WO2003053860A1

WO2003053860A1 - Method for purifying waste water and magnetic adsorbents suited therefor

Info

Publication number: WO2003053860A1
Application number: PCT/EP2002/013586
Authority: WO
Inventors: Christian N. Kirsten; Olaf Lammerschop; Marcel Roth
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 2001-12-11
Filing date: 2002-12-02
Publication date: 2003-07-03
Also published as: DE10160664A1; AU2002358074A1

Abstract

The invention relates to a method for purifying waste water during which adsorbents having magnetic properties are used in order to remove harmful substances more easily, in particular, to remove metallic salts more easily.

Description

Wastewater treatment processes and suitable magnetic ones

adsorbents

The invention relates to a process for wastewater purification, in which adsorbents with magnetic properties are used for easier removal of harmful substances, in particular for easier removal of metal salts.

A large number of chemical processes, such as those carried out in almost all areas of industrial production of capital and consumer goods, produce waste water. In the course of ever increasing environmental awareness, it is expected that such wastewater will be subjected to purification before being released into the environment, in which heavy metals will be removed from the wastewater, among other things. Heavy metals are particularly undesirable as wastewater ingredients because they are said to have a variety of toxic, carcinogenic and mutagenic properties.

Especially when processing ore and galvanizing metal surfaces, wastewater is often generated which is contaminated with heavy metals. However, the complete removal of such heavy metals from the wastewater is difficult in practice due to the high solubility of many heavy metal salts. For example, precipitation processes, solvent extraction, distillation, membrane processes or ion exchange have been used to remove heavy metals from aqueous solutions. However, many of the processes mentioned have a number of disadvantages, in particular expensive equipment, complicated processes which can only be operated by trained personnel, large amounts of waste or large space requirements. In recent years, the addition of adsorbents has proven to be a suitable and therefore often used agent. Waste water for the removal of heavy metals is therefore often treated with adsorbents that bind heavy metal ions due to ionic or complex interactions.

For example, AI Zouboulis and KA Matis describe in "Removal of Metal Ions from Dilute Solutions by Sorptive Flotation", Critical Reviews in Environmental Science and Technology, 27 (3): 195-235 (1997) a process for removing soluble ionic metal cations or oxyanions from dilute aqueous solutions. The method comprises treating the solutions with particulate sorbents, the particle size of which is in the ultra-fine size range, the separation of the particles being achieved by a flotation process. However, a problem with the methods described is that the separation of very fine particles by flotation generally does not succeed so completely that the heavy metal content can be reduced below the detection limit. In addition, the foam formed during flotation has a high water content, the water having to be removed from the foam in subsequent processes. However, the flotation generally separates the majority of the suspended matter in the wastewater, which means that in addition to the adsorbed heavy metals, other suspended matter also gets into the adsorbate to be disposed of as special waste. In addition, flotation is an energy-intensive process.

Ebner et al. in "New Magnetic Field-Enhanced Process for the Treatment of Aqueous Wastes", Separation Science and Technology, 34 (6 & 7), pp. 1277-1300, 1999, describe a process for separating plutonium and americium from waste water. In the process described, compounds are used to remove the plutonium and the americium which consist of non-porous ammonia-epichlorohydrin polymer balls with magnetite adhesions. However, due to the properties of the metals removed, the process described cannot be transferred to the removal of heavy metal ions. In addition, the magnetite content in the systems described is so low that separation is difficult. Furthermore, the small surface area of the polymer particles described allows only a low specific loading with metal ions.

Lin et al. describe in their lecture manuscript presented at the Recovery, Recycling, Reintegration fair in 1999 in Geneva in 1999 the removal of copper and lead ions from waste water by adding fly ash. The problem with the described method is that the removal of the absorbent particles from the wastewater is a time-consuming process. Magnetization of the material is not described.

