WO2007048941A2 - Method of using an additive for water chlorinated with javelle water - Google Patents

Abstract

The invention relates to a method of using anhydrous monosodium phosphate having formula NaH2PO4 in aqueous solution as a chemical additive for water chlorinated with Javelle water in order to optimise the disinfectant action thereof, to provide scale preventive and anticorrosive properties and to break down mineral and/or organic deposits.

Description

 METHOD OF USING ADDITIVE FOR BLAVES WATER

The present invention relates to a method of using a chemical additive for bleached water to optimize the action of bleach in water while providing anti-scaling and anti-corrosion properties and by weakening them. mineral and / or organic deposits.

The present application has priority PCT patent / FR2005 / 002691 of the same applicant and filed on 27/10/2005, which is incorporated by reference in its entirety in the present description.

The waters conveyed and used in domestic, technical, agricultural or industrial installations may be contaminated by corrosions, mineral deposits, bacteria, viruses, fungi and algae, the latter finding food and shelter thanks to the former. These products, deposits and contaminations can be the cause of serious disorders and may, in the case of water intended for domestic use, affect the health of users.

There are many chemicals that can inhibit corrosive and / or scaling reactions as well as many chemicals that disinfect these waters. In this we find phosphates, silicates, chlorine and its derivatives, ozone, ammoniums, hydrogen peroxide, iodine, bromine, etc.

These products are not always compatible and to the knowledge of the applicant, there was currently no product to optimize the action of bleach in the water to be disinfected while inhibiting scaling reactions and / or corrosion and / or by weakening the mineral and or organic deposits.

According to the subject of the invention, the applicant proposes a method of using a chemical additive for bleached water to reinforce the disinfectant action initially sought while providing antiscaling and / or anticorrosion and / or dispersant properties at the same time. waters thus treated.

The bleach contains soda necessary for its stability. It is known to one skilled in the art that when bleach is added to the water to be treated, the sodium hypochlorite reacts rapidly to form hypochlorous acid and the HOCl equilibrium - ^ H ⁺ + OCl ^"is a function of pH of the water thus, an increase in pH shifts the equilibrium to the right and thus decreases the amount of the species HOCl (hypochlorous acid) _*.

The addition of bleach in water increases the pH of the latter in proportion to the amount of bleach introduced due to the presence of soda in said bleach and its dilution in said water.

According to the subject of the invention, the additive is an acid capable of reacting with soda to reduce too much the pH value of the bleached water in order to optimize the disinfecting action while limiting the associated disadvantages to bleach.

It is known to one skilled in the art that the bleaching of water at high concentrations (> 50 mg / l of total chlorine) required for rapid disinfection causes what is called a "caustic shock" and that certain bacteria such as legionella lose their virulence without as much to die. As a result, despite initial successful results, there is regular recontamination of water and facilities treated.

The disinfecting properties of bleach are due mainly to the bactericidal power of hypochlorous acid that diffuses through the cell wall of bacteria by destroying membrane proteins. Moreover, HClO acts on the synthesis metabolism of bacteria. Unloaded HClO is nearly 100 times more bactericidal than the hypochlorite ion. In the case of HClO viruses would act by attacking the amidated bonds of the proteins.

It would therefore be useful to be able to promote or even increase the fraction of active chlorine in water added with bleach. It is known to those skilled in the art that bleached water is corrosive. Similarly, it is known to those skilled in the art that a hard water will be all the more incriminating as the addition of bleach will be important (presence of soda).

It is known to those skilled in the art that the addition of an acid to the bleach can lower its pH however it is not without risk and a dosage error can cause the formation of di -chlorine in gaseous form dangerous for the operator.

It is known from CA 2 028 930 A1 to add sodium dihydrogenphosphate to a hypochlorite salt in solution by providing a molar ratio of NaH ₂ PO ₄ / NaOH greater than or equal to 2. However, this document does not relate to a process of addition of a dihydrogenphosphate additive to bleached water. Indeed CA 2 028 931 A1 relates to the manufacture of a sterilizing solution to be used such as it, in particular for disinfecting medical instruments and sterilizing surfaces. The method implemented according to CA 2 028 931 A1 does not, however, solve the problem of corrosion, quite the contrary since it must add corrosion inhibitors, or even provide a kit comprising an aluminum plate to protect against corrosion the metal devices to be sterilized. The technique, the concentrations, the field of application, in short everything in this patent differs from the subject of the present application and it would not come to the mind of those skilled in the art to use his teaching to achieve the purpose of the invention. This document also provides no upper limit of the molar ratio NaHaPO ₄ / NaOH.

