MXPA99004516A - Inhibition and delay of deposit formation in membrane processes - Google Patents

Abstract

The invention relates to the use of polyasparaginic acids and their mixtures with tensides and emulgators in methods for carrying out membrane processes to inhibit or delay scale formation through hardly soluble organic and inorganic components in the membrane feed.

Description

INHIBITION AND DELAY OF THE FORMATION OF COATINGS IN THE PROCESSES WITH MEMBRANES. Field of the invention. The invention relates to the use of polyasparaginic acid and its mixtures with surfactants and emulsifiers to inhibit or retard the formation of coatings by organic and inorganic components that are difficult to dissolve in the process feed with membranes. Description of the prior art. In the separation of fluidized systems plays a significant role the technology of the membranes. The procedures of the -technique, which have been imposed, currently belong to the obtaining of drinking water from sea water through reverse osmosis as well as the production of products through ultra and nanofiltration. In membrane processes, diluted solutions are usually concentrated and organic solvents, water or salt solutions are separated. In this case, valuable products or noxious products are obtained in concentrated solutions and, if necessary, low in salts, whereby subsequent storage, transport, disposal and reuse can be configured in a less costly manner. In the case of the processing of wastewater, the objective of membrane treatment is to obtain most of the volume as a permeate in a non-polluted or only slightly contaminated form, for example for reuse. . The concentrated retentate can be produced at a low cost in terms of the valuable products still present or can be eliminated at a favorable cost in this way, for example by its combustion. The field of procedures with membranes covers very different processes. Correspondingly, the membranes and their industrial forms of construction, the modules, are also very diverse. The commercially available membranes are produced, for example, from organic materials, such as polysulfone, cellulose acetate, polyamide or PVDF or from inorganic materials such as Ti02, Zr02 or A1203; These are used in the form of capillary, tubular or flat windows. The processes with industrially relevant membranes are predominantly carried out in the form of filtration with transverse current. The high stresses of pushing on the walls, due to the high flow velocities and especially to the constructions of the modules, should minimize or prevent the soiling of the membranes. In general it is evident in the industrial processes with membranes in the case of the concentration of feed currents, however a decrease in the permeate power as a consequence of Fouling, the accumulation of material on the membrane. Scaling, the incrustation of the membrane by inorganic salts as a consequence of the exceeding of its solubility limit, is a special case of Fouling. As inorganic salts, calcium, magnesium carbonates, hydroxides, phosphates, sulphates and fluorides of calcium and magnesium due to the hardness of water formers must be mentioned in this case. The hydroxides of heavy metals, such as, for example, iron and chromium hydroxide, are an additional problem in the preparation of residual waters. Scaling must always be counted when high yields are sought in permeate in a process, such as, for example, in the case of the concentration of wastewater, of obtaining pure, potable water. Also in the case of desalination and concentration of product solutions, this phenomenon can naturally occur. The procedures with membranes considered in this case are ultra and nanofiltration, reverse osmosis, dialysis and perevaporation. Fouling and Scaling as a special case of Fouling cause the performance of the permeation of a membrane inela- tation to finally fall to a minimum antieconomic magnitude. From time to time, the supply current must be switched off and the membrane cleaned. Such a cleaning process, however, has several drawbacks: cleaning means an interruption of operation. A continuous operation can therefore be maintained only by the provision of a device with a parallel membrane. It also requires the use of chemical cleaning agents according to the type of deposits, often contain surfactants and complexing agents that are difficult to biodegrade and have to be removed separately. Finally, the totality of the deposit is not eliminated during the cleaning in general, whereby the membranes rarely reach the original permeate flow when they are reused. If in a process it is necessary to have the Scaling, they can be taken to avoid the same, measure of previous treatment, for example through the use of ion exchangers, which are known in the field of the elimination of water hardness. In addition, the specific incorporation of solid particles allows in the seeding and fluidized bed technology with certain descaling and modular systems a physical control of membrane fouling (Chem-Ing. -Tech 59 (1987) 187). Hydroxide deposits can often be avoided by adjusting an appropriate pH value. Nor have there been attempts to add to the feed stream to be processed and to form complexes such as NTA or EDTA. In addition to ecotoxicological properties and unquestionable drawbacks, complexes are not to be added in equimolar amounts. Contrary to what occurs in the case of complexing agents, the dispersing agents, so-called Threshold inhibitors, can be employed in substoichiometric quantities in an efficient manner to prevent or retard Fouling and Scaling in membrane processes. In the publication Desalination 54, 263-76 (1985), cited in Chem. Abetracts, 104, 56 102, polyphosphates, foefonatoe, polystyrenesulfonates, polyacrylamides and polyacrylates have been tested for their inhibition effect on fouling. In US Pat. No. 5,256,303, the inhibition of the crystallization of calcium sulphate and the formation of deposits in the feed streams, which are conducted through a membrane system, have been tested. In this case, N-substituted polyacrylamides and phosphonobutane-1,2,4-tricarboxylic acids are used as scale inhibitors. In EP 0 705 794 a method is described for preventing the crystallization of sulfates in aqueous systems. In this case, one or several polyamino acids and one or several inorganic