ES2272191B1 - USE OF FITATE FOR WATER TREATMENT. - Google Patents

Abstract

Use of phytate for water treatment. Use of phytate to inhibit the nucleation and growth of salts of a divalent cation selected from Ca2 + and Mg2 + in water. In this way it is possible to avoid the crystallization of calcium and magnesium salts, using very small amounts of product, without reducing the concentration of other essential mineral elements present in said water.

Description

Use of phytate for the treatment of Water.

Field of the Invention

The present invention is related to water treatment methods to prevent the formation of precipitates

In particular, the present invention relates to the use of phytate to inhibit nucleation and growth of calcium carbonate and other salts of a cation divalent selected from Ca 2+ and Mg 2+ in water.

Background of the invention

When a system contains solute amounts exceeding the amount allowed for its solubility, it is found in an unstable situation from the thermodynamic point of view (supersaturated system) and sooner or later crystallizes to reach balance. The time it takes for a supersaturated system in precipitating it can last from seconds to years and depends on kinetic factors

It is said that a water is hard when its content in dissolved ions Ca 2+ and Mg 2+ exceeds what is tolerated for use to which this water is intended. In the case of drinking water, the hardness is expressed as mg / L of CaCO 3 and its maximum value Permissible is 300 mg / L of CaCO 3. Much of the Drinking water supplies have a hardness of the order of 250 mg / L. The following table establishes a water classification according to its hardness:

Mg / L CaCO 3 Category 0-75 Soft water 75-150 Little water hard 150-300 Hard water > 300 Very hard water

Hard water presents the formation problem of precipitates (mainly calcium carbonate but also other salts that coprecipitate) in the walls of the pipes and systems through which it circulates, reducing the lifetime of appliances if such deposits are not periodically removed precipitates and being able to seal the pipes. This problem it is accentuated when the water is heated, in which case they can be reached to cause breakage or explosion due to overheating of pipes or boilers. Precisely for this reason the hard water does not It can be used in steam boilers.

On the other hand, hard waters decrease the effectiveness of detergents. Detergents are sodium salts or potassium of a long chain fatty acid formed by the reaction of fats and oils with an alkaline compound. These detergents they are soluble in water or at least they can be dispersed in it to form a colloid However, the calcium and magnesium salts of long chain fatty acids are insoluble in water, so that precipitate and do not foam.

There are various methods for the treatment of hard waters that consist mainly of a decrease in ion concentration (also called methods of water softening), such as ion exchangers, reverse osmosis systems, the formation of stable complexes or the  precipitation.

Phonic exchangers are generally Zeolites and ion exchange resins. The zeolites are water-insoluble natural or artificial aluminosilicates and chemically constitute neutralized fixed macroanions electrically with cations. The exchange is done by making the water crosses a bed of a certain thickness, finding little little by little with pure sodium zeolite. When the zeolite is depleted it regenerates with sodium chloride.

There are also artificial exchangers such as swap and exchange resins. The resins act in a similar way to zeolites.

Reverse osmosis equipment reduces the content of salts dissolved in water by applying high pressure through a semipermeable membrane. When a semipermeable membrane separates two different solutions saline concentration, water circulates from the most diluted medium to more concentrated, establishing a pressure difference between each of the two sides of the membrane, called osmotic pressure. The application of a pressure higher than this osmotic pressure reverses the flow obtaining a solution less and less concentrated and another increasingly concentrated.

Sometimes several are used polyamino acids (polyaspartic acid, polyarginine, polycysteine) joined directly on the surface of the membrane pores of hybrid reverse osmosis and nanofiltration systems for remove more effectively certain ions from the solution. Also I know has described the use of polyacrylic acid synergistically with the phytic acid to inhibit the formation of scale calcium, magnesium and iron in the membranes of the systems reverse osmosis (See, e.g., Spanish patent no. 520,904 / 8).

To treat water hardness, they are also used widely chelating agents or sequestrants. These agents are combined with metal ions (chelants are preferably used of calcium) in the water. The metal ion is surrounded by the sequestrant and an anionic charge complex is formed. This fact, the effective concentration of the ion decreases, so it is reduced supersaturation with respect to certain salts; thus, the formation of solid deposits and the decrease in effectiveness of detergents Some chelants used are phosphates. Traditionally, tripolyphosphate has been used in detergents, which is combined with calcium and magnesium by formation of soluble complexes, although it also sequesters iron and dissolved manganese (which interfere with detergency). Certain environmental aspects have caused others to be used alternative sequestering agents such as ethylenediamine acid tetraacetic (EDTA).

The techniques and methods above are based on decrease the concentration of ions responsible for hardness of the water. In the case of ion exchangers, osmosis Inverse and precipitation these are eliminated directly causing, in addition, the precipitation of other ions that are beneficial for human health In the case of chelating agents generally we resort to substances that harm the environment or are toxic for human consumption.