It is known from FR 2 835 702 A to add sodium dihydrogenphosphate to bleach. However, this document does not use sodium dihydrogenphosphate alone in aqueous solution form by adding it to a bleached water, on the contrary, it provides for the use of a ready-to-use solution already containing a water mixture. javel - sodium dihydrogen phosphate to be added to untreated water. In addition, it does not provide an upper limit of the molar ratio NaHaPO ₄ / NaOH.

Even by combining selected characteristics of the teachings of the two documents cited, which would not be natural in view of the goals completely different from these documents, it would remain that none of the documents are found upper limits of the molar ratio NaH ₂ PO ₄ / NaOH.

According to the subject of the invention, for drinking or drinking water and water for agricultural uses, the additive is compatible with their sanitary or indirect food uses.

According to the subject of the invention, the additive makes it possible to prevent the bleached water from being neutralized before being discharged into the effluents. Indeed, when the desired treatment requires a high concentration of bleach in water, the pH of it reaches values that are incompatible with the norms usually in force, which require reducing the pH of the water to a value close to neutrality before rejection.

The present invention relates to the use of anhydrous monosodium phosphate of formula NaH ₂ PO ₄ in aqueous solution, called sodium dihydrogenphosphate here, as a chemical additive to bleached water.

According to the present invention, the addition of anhydrous monosodium phosphate in aqueous solution is carried out in such a quantity that the molar ratio ([NaH ₂ PO ₄ ] added) / ([NaOH] initially contained in the bleached water) is <10, respectively ≤ 3.

According to another aspect, the present invention relates to a use of anhydrous monosodium phosphate of formula NaH ₂ PO ₄ in aqueous solution as a chemical additive to bleached water in which the addition of anhydrous monosodium phosphate in aqueous solution is carried out in an amount such that the molar ratio ([NaH ₂ PO ₄ ] added) / ([NaOH] initially contained in bleach or bleach) is ≥ 2 and <10, respectively> 2 and ≤ 3.

These values can easily be reached either by knowing or by measuring the amount of NaOH added in a reference volume of bleached water during bleaching, or by measuring the amount of NaOH present in a reference volume of bleached water of any a manner known in itself to those skilled in the art. The amount of NaH ₂ PO ₄ to be added to the same reference volume is then readily deduced from the amount of known NaOH, respectively the amount of NaOH measured.

According to the subject of the invention, the anhydrous monosodium phosphate of formula NaH ₂ PO ₄ diluted in aqueous solution added to chlorinated water in determined proportions makes it possible to obtain the characteristics and compatibility of use sought.

According to the subject of the invention, the addition of anhydrous monosodium phosphate of formula NaH ₂ PO ₄ in aqueous solution to chlorinated water increases their disinfection power by giving them a pH close to neutrality and corrosion inhibiting characteristics. and scaling and embrittlement of mineral and / or organic deposits.

According to the subject of the invention, the anhydrous monosodium phosphate in aqueous solution is mixed with chlorinated water in a proportion such that the molar ratio (NaH ₂ PO ₄ ) / (NaOH) is sufficient to react with the 100% of the sodium hydroxide supplied during the chlorination and less than or equal to 10, respectively less than or equal to 3. The second term NaOH corresponds to the number of moles of sodium hydroxide supplied during the bleaching to a certain volume of bleached water and the first term Na H ₂ PO ₄ corresponds to the number of moles of anhydrous monosodium phosphate added to the same volume of bleached water.

The monosodium phosphate reacts partly with the totality of the sodium hydroxide contained in the javellated water according to the reaction:

Na ⁺ + H ₂ PO ₄ - + (Na ⁺ + HO ^" ) → 2Na ⁺ + HPO ₄ ^2" + H ₂ O

The salt obtained is a sodium hydrogenosaldehyde phosphate disodium, its chemical formula contains atoms of the hydrogen element likely to have the reactions acidobasiques sought for inhibition of scaling and corrosion reactions and embrittlement of mineral and / or organic deposits.

The pKa of the disodium hydrogen phosphate is 7.2, it is therefore necessary to add an excess quantity of dihydrogenphosphate (anhydrous monosodium phosphate in aqueous solution) so that the pH of the bleached water does not increase. According to the applicant's experience, however, the amount of dihydrogenphosphate supplied must remain at <10, respectively <3 (molar ratio (NaH ₂ PO ₄ ) / (NaOH)) in order to allow sufficient acidification without being excessive. and therefore dangerous.

