AU713866B2

AU713866B2 - Water removal device

Info

Publication number: AU713866B2
Application number: AU76318/96A
Authority: AU
Inventors: Graham John Bratton; Karon Doreen Buck; Timothy De Villiers Naylor
Original assignee: Smart Isle of Man Ltd
Current assignee: Smart Isle of Man Ltd
Priority date: 1995-11-22
Filing date: 1996-11-20
Publication date: 1999-12-09
Anticipated expiration: 2016-11-20
Also published as: GB9523854D0; KR19990071526A; CN1202839A; EP0863791A1; CA2237436A1; AU7631896A; WO1997018886A1; JP2000500394A

Description

1 The present invention relates to equipment for separating liquids, more particularly it relates to equipment which can be used to separate water from other liquids.

It is known that zeolite membranes can be used to separate water from other liquids and European Patent application 0481660 discloses and discusses prior art zeo-type membranes and refers in particular to US Patents 3244643, 3730910 and 4578372, Applied Catalysts 49(1989) 1-25, DE-A-3827049, CA1235684, JP-A-63287504, JP-A- 63291809, EP-A-135069.

Conventional use of membranes in liquid separation either involves through-flow methods, where the liquids to be separated are one side of the membrane and by the use of pressure differential or gravity one liquid is passed through the membrane leaving the liquid mixture on the other side of the membrane.

15 Alternatively, cross-flow separation is used, where the liquid mixture is passed across 0 the surface of the membrane in a continuous or semi-continuous stream and one liquid is removed from the stream by a pressure differential applied across the membrane.

0o0 The equipment used in such applications is purpose built and can involve complex pumping and control systems and the liquids are poured into the equipment.

S S We have devised a simpler and more convenient means of separating liquids which is easier to use in situ.

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Accordingly in one aspect the invention provides a device for removing water from mixtures containing water which device comprises a tubular support matrix having a first end which is open and a second end which is closed, there being a zeolite membrane grown on the second end of the support matrix.

The tubular means can be of any cross-sectional shape, e.g. circular, oval, ellipsoidal, rectangular, square, etc., although circular or oval cross-sectional MAW:NP:#28388.RS1 27 September 1999 WO 97/18886 PCT/GB96/02861 2 shapes are preferred. The ratio of length to cross-sectional area of the tubular means is not critical and, depending on its application, a very wide range of shapes can be used, e.g. from long thin tubes to shorter wider tubes.

The part of the tubular means containing a zeolite membrane is preferably a zeolite membrane on a supported matrix such as a metal mesh or sieve, ceramic, a polymer such as a polysulphone or a polyether sulphone etc. as disclosed in the above references. In the present invention the supported membrane can be formed into the desired shape to comprise part of the tubular means.

Preferably the zeolite membrane part of the tubular means is adjacent to the closed end and, if desired, the end can be formed of a zeolite membrane.

The other part of the tubular means can comprise the uncoated membrane support or it can be made of a metal, ceramic, plastic, etc. material. The material is not critical but it should be sufficiently strong enough and dimensionally stable to be suitable. It can be porous or non-porous, depending on how it is to be used.

The zeolite membranes should be substantially free of defects so as to provide an effective separation and zeolite membranes as described in our co-pending application PCT/GB95/02221 in which zeolite membranes are treated with a silicic acid are preferred.

Methods of making silicic acids are described in GB Patent Application 2269377 and a preferred method is by acidification of a sodium silicate solution followed by separation of the silicic acid by phase separation using an organic solvent such as tetrahydrofuran. The organic phase can then be dried and anhydrous silicic acid separated e.g. by addition of n-butanol to obtain a substantially anhydrous solution of silicic acid. The degree of polymerisation of the silicic acid depends on the actual conditions used e.g. the time the sodium silicate solution is in contact with the acid before addition of the organic solvent, temperature etc.

The silicic acid used in the present invention preferably has an average molecular weight in the range of 96 to 10,000 and more preferably of 96 to 3220.