acids are used, which nevertheless have to be eliminated in a costly manner or which cause the eutrophication of the waters of the deeagüee. US Pat. No. 5,286,810 describes the preparation of high molecular weight polyaspartic acid copolymers, which can also be used as scale inhibitors in various industrial and hygiene sectors; without specific details of the details, membranes for reverse osmosis are also mentioned. US Pat. No. 5,525,257 describes mixtures of polyasparagin-css acids and their derivatives with other polycarboxylic acids and their use in the treatment of lae aguae. As polycarboxylic acids, polyacrylates, polymaleate and polysulfonate are mentioned; also in eete caeo cites the reverse osmosis without further details. According to US Pat. No. 5,466,760 copolymers of polysuccinimide and maleic acid, ammonia and of a polyamine are used as inhibitors of the e-decene. In EP-B 530 358 (= US 5 373 086) a special composition of polyasparagic acid is described, which is obtained by heating powdery L-asparagic acid to at least 188 ° C and condensation, subsequent heating to the less at 216 ° C, until at least 80% of the formation of the polysuccinimide has been developed, followed by hydrolysis of the polysuccinimide, which is present in a proportion greater than 50% in the β-form and which pre-weighs molecular from 1,000 to 5,000 (average weight), which is used to inhibit precipitation of CaC03 or Ca3 (P04) 2. This special polyaspartic acid should be able to be used in another industrial field from the treatment of wastewater to the extraction of oil; In addition, reverse osmosis is also mentioned without further details. Thus it can be said as a summary that according to the current state of the art in membrane processes, foefonate and polyacrylate have been used as scale inhibitors. Polyasparagic acids are cited in a large number of previous publications as inhibitors employable against encrustation. However, up to the present there was no result demonstrating the possibility of the use of polyaspartic acids in processes with membranes. In this case, the person skilled in the art knows that an effective inhibition against incrustation always depends on the system as a whole, that is, on all the participating components and the conditions. Precisely in the processes with membranes there are preeentee uchoe chemical and physical factors that do not allow to wait that an inhibitor against the incrustation, tested in another field of application with good success, is precisely also active in processes with membranes. Object of the invention. It has now surprisingly been found that when polyaspartic acids and their mixtures with surfactants and emulsifiers are used in various processes with membranes, inhibition and retardation of scale formation due to the poorly soluble organic and inorganic components can be found on the membranes. . The use of biodegradable polyasparagic acids is advantageous since they can replace phosphonates and non-biodegradable or hardly biodegradable polyacrylates., increase the availability of installations with membranes and reduce the number of cleaning intervals. Detailed description of the invention. Thus, the invention relates to a process for carrying out processes with membranes for the treatment of aqueous feed with inorganic and organic components with inhibition or retardation of the formation of scale on the membranes by the addition of an inhibitor of the embedding, characterized in that polyasparaginic acids and their mixtures with surfactants, emulsifiers or several of them are used as inhibitors of the encrustation, polyaspartic acids being used in an amount of 50,000 ppm, based on the aqueous feed. In another embodiment, the invention relates to the use of polyaspartic acids and of mixtures thereof with surfactants and emulsifiers in the presence of polyacrylate or phosphonates, such as, for example, phosphonobutanetricarboxylic acids or several thereof, since biodegradability is improved of such mixtures by the addition of polyaspartic acids. The polyaspartic acids to be used according to the invention can be prepared in various ways. In this way, the preparation can be carried out from maleic acid anhydride, water and ammonia and / or products derived therefrom, such as, for example, the NH 4 salt of maleic acid, maleinamide acid, aegyptinic acid, aeparagine and iminodieuccinic acid. They can also employ eue ealee de ammonio. Equally, mixtures in which the abovementioned components are contained together can be used to obtain the polyaspartic acid. The preparation can also be carried out from the aforementioned components thermally - in the presence of acid catalysts, such as, for example, phosphoric acid, phosphonic acids, sulfonic acids or eulphuric acids, which are required for the formation of the bonds peptides. The polyaspartic acids or the poly-succinimides which are first formed in the condensation are generally subjected to solvolysis or hydrolysis, preferably alkaline hydrolysis, if appropriate in the presence of amines, such as, for example, ethanolamines. , or alcohols, such as for example ethylene glycol or propanetriol. The polyaspartic acids formed in this way will preferably be used in the form of their salts to inhibit and retard fouling. The examples of obtaining polyaspartic acids to be used according to the invention are contained in the following publications: in J. Org. Chem. 26, 1084 (1961) prepares polyasparagic acid by thermal deaeration of aegyptinic acid. In US 4 839 461 ee, maleic acid and ammonia are reacted at 120-150 ° C. In US 5 288 783, maleic acid and fumaric acid are reacted with ammonia at 170-350 ° C. In US 5 493 004 polyaspartic acids are formed from the reaction of maleic acid anhydride and ammonia in a tubular reactor. The resulting product in this case can be polymerized additionally, if appropriate, in a high-viscosity reactor.All the methods of production have in common that the polysuccinimidae, formed first, are then subjected to solvolysis or hydrolysis, preferably alkaline hydrolysis. For the formation of the derivatives can also be used amines, amino alcohols and alcohols. The polyaspartic acids to be used according to the invention may contain, depending on the production process, the following structural elements in varying amounts: a) Aspartic acid units.