There was therefore a need for a process for separating heavy metal ions from waste water which does not have the disadvantages of processes known from the prior art. There was also a need for a process for separating heavy metal ions from waste water, in which complex filtration steps are either eliminated or at least significantly accelerated. There was also a need for a process for separating heavy metal ions from waste water which has only low energy consumption.

The present invention was based on the task of fulfilling the above-mentioned needs. It has now been found that the use of magnetic adsorbents for the purification of waste water contaminated with heavy metals solves the above-mentioned tasks.

The present invention therefore relates to a process for cleaning waste water contaminated with metal salts, in which a magnetic adsorbent is mixed with the waste water and the adsorbent is separated from the waste water in a magnetic field after the adsorption of metal salts from the waste water.

In the context of the present invention, “metal salts” mean metal salts which have a water solubility of at least about 0.1 g / l and are adsorbable on a suitable adsorbent. In the context of a preferred embodiment of the present invention, heavy metal salts are removed from the treated waste water in the process according to the invention. In the context of the present invention, “heavy metals” means in particular the elements lead, cadmium, chromium, cobalt, iron, gold, copper, manganese, molybdenum, nickel, platinum, mercury, selenium, silver, vanadium, zinc and tin. The method according to the invention is suitable for removing metal salts from waste water contaminated with such metal salts. In principle, metal salts in any concentration can be removed from waste water with the aid of the method according to the invention. In the context of a preferred embodiment of the present invention, however, the method according to the invention is applied to waste water which has a low heavy metal concentration, in particular a heavy metal concentration which can be removed from the waste water with great effort or not at all using methods known from the prior art. Suitable heavy metal concentrations are, for example, within a range from about 0.01 to about 1000 mg / l, for example about 0.1 to about 100 mg / l.

A method according to the invention includes the use of a magnetic adsorbent. In the context of the present invention, the term “magnetic adsorbent” encompasses adsorbents which as such have no magnetic properties, but have been provided with magnetic properties by treatment with corresponding compounds, in particular by treatment with nanoparticles.

In the context of the present solid particles, “nanoparticles” are understood to comprise a particle size of approximately 1 to approximately 1000 nm, for example approximately 2 to approximately 500 nm or approximately 5 to approximately 300 nm, eg approximately 200 nm or approximately 30 to approximately 100 nm The size specifications relate to the totality of the nanoparticles contained in the adsorbent, at least 90% by weight of the nanoparticles being intended to meet the size specifications mentioned above.

The nanoparticles which can be used in the context of the present invention have magnetic, in particular ferromagnetic, properties. In a preferred embodiment of the invention, the nanoparticles therefore have at least one element selected from the group consisting of Fe, Co, Ni, Cr, Mo, W, V, Nb, Ta, Ce, Pr, Nd, Pm, Sm, Eu, Gd , Tb, Dy, Ho, Er, Tm, Yb, Lu, alloys of two or more of said elements, oxides of said elements or ferrites of said elements, or a mixture of two or more thereof. For example, the nanoparticles magnetite, macchiemite, goethite or a ferrite of the general formula MeOFe ₂ θ ₃ , where Me is an element selected from the group consisting of Mn, Co, Ni, Cu, Zn, Mg or Cd, or a mixture of two or more of them.

