COMPRESSED SALT OBJECTS

Abstract

Provided are objects constructed of compressed salt combinations including salt and at least one additive, wherein the at least one additive is selected to impart the object with resistance to water and humidity.

Claims

1. An object constructed of a compressed salt combination comprising salt and at least one additive, the at least one additive being selected to impart the object with resistance to water and humidity, the compressed salt combination being characterized by a compressive strength of at least 20 MPa, wherein the salt combination comprises at least 90% sodium chloride.

2. An object constructed of a compressed salt combination comprising salt and at least one additive, the at least one additive being selected to impart the object with resistance to water and humidity, the compressed salt combination being non-deliquescent, when measured at 40 C. at below 74% relative humidity, wherein the salt combination comprises at least 90% sodium chloride.

3. An object constructed of a compressed salt combination comprising salt and at least one additive, the at least one additive being selected to impart the object with resistance to water and humidity by interacting with at least one component present in said salt combination to afford a water-insoluble material, the compressed salt combination being non-deliquescent, when measured at 40 C. at below 74% relative humidity, or of a compressive strength of at least 20 MPa, wherein the salt combination comprises at least 90% sodium chloride.

4. The object according to claim 1, wherein the compressed salt combination being non-deliquescent, when measured at 40 C. at below 74% relative humidity.

5. The object according to claim 1, wherein the at least one additive is selected to interact in situ with at least one component present in said salt combination.

6.-12. (canceled)

13. The object according to claim 1 wherein the compressed salt combination consists a salt combination and at least one additive.

14. The object according to claim 1 wherein the amount of the at least one additive, relative to the total weight of the salt combination, is at least 0.1 wt %.

15.-18. (canceled)

19. The object according to claim 1, wherein the at least one additive is selected from water-soluble or water-insoluble carbonate salts, C.sub.12 to C.sub.20 carboxylates, C.sub.12 to C.sub.20 carboxylic acids, water soluble silicates, siloxane polymers, siloxane polymer precursors, phosphate salts, hydroxide salts, gypsum, lime slag cements and combinations thereof.

20.-43. (canceled)

44. The object according to claim 19, wherein the at least one additive is gypsum, or lime, or a silicate or a siloxane or a siloxane polymer.

45.-52. (canceled)

53. The object according to claim 1, wherein the compressed salt combination consists of sodium chloride and at least one additive.

54.-63. (canceled)

64. The object according to claim 1, being non-deliquescent.

65. A non-deliquescent object constructed of a compressed salt combination comprising salt and at least one additive, the at least one additive being selected to impart the object with resistance to water and humidity, the compressed salt combination having a compressive strength of at least 20 MPa.

66. The object according to claim 65, having a surface contact angle of at least 65.

67. (canceled)

68. The object according to claim 1, surface coated on at least one surface region thereof with a film or a coating of at least one coating material.

69.-85. (canceled)

86. The object according to claim 1, being in the form of a block or a board.

87. The object according to any claim 1 for use as a building or construction unit.

88. (canceled)

89. A structure constructed of two or more objects according to claim 1.

90. The object according to claim 89, wherein the salt combination comprises at least one of 22% wt sodium; at least 53% wt chloride; at least 0.1% wt magnesium or calcium; at least 0.05% wt potassium; at least 0.05% wt bromine; and at least 0.05% wt sulfate, wherein the amount of magnesium chloride or calcium chloride is less than 0.001% wt.

91. The object according to claim 1, wherein the salt combination comprises at least one of 22% wt sodium; at least 53% wt chloride; at least 0.1% wt magnesium or calcium; at least 0.05% wt potassium; at least 0.05% wt bromine; and at least 0.05% wt sulfate, wherein the amount of magnesium chloride or calcium chloride is less than 0.001% wt.

92. A loose granulate or powder composition suitable for compressing into a stable object by application of pressure, the composition being characterized by ICP (on a dry matter basis) to comprise: at least 22% wt sodium; at least 53% wt chloride; and at least 0.1% wt magnesium or calcium wherein the amount of magnesium chloride or calcium chloride is less than 0.001% wt.

93. The composition according to claim 92, further comprising one or more of: at least 0.05% wt potassium; at least 0.05% wt bromine; and at least 0.05% wt sulfate as calculated on dry matter basis.

94. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0136] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0137] FIGS. 1A-B provide SEM images of a pellet of a Dead Sea compressed salt coated with gypsum-PDMS coating according to some embodiments of this invention at magnification of 50.

[0138] FIGS. 2A-B provide further magnifications of the SEM image of FIGS. 1 to 100, and elemental analysis of the layers observed in back scattering.

[0139] FIGS. 3A-D are SEM images of a pellet of the Dead Sea compressed salt coated with a first layer of gypsum and a second layer of a commercial outdoor paint.

[0140] FIGS. 4A-F show compressive strength testing of compressed salt cubes, comparing Dead Sea salt (FIG. 4A) to treated salt by several treatments (FIGS. 4B-F) to overcome deliquescence.

[0141] FIG. 5 depicts water uptake when conditioning a compressed formulated DSS at 80% RH and water release when reversing the conditions to 45% RH, both conditions at 40 C.

[0142] FIG. 6 shows schematically the pressing of salt boards in a roll press.

[0143] FIG. 7 shows thermograms of DSS as measured by simultaneous TGA and DSC, and the emission of water and CO.sub.2 from the sample as analyzed by MS.

[0144] FIG. 8 shows thermograms of formulated DSS as measured by simultaneous TGA and DSC, and the emission of water and CO.sub.2 from the sample as analyzed by MS.

DETAILED DESCRIPTION OF EMBODIMENTS

NON-LIMITING EXAMPLES

Example 1

General Procedure for Coating of a Model Pellet Made of the Dead Sea Salt (DSS) by Gypsum

[0145] A salt from the Dead Sea was collected on the beach of the sea. The salt was oven dried at 120 C. for 2 hours. 0.5 g salt was presses into pellet using a die for making IR disks. A PIKE press was used at 3.5-4.6 ton pressure to form a solid pellet. To prepare the gypsum coating, about 1 g of PDMS (SA#481955, MW 2500-2800) was mixed with the water. 0.5 g CaSO.sub.4.2H2O (SA#31221) was grounded and mixed with 24.5 g commercial calcined gypsum bought at the local hardware shop. The dry mixture was added over 30 s into the water, then mixed with a spatula for 60 s and poured into a vial. Salt pellets were dipped for 10 s into the mixture and pulled slowly, once it was viscous enough. Samples were either allowed to dry at r.t., or first heated in an oven to 100 C. for 5 minutes, then allowed to dry at r.t. for 24 hours. Some of the dried samples were dipped into a commercial paint suitable for outdoor painting (Tambur, blue 487-438 paint for walls).

Example 2

SEM Image of a Pellet Coated with Gypsum Comprising PDMS

[0146] A pellet was carefully cut by hand in its middle. The sample was characterized in an environmental SEM microscope Quanta 200 (FEI Company). Sample NL20160112-3 is provided in FIG. 1 and FIG. 2. Clear boundaries were observed between the core salt and the gypsum coating at 50 magnification in FIG. 1, both in direct mode, A, and in back scattering, B. Further magnification of the coating layer, 100, shown in FIG. 2, shows a clear darker area comprising PDMS at the air interface of the coating and brighter inner layer of the coating, as confirmed by elemental analysis for gypsum, A, and a mixture of gypsum and PDMS, B.

Example 3

SEM Image of a Pellet Coated with Gypsum Comprising PDMS

[0147] A sample prepared according to Examples 1 and 2 was coated with a commercial blue paint by dipping. The coated pellet was carefully cut by hand at its middle, and characterized by SEM. The three layers are clearly seen at 200 magnification in FIG. 3A, and further at 1000 magnification in FIG. 3B. Chemical analyses shown in FIG. 3C and 3D confirm the compositions of the layers to be gypsum and paint respectively.

