IMPROVEMENTS RELATING TO WATER PURIFICATION

Abstract

A method of obtaining water from a liquid composition comprising water, the method comprising: (a) providing a sorbent material; (b) contacting the sorbent material with the liquid composition comprising water; (c) separating the sorbent material and the liquid composition comprising water; and (d) desorbing water from the sorbent material; wherein the sorbent material is a metal-organic material.

Claims

1. A method of obtaining water from a liquid composition comprising water, the method comprising: (a) providing a sorbent material; (b) contacting the sorbent material with the liquid composition comprising water; (c) separating the sorbent material and the liquid composition comprising water; and (d) desorbing water from the sorbent material; wherein the sorbent material is a metal-organic material.

2. A device for obtaining water from a liquid composition comprising water, the device comprising: a sorbent material movable between a first position and a second position; wherein in the first position the sorbent material is contactable with the liquid composition comprising water and in the second position the sorbent material is located within a conduit.

3. The method according to claim 1, wherein the sorbent material is a metal-organic material and preferably wherein the metal-organic material comprises metal species and ligands.

4. The method as claimed in claim 3 wherein the metal species is selected from copper, cobalt, nickel, iron, zinc, cadmium, zirconium, magnesium, calcium and aluminium.

5. The method as claimed in claim 4 wherein the ligands are selected from 4,4′-bipyridine (L1), 1,4-bis(4-pyridyl)benzene (L2), 4,4′-(2,5-dimethyl-1,4-phenylene)dipyridine (L3), 1,4-bis(4-pyridyl)biphenyl (L4), 1,2-di(pyridine-4-yl)-ethene (L5), 2,4-pyridinedicarboxylic acid (L80), benzotriazole-5-carboxylic acid (L128), glutaric acid (L141) and benzene-1,4-dicarboxylic acid (L156), preferably wherein the sorbent material is [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)].

6. The method as claimed in claim 1, wherein the liquid composition comprising water is highly salted water and/or waste water or effluent water.

7. The method as claimed in claim 1, wherein in step (b) the liquid composition comprising water is housed within a container.

8. The method as claimed in claim 1, wherein in step (c) the sorbent material is rotated to remove it from the liquid composition comprising water.

9. The method according to claim 1, wherein step (d) involves contacting the sorbent material with warm air and/or dry air, preferably further comprising step (e) of condensing the desorbed water vapour to provide liquid water.

10. The device according to claim 2, wherein the sorbent material is arranged such that a portion of the sorbent material is in the first position and a portion of the sorbent material is in the second position.

11. The device according to claim 2, wherein the sorbent material is provided in a disc-shaped or annular body, preferably wherein the device is configured to rotate around the central axis of the disc-shaped or annular body.

12. The device according to claim 2, wherein the conduit comprises an inlet and an outlet to direct the flow of air.

13. The device according to claim 2, wherein the device comprises a desorption means.

14. The device according to claim 2, further comprising a receptacle for collecting desorbed water or means for directing desorbed water into a water delivery system.

15. The method according to claim 1, carried out using a device comprising: a sorbent material movable between a first position and a second position; wherein in the first position the sorbent material is contactable with the liquid composition comprising water and in the second position the sorbent material is located within a conduit.

16. The device according to claim 2, wherein the sorbent material is a metal-organic material and preferably wherein the metal-organic material comprises metal species and ligands.

17. The device as claimed in claim 16 wherein the metal species is selected from copper, cobalt, nickel, iron, zinc, cadmium, zirconium, magnesium, calcium and aluminium.

18. The device as claimed in claim 4 wherein the ligands are selected from 4,4′-bipyridine (L1), 1,4-bis(4-pyridyl)benzene (L2), 4,4′-(2,5-dimethyl-1,4-phenylene)dipyridine (L3), 1,4-bis(4-pyridyl)biphenyl (L4), 1,2-di(pyridine-4-yl)-ethene (L5), 2,4-pyridinedicarboxylic acid (L80), benzotriazole-5-carboxylic acid (L128), glutaric acid (L141) and benzene-1,4-dicarboxylic acid (L156), preferably wherein the sorbent material is [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)].

19. The device as claimed in claim 2, wherein the liquid composition comprising water is highly salted water and/or waste water or effluent water.

Description

[0210] The invention will now be further described with reference to the accompanying drawings, in which

[0211] FIG. 1 shows a cross sectional view of a device according to the present invention; and

[0212] FIG. 2 shows a detailed view of the circular rotor.