Also suitable for use as nanoparticles in the context of the present invention are materials such as tungsten (FeMnWO ₄ ), ferberite (FeWO ₄ ), permanently magnetic aluminum-nickel-cobalt alloys, the main constituents being iron, cobalt, nickel, aluminum, copper or titanium or mixtures contained two or more of them. Furthermore, alloys made of platinum and cobalt, alloys made of iron, cobalt, vanadium and chromium, Ludwigit (Mg ₂ Fe ³⁺ [O ₂ / BO ₃ ]), Vonsenit (Fe ₂ ²⁺ Fe ³⁺ [O ₂ / BO ₃ ] ), Cobalt-nickel gravel of the general formula A ²⁺ B ³⁺ ₂ X ^{2 "} in which A represents iron, cobalt, nickel or copper, B represents iron, cobalt, nickel or chromium or a mixture of two or more thereof and X represents S, Se or Te or a mixture of two or more of them, iron oxides such as iron (II) oxide (FeO) or iron (III) oxide (Fe ₂ O ₃ ) in its ferromagnetic modification γ-Fe ₂ O ₃ (Macchiemit ) with spinel, magnetite (Fe ₃ O ₄ ), cobalt alloys such as the alloys usually used as high-temperature materials with Co-Cr matrix, Ni-Fe-Al-Co casting alloys with up to about 36% by weight cobalt, alloys of the type CoCrW, chromium (IV) oxide (CrO ₂ ), the oxide-ceramic materials of the general composition M ₂ Fe ³ ₂ O ₄ or M ² O * Fe ₂ O ₃ , which are assigned to the group of ferrites, and which have permanent m contain magnetic dipoles, where M stands for zinc, cadmium, cobalt, manganese, iron, copper, magnesium and the like, as well as iron itself.

The production of magnetite or macchiemite nanoparticles can be achieved, for example, by using microemulsion technology. The disperse phase of a microemulsion is used to limit the size of the particles formed. A metal-containing reagent is dissolved in the disperse aqueous phase in a W / O microemulsion. The reagent is then converted in the disperse phase to a preliminary stage of the desired magnetic compound, which then already has the desired size in the nanometer range. Then use a careful Oxidation step, the metal oxide, in particular iron oxide in the form of magnetite or Macchiemit, produced. A corresponding method is described, for example, in US Pat. No. 5,695,901.

Furthermore, nanoscale magnetic particles of Fe ₃ O, D-Fe ₂ O ₃ or corresponding hydroxides can be converted into iron (II) - and / or iron () by converting an acidic iron (II) and / or iron (III) salt solution. III) carbonate by adding an equivalent amount of alkali carbonates such as sodium hydrogen carbonate, sodium carbonate or ammonium carbonate and the subsequent thermal oxidation to magnetic iron hydroxide and further to magnetic iron oxide.

The size of the particles can be controlled by the thermal reaction rate and concentration of the iron salt solution. So small diameters of 20-100 nm with time-separated formation of iron (II, III) carbonate at temperatures of 1-50 ° C, preferably 5-10 ° C, and subsequent heating, larger particles of 100-1000 nm Reaction temperatures of 60-100 ° C and the associated faster transfer of iron (II, III) carbonate to iron (II, III) hydroxide reached. The conversion of an iron (II) and / or iron (III) salt solution into an iron (M) and / or iron (III) complex by adding one or more complexing agents such as, for. B. ethylenediamine tetraacetic acid, citric acid, tartaric acid or salts thereof, the subsequent neutralization with moderately basic reagents such as ammonia or alkali carbonates and the precipitation of the iron hydroxides by adding strong alkalis such as sodium hydroxide solution to a pH of 11, likewise give desired magnetic particles , The rate of titration during alkalization determines the size of the magnetic particles.

Particle configurations suitable according to the invention can also be synthesized by treating an iron (II) and / or iron (III) salt solution with basic anion exchange resins. These are added to the iron salt solution at such a rate that a constant increase in the pH to 7-10 is ensured. The resulting particle sizes can be controlled by selecting different types of anion exchangers. So arise when using weakly basic anion exchangers, such as. B. are known under the trade name Amberlit IR 45, small particle diameter, with strongly basic such. B. Amberlite IRA 420 larger particles.

With a molar ratio of iron (II) / iron (III) salt solution of 1: 2, the ferrimagnetic Fe ₃ O (magnetite) is formed during alkalization. Its mild oxidation results in ferrimagnetic D-Fe ₂ O ₃ . As iron salts z. B. iron (III) chloride, iron (III) sulfate, iron (III) nitrate and iron (II) chloride, iron (II) sulfate or the respective double salts such as iron (II) / iron (III) - ammonium sulfates are used.