Example 4

Deliquescence and Prevention of Deliquescence Phenomena

[0148] A) Control: Oven dried DSS (120 C., 2h) was compressed into a 202020 mm.sup.3 (z direction1 mm) cubes (8 ton pressure for 5-10 minutes at r.t.). Volume density of the cube was 1.875 g/cm.sup.3. Sample cubes were left on a petri dish at open air, control samples were kept in a desiccator. After 3-4 days, the samples held at open air became visually wet, and a pool of water was collecting under them, while samples held in a desiccator were stable. The samples in the petri dish eventually lost their integrity over days, and partially dissolved. Further samples were coated with gypsum as described in Example 1. After drying the coating, a bi-component epoxy was applied to glue the cube to a wooden stick. Once dried, the stick was used to hang the coated salt cube above a laboratory beaker, such that water would drip from the cube to the beaker but the cube is maintained not in contact with the water. A pool of water was collected under the cube, but the cube maintained its shape and integrity for months.

[0149] B) Pretreatment by Na.sub.2CO.sub.3 dissolved in water: a solution was prepared by dissolving 65 g of Na.sub.2CO.sub.3 in 250 ml deionized water. 25 ml of the resulting solution was thoroughly mixed by hand with 30 g oven dried and ground with DSS. The resulting moist salt was dried again in the oven, and then pressed in the same manner as in sample (A). Samples left on the bench in a petri dish for weeks did not show any deliquescence.

[0150] C) Pretreatment by Na.sub.2CO.sub.3 dissolved in water: a solution was prepared by dissolving 65 g of Na.sub.2CO.sub.3 in 250 ml deionized water. 10 ml of the resulting solution was thoroughly mixed by hand with 30 g oven dried and ground with DSS. The resulting moist salt was dried again in the oven, and then pressed in the same manner as in sample (A). Samples left on the bench in a petri dish showed some deliquescence, evident by formation of some water in the petri dish, the amount was much smaller as compared to the control sample, showing that partial ion exchange occurred.

Example 5

Prevention of Deliquescence Phenomena by Powder Mixing

[0151] 6.5 g Na.sub.2CO.sub.3 was grounded in a kitchen grinder with 30 g of oven dried and ground DSS. The resulting fine powder was allowed to stand in a petri dish on the bench. After few days under exposure to humidity in the room, the powder agglomerated, showing no deliquesce, i.e. no water was visible.

[0152] The powder mix was pressed in the same manner as in Example 4. Samples left on the bench showed wetting for the first 3 days, but then dried up. This is attributed to in-situ ion exchange occurring once moisture is absorbed, resulting in stabilizing of the cube once MgCO.sub.3 was formed.

Example 6

Stabilized Formulation of DSS

[0153] 1 g of sodium stearate was added to 20 ml of water and the mixture was heated and stirred until a clear solution was obtained. 30 g of dried (120 C.) DSS was dissolved in 50 ml of water and the solution was heated at the same temperature of the sodium stearate solution. The hot soap solution of sodium stearate was added to the hot salt solution under stiffing, causing visible precipitation of calcium and magnesium stearate. The residual calcium and magnesium in the salt solution was precipitated as carbonate by addition of 25 ml of 260 g/L sodium carbonate solution. Water was evaporated on hot plate and the salt obtained was completely dried in oven at 120 C.

Example 7

Stabilized Formulation of DSS

[0154] 1 g of sodium stearate was added to 20 ml of water and the mixture was heated and stirred until a clear solution was obtained. 30 g of DSS was suspended in the water and mixed for 1 h at 50-80 C. 6.5 g Na.sub.2CO.sub.3 was added and mixed with the slurry for additional 30 minutes. The solid was collected and dried.

Example 8

Compression Strength Testing of Compressed Salt Cubes

[0155] 15 grams of salt were compressed in a die, where the area was 2020 mm.sup.2, by pressing for 5 min at 2 ton/cm.sub.2. The height of the pressed cubes was 17.7 to 20.5 mm. The salt treated according to Examples 4, 5, 6 and 7 were all compressed successfully, as well as untreated Dead Sea salt. All compressed cubes were physically stable and could be handled. 3 cubes of each treatment were tested for compression strength in an Instron model 4500-10 KNtensile compressive strength tester, 10 KN cell. The results are presented in FIG. 4. Untreated salt cubes could not be broken under the maximum applied pressure of this instrument, i.e. their compressive strength was greater than 22.5 mPa and Young modulus of 800+100 mPa. Stabilizing according to Example 5 followed by incubation of the salt on the bench yielded cubes with Young modulus of 700100 mPa (Treatment A); incubating the same in a moisture oven at 30 C., 50% RH for 3 days yielded cubes with Young modulus of 81020 mPa (Treatment B); stabilizing the salt according to Example 4B yielded cubes with Young modulus of 79070 mPa (Treatment C), all three conditions showed compressive strength greater than 22.5 mPa. Only treatment according to Example 5, followed by incubating the salt in a closed dry contained yielded weak cubes having Young modulus of 400200 mPa and compressive strength of 103 mPa (Treatment D). Stabilizing and hydrophobizing according to Example 6 also yielded cubes having Young modulus of 71070 mPa, and compressive strength greater than 22.5 mPa (Treatment E).