Summary Description of the Invention

It is an objective of the present invention provide an alternative method to existing ones, which allows avoid the formation of precipitates in the water without modifying the phonic composition of it.

In particular, the present invention relates to the use of myo-inositol hexaphosphate for inhibit the nucleation and growth of calcium carbonate salt and from other salts of a divalent cation selected from calcium and magnesium in the water.

Before entering to discuss the details of the present invention, a definition of the terms is provided specific related to the main aspects of the invention.

Definitions

In the present invention, "phytate" or " myo -inositol hexaphosphate" means the molecule corresponding to the formula

one

and their corresponding salts, the which include, but are not limited to sodium, potassium salts, calcium, magnesium or calcium-magnesium

Myo - inositol hexaphosphate the (phytate) is a natural product that accumulates in the seeds of cereals, legumes and nuts and has numerous beneficial health effects such as an antioxidant or preventive effect of certain types of cancers.

In the present invention by "inhibitor of crystallization "means a substance that is capable of decrease or prevent the formation of a nucleus or the development of said crystal core. This inhibitory effect is due to the fact that phytate adsorbs on the forming nucleus or crystal growing and inhibit its development. It is, as will be explained in detail below, of a purely kinetic factor that does not change the supersaturation of the compound and therefore does not eliminate water ions

In the present invention by "turbidity" is understands the presence of precipitated particles of calcium salts or magnesium in suspension in a liquid, not being adhered to no surface

In the present invention by "doser" Any system that allows the introduction of a substance is understood to water in known doses.

In the present invention by "devices e water management facilities "is understood any system used for domestic supply or industrial water, which include but are not limited to ducts, pipes, wells, cisterns, appliances or warehouses where temporarily stores water.

Figures

Figure 1: shows the phytate inhibitory effect on the crystallization of salts in a sample of synthetic water which has a calcium concentration of less than 300 mg / L and at a carbonate concentration of 350 mg / L. The concentrations of Phytate used were: 0 mg / L (bul), 1 mg / L (?) and 2 mg / L (?).

Figures 2 and 3: corresponds to a chemical analysis of phytate treated water, revealing that at concentrations increasing phytate the concentration of calcium and carbonate in dissolution was greater, so it is shown that the added phytate Water prevents crystallization of calcium salt.

Detailed description of the invention

The general objective of the present invention is avoid the formation of calcium carbonate salts and other salts that can coprecipitate in cisterns, wells, pipes, ducts, appliances and faucets, and other points that frequently suffer deposits of calcium carbonate precipitates and other salts where this water circulates and which lead to deterioration and poor operation of said facilities and devices, with the expense which involves the repair and / or replacement of the consumer these.

In particular, the purpose of this invention is the use of phytate to inhibit nucleation and the growth of salts of a divalent cation selected from between calcium and magnesium, in the water.

In a preferred embodiment, said salt of a Divalent cation is calcium carbonate.

The incorporation of phytate is aimed at avoid the formation of precipitates of calcium carbonate and others calcium and magnesium salts thanks to the inhibitory action of the crystallization presented by phytate.

He is well known to those skilled in the art,  that the crystallization of solids is the result of the action of three factors: supersaturation (driving force of the crystallization, thermodynamic factor), the presence of substances promoters (kinetic factor) and the presence of substances crystallization inhibitors (kinetic factor).

There is numerous literature describing the stages of a crystallization process (see, eg Söhnel O., Garside J. [1992] Precipitation: basic principies and industrial applications , Butterworth, Oxford; Frases F., Costa-Bauzá A., Sóhnel O [2000] Crystallization in dissolution Basic concepts , Editorial Reverté SA, Barcelona). Briefly, the crystallization process within a solution consists of the following stages:

a) Nucleation: it is the first of the stages of the  crystallization and involves the formation of clusters of atoms, molecules or ions that constitute a new solid phase. Until these groupings do not have a certain critical size (10-100 structural units) are not stable and are they dissociate, again, the free ions being dissolved. When, with the successive incorporation of atoms, molecules or ions it reaches that critical size, it is said that a germ has formed stable minimum (core). There are two types of nucleation:

a.1. Homogeneous nucleation: it is the formation of a  solid within a solution as a result of its supersaturation, that is, that the substance is in dissolution in amounts greater than those allowed by its solubility product, and is a consequence of the sequential shock of several particles of the solid future to form what is known as a minimum stable germ;

a.2. Heterogeneous nucleation: corresponds to the formation of a solid within a solution on the surface of a preexisting solid particle composition chemistry different from that of the solid in formation;

b) Crystal growth: once you have had place the nucleation, the formed nucleus grows by incorporation successive of atoms, molecules or ions. It is a simpler stage than the previous one because the growth is carried out on a pre-existing particle that is already stable (while at the stage nucleation nucleus can be excised before reaching size critical); Y

c) Secondary processes: once it has been formed the crystal is given several processes such as recrystallization, Aging or secondary aggregation. The latter consists of the grouping of solid particles (crystals) already formed, giving Place to larger ones.