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As well as treatment with silicic acids the zeo-type materials can be treated with alkylorthosilicates such as tetra ethyl ortho silicate (TEOS) and tetra isopropyl ortho silicate (TIPOT) akoxyorthosilicates such as tetramethoxyortho silicate which form a polysilicic acid when applied to the zeo-type material. These alkylorthosilicates and alkoxyorthosilicates form mesoporous silica compounds which consist essentially of a series of polysilicic acid units linked together, each unit comprising a polysilicic acid molecule as described in GB Patent Application 2269377 and comprising a plurality of three dimensional species linked together with each species either having silicon atom bridges with an oxygen atom between each silicon atom or hydroxyl groups on the silicon.

In one embodiment the tubular means is formed from a matrix which can be used as a support for a zeolite membrane and a zeolite membrane is then deposited, grown, crystallised or formed on part of the support, leaving the other part untreated.

The equipment of the invention can be used in two different ways. In the first way, the device of the invention is placed within a receptacle and the liquid mixture placed within the tubular means so that the liquid mixture is only in contact with the zeolite membrane or non-porous part of the tubular means. The liquid, which can pass through the zeolite membrane, e.g. water passes through the membrane into the receptacle, thus separating the liquids. A pressure differential is preferably applied across the membrane to facilitate the separation.

In another aspect the invention provides a method for separating water from liquids 25 containing water which method comprises placing the liquid in a vessel and immersing, in the liquid, a device which comprises a tubular support matrix having a first end which is open and a second end which is closed, there being a zeolite membrane grown on the second end of the support matrix and the device being immersed in the liquid so that the liquid is in contact with the zeolite membrane so that water passes through the membrane into the device.

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S 55 *5 0 55 MAW:NP:#28388.RS1 27 September 1999 In an alternative way of operation, the liquid mixture is contained in a receptacle and the device is placed in the liquid, with a portion of the tubular means comprising the zeolite membrane in contact with the liquid mixture. The liquid, which can pass through the membrane, will then pass into the tubular means and can be removed. A pressure differential can be applied across the membrane to facilitate the separation.

The device is particularly useful in removing water from the liquid mixtures containing water, for example, to lower the water content to acceptably low levels, e.g. in solvents, thinners and other liquids which can be contaminated with

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Of0 MAW:NP:#28388.RS1 27 September 1999 WO97/18886 PCT/GB96/02861 4 water and biological and pharmaceutical materials and other thermally sensitive materials. In one example, the liquid containing water is contained in a receptacle such as a beaker, Winchester, etc., the device of the invention placed within the liquid and a vacuum applied to the tubular means. The water in the liquid mixture is then drawn through the membrane. The system can be left running until the required degree of dehydration in the liquid mixture is obtained.

The device can then be removed, cleaned and used again, or if contaminated e.g.

by biological or pharmaceutical material, thrown away.

Thus, an easily transportable device can be obtained for removing water from water containing liquid mixtures, which is adaptable, easy to use and can be employed at the point of use of the liquid mixtures.

It is a feature of the invention that it enables water to be removed from liquid mixtures without the need for high pressure differentials across the membrane as in previously disclosed uses of zeolite membranes.

The invention is described in the Examples and drawing in which the Examples exemplify the preparation of the membrane and the drawing illustrates apparatus for application of the membranes.

Example I Membrane Growth The substrate used was a Pall PSS (Trade Mark) CP 1606 P05 316L porous sintered stainless steel cylinder filter as illustrated in fig. 1 in which is the cylinder filter and is a screw thread see Example 3.) The cylinder was placed in a 1 litre glass vessel which had previously been cleaned by washing with de-ionised water, acetone, toluene and finally acetone before being dried in an oven at 90 degrees C. for 3 hours.

WO 97/18886 PCT/GB96/02861 Cobalt pre-treatment: The cylinder was placed in a 1 litre glass vessel to which was added 800ml of 0.1 M cobalt nitrate solution and left to soak for 1 hour, after which the cobalt nitrate solution was decanted and the beaker was placed in an oven at 0 C to dry, the cylinder was removed from the beaker and fired at 250 0 C for 4 hours. The cylinder was removed from the furnace and allowed to cool.

