WO2000029326A1 - Method for production of magnesium hydroxide from sea water - Google Patents

Method for production of magnesium hydroxide from sea water Download PDF

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Publication number
WO2000029326A1
WO2000029326A1 PCT/NO1999/000343 NO9900343W WO0029326A1 WO 2000029326 A1 WO2000029326 A1 WO 2000029326A1 NO 9900343 W NO9900343 W NO 9900343W WO 0029326 A1 WO0029326 A1 WO 0029326A1
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WO
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Prior art keywords
sea water
membrane
electrodialysis
nanofiltration
feed
Prior art date
Application number
PCT/NO1999/000343
Other languages
French (fr)
Inventor
Thor G. Thorsen
Roger I. Hagen
Ole Waernes
Birger Langseth
Original Assignee
Norsk Hydro Asa
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Norsk Hydro Asa filed Critical Norsk Hydro Asa
Priority to AU11914/00A priority Critical patent/AU1191400A/en
Publication of WO2000029326A1 publication Critical patent/WO2000029326A1/en

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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
    • C01F5/14—Magnesium hydroxide
    • C01F5/22—Magnesium hydroxide from magnesium compounds with alkali hydroxides or alkaline- earth oxides or hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D1/00—Oxides or hydroxides of sodium, potassium or alkali metals in general
    • C01D1/04—Hydroxides
    • C01D1/28—Purification; Separation
    • C01D1/38—Purification; Separation by dialysis