In accordance with the present invention, phytate acts at the kinetic level, avoiding nucleation and growth (early stages of crystallization). In particular, phytate, due to its affinity for divalent cations, including the calcium, is adsorbed on the crystalline nucleus in formation or on the growing crystal avoiding or delaying its formation (initial stages (a) and (b)). The addition of phytate does not modify the mineral composition of water and also, advantageously, is incorporated in very small quantities a natural product (phytate) that It has numerous beneficial properties for health.

In state procedures and devices of the art, such as ion exchange systems (exchange resins or zeolites) and reverse osmosis systems, the objective is to carry out what is known as "softening of the water "(that is, act on supersaturation). In these cases, the objective is to eliminate the ions responsible for the formation of precipitates in water (carbonate, sulfate, calcium, magnesium, etc.) The elimination of these ions leads to loss of other essential mineral elements for the organism. This aspect is of special relevance in the event that the water is intended for human consumption.

On the other hand, the treatment processes of state of the art water act at supersaturation level, of so that the ions responsible for the formation of a solid or are kidnapped (as in the case of the use of complexing agents such as EDTA), and those that act at the kinetic level avoid secondary aggregation (last stage of the process of crystal formation). Instead, with the method of this invention is achieved to avoid the crystallization of calcium salts inhibiting nucleation (homogeneous or heterogeneous) using very small quantities of product and not being diminished the concentration of other essential mineral elements present in Water. Advantageously, therefore, for the purpose of this invention, the formation of carbonate precipitates of calcium and other salts

In an embodiment of the present invention, the amount of phytate is less than 10 mg per liter of water to be treated.

In another preferred embodiment, the amount of Phytate ranges between 0.1 and 5 mg per liter of water to be treated.

Preferably, said phytate is used in a amount ranging from 0.1 to 2 mg of phytate per liter of water to be treated.

In an embodiment of the present invention, using a laboratory crystallizer, it has been observed that with fully controlled synthetic water, 1 mg / L of phytate completely prevents the crystallization of calcium carbonate when calcium concentrations were below 300 mg / L (see Figure 1) and carbonate concentration were 350 mg / L. It should be noted that a hard drinking water contains some 100-120 mg / L calcium and carbonate ranges 200-500 mg / L. The recommended pH ranges are 6.5-8.5, but the maximum allowed value is 9.5.

In another embodiment of the present invention, through a model that simulates the circulation of water through the inside a pipe, it has been found that the presence of 2 mg / L phytate in circulating water containing 136 mg / L of calcium and 350 mg / L carbonate at a pH = 8.00, resulted in a 95% decrease in carbonate precipitate development calcium and 92% magnesium salts at 30 ° C, while 5 mg / L of phytate under the same concentration and pH conditions, but working at 65 ° C, resulted in a 98% decrease in development of calcium carbonate precipitates.

In yet another embodiment of the present invention, it was found that the addition of 1 mg / L phytate to water of a 10,000 liter tank recently filled with water from a vein well ([Ca 2+] = 107.7 mg / L, [carbonate] = 311.1 mg / L, pH = 7.92), completely eliminated the development of turbidity / suspended microparticles and precipitates in the bathroom and kitchen facilities (faucets, bathtubs, etc.) during the week it took to consume that water. In addition, the analysis Water chemist with phytate treatment revealed that to increasing concentrations of phytate the concentration of calcium and carbonate in solution was higher, so it is shown that the phytate added to water prevents crystallization of said salt due at its inhibitory capacity.

In still another embodiment, the phytate is supplies the water to be treated in a dispenser for both use domestic or private

In a second aspect, the present invention is refers to a dispenser that contains myo-inositol hexaphosphate to prevent the formation of carbonate precipitates calcium and other calcium or magnesium salts inside devices and facilities for water management.

Examples of embodiment of the invention

Example one

Homogeneous nucleation

10 ml of synthetic water was introduced into laboratory crystallizers prepared according to the table next:

Compound Concentration (mg / L) MaSO_ {4} \ cdot 7H2 {O} 40 KNO_ {3} 3 Ca (NO 3) 2 \ cdot 2H 2 O 80

(Continuation)

Compound Concentration (mg / L) CuSO_ {4} \ cdot 5H2 {O} 0.2 ZnCl2 2 CaCl2 Variable (see Figure 1) NaHCO 3 490 (equivalent to 350 mg / L carbonate)

Each of the solutions was prepared in a way  containing 0, 1 or 2 mg / L of phytate. 15 seconds after water preparation turbidimetry measurements were performed using a photometer (Metrohm 662) equipped with a cell 2 x 10 mm reflector optical pitch optical fiber and using light monochromatic (550 nm). The crystallization processes took carried out at 25 ° C and the pH of all solutions was adjusted to 9.8.