Shape to Form ß b) Succinimide units.

OR c) Malic acid units. d) Olefinic units. e) Iminodisuccinic acid inhibitors.

In all the structural elements represented, R = OH, ONa, OLI, OK, ONH4, NH2, OH3NCH2CH2OH, OH2N (CH2CH2OH) 2, OHN (CH2CH2OH) 3 or OCH2CH2OH. The polyaspartic acids to be used according to the invention can have molecular weights, relative to the weight average Mw according to GPC (gel permeation chromatography), from 500 to 50,000, preferably from 1,000 to 20,000, and particularly preferably from 1,500 to 10,000. . The qualitative and quantitative determination of the structural elements was carried out by means of NMR and FT-IR spectroscopy, mass spectrometry, HPLC, GC and elemental analysis. Peptide bonds can occur in form a and ß. In general, polyaspartic acids have an a / b mixture, the proportion of the formula being greater than the proportion of the form. The polyaspartic acids can be used according to the invention in combination with a surfactant, in particular with an emulsifier. Anionic, cationic, nonionic and ampholytic surfactants (emulsifiers) are suitable. Examples which may be mentioned are the anionic alkylsulfonate and the nonionic polyglycol ethers (alkoxylates). The use of linear alkyl sulfonates and polyglycol ethers of aliphatic alcohols is preferred. particularly preferred is the use of linear alkylsulfonates having 12 to 17 carbon atoms and unsaturated and / or saturated, aliphatic alcohols having 10 to 20 carbon atoms, which are etherified with 6 to 60 ethylene oxide units.

Mixtures consisting of polyaspartic acids and, if appropriate, surfactants, special emulsifiers, must be sized in such a way that they fulfill the task of retarding the formation of incrustations and preventing the formation of scale. If the formation of deposits due to inorganic and organic salts of alkaline earth metal and heavy metal ions is predominant, polyasparaginic acids will be used predominantly. Insofar as the formation of deposits is preponderant due to organic substances apo-laree, surfactants (emulsifiers) will be used to a greater extent. Depending on the Fouling and Scaling in a process with membranes, the quantitative proportions between polyaspartic acids and surfactants and / or emulsifiers can be dimensioned. The weight ratio between the polyaspartic acids and the surfactants and / or the emulsifiers can therefore be from 100: 0 to 1:99, preferably from 100: 0 to 10:90, particularly preferably from 100: 0 to 50. :fifty. Polyaspartic acids can be used either alone or in mixtures with surfactants (emulsifiers) in combination with polyacrylates and phosphonates. In this case, the biodegradability of the mixture resulting from the active products is increased, in comparison with the biodegradability of polyacrylates and phosphonates without reducing the inhibitory effect of the deposits. The polyaeparaginic acid and its mixtures with surfactants (emulsifiers) will be used in the membranes with pH values from 3 to 12.5, preferably from 4.5 to 11, particularly preferably from 6 to 10. In as long as the pH value is not determined by the feed stream used in the membrane process, acids and ba-see of any type can be used for adjusting the pH value, preferably those acids and bases that do not produce salts that are hardly soluble with the other components of the diet. The acids and bases should certainly not exert any harmful effect on the components of the feed stream, on the valuable metallic products or on the membranes. The polyaeparaginic acid and its mixtures with surfactants, special emulsifiers, will be used in membrane processes at temperatures of 10 to 90 ° C, preferably 15 to 70 ° C, particularly preferably 20 to 50 ° C. The membranes used in membrane processes can consist of inorganic materials, such as ceramic, Ti02, Zr02, or A1203, or by talee organic polymers such as cellulose esters (cellulose acetate, cellulose acetobutyrate, cellulose acetopropionate), polyamides, polyimides, polyesters, polyethersulfone, polyetherkene-na, polysulfone or PVDF. Preferably, the process according to the invention will be applied on nanofiltration and ultrafiltration membranes of the aforementioned materials, in another preferred form the process according to the invention will be applied on reverse osmosis membranes with a selective separation layer of polyamide. Particularly preferably, the selective separation layer for the membranes of all the processes mentioned is constituted by polyamide. All the membranes used in the process according to the invention are of asymmetric type or thin-layer type-compound according to a form known to those skilled in the art. Polyaspartic acids and their mixtures with surfactants, especially emulsifiers, can be used to inhibit and retard the formation of incrustations on membranes in membrane processes, which are fed with aqueous and aqueous feed streams containing solvents. In general, the feeding currents must be of such a nature that the active products are dissolved in the first place and, in this way, they can develop their effect.