Definitions

  • the existing processes need chemicals corresponding to a chemical equivalent amount of base to that of sodium hydroxide (NaOH).
  • a precipitation process with use of NaOH may be a simple way to reach the product if the price on NaOH is low enough.
  • the object of the invention is thus to produce magnesium hydroxide from sea water in a cheap and efficient way. Another object is to eliminate the drawbacks of already existing methods.
  • the invention concerns a method for production of magnesium hydroxide from sea water, where magnesium hydroxide is precipitated with sodium hydroxide produced from the same sea water by use of electrodialysis (ED).
  • ED electrodialysis
  • the magnesium hydroxide could be used as raw material for production of magnesium metal.
  • the feed to the electrodialysis unit is treated by nanofiltration to remove divalent ions, which can interfere with the electodialysis membrane.
  • the resulting sea water is fed to an electrodialysis membrane plant to produce NaOH instead of using the conventional chlor/alkali electrolysis, whereafter magnesium hydroxide is precipitated from the sea water with NaOH solution from the electodialysis plant. It is preferred to remove humic substances and silicates or other naturally occurring substances in sea water which can foul or poison the electrodialysis membrane by a membrane process.
  • the ED-stack preferably consists of repeating ED-cells which are based on a 3-chamber system consisting of a bipolar membrane, a mono-ion selective cation permeable membrane and an anion permeable membrane in a repeating sequence.
  • the alkaline chamber adjacent to the bipolar membrane has a feed solution with low concentration of divalent ions, below 2 mg/l for Mg and Ca. It is preferred that the feed to the other chambers will be sea water or alternatively NF treated sea water. The sea water can be stripped with HCI or acid sea water to remove CO 2 before the precipitation step.
  • Figure 1 shows a flow sheet for a process producing NaOH for precipitation of
  • Figure 2 shows a flow sheet for a process producing NaOH for precipitation of
  • Mg(OH) 2 from sea water with use of nanofiltration in front of the precipitation stage.
  • Figure 3 shows the robust construction of the electrodialysis cell and the flow to the different chambers.
  • the proposed method is based on the use of sodium hydroxide to precipitate magnesium hydroxide from sea water.
  • the important part of the invented method is to produce also the sodium hydroxide from the sea water.
  • electrodialysis ED
  • NF nanofiltration
  • One of the advantages by using sodium hydroxide would be the homogeneous reaction for the precipitation, with a straight forward filtration of the product and the minimum impact on the environment.
  • the feed to the electrodialysis plant may be performed in several ways.
  • it is important to remove the divalent ions which may interfere with the electrodialysis membranes.
  • the method employs nanofiltration for the removal of divalent ions and particles and organic compounds in the sea water.
  • the particulate and organic composition of the sea water may be considered best to be removed by micro filtration or other methods.
  • the first alternative is to use the permeate from nanofiltration of sea water for the NaOH-production, that is a raw feed with 29-35 g/l NaCI. Since the efficiency of an electrodialysis cell is very dependent on the conductivity of the electrolyte, the proposed method also includes the possibility of concentrating the sea water to 70-100 g/l NaCI.
  • FIG 1 is presented a process with the use of electrodialysis (ED) for the production of sodium hydroxide to be used in the precipitation process.
  • ED electrodialysis
  • the feed sea water is treated in a stripper with HCI or acid sea water to remove CO 2 .
  • the sea water feed-stream is then led to the precipitation process where Mg(OH) 2 is precipitated with NaOH-solution from the ED-plant.
  • a sub-stream of used sea water from the filtrate and/or clarified process liquid is sent to a nanofiltration unit for the separation of divalent ions.
  • This option has the advantage that Mg is already removed from the stream to the electrodialysis unit.
  • the focus may therefor be on removing Ca 2+ in the feed to the ED-plant.
  • the removal of calcium is based on a nanofiltration unit with high retention of Ca 2+ and low retention of NaCI.
  • the sea water sub-stream to the ED-plant is taken from the permeate side of the nanofiltration unit. In this way the Ca 2+ and rest of
  • Mg 2+ -concentration is reduced by 90% or more, which may reduce the main problems with scaling in the ED-plant. Further scaling problems will be reduced with the use of an antiscalant.
  • the ED-plant may produce HCI or acid sea water dependent on whether the ED-cell is based on a two or three compartment system.
  • figure 2 is shown a second process alternative for the use of electrodialysis for the production of sodium hydroxide to be used in the precipitation process.
  • the feed sea water is treated with HCI or acid sea water to remove CO 2 .
  • the feed is sent to a nanofiltration unit for the separation of divalent ions before the precipitation.
  • the residual sea water, which is concentrated in divalent ions, is further sent to precipitation of Mg(OH) 2 using NaOH produced in the ED-plant.
  • the sea water sub-stream to the ED-plant is taken from the permeate side of the nanofiltration unit.
  • the Ca+ 2 and Mg 2+ -concentration is reduced by 90% or more which may reduce the main problems with scaling in the ED-plant. Residual scaling problems may be reduced with addition of antiscalant.
  • the advantage of this alternative is that the flow to the precipitation plant is reduced with the same production of Mg(OH) 2 .
  • Reverse osmosis membranes are semipermeable membranes that are permeable by water but not salts. If a high operating pressure is applied to sea water that is fed to one side of the membrane, freshwater will appear on the opposite side of the membrane.
  • the maximum salt concentration that can be reached by reverse osmosis with regular commercial membranes is about 70 g/l.
  • the reverse osmosis can be combined with nanofiltration to obtain concentrations in the order of 100g/l.
  • the electrodialysis cell is of an unusual construction to serve spesial purposes and to be robust in operation as shown in figure 3.
  • the ED-stack consists of repeating ED-cells, which are based on a 3-chamber system consisting of a bipolar membrane (B), a mono-ion selective cation permeable membrane (CM) and an anion permeable membrane (A) in a repeating sequence.
  • Chamber 1 between the bipolar membrane and the mono-ion selective cation permeable membrane will have a feed of NaCI-solution with low concentration of divalent ions.
  • the feed will come from the nanofiltration unit and the concentration of Ca 2+ and Mg 2+ should be below 2 mg /I according to equipment suppliers.
  • an alkaline solution is produced by transferring sodium from sea water with low transport of divalent ions.
  • a purified sea water stream in chamber 1 without recirculation the concentrating of the divalent ions in the alkaline product is avoided and sufficient electrical conductance is obtained.
  • a three chamber system with sea water flow in chamber 3 the current efficiency with respect to base production is increased.