The results are shown in figure 1 obtained. As can be seen, with a concentration of 1 mg / L of phytate completely prevented the crystallization of carbonate calcium when the calcium concentration was less than 300 mg / L and the carbonate concentration was 350 mg / L.

Example 2

Heterogeneous Nucleation and Growth

Synthetic water was recirculated (see table from example 1) (a) for 48 h (30 ° C) and (b) for 24 h (65 ° C) at through a copper pipe 20 cm long, 4 mm internal diameter and 6 mm external diameter. It worked with calcium concentrations of 100 and 200 mg / L. The pH of all solutions were adjusted to 8.00 and every 24 h the water was renewed synthetic

After 24 or 48 hours, the precipitate formed in the walls of the pipe with 1 M HCl and it determined calcium by atomic emission spectroscopy using an inductively coupled plasma (ICP-AES).

In this way it was found that the presence of 2  mg / L phytate in the circulating water contained containing 136 mg / L calcium and 350 mg / L carbonate at a pH = 8.00, took place a 95% decrease in the development of precipitates of calcium carbonate at 30 ° C, while 5 mg / L phytate in the same concentration and pH conditions, but working at 65 ° C, resulted in a 98% decrease in the development of precipitates of calcium carbonate.

As is well known, the higher the water temperature, the higher the precipitation and deposition of the calcium and magnesium salts in the pipes, appliances, etc. with the disadvantages that this entails consumer.

As demonstrated in the present example, phytate is equally effective at moderate temperatures (30ºC) that at elevated temperatures (65 ° C). This aspect is special relevance in the case of household appliances (e.g. washing machines), pipes, etc., where hot water circulates.

Example 3

Homogeneous and heterogeneous nucleation

We worked with a 10,000 l tank capacity coated internally by a layer of cement. Bliss cistern is used to supply three families and in Normal conditions are filled weekly. It filled periodically the cistern with water from a vein well and was added phytate so that the concentration inside the tank was in the range 0-1 mg / L. During the week of use of each concentration of phytate were evaluated qualitatively the remains of calcium carbonate precipitates in House faucets and bathroom accessories. Also, after 48 hours of filling the cistern a water sample was collected from a tap of one of the three families and the determination was made Quantitative pH, calcium and bicarbonates.

In this way it was found that the addition of 1 mg / L phytate eliminated the development of turbidity / micro-
suspended particles and calcium precipitates in water installations (faucets, bathtubs, etc). In addition, the chemical analysis revealed that at increasing concentrations of phytate, the concentration of calcium and carbonate in solution was higher, so it is shown that phytate added to water prevents the precipitation of said salt due to its inhibitory capacity.

Claims (15)

1. Use of myo-inositol hexaphosphate to inhibit the nucleation and growth of salts of a divalent cation selected from Ca 2+ and Mg 2+ in the Water. 2. Use according to claim 1, wherein said salt is calcium carbonate. 3. Use according to claim 1 wherein said nucleation is homogeneous. 4. Use according to claim 1 wherein said nucleation is heterogeneous. 5. Use according to any of the claims 1 to 4 to decrease water turbidity stream. 6. Use according to any of the previous claims wherein said myo-inositol hexaphosphate is administered to water in aqueous composition form. 7. Use in accordance with any of the previous claims wherein said myo-inositol hexaphosphate is administered in a amount less than 10 mg per liter of water to be treated. 8. Use according to claim 7 wherein said ratio ranges between 0.1 and 5 mg of myo-5 inositol hexaphosphate per liter of water to be treated. 9. Use in accordance with any of the claims 7-8, wherein said ratio ranges between 0.1-2 mg of myo-inositol hexaphosphate per liter of water to be treated. 10. Use in accordance with any of the  previous claims wherein the myo-inositol hexaphosphate is applied in the form of dispenser inside devices and facilities for water administration 11. Use according to claim  10 wherein said device is an appliance. 12. Use in accordance with any of the  claims 10 to 12 wherein said installation is a resistance. 13. Doser containing phytate to avoid the formation of calcium carbonate precipitate deposits and of other calcium or magnesium salts adhered inside devices and facilities for water management. 14. Device according to claim  13 wherein said device is an appliance. 15. Device according to any of the  claims 13-14 wherein said installation It is a resistance.