In the same way, for an optimum effect, the compounds / salts that cause Scaling / Fouling must be dissolved first and only the solubility limit must be exceeded during the membrane process. Examples of feeds, which can be treated according to the invention, are: seawater, wastewater infiltration, industrial and communal wastewater, product streams with a potential for incrustation formation. The polyaspartic acid and mixtures thereof with surfactants (emulsifiers) will be added to the feed stream to be treated in a membrane installation, in an amount of 1 to 50,000 ppm, preferably to an amount of 5 to 5,000 ppm, in particular preferably from 10 to 500 ppm, very preferably from 50 to 500 ppm. Examples: Example 1. A laboratory module of 20 plates, respectively with a plate (= 2 surface membranes) of an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane of the Desalination Systems Firm, USA, was provided. . In the first place, the permeation performance with completely desalinated water was determined at 25 ° C and with an inlet pressure in the 20 bar module. PAS (approximate molecular weight 6,000) was added to the feed in two concentrations. The effect on the permeation performance was observed. Results: Example 2. a) 200 liters of a solution, prepared from completely desalinated water and 2.0 g / 1 of CaS04 • 2 H20, were concentrated with a nanofiltration membrane (sulfate retention> 95%) in one form of construction in spiral wound module (2.5"x 40", 47 thousand Spacer), firstly in 50% (conditions: 25 ° C, 30 bars of output pressure of the module, 1.25 m3 / h input in the module). The permeate performance was then measured several times according to a closed circuit form, ie with reflux of the retentate and the permeate to the tank. b) Test a) was repeated with addition of 50 ppm PAS (molecular weight 6,000). c) Test a) was repeated with addition of 50 ppm of PAS (molecular pee 6,000) and 1% of NaCl. After approximately 3 hours in the closed-circuit procedure, an additional concentration was carried out so that a concentration in CaS04 • 2 H20 of approximately 14 g / 1 was carried out in the feed. Results: Without the addition, the permeate output failed due to CaS04 • 2 H20 deposited by crystallization (solubility in H20 at 25 ° C, 2.9 g / 1). With PAS, a 4.5-fold over-saturation could be performed without loss in permeation performance. The added electrolytes did not harm. Results of Example 2: Density of permeate flow in l / m2-day as a function of time under the conditions of example 2a, 2b or 2c and achievable CaS04 concentrations.