Nanocrystalline magnetic particles of double oxides or hydroxides of bivalent or trivalent iron with bivalent or trivalent metals or mixtures of the mentioned oxides or hydroxides can also be produced by the above-mentioned processes, in that a solution of salts of bivalent or trivalent iron and bi- or trivalent metals is implemented. Magnetic double oxides or hydroxides of trivalent iron are preferred with divalent metal ions from the first row of transition metals, such as. B. Co (II), Mn (II), Cu (II) and Ni (II) are synthesized, that of divalent iron with trivalent metal ions such as Cr (III), Gd (IM), Dy (I) or Sm (IM) ,

The magnetic particles produced in this way are purified by filtration, ultrafiltration, dialysis or magnetic separation of foreign ions, if appropriate concentrated, and are available for further processing.

According to the invention, very small superparamagnetic particles can be produced by precipitation from a saturated iron salt solution containing organic solvents with lyes.

It was found that almost monodisperse superparamagnetic particles can be produced very easily by adding a water-miscible solvent, such as acetone, to an iron salt solution. Ethyl methyl ketone or dioxane is added until the first beginning turbidity just dissolves again by stirring. The superparamagnetic particles can be precipitated from such a solution, for example with sodium hydroxide solution. The concentration of the iron salt solution determines the resulting particle size. The more concentrated the iron salt solution, the smaller the particles. The magnetic particles are in the diameter range from 1 to 20 nm, preferably from 3-10 nm.

In addition, corresponding magnetic nanoparticles can in principle be produced by conventional precipitation reactions as are generally known to the person skilled in the art.

It has been found, however, that the magnetic adsorbents used in the process according to the invention have particularly good properties with regard to their separability in the magnetic field if the precipitation reaction is carried out in the presence of the adsorbent to be used. This procedure is explained in more detail in the further text.

Suitable adsorbents are basically all adsorbents which are suitable for removing metal salts, in particular heavy metal salts, from waste water. In the context of the present invention, for example, organic and inorganic adsorbents are suitable.

Examples of suitable inorganic adsorbents are hollow bodies based on silicate, for example those with a spherical structure.

According to a further embodiment of the method according to the invention, such a silicate material can contain, for example, essentially closed hollow bodies.

Suitable silicate-based materials have, for example, a diameter of less than approximately 200 μm, in particular less than approximately 100 μm. Suitable particles with a diameter of approx. 50 μm usually have a wall thickness of approximately 1 μm, while smaller particles with a diameter of approximately 1 μm have a wall thickness of approximately 0.1 μm. The particle sizes given relate to the diameter of the individual particles.

In a further embodiment, at least partially agglomerated silicate-based material can also be used as the adsorbent.

For example, micro glass hollow spheres are suitable as adsorbents. Such hollow glass microspheres are normally used as an additive in plastics. It is particularly advantageous that the microglass hollow spheres are commercially available and have the required structural features.

In the context of a further embodiment of the present invention, aluminum oxide, clay materials such as bauxite, silicates such as activated carbon, pumice stone, layered silicates, zeolites, molecular sieves, silica gel, ceramic hollow filaments, the compounds obtainable under the trade name Reapor® or filter ash (fly ash) can be used as inorganic adsorbents ,

Suitable inorganic adsorbents, for example, have a particle surface area of approximately 5 to approximately 1000 m ² / g, in particular approximately 10 to approximately 300 m ² / g.

