalcites, using brine and alkaline-digested bauxite as raw materials as claimed in Claim 2 where the said bauxite contains mainly boehmite or diaspore or gibbsite or mixture of two or more of them, which can be utilized industrially as raw materials for extracting of aluminum. Claim 8. A method of synthesizing layered double hydroxides (LDH), also known as hydrotalcites, using brine and alkaline-digested bauxite as raw materials as claimed in Claim 2 where the said alkaline-digested bauxite solution is the mixture of caustic soda, sodium aluminate and soda, with the typical compositions of Na 2 O 250 300 g/L, A1 2 0 3 280 350 g and Na 2 CO3 10 50 g/L. Claim 9. A method of synthesizing layered double oxides (LDO) and layered double hydroxides (LDH), also known as hydrotalcites, using brine and red mud from the Bayer process of alumina production as raw materials as claimed in Claim 3 where the said red mud is the solid residue after removal of aluminum during the Bayer process, it has particle sizes from micron to sub-micron and the typical chemical compositions are Fe 2 03 30 60%, A1 2 0 3 10 SiO 2 3 50%, Na 2 O 2 15%, CaO 0 8% and TiO 2 0 Claim Methods of synthesizing layered double oxides (LDO) and layered double hydroxides (LDH), also known as hydrotalcites, using brine as a raw material as claimed in Claims 1, 2 and 3, where the said water soluble carbonates or bicarbonates can be sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, their hydrates or a combination of them. Name of Applicants V/U w Ying YE Shanshan JI Daidai WU Wei-Jui CHANG Dated this 9th of December, 2004
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| WO2016184055A1 (en) * | 2015-05-18 | 2016-11-24 | 北京化工大学 | Process method for extracting magnesium and lithium from brine and coproducing hydrotalcite |
| CN109225220A (en) * | 2018-08-28 | 2019-01-18 | 北京化工大学 | It a kind of calcined hydrotalcite catalyst with magnetic core, preparation and is reacted for Benzyl Side-Chain carbaldehyde alkylization |
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| CN111217385A (en) * | 2020-02-23 | 2020-06-02 | 武汉工程大学 | Method for preparing calcium-magnesium-aluminum hydrotalcite by using phosphate tailings |
| CN111998335B (en) * | 2020-09-02 | 2022-11-18 | 中国石油化工股份有限公司 | Auxiliary combustion oxygen carrier composition and preparation method and application thereof |
| CN112456638B (en) * | 2020-09-29 | 2023-03-17 | 江苏环保产业技术研究院股份公司 | Modified steel slag filler and preparation method and application thereof |
| CN113941332A (en) * | 2021-09-09 | 2022-01-18 | 华北电力大学 | Heterogeneous CoFe/Mg-LDO catalyst, preparation method and dimethylamine wastewater treatment method |
| CN115745003B (en) * | 2022-12-02 | 2024-06-14 | 华北科技学院 | A kind of iron magnesium aluminum carbonate type hydrotalcite material prepared by red mud and its preparation method and application |
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Non-Patent Citations (1)
| Title |
|---|
| Perottta A. J. et al. Layered Double Hydroxide Formation in Bayer Liquor and its Promotional Effect on Oxalate Precipatation Light Metals (1996) 17-28 * |
Cited By (2)
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|---|---|---|---|---|
| WO2016184055A1 (en) * | 2015-05-18 | 2016-11-24 | 北京化工大学 | Process method for extracting magnesium and lithium from brine and coproducing hydrotalcite |
| CN109225220A (en) * | 2018-08-28 | 2019-01-18 | 北京化工大学 | It a kind of calcined hydrotalcite catalyst with magnetic core, preparation and is reacted for Benzyl Side-Chain carbaldehyde alkylization |
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