This procedure was repeated 2 more times to obtain a good cobalt oxide coating.

Zeolite Pre-treatment Zeolite 4A powder was rubbed into the outside of the substrate, which had already been cobalt coated as above, using a gloved finger, until no more zeolite will rub into the surface, any excess zeolite was tapped off.

Two solutions A and B were prepared separately in two 500 ml glass bottles as follows:- Solution A 73 4 7 g Sodium Aluminate, 11.25g Sodium Hydroxide and 4 45.8g de-ionised water were mechanically shaken until dissolved. The Sodium Aluminate had an actual composition 62.48% A1 2 0 3 35.24% Na20, and 2.28% H 2 0.

Solution B 151.71g Sodium Silicate of composition 14.21% Na20, 35.59% SiO 2 and 50.20% H 2 0 was dissolved in 4 4 5.80g de-ionised water.

Solution A was added slowly to solution B with both stirring and shaking by hand to ensure complete and even mixing (it is important that no lumps of hydrogel are formed). This resulted in a hydrogel having a molar composition 2.01 Na20 A1 2 0 3 2.0 SiO 2 120.0 H 2 0 WO 97/18886 PCT/GB96/02861 6 800 ml of the hydrogel was slowly poured into a growth vessel containing the cobalt oxide treated and zeolite rubbed cylinder in a vertical position. The growth vessel was placed in a pressure cooker together with a beaker containing the remaining hydrogel solution. The pressure cooker was placed in an oven preheated to 100 degrees C. for 5 hours. Subsequently it was removed from the oven and allowed to cool for 30 minutes. The growth vessel was removed and the solution poured away.

The cylinder was carefully removed from the vessel. The cylinder was placed in a glass vessel and washed three times with 800ml aliquots of de-ionised water, swirling the solution each time to ensure complete removal of residues and the membrane was allowed to air dry in air at 70 0 C for 2 hours.

The surface of the dried coated cylinder was subsequently wiped clean with a clean lens tissue in order to remove any loose powdery deposits which may have formed on the surface. It was then washed with de-ionised water and left to in an oven at 70(C for 2 hours. This growth and washing process was repeated two more times.

X-ray Analysis showed this to be a Zeolite 4A Exampkle Preparation of TEOS For Post Treatment of Membrane The post treatment solution was prepared by placing 120ml of (TEOS) into a clean, dry beaker, adding 540 ml of deionised water and 540ml of ethanol.

The mixture was then stirred at 3 00r.p.m. for a period of 5 mins.

Examplep3 Membrane Test Procedure The cylinder was placed in a 1 litre glass vessel on a heater/stirrer hot plate and a vacuum line was attached to the end of the cylinder by a screw thread.

The glass vessel cell was filled with an isopropanol/water

(IPA/H

2 0) mixture (90/10 wt. respectively). The membrane was tested at approximately 0

C.

WO 97/18886 PCT/GB96/02861 7 The pressure on the side of the membrane remote from the liquid i.e. inside the cylinder was reduced to 4 mbar (0.4 kN). Permeate was collected over periods of 8 hours and weighed, and small aliquots were analysed, feed water concentration was monitored throughout.

Example 4 Post-treatment Procedure of Membrane After the initial test of the untreated membrane in the apparatus of Example 3 with IPA/Water, the glass vessel was emptied, rinsed with 2 x 100 ml aliquots of ethanol and then another 100ml aliquot of ethanol was placed into the glass vessel and cylinder was then placed under vacuum for 30 mins.

The ethanol was removed from the glass vessel and the TEOS post-treatment solution prepared as in Example 2 was poured into the glass vessel. The cylinder cell was then treated at 70°C for a period of 24 hours, with the inside of the cylinder under vacuum. After this period, the mix was removed, the heat switched off, vacuum removed and then compressed air was passed over the membrane for a period of one hour.

Example i A membrane produced by the method of Example 1 was treated under pervaporation conditions described in Example 3 and the post treatment described in example 4 and the results shown in Table 1 below WO 97/18886 PCT/GB96/02861 8 Table 1 Isopropanol/Water mixture at 70 0

C.