In a preferred embodiment of the present invention, fly ash is used as the inorganic adsorbent. In the context of the present invention, “fly ash” is understood to mean a powdery material consisting predominantly of glassy beads of light to dark gray color. Fly ash is preferably used in the context of the present invention, as it arises during the combustion of hard coal (hard coal fly ash). The main components of the coal fly ash silicon, aluminum and iron oxide from the accompanying minerals of coal. In addition, there are small amounts of unburned carbon particles as so-called flying coke or loss of ignition. The hard coal fly ash which is preferably used in the context of the present invention preferably originates from a combustion process in which the coal in coal mills has grain sizes of less than about 90 microns ground and blown into a kettle. Depending on the coal used, 5 to 35% non-combustible mineral rock is also blown into the boiler, which remains as ash. If this process is carried out in dry combustion plants, the ash will not become liquid due to low temperatures of around 1200 ° C. In this process, the non-combustible mineral components are only melted on the surface and entrained with the flue gas stream when they are blown into the boiler. The majority of this ash is rapidly cooled in the flue gas stream and forms spherical, predominantly amorphous particles. To separate the hard coal fly ash used in the present method, the flue gas stream is passed through multi-stage electrostatic precipitators, from which the fly ash is discharged.

Fly ash preferably used in the process according to the invention has a loss on ignition of from about 1.5 to about 5.0% by weight. The bulk density is about 2.1 to about 2.4 kg / dm ³ , while the bulk density is about 0.7 to about 1.1 kg / dm ³ . The particles of the fly ash preferably have an average particle size (d50) of less than about 300 μm, preferably less than 200 or less than 150, for example less than 130, less than 110, less than 90 or less than 60 μm.

In the context of a preferred embodiment of the present invention, the fly ash has a carbon content of at most about 30% by weight, for example at most about 20% by weight or at most about 10 or 5% by weight.

Instead of the inorganic adsorbents mentioned above or in addition thereto, inorganic adsorbents can be used in the process according to the invention. Organic compounds which can be of natural or synthetic origin are suitable as organic adsorbents in the context of the present invention. It has been found in the context of the present invention that organic adsorbents are particularly suitable in the context of the present invention if they are either water-soluble or, if they are not water-soluble, have a porous structure. In particular, essentially spherical particles are preferred.

Organic adsorbents of natural origin include, for example, adsorbents based on alginate, cellulose or starch. Water-soluble or water-dispersible starch and / or starch derivatives or cellulose derivatives, in particular cellulose ethers, are particularly suitable.

If starch is used as the organic adsorbent in the process according to the invention, water-swellable modified starch is used in the context of a preferred embodiment of the present invention. Partially degraded starch or swelling starch are suitable, for example. If starch derivatives are used, starch esters or starch ethers, in particular carboxylated, alkoxylated or starches modified in some other way to improve their properties as reagents which bind heavy metals, are suitable. Suitable carboxylated or alkoxylated starches are all appropriately modified natural starch types from potatoes, corn, wheat, rice, milo, tapioca and the like, starch derivatives based on potatoes or corn starch being preferred. Suitable starch derivatives have, for example, a degree of carboxylation of about 0.1 to about 2.0 (DS) or an degree of alkoxylation of 0.05 to 1.5 (MS).

Starch or cellulose ethers are understood to mean starch or cellulose derivatives which are produced by partial or complete substitution of hydrogen atoms in the hydroxyl groups of starch or cellulose by alkyl and / or (ar) alkyl groups. The alkyl and / or (ar) alkyl groups preferably additionally carry nonionic, anionic or cationic groups. The individual molecules are generally substituted differently so that their degree of substitution is an average.

The etherification of the starch or cellulose is generally carried out by the action of (ar) alkyl halides, for example methyl, ethyl and / or benzyl chloride, 2-chloroethyldiethylamine or chloroacetic acid, and / or epoxides, for example ethylene, Propylene and / or butylene oxide, glycidyltrimethylammonium chloride, and / or activated olefin, for example acrylonitrile, acrylamide or vinylsulfonic acid, carried out on cellulose activated with bases, usually with aqueous sodium hydroxide solution. In the context of the present invention, preference is given to carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyalkyl cellulose, in particular hydroxyethyl cellulose or their mixed ethers, such as methylhydroxyethyl or hydroxypropyl cellulose, carboxymethylhydroxyethyl cellulose and / or

Ethyl.