Example 9

Stabilized Formulation of DSS

[0156] Sodium stearate (0.4-1.6% wt/DSS wt) was dissolved in 83 ml DI water at 75 C. and added to 100 g DSS powder (ca. 95% NaCl) while stiffing. 16.6 ml Sodium carbonate solution (65 g Na.sub.2CO.sub.3 in 250 ml DI water) was added to the DSS slurry until pH was 10 or higher. A solution of 1.6 g CaCl.sub.2 dissolved in 10 ml water was added while stiffing, followed by a solution of 2.05 g Na.sub.2SO.sub.4 dissolved in 10 ml water. The slurry was heater to 80 C., then dried at 50 C. and ground.

Example 10

Stabilized Formulation of DSS

[0157] Sodium stearate (0.4-1.6% wt/DSS wt) was dissolved in 83 ml DI water at 75 C. and added to 100 g DSS powder (ca. 95% NaCl) while stiffing. 16.6 ml Sodium carbonate solution (65 g Na.sub.2CO.sub.3 in 250 ml DI water) was added to the DSS slurry until pH was 10 or higher. A cementing agent was added while stiffing, see Table 1. The slurry was dried at 50 C. and ground.

TABLE-US-00001 TABLE 1 cementing agents added to the formulation. Type Amount, g Water, ml Gypsum 2 20 Hydraulic Lime NHL 3.5 2 20 Cement CIII/B 42.5N 239 2 20 (Slag cement)

Example 11

Stabilized Formulation of DSS

[0158] Sodium stearate (0.4-1.6% wt/DSS wt) was dissolved in water (25 ml per 30 g DSS) at 75 C. and added to the DSS powder (ca. 95% NaCl) while stiffing. Sodium carbonate solution (65 g Na.sub.2CO.sub.3 in 250 ml water) was added to the DSS slurry until pH was 10 or higher (ca.17 ml per 100 g DSS). 19 ml of saturated NaCl solution was added with stiffing. The slurry was filtered on a Buchner using Whatman No. 1 filter paper, the solid was collected and dried.

Example 12

Stabilized Formulation of DSS

[0159] Sodium stearate (0.4-1.6% wt/DSS wt) was dissolved in 83 ml DI water (25 ml per 30 g DSS) at 75 C. and added to the DSS powder (ca. 95% NaCl) while stirring.16.6 ml Sodium carbonate solution (65 g Na.sub.2CO.sub.3 in 250 ml DI water) was added to the DSS slurry until pH was 10 or higher. 0.1-5% sodium silicate solution (24.5 g NaOH and 49 g of SiO.sub.2 dissolved in 100 ml DI water) was mixed with 4 times as much HCl solution (ca. 1.5%). The mixture was added to the slurry while stiffing. The slurry was dried at 120 C.

Example 13

Stabilized Formulation of DSS

[0160] Trimethylsiloxy silicate (TMSS, 0.25 g) was dissolved in 25 ml ethanol at 65 C. Sodium stearate (0.25 g) was added to this solution. The resulting ethanol solution was added to DSS (15 g) at 70=75 C. Once ethanol starts to boil, 12.5-25 ml of a sodium carbonate solution (65 g Na.sub.2CO.sub.3 in 250 ml DI water) is added while stiffing. The resulting slurry is dried at 100 C. for 1 hour.

Example 14

TMSS Coating

[0161] A pellet prepared according to Example 12 was coating with TMSS by dipping for 1.5 minute into a solution of TMSS in ethanol (1 g TMSS in 8 ml ethanol).