Time on Stream Feed Water Permeate Water Permeate Water Flux (hours) Weight Weight Kg/m 2 /day 7.99 82.18 27.25 7.60 80.40 23.26 7.35 78.14 22.39 6.45 75.38 21.14 5.84 72.52 19.79 5.23 69.45 18.36 4.88 66.14 18.46 4.41 60.90 16.14 3.75 57.61 15.05 3.46 57.32 13.25 3.16 48.26 13.18 2.69 45.93 12.30 2.19 42.16 8.76 1.90 38.42 8.27 1.59 33.15 8.44 1.47 29.51 7.89 1.18 26.44 6.98 1.16 25.77 6.44 1.00 22.02 5.56 10.0 0.86 21.31 4.87 10.5 0.75 20.34 4.35 11.0 0.66 18.16 3.91 11.5 0.60 16.06 3.26 12.0 0.52 13.98 2.68 12.5 0.44 10.59 1.89 An embodiment of the invention showing equipment in use is shown if fig. 2 in which a receptacle contains a liquid mixture containing water. A tube (3) made of metal mesh has a lower portion on which is deposited a zeolite membrane.

In use the tube is placed in the water-containing liquid in the receptacle and a vacuum is applied at Water is drawn through membrane into the tube, as shown at from where it can be removed. Thus, the liquid left behind, contains a lower proportion of water.

In an alternative application the water containing liquid is placed within the tube and the pressure reduced outside the tube. Water then passes through the membrane leaving a liquid with reduced water content in the tube.

The claims form part of the disclosure of the invention. The term "comprises" is non exclusive.

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MAW:NP:#28388.RS1 27 September 1999

Claims

1. A method for separating water from liquids containing water which method comprises placing the liquid in a vessel and immersing, in the liquid, a device which comprises a tubular support matrix having a first end which is open and a second end which is closed, there being a zeolite membrane grown on the second end of the support matrix and the device being immersed in the liquid so that the liquid is in contact with the zeolite membrane so that water passes through the membrane into the device.

2. A method as claimed in claim 1 in which the support matrix is a metal mesh.

3. A method as claimed in claim 1 in which the support matrix is a porous ceramic support.

4. A method as claimed in any one of claims 1 to 3 in which the zeolite membrane has been treated by being contacted with a silicic acid to form a membrane substantially free of holes.

A method for separating water from liquids containing water which method comprises placing the liquid inside a device which comprises a tubular support matrix having a first end which is open and a second end which is closed, there being a zeolite membrane grown on the second end of the support matrix and the device being immersed in the liquid so that the liquid is in contact with the zeolite membrane so that water passes out through the membrane.

6. A method as claimed in claim 5 in which the support matrix is a metal mesh.

7. A method as claimed in claim 5 in which the support matrix is a porous ceramic support.

8. A method as claimed in any one of claims 5 to 7 in which the zeolite membrane has been treated by being contacted with a silicic acid to form a membrane substantially free of holes. MAW:NP:#28388.RSI 27 September 1999 I I 11

9. A device for removing water from mixtures containing water which device comprises a tubular support matrix having a first end which is open and a second end which is closed, there being a zeolite membrane grown on the second end of the support matrix.

A device as claimed in claim 9 in which the support matrix is a metal mesh.

11. A device as claimed in claim 9 in which the support matrix is a porous ceramic support.

12. A device as claimed in any one of claims 9 to 11 in which the zeolite membrane has been treated by being contacted with a silicic acid to form a membrane substantially free of holes. 15

13. A method according to any one of claims 1 to 8 substantially as hereinbefore described with reference to the examples.

14. A device according to any one of claims 10 to 12 substantially as hereinbefore described with reference to the examples. DATED: 27 September 1999 CARTER SMITH BEADLE Patent Attorneys for the Applicants: S Graham John BRATTON, Timothy de Villers NAYLOR and Karon Doreen BUCK S MAW:NP:#28388.RS1 27 September 1999