Abstract

A method is described for the production of magnesium hydroxide from sea water wherein the magnesium hydroxide is precipitated with sodium hydroxide which is produced from sea water through the use of electrodialysis.

Description

METHOD FOR PRODUCTION OF MAGNESIUM HYDROXIDE FROM SEA WATER
In the production of magnesium hydroxide Mg(OH)2 from sea water, the existing processes in some way need a chemical base to reach the end product. Current processes for recovery of magnesium from sea water make use of lime or dolomite as the alkaline reagent. In the existing production there is a considerable CO2 emission from the production of burnt dolomite, and in addition raw materials have to be transported to the plant as dolomite.
The existing processes need chemicals corresponding to a chemical equivalent amount of base to that of sodium hydroxide (NaOH). A precipitation process with use of NaOH may be a simple way to reach the product if the price on NaOH is low enough.
The object of the invention is thus to produce magnesium hydroxide from sea water in a cheap and efficient way. Another object is to eliminate the drawbacks of already existing methods.
These and other objects of the invention are achieved by the method for production of magnesium hydroxide as described below. The invention is further described and characterised by the enclosed patent claims.
The invention concerns a method for production of magnesium hydroxide from sea water, where magnesium hydroxide is precipitated with sodium hydroxide produced from the same sea water by use of electrodialysis (ED). The magnesium hydroxide could be used as raw material for production of magnesium metal. The feed to the electrodialysis unit is treated by nanofiltration to remove divalent ions, which can interfere with the electodialysis membrane. The resulting sea water is fed to an electrodialysis membrane plant to produce NaOH instead of using the conventional chlor/alkali electrolysis, whereafter magnesium hydroxide is precipitated from the sea water with NaOH solution from the electodialysis plant. It is preferred to remove humic substances and silicates or other naturally occurring substances in sea water which can foul or poison the electrodialysis membrane by a membrane process. It is preferable to concentrate the feed to the electrodialysis unit by reverse osmosis (RO) and/ or nanofiltration. The reverse osmosis may take place before or after the nanofiltration. The ED-stack preferably consists of repeating ED-cells which are based on a 3-chamber system consisting of a bipolar membrane, a mono-ion selective cation permeable membrane and an anion permeable membrane in a repeating sequence. The alkaline chamber adjacent to the bipolar membrane has a feed solution with low concentration of divalent ions, below 2 mg/l for Mg and Ca. It is preferred that the feed to the other chambers will be sea water or alternatively NF treated sea water. The sea water can be stripped with HCI or acid sea water to remove CO2 before the precipitation step.
The new method will be further described with reference to the accompanying figures 1 -3, where
Figure 1 shows a flow sheet for a process producing NaOH for precipitation of
Mg(OH)2 from sea water with removal of Ca Mg by a nanofiltration unit in the sub stream from the precipitation process to the electrodialysis plant.
Figure 2 shows a flow sheet for a process producing NaOH for precipitation of
Mg(OH)2 from sea water with use of nanofiltration in front of the precipitation stage.
Figure 3 shows the robust construction of the electrodialysis cell and the flow to the different chambers.
The proposed method is based on the use of sodium hydroxide to precipitate magnesium hydroxide from sea water. The important part of the invented method is to produce also the sodium hydroxide from the sea water. One has surprisingly found that it is possible to produce sodium hydroxide directly from the sea water by use of electrodialysis. This has been considered a difficult task because divalent ions will destroy the electrodialysis membranes in a basic environment. However, by combining the electrodialysis (ED) with nanofiltration (NF), it is possible to remove divalent cations to avoid scaling in the ED-process. One of the advantages by using sodium hydroxide would be the homogeneous reaction for the precipitation, with a straight forward filtration of the product and the minimum impact on the environment.
The feed to the electrodialysis plant may be performed in several ways. In the proposed method it is important to remove the divalent ions which may interfere with the electrodialysis membranes. The method employs nanofiltration for the removal of divalent ions and particles and organic compounds in the sea water. In a large scale plant the particulate and organic composition of the sea water may be considered best to be removed by micro filtration or other methods.
The first alternative is to use the permeate from nanofiltration of sea water for the NaOH-production, that is a raw feed with 29-35 g/l NaCI. Since the efficiency of an electrodialysis cell is very dependent on the conductivity of the electrolyte, the proposed method also includes the possibility of concentrating the sea water to 70-100 g/l NaCI.
Two possible concepts based on precipitation with caustic produced from sea water are presented in the following text:
In figure 1 is presented a process with the use of electrodialysis (ED) for the production of sodium hydroxide to be used in the precipitation process. The feed sea water is treated in a stripper with HCI or acid sea water to remove CO2. The sea water feed-stream is then led to the precipitation process where Mg(OH)2 is precipitated with NaOH-solution from the ED-plant. Then a sub-stream of used sea water from the filtrate and/or clarified process liquid is sent to a nanofiltration unit for the separation of divalent ions.
This option has the advantage that Mg is already removed from the stream to the electrodialysis unit. The focus may therefor be on removing Ca2+ in the feed to the ED-plant. The removal of calcium is based on a nanofiltration unit with high retention of Ca2+ and low retention of NaCI. The sea water sub-stream to the ED-plant is taken from the permeate side of the nanofiltration unit. In this way the Ca2+ and rest of
Mg2+-concentration is reduced by 90% or more, which may reduce the main problems with scaling in the ED-plant. Further scaling problems will be reduced with the use of an antiscalant. The ED-plant may produce HCI or acid sea water dependent on whether the ED-cell is based on a two or three compartment system. In figure 2 is shown a second process alternative for the use of electrodialysis for the production of sodium hydroxide to be used in the precipitation process. The feed sea water is treated with HCI or acid sea water to remove CO2. Then the feed is sent to a nanofiltration unit for the separation of divalent ions before the precipitation. The residual sea water, which is concentrated in divalent ions, is further sent to precipitation of Mg(OH)2 using NaOH produced in the ED-plant. The sea water sub-stream to the ED-plant is taken from the permeate side of the nanofiltration unit. In this way the Ca+2 and Mg2+ -concentration is reduced by 90% or more which may reduce the main problems with scaling in the ED-plant. Residual scaling problems may be reduced with addition of antiscalant. The advantage of this alternative is that the flow to the precipitation plant is reduced with the same production of Mg(OH)2.
In both alternatives there are options with concentrating of the streams also with respect to the concentration of NaCI. For optimal operation of the ED-unit, regarding to the power consumption, it is beneficial to concentrate the sea water to a higher NaCI concentration. Concentration of the sea water may be desirable in both of the previously presented process configurations. In figure 1 is shown a combined reverse osmosis/ nanofiltration unit (RO/NF) In figure 2 the concentrating of NaCI (by reverse osmosis ,RO) may take place both before and after the nanofiltration unit.
Moderate concentration of sea water by reverse osmosis is conventional technology. Reverse osmosis membranes are semipermeable membranes that are permeable by water but not salts. If a high operating pressure is applied to sea water that is fed to one side of the membrane, freshwater will appear on the opposite side of the membrane. The maximum salt concentration that can be reached by reverse osmosis with regular commercial membranes is about 70 g/l. For further concentration of the salt solution, the reverse osmosis can be combined with nanofiltration to obtain concentrations in the order of 100g/l.
The electrodialysis cell is of an unusual construction to serve spesial purposes and to be robust in operation as shown in figure 3. The ED-stack consists of repeating ED-cells, which are based on a 3-chamber system consisting of a bipolar membrane (B), a mono-ion selective cation permeable membrane (CM) and an anion permeable membrane (A) in a repeating sequence. Chamber 1 between the bipolar membrane and the mono-ion selective cation permeable membrane will have a feed of NaCI-solution with low concentration of divalent ions. The feed will come from the nanofiltration unit and the concentration of Ca2+ and Mg2+ should be below 2 mg /I according to equipment suppliers. We expect that much higher concentration of Ca2+ may be tolerated if precipitation with certain anions like CO3 2" and SO4 2" can be avoided. This will give a cheaper process. Into chamber 3 between the mono-ion selective cation permeable membrane and the anion permeable membrane the feed will be precipitated and clarified sea water. In chamber 2 between the anion permeable membrane and the acid side of the bipolar membrane, a stream will be circulated with feed of precipitated sea water and bleed of acid sea water. The acid sea water may be used to adjust the pH in chambers 2 and 3.
By using a mono-ion selective membrane between chamber 1 and 3 an alkaline solution is produced by transferring sodium from sea water with low transport of divalent ions. By using a purified sea water stream in chamber 1 without recirculation, the concentrating of the divalent ions in the alkaline product is avoided and sufficient electrical conductance is obtained. By using a three chamber system with sea water flow in chamber 3 the current efficiency with respect to base production is increased.
Results from laboratory experiments.
In laboratory experiments with recirculation the following parameters are measured:
Table 1. Results from test with electrodialysis.
Figure imgf000007_0001
In the laboratory tests the feeds to chambers 2 and 3 had the composition of sea water to demonstrate the separation degree for divalent ions. In the proposed process the feed concentration of divalent ions will be much lower due to the precipitation process and the nanofiltration step. Nanofiltration of sea water by use of a membrane from DOW, NF-45 gave the following retentions at two different pH.
Table 2. Results from nanofiltration tests on sea water. Retention for several ions.
Figure imgf000008_0001