Example 15

Properties of Compressed Objects of Different Formulations in Contact with Water

[0162] Properties of formulated compressed objects were evaluated by 3 methods: (i) measurement of the contact angle of a drop of water was conducted using a Rame-hart instrument, model 100-00 goniometer, USA; (ii) the time needed for the object to absorb a drop of 10 microliter of water was measured; (iii) a compressed disk of 0.5 g was immersed in 50 ml DI water, the conductivity of the water was measured and the amount of salt dissolved was calculated (assuming all the dissolved salt is NaCl). The results are summarized in Table 2.

TABLE-US-00002 TABLE 2 Properties of different formulations and treatments of compressed DSS samples. hexadecane Wt Salt composition sulfonic hexadecyl Curing Water Conductivity loss at DSS. NaCl, Mg, Ca, CO.sub.3, Stearate acid salt phosphonic TMS time. Contact penetration at 20 min. 20 min. % wt % wt % wt % wt % wt % wt % wt acid % wt % wt wk angle, time, min mS mg 97.9 74.6 0.6 0.2 2.1 0 34.4 5 97.8 74.5 0.6 0.2 2.1 0.1 48.05 8.5 97.7 74.4 0.6 0.2 2.1 0.2 63.03 14.5 97.5 74.2 0.6 0.2 2.1 0.4 60.5 20 97.1 73.9 0.6 0.2 2.1 0.8 70.78 34 96.3 73.3 0.6 0.2 2.1 1.6 74.85 40 4249 138.1 96.3 73.3 0.6 0.2 2.1 1.6 2 129.9 60 96.3 73.3 0.6 0.2 2.1 1.6 45.28 35 5771 187.6 96.3 73.3 0.6 0.2 2.1 1.6 Cannot 30 6769 220 measure 96.3 73.3 0.6 0.2 2.1 1.6 28 5 7015 228 94.8 72.2 0.6 0.2 2.0 1.6 1.6 68 90 4800 156 93.6 72.2 0.6 0.2 3.2 1.6 1.6 79.6 95 3830 124.5 92.8 72.2 0.6 0.2 4.0 1.6 1.6 79.2 100 3800 123.5 94.8 72.2 0.6 0.2 2.0 1.6 1.6 2 78.05 120 4300 139.8 94.8 72.2 0.6 0.2 3.2 1.6 1.6 2 100.35 150 2940 95.6 92.8 72.2 0.6 0.2 4.0 1.6 1.6 2 94.05 150 3210 104.3 94.8 72.2 0.6 0.2 2.0 1.6 1.6 4 106.2 4020 130.7 94.8 72.2 0.6 0.2 3.2 1.6 1.6 4 91 2280 74.1 92.8 72.2 0.6 0.2 4.0 1.6 1.6 4 860 28 94.8 72.2 0.6 0.2 3.2 1.6 1.6 3 + 120 299 9.7 (TMS coating)

[0163] As shown in Table 2, the various treatments improve the durability of the compressed sample to direct contact with water by the 4 types of tests outlined above.

Example 16

Cementing Compress Salt Objects

[0164]

TABLE-US-00003 TABLE 3 cementing formulae of cementing agents capable of cementing together objects Amount, Water amount, Type g ml Application method Gypsum 2 1 Add gypsum to water over 30 s, mix for 1 minute, apply paste and allow to dry for 5 days. Hydraulic Lime NHL 3.5 2 1 Apply paste, press together for 28 days curing cement CIII/B 42.5N 239 8 3 Apply paste, press together for 28 (Slag cement) days curing

Example 17

Stabilized Formulation of DSS

[0165] 10 ml of Na.sub.2CO.sub.3 solution (26% wt/wt) was added to DSS granules (as received from The Dead Sea Works). The slurry was mixed by a mechanical stirrer until uniformity, pH of the free liquid 10. Optionally, magnesium stearate was added (0.4-1.6% wt/DSS wt) and mixed well. Optionally, calcium stearate (0.4-1.6% wt/DSS wt) was added and mixed well. The wet solid was dried in an oven for 0-24h at 125 C.