In fact, since the pKa of disodium dihydrogenphosphate is 2.15, it brings an acidification proportional to its concentration in the solution. For example, when added directly to chlorinated water in a molar ratio (Na H ₂ PO ₄ ) / (NaOH) equal to 2.6, the pH of the water will only be slightly increased if is initially <7.2 and decreased for higher initial pH values.

The disodium dihydrogenphosphate salt is also a sodium hydrogenosal, its chemical formula contains atoms of the hydrogen element likely to have the acidobasic reactions sought for the inhibition of scaling and corrosion reactions.

According to the subject of the invention, the addition to bleached water of anhydrous monosodium phosphate in the form of an aqueous solution of disodium dihydrogen phosphate in a molar ratio (NaH ₂ PO ₄ ) / (NaOH) sufficient to remove the soda provided by the bleaching of the water and less than or equal to 10, respectively less than or equal to 3 promotes the formation of a large amount of hypochlorous acid in the water javellisée.

According to the subject of the invention, the sodium hydrogencels present in the bleached waters provide the inhibiting characteristics of scaling and corrosion and embrittlement of the mineral and / or organic deposits sought in conjunction with the disinfection of water for protection. facilities that convey them and for their actions with regard to deposits that may form there.

According to the subject of the invention, a non-foaming detergent effect of the additive can be sought in particular during the treatment of cooling water circuit waters and cooling water. According to the applicant's experience, such an effect is obtained by the addition of polyglycolic ether of fatty alcohol. This nonionic surfactant can be added in solid form (powder) or in liquid form during the preparation of the additive and in an adequate amount.

According to the subject of the invention, the detergent and foaming effects of the bleached waters thus packaged can be sought in particular during the disinfection of surfaces. According to the applicant's experience, such effects are obtained by the joint addition of polyglycol fatty ether and a mixture of sodium olefin sulphonate and sodium salt of a secondary alkanesulfonate in an adequate amount.

The object of the invention finds its main applications in particular in water purification and curative decontamination, or preventive agricultural irrigation systems, drinking water distribution, dry cooling circuits, cooling circuits and networks fire, this list being in no way limiting.

Claims

1. A method of using a sodium dihydrogenphosphate additive characterized in that it allows the improvement of the disinfection activity of a bleached water and jointly the inhibition of scaling and / or corrosion reactions and or the embrittlement of mineral and / or organic deposits and in that it consists in adding to a bleached water an anhydrous monosodium phosphate additive of formula NaH ₂ PO ₄ in aqueous solution (sodium dihydrogenphosphate) at a concentration at least sufficient to neutralize all of the sodium hydroxide present in the bleached water and at a molar ratio of NaH ₂ PO ₄ / NaOH of less than or equal to 10, the second term NaOH corresponding to the number of moles of sodium hydroxide added to a certain volume of bleached water during the chlorination and the first term NaH ₂ PO ₄ corresponding to the number of moles of sodium dihydrogen phosphate added to the same volume of javellisée water.

2. A method of using an anhydrous monosodium phosphate additive of formula NaH ₂ PO ₄ in aqueous solution (sodium dihydrogenphosphate) according to claim 1, characterized in that it allows the improvement of the disinfection activity of a bleached water and jointly the inhibition of scaling and / or corrosion reactions and / or the embrittlement of mineral and / or organic deposits and in that it consists in adding to a bleached water an anhydrous monosodium phosphate additive of formula NaH ₂ PO ₄ in aqueous solution (sodium dihydrogenphosphate) at a concentration at least sufficient to neutralize all of the sodium hydroxide present in the bleached water and at a molar ratio of NaH ₂ PO ₄ / NaOH of less than or equal to 3, the second term NaOH corresponding to the number of moles of sodium hydroxide added to a certain volume of water javellisée during the javellisation and the first term NaH ₂ PO ₄ corresponding to the number of moles of dihydrog sodium enophosphate added to the same volume of bleached water.

3. Method according to claim 1, characterized in that the molar ratio NaH ₂ PO ₄ / NaOH is less than or equal to 10 and greater than or equal to 2.

4. Method according to claim 2, characterized in that the molar ratio NaH ₂ PO ₄ / NaOH is less than or equal to 3 and greater than or equal to 2.