Claims

1. Method for production of magnesium hydroxide from sea water, characterised by the combination of the following steps: a) divalent ions, which can interfere with an electrodialysis membrane, are removed from sea water by nanofiltration, b) the resulting sea water is fed to an electrodialysis membrane plant to produce NaOH, c) Mg(OH)2 is precipitated from the sea water with NaOH solution from the electrodialysis plant.
2. Method according to claim 1 , characterised in that humic substances and silicates or other naturally occuring substances in sea water which can foul or poison the electrodialysis membrane are removed from sea water by a membrane process.
3. Method according to claim 1 , characterised in that a reverse osmosis step to increase salt concentration may be inserted before or after the nanofiltration.
4. Method according to claim 3, characterised in that reverse osmosis may be combined with nanofiltration to achieve a higher salt concentration.
5. Method according to claim 1 , characterised in that the ED-stack consists of repeating ED-cells which are based on a 3-chamber system consisting of a bipolar membrane, a mono-ion selective cation permeable membrane and an anion permeable membrane in a repeating sequence.
6. Method according to claim 5, characterised in that the alkaline chamber adjacent to the bipolar membrane has a feed solution with low concentration of divalent ions, below 2 mg/l for Mg and Ca.
7. Method according to claim 5, characterised in that the feed to the other chambers will be sea water or alternatively NF treated sea water.
8. Method according to claims 1 - 7 characterised in that the feed sea water is stripped with HCI or acid sea water to remove CO2 before the precipitation step.
PCT/NO1999/000343 1998-11-13 1999-11-12 Method for production of magnesium hydroxide from sea water WO2000029326A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU11914/00A AU1191400A (en) 1998-11-13 1999-11-12 Method for production of magnesium hydroxide from sea water

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO19985320 1998-11-13
NO985320A NO985320L (en) 1998-11-13 1998-11-13 Process for producing magnesium hydroxide from seawater