Figure 1 shows the graphic representation of the table. Example 3. In the synthesis of a stilbene brightener with sulfo groups, sodium bicarbonate fluidized with calcium phosphate was used. The solution of the product with Ca3 (P04) 2, CaC03, NaCl and with the brightener as the most important component was released by means of tubular nanofiltration membranes (1.2 m module, 1/2") of the contained salt of synteeis (NaCl) and Concentrated approximately 55% of the volume (module output 1 m3 / h, 55 ° C, 25 inlet pressure) .The calcium content increased from 70 mg / l to 140 mg / l in the final concentrate. The solubility of Ca3 (P04) 2 of 20 mg / l was clearly exceeded, and by the addition of 100 ppm of PAS the same permeate yield was achieved as in the case of the preparation of the product solution, which did not contain Ca3 ( P04) 2, that is, it was prepared without the use of fluidized sodium bicarbonate (permeate flux density: 2,300 1 / (m2d) in the diafiltration, 1,000 1 / (md) in the concentration). again the performance of the original permeate by rinsing with water Example 4. When it is added 500 ml of a solution, containing 1 mmol of sodium carbonate, 1 mmol of sodium sulfate and 1 mmol of sodium fluoride, 500 ml of a solution containing 3 mmol of calcium chloride, resulted in a solution that was oversaturated 4, 5 times in relation to CaF2 and 7 times in relation to CaC03 and from which it was formed, at pH >8, a voluminous precipitate rapidly and at pH 5 a finely crystalline precipitate was formed and delayed. When 50 ppm of PAS was added (molecular weight 6,000), no precipitate formation occurred. Example 5. Sulfuric acid mother liquors were neutralized from dye production, as a step prior to their production by membrane technology, by the addition of lime slurry. After the separation of the neutralization sludge, the solution was concentrated, which is now re-examined by yeeo, by means of an ultrafiltration membrane in an eepiral-coiled construction form (2.5"x 40", 47,000, inlet pressure). in the module 30 bar, 25 ° C, module output 1.250 1 / h). The following assay settings were compared: a) During the 20% concentration of the initial volume and in a subsequent closed-loop work form the permeate output was measured. b) 50 ppm of a mixture consisting of PAS and polyaspartic acid (3: 1) were added to the feed. Results: The permeate yields in the test 5b) were, during the concentration and closed-loop driving phase, significantly higher than in the addition.

Results of Example 5: Permeate flow densities in l / m-day as a function of time under the conditions of example 5a or 5b and concentrations achievable in CaS04.

Figure 2 shows the graphic representation of the table. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (10)

1. CLAIMS Having described the invention as above, OC? D xpcfac lo cxxi apdb is written in the skj Tientes xsáspxáics áapES. 1.- Process for the realization of processes with membranes for the treatment of aqueous feeds with inorganic and organic components with inhibition or retardation of the formation of scale on the membranes by adding an inhibitor of the scale, characterized because as an inhibitor of the incrustation polyaspartic acids are used and mixtures thereof with surfactants, preferably emulsifiers, with polyaspartic acids being used in an amount of 1 to 50,000 ppm, based on the aqueous feed.
2. 2. Process according to claim 1, characterized in that polyaeparaginic acids are used and mixtures with surfactants, preferably emulsifiers, in the presence of polyacrylates or phosphonates or a mixture thereof.
3. 3. Process according to claim 1, characterized in that polyaspartic acids are used which have an average weight Mw of 500 to 50,000, preferably 1,000 to 20,000, particularly preferably 1,500 to 10,000, determined by gel permeation chromatography.
4. 4. Process according to claim 1, characterized in that polyaspartic acids are used, which are prepared from maleic anhydride and ammonia in the presence of water or from their derivative products such as, for example, the maleic acid NH4 eal, acid maleinamide, aeparaginic acid and asparagine as well as the ammonium salts of maleic acid, maleinamide acid, asparagine acid, asparagine and iminodisuccinic acid or mixtures thereof by thermal condensation, if appropriate in the presence of acid catalysts to give polysuccinimides and subsequent solvolieis or hydrolysis for example to give lae salts of polyaspartic acid.
5. 5. Process according to claim 4, characterized in that polyasparagic acids are used as Na salts.
6. Method according to claim 1, characterized in that the surfactants which can be used in admixture with polyaspartic acids, preferably emulsifiers, are those from the group consisting of surfactants and anionic, cationic, nonionic and ampholytic emulsifiers, preferably alkylsulfonates and alkoxylates, Particular preference is given to linear alkene-eulphonate with 12 to 17 carbon atoms and polyethers based on unsaturated and / or saturated alcohols with 10 to 20 carbon atoms and 6 to 60 units of ethylene oxide.
7. 7. Method according to claim 1, characterized in that the processes with membranes are carried out at a pH value of 3 to 12.5, preferably 4.5 to 11, particularly preferably 6 to 10.
8. 8. Process according to claim 1, characterized in that the polyaspartic acids and all the surfactants and / or emulsifiers are used in proportions by weight of 100: 0 to 1:99.
9. 9. Process according to claim 1, characterized by membranes using nanofiltration membranes or ultrafiltration.
10. 10. Process according to claim 1, characterized in that reverse osmosis membranes are used with a selective separation layer of polyamide.