Example 18

Durability to Water

[0166] Cubes of 222 cm.sup.3 were compressed from DSS as received, or formulated according to Example 17. Some of the cubes were fully submerged in water for 15 min, then were taken out and allowed to dry. Some of the cubes were held in a humidity chamber at 80% RH, 37 C. for 3 days. The compressive strength of the cubes was tested on an Automax compressive stress testing machine. Table 4 summarizes the ultimate compressive strength reports as stress at break (MPa).

[0167] It is observed that (a) the formulated compressed salt shows a much higher compressive strength than a reference cement cube; (b) even after submerging the cube in water or exposing it to high humidity, the reduced compressive strength is still significantly higher than that of the cement reference.

TABLE-US-00004 TABLE 4 compressive strength measurements of various native and formulated DSS cubes, dry and after exposing them to liquid water or to humidity. Ultimate Compressive Sample Treatment Strength, MPa DSS, coarse Dry 36.7 DSS, coarse Submerged 4.3 DSS, fine grinding Submerged 11.3 Formulated, medium Dry 50.5 grinding Formulated, coarse Dry 41.7 Formulated, coarse Humidity 27.1 Formulated, coarse Submerged 14.9 Cement reference 4

[0168] It is observed that water or humidity exposure reduces the ultimate compressive strength the cube can take before breaking, but at all cases the compressive strength is about 3 fold higher compared to a cement cube of same dimensions.

Example 19

Active Wall to Support Controlled Humidity Rooms

[0169] Humans prefer staying in rooms where humidity is in the range of 30-55% RH. Higher values cause humans to feel uncomfortable, as such humidity prevents cooling of the body by perspiration and evaporation. A salt wall can act as an active humidity controller: when humidity is high, the salt absorbs the humidity. When it is low, the salt releases the humidity to the air. This can be seen in FIG. 5: conditioning of a compressed formulated DSS at 80% RH, 40 C. shows weight increase of the cube due to water vapor take up by the salt for 8 hours. Once the relative humidity is lowered to 45% RH, the salt cube releases the water back to the environment.

Example 20

Preparation of Compressed Salt Board by Roll Pressing

[0170] Roll press is commonly used as a low cost method to produce metal foil from metal powders by compression Similar technique can be applied to produce compressed salt boards, with the potential of scaling up production at low cost and high throughput.

[0171] Formulated DSS granules or powder is poured gradually over the rollers of a roll press, as seen in the scheme in FIG. 6. The width of the board is determined by the distance between the rollers. A board is formed, where the center is well pressed, the edges are less compressed. Optionally, the edges are shaved off by a sharp knife.

[0172] Optionally, thin paper sheets are fed along with the salt powder, such that the come in direct contact with the rollers on either side, holding the salt between them.

[0173] In another option compression is applied in several steps, providing gradual compression: the salt powder is placed between two metal foils, that have a sponge spaced in between them, where the sponge spacer is glued to the bottom metal foil, such that a box is created for holding the salt powder. The box is inserted between the rollers multiple times, each time the space between the rollers is shortened. Consequently, the salt is compressed more by each passage. Gradual compression can be scale up to a high throughput process where salt is fed at one end, and is gradually compressed to boards.

Example 21

Utilization of Used Desalination Membranes

[0174] Given the global shortage in clean water, more and more desalination plants that purify sea or brackish water by reverse osmosis (RO) are built and operated worldwide. Along with that a growing tonnage of RO membranes that are no longer usable is being disposed, mostly by landfill (W. Lawler et al./Desalination 357 (2015) 45-54). An average of a hundred 8 RO modules, weighing 13 to 15 kg each that have a lifespan of 5-8 years is required to produce 1000 m.sup.3 water per day. Larger modules are also in use in desalination plants, overall weight is about 50 kg each. The heart of these modules is the RO membrane, which is capable of rejecting ions and letting through only water molecules. The RO membrane comprises about 33-35% of the module weight. Modern membranes are sophisticated, multi-layered membranes, commonly polyester (PET) base with polysulfone (PSf) supporting layer and polyamide (PA) active layer. There is much RD activity in this field resulting in improved membranes offered by dozens of companies worldwide. The module is encased in a fiberglass-polyester resin case, and contains also various separators and other structural parts made of polypropylene, polyester, Acrylonitrile butadiene styrene and glue.