[0213] The device comprises a reservoir (1) and a conduit (2). A liquid composition comprising water (3) is housed within the reservoir (1). A disc of sorbent material (4) is suspended from a motor (5) by a belt (6) which allows the sorbent material to rotate through 360°. The disc of sorbent material cycles between a first position (A) wherein the sorbent material is immersed in the liquid composition comprising water in the reservoir (1) and a second position (B) within the conduit (2). In the second position the sorbent material is exposed to a continuous flow of dry air which passes through the conduit via an inlet (7). Water vapour exits through an outlet (8) and is condensed.

[0214] The invention will now be further described with reference to the following non-limiting examples.

[0215] In the following examples, powder X-ray diffraction (PXRD) measurements were taken using microcrystalline samples using a PANalytical Empyrean™ diffractometer equipped with a PIXcel3D detector. The variable temperature powder X-ray diffraction (VT-PXRD) measurements were collected using a Panalytical X'Pert diffractometer.

[0216] Single crystal X-ray diffraction (SCXRD) measurements were also collected on a number of compounds. The data was collected using a Bruker D8 Quest diffractometer.

[0217] Thermogravimetric analysis (TGA) was carried out under nitrogen using the instrument TA Q50 V20.13 Build 39 and data was collected in the high resolution dynamic mode.

[0218] Fourier Transform Infrared (FT-IR) spectra were measured on a Perkin Elmer spectrum 200 spectrometer.

[0219] Low-pressure N2 adsorption measurements were performed on approximately 200 mg of sample using ultra-high purity grade Nz. The measurements were collected using a Micrometrics TriStar II PLUS and a Micrometrics 3 Flex was used to analyse the surface area and pore size.

[0220] Vacuum dynamic vapour sorption (DVS) studies made use of a Surface Measurement Systems DVS Vacuum, which gravimetrically measures the uptake and loss of vapour. The DVS methods were used for the determination of water vapour sorption isotherms using approximately 15 to 30 mg of sample. Pure water was used as the adsorbate for these measurements and temperature was maintained by enclosing the system in a temperature-controlled incubator.

EXAMPLE 1

Synthesis and Properties of [Cu.SUB.2.(Glutarate).SUB.2.(4,4′-Bipyridine)] (ROS-037)

[0221] Synthesis of [Cu.sub.2(Glutarate).sub.2(4,4′-Bipyridine)]

[0222] Cu(NO.sub.3).Math.3H.sub.2O (242 mg, 1 mmol), glutaric acid (132.1 mg, 1 mmol), and 4,4′-bipyridine (78 mg, 0.5 mmol) were mixed in water (100 ml). NaOH was added dropwise with swirling to the solution to prevent precipitation. The blue solution was placed in an oven preheated to 85° C. Green powder was obtained after 24 to 48 hours. This compound may also be referred to as ROS037. FIGS. 3A and 3B shows the crystallographic structure of this compound.

Water Vapour Sorption Studies of [Cu.sub.2(Glutarate).sub.2(4,4′-Bipyridine)]

[0223] Water vapour sorption studies for [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] were performed at 25° C., shown in FIG. 4. The sample shows a very narrow hysteresis gap, indicating that water desorption is not restricted.

Kinetic Studies of [Cu.sub.2(Glutarate).sub.2(4,4′-Bipyridine)]

[0224] Water sorption and desorption kinetics for [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] were obtained at 25° C., demonstrated in FIG. 5. The kinetics data in FIG. 5 show that all steps reach equilibrium over a range of temperatures. The removal of water from the structure does not require any additional heating or vacuum, as evidenced by the mass returning to its original value at 0% relative humidity.

Reversibility Studies of [Cu.sub.2(Glutarate).sub.2(4,4′-Bipyridine)]

[0225] Nineteen cycles of adsorption and desorption at 25° C. were performed in total. Reversible switching isotherms are observed and no hysteresis gap is detected, indicating water desorption is not restricted. [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] shows a high working adsorption capacity in the low partial pressure range 30% P/Po), as demonstrated in FIG. 6.

EXAMPLE 2

Alternative Synthesis of [Cu.SUB.2.(Glutarate).SUB.2.(4,4′-Bipyridine)]

[0226] In a beaker, Cu(OH).sub.2 (488 mg, 5 mmol) was suspended in 100 mL of water with stirring for 5 minutes. Glutaric acid (1.32 g, 10 mmol) was added and allowed to stir for 5 minutes. The solution became clear and dark blue in colour. 4,4′-bypyridyl (390.5 mg, 2.5 mmol) was added and a green precipitate was formed in 10 minutes. The mixture was filtered and washed with 50 mL of water to obtain the solid product, Yield, 1.332 g, >94%.

[0227] Characterisation of the product confirmed this to be identical to the product obtained in Example 1.