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2070583A3 (en) * 2002-08-02 2009-11-04 University Of South Carolina Production of purified water and high value chemicals from salt water
ES2388252A1 (en) * 2012-07-18 2012-10-11 Universidad De Cantabria Method for converting brines into acids and bases, and products obtained
WO2013023249A1 (en) * 2011-08-17 2013-02-21 Ahilan Raman Process and system for producing sodium chloride brine
EP3074349A4 (en) * 2013-11-25 2017-07-12 Enviro Water Minerals Company, Inc. System and mehtod for removing minerals from a brine using electrodialysis
AU2012297568B2 (en) * 2012-08-16 2018-04-05 Pereira, Silvester Process and system for producing sodium chloride brine
IT201800004691A1 (en) * 2018-04-23 2019-10-23 Liberto Francesco Di PRODUCTION OF MAGNESIUM HYDROXIDE, BROMINE AND USE OF THE CHLORINE OBTAINED IN THE CYCLE TO PRODUCE CHLORODERIVATES.
CN114163037A (en) * 2021-12-15 2022-03-11 四川环科美能环保科技有限公司 High-salinity wastewater concentration system and concentration method
DE102023100537A1 (en) 2022-04-07 2023-10-12 Rainer Pommersheim Method and device for producing particles with a high magnesium content from seawater
WO2023193981A1 (en) 2022-04-07 2023-10-12 Rainer Pommersheim Method and device for producing particles with a high magnesium content from sea water

Citations (4)

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Publication number Priority date Publication date Assignee Title
US3787558A (en) * 1969-10-17 1974-01-22 Steetley Mfg Ltd Magnesium hydroxide production
JPS52106367A (en) * 1976-03-05 1977-09-06 Hitachi Ltd Pre-treatment of sea water
GB1502422A (en) * 1975-03-06 1978-03-01 Steetley Minerals Ltd Process for making magnesium hydroxide
EP0596712A1 (en) * 1992-11-03 1994-05-11 Adcock Ingram Limited Magnesium hydroxide revovery

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3787558A (en) * 1969-10-17 1974-01-22 Steetley Mfg Ltd Magnesium hydroxide production
GB1502422A (en) * 1975-03-06 1978-03-01 Steetley Minerals Ltd Process for making magnesium hydroxide
JPS52106367A (en) * 1976-03-05 1977-09-06 Hitachi Ltd Pre-treatment of sea water
EP0596712A1 (en) * 1992-11-03 1994-05-11 Adcock Ingram Limited Magnesium hydroxide revovery

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 197742, Derwent World Patents Index; AN 1977-74870Y *
PATENT ABSTRACTS OF JAPAN *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2070583A3 (en) * 2002-08-02 2009-11-04 University Of South Carolina Production of purified water and high value chemicals from salt water
WO2013023249A1 (en) * 2011-08-17 2013-02-21 Ahilan Raman Process and system for producing sodium chloride brine
ES2388252A1 (en) * 2012-07-18 2012-10-11 Universidad De Cantabria Method for converting brines into acids and bases, and products obtained
WO2014013100A1 (en) * 2012-07-18 2014-01-23 Universidad De Cantabria Method for converting brines into acids and bases, and products obtained
AU2012297568B2 (en) * 2012-08-16 2018-04-05 Pereira, Silvester Process and system for producing sodium chloride brine
EP3074349A4 (en) * 2013-11-25 2017-07-12 Enviro Water Minerals Company, Inc. System and mehtod for removing minerals from a brine using electrodialysis
AU2014352663B2 (en) * 2013-11-25 2017-12-07 Enviro Water Minerals Company, Inc. Systems and methods for removing minerals from a brine using electrodialysis
US10246357B2 (en) 2013-11-25 2019-04-02 Enviro Water Minerals Company, Inc. System and methods for removing minerals from a brine using electrodialysis
IT201800004691A1 (en) * 2018-04-23 2019-10-23 Liberto Francesco Di PRODUCTION OF MAGNESIUM HYDROXIDE, BROMINE AND USE OF THE CHLORINE OBTAINED IN THE CYCLE TO PRODUCE CHLORODERIVATES.
CN114163037A (en) * 2021-12-15 2022-03-11 四川环科美能环保科技有限公司 High-salinity wastewater concentration system and concentration method
DE102023100537A1 (en) 2022-04-07 2023-10-12 Rainer Pommersheim Method and device for producing particles with a high magnesium content from seawater
WO2023193981A1 (en) 2022-04-07 2023-10-12 Rainer Pommersheim Method and device for producing particles with a high magnesium content from sea water

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NO985320D0 (en) 1998-11-13
AU1191400A (en) 2000-06-05

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