[0175] Inevitably, the modules have a finite lifespan. The membranes eventually get fouled, or damaged by chlorine used as a disinfectant in the desalination plant (Geise et. al, J. Poly. Sci. Part B Polymer Physics 48 (2010) 1685-1718). While some technologies are available for refurbishing these modules, eventually they have to be disposed. Other than landfill disposal, any repurposing for any use required dismantling and shredding of the membranes, so such material is available commercially.

[0176] The membranes used in the RO modules were designed for long term operation under pressure and heat in salt water for prolonged years. They are therefore highly suitable to incorporate with solid salt objects of the invention.

[0177] The spent RO membranes are ground or shredded to fibers having the dimensions x, y, z, wherein z is the thickness of the membrane, which is not altered, x is the length of the shredded membrane and y is the width of the shredded membrane. The ratio between x and y is such that x is at least 2 times greater than y. The value of y can be 0.1 to 10 mm. Optionally, y is about 0.35 to 1 mm Optionally, x is 2, 3, 4, 5, 6, 7, 8, 9, 10 times greater so that the shape is elongated in one dimension.

[0178] The shredded membrane is mixed with the formulated salt aggregate or powder by any known mixing technique to obtain a well-mixed composition, at a ratio of about 0.01, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5% wt/wt. This mixture is pressed to form salt objects. The salt objects formulated with shredded RO membrane have improved elasticity properties. For example, a strain-stress graph shows a Young modulus that is at least 2, 3, 4, 5, fold greater. The yield point is increased at least 2, 3, 4, 5 fold.

Example 22

ICP Analysis of Salts

[0179] Samples of salts that can be used for producing formulated salt objects were collected at different sites of the Dead Sea. All samples were characterized for their composition by ICP-AES analysis. The results are summarized in Table 5. All samples were successfully formulated according to one of the examples above to provide formulated salt that can be utilized to make salt objects, which is deliquescent free up to conditions of 74% RH at 40 C.

TABLE-US-00005 TABLE 5 ICP analyses of samples collected at different sites at the Dead Sea. Sulfate concentrated was calculated assuming all sulfur is present as sulfate. Sample 1 Sample 2 Sample 3 Sample 4 Element % wt % wt % wt % wt Na 23 32.7 34.4 39.6 Mg 4.5 2.1 0.6 0.3 Ca 0.8 0.7 0.2 0.3 Cl 54 57.6 60.6 60.2 K 4.6 1.5 0.5 0.1 Br 0.4 0.2 0.1 0.1 SO.sub.4.sup.2 0.2 0.3 0.1 0.4

Example 23

Thermal Analyses of DSS and Formulated DSS

[0180] Samples of DSS and of DSS formulated according to Example 17. Each sample was analyzed in a Simultaneous Thermal Analyzer (STA, Netzsch, model STA 449 F3 Jupiter) under nitrogen. The volatiles outlet of the STA instrument was coupled to a Quadrupole Mass Spectrometer (Netzsch, TGA/STA-QMS 403 D Aolos) such that volatiles released as a result of heating the sample are directly transferred via a fused silica capillary, heated to 300 C., into the electron impact source of the MS.

[0181] The thermograms of DSS are shown in FIG. 7, with the mass spectrometer set to follow H.sub.2O and CO.sub.2 evaporation. The DSC scan shows 5 endotherms in the range 50 to 250 C., each endotherm associated with release of water molecules from different species of magnesium chlorides salts where the crystalline structure comprises hydrates, the peaks correspond to the following species: MgCl.sub.2(H.sub.2O).sub.4, MgCl.sub.2(H.sub.2O).sub.2, MgCl.sub.2(H.sub.2O).sub.n wherein 1<n<2, Mg(OH)Cl, Mg(OH)Cl(H.sub.2O).sub.0.3, and Mg(OH)Cl.

[0182] FIG. 8 shows similar thermograms of formulated DSS. No endotherms are observed up to 800 C., corresponding to melting of NaCl. No endotherms are observed at the range 50 to 250 C., no release of water molecules is observed at that range as expected.