EXAMPLE 3

Lab-Scale Synthesis of [Cu.SUB.2.(Glutarate).SUB.2.(4,4′-Bipyridine)]

[0228] ROS-037 was synthesized in lab scale by a modified literature protocol as follows: 350 mL of water was taken in a 500 mL conical flask and glutaric acid (24.3 g, 0.184 mol) was added followed by the addition of NaOH (14.7 g, 0.368 mol) and stirred until a clear solution was obtained. Cu(NO.sub.3).sub.2.Math.2.5H.sub.2O (42.7 g, 0.184 mol) was added and allowed to stir for 10 minutes. 4,4′-bypyridyl (14.4 g, 0.092 mol) was added and the mixture was allowed to stir for 1 hour at 70° C. Once the reaction was completed, the solution was filtered to obtain the solid product, and further washed with water to remove any traces of unreacted reactants and air dried.

[0229] Yield, 48 g, >98%.

[0230] Characterisation of the product confirmed this to be identical to the product obtained in Example 1.

EXAMPLE 4

Scale-Up Synthesis of [Cu.SUB.2.(Glutarate).SUB.2.(4,4′-Bipyridine)]

[0231] ROS-037 can be scaled up to mini-plant scale by water slurry method as follows. 3.5 L of water was added to the 5 L reactor and the stirrer was set to 750 rpm. Glutaric acid (243 g, 1.84 mol) was added and allowed to dissolve for 10 minutes. NaOH (147 g, 3.68 mol) was added and the temperature of the reactor was set to 70° C. (Note: Reaction can be carried out at room temperature also, however more reaction time is required). Once a clear solution was obtained, Cu(NO.sub.3).sub.2.Math.2.5H.sub.2O (427 g, 1.84 mol) was added and allowed to stir for 15 minutes. 4,4′-bypyridyl (144 g, 0.92 mol) was added and the mixture was allowed to stir for 6 hours. Once the reaction was complete, the solution was filtered to obtain the solid product, which was further washed to remove any traces of NaOH and unreacted reactants and air dried. Yield, 481 g, >98%.

EXAMPLE 5

Loading of [Cu.SUB.2.(Glutarate).SUB.2.(4,4′-Bipyridine)] (ROS-037) on a Paper Support

[0232] [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] powder was added in a standard cellulose paper making process that anyone skilled in the art could perform. Cellulose fiber was first dispersed in water at approximately 3-5% solids. [Cu.sub.2(glutarate)2(4,4′-bipyridine)] powder was added to the fiber mixture and agitated in order to disperse. The blend was then diluted to very low solids content (1% or less) to provide an attraction between the fibers and the desiccant powder. The evenly dispersed mixture was drained through a screen. The remaining water was removed from the wet sheet of fibers/powder through vacuum, pressing, and drying. Good adsorption and desorption properties were recorded for the resulting material.

[0233] FIG. 7 shows the Powder X-ray diffraction spectrum of the paper composite (top line) in comparison with as synthesized powder (middle line) and calculated powder (bottom line).

[0234] FIGS. 8 and 9 respectively show flat section and cross section SEM images of the paper composite.

[0235] FIG. 10 shows experimental isotherms for water vapour sorption at 27° C. on [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] powder and its paper composite, respectively from the top down. In-situ pre-treatment (intrinsic-DVS) before collecting isotherm at 40° C. for 120 min.

[0236] Isotherm collected at 27° C. (Intrinsic-DVS). dm/dt<0.01%/min.

EXAMPLE 6

Desalination Testing Using [Cu.SUB.2.(Glutarate).SUB.2.(4,4′-Bipyridine)]

[0237] [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] samples were placed in an oven for 12 h at 80° C. Afterwards, the container was sealed and kept under nitrogen flow for 2 h. Adsorbent-solution (solution of 30 mL of saline (NaCl) aqueous solution in a concentration range from 0.0 to 111.1 g/L exposed to 1 g/L, 50 g/L or 500 g/L of adsorbent) were studied at 25° C. Suspensions were stirred using a magnetic stirrer for 8 h. The resulting slurry was filtered with a syringe filter (0.22 μm pore size) and the residual saline solution was collected. NaCl concentration in all aqueous solution (before and after soaking [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] at different concentrations) was analysed by using a conductivity meter (model: JENWAY 4510). Measurements were performed three times and the mean was calculated. The concentration of NaCl (g/L) was determined by correlating the conductivity (mS) and a [NaCl] calibration curve. The results indicate that [Cu.sub.2(glutarate).sub.2(4,4′-bipyridine)] increased NaCl concentration by the expected amount in every experiment showing that the material can adsorb water from concentrated salt solutions.