The following types are particularly suitable as cellulose ethers: carboxymethyl cellulose (CMC), carboxymethyl methyl cellulose (CMMC), ethyl cellulose (EC), hydroxyethyl cellulose (HBC), hydroxybutyl methyl cellulose (HBMC), hydroxyethyl cellulose (HEC), hydroxyethyl carboxymethyl cellulose (HECMC) hydroxyl cellulose (HPECC) hydroxyl cellulose ), Hydroxypropylcarboxymethylcellulose (HPCMC), Hydroxypropylmethylcellulose (HPMC), Hydroxyethylethylcellulose (HEMC) Methylhydroxyethylcellulose (MHEC), Hydroxyethylmethylcellulose (HEMC) Methylhydroxyethylcellulose (MHEC), Methylcellulose (MC) and Propylcellulose (PC), where appropriate, carboxymethylcellulose, and methyloxymethylcellulose, and methyloxymethylcellulose as well alkoxylated, especially ethoxylated methyl cellulose are preferred. Derivatives of the compounds mentioned, which have been modified to improve their adsorption capabilities against heavy metals, can also be used in the context of the present invention.

Described derivatives of other polysaccharides or their degradation products, e.g. Dextran, carrageenan, agar, tragacanth, gatti gum, karaya gum, guar gum, tara gum, alginates, pectin or chitin can also be used as organic adsorbents. Derivatives of proteins such as casein, collagen or gelatin and their degradation products also meet the requirements of the invention.

Synthetic organic compounds are also suitable for use in the process according to the invention. To the within the Synthetic organic compounds suitable for the process according to the invention include, for example, the organic synthetic polymers.

Organic polymers suitable in the context of the present process are, for example, polymers which can be prepared by polycondensation or polyaddition, such as polyesters, polyethers, polyamides or polyurethanes, or polymers which can be prepared by polymerization, such as polyacrylates, polymethacrylates, styrene-acrylate and styrene-methacrylate copolymers and the like.

Polyesters suitable for use in the process according to the invention are, for example, polymers with NH, OH or COOH groups. In the process according to the invention, preference is given to using polyesters which have been modified in such a way that their absorption capacity for heavy metals is at least sufficient to carry out the process according to the invention. Suitable for this purpose are, for example, polyesters that have a sufficient number of ionic centers.

Suitable polyesters can be produced, for example, by polycondensation. For example, difunctional or trifunctional alcohols or a mixture of two or more thereof, with dicarboxylic acids or tricarboxylic acids or a mixture of two or more thereof, or their reactive derivatives, can be condensed to give polyester polyols. Suitable dicarboxylic acids are, for example, succinic acid and its higher homologues with up to 44 carbon atoms, furthermore unsaturated dicarboxylic acids such as maleic acid or fumaric acid and aromatic dicarboxylic acids, in particular the isomeric phthalic acids such as phthalic acid, isophthalic acid or terephthalic acid. Citric acid or trimellitic acid, for example, are suitable as tricarboxylic acids. Polyester polyols from at least one of the dicarboxylic acids and glycerol mentioned, which have a residual OH group content, are particularly suitable within the scope of the invention. Particularly suitable alcohols are hexanediol, ethylene glycol, diethylene glycol or neopentyl glycol or mixtures of two or more thereof.

Examples of polyols which can be used as polyol components for the production of the polyesters are diethylene glycol or higher polyethylene glycols with a Molecular weight (M _n ) from about 100 to about 22,000, for example about 200 to about 15,000 or about 300 to about 10,000, in particular about 500 to about 2,000.

Polyurethanes, as can be used in the process according to the invention, are usually produced by reacting at least one polyisocyanate, preferably a diisocyanate, and a polyol component, which preferably consists predominantly of diols. The polyol component can contain only one polyol, but a mixture of two or more different polyols can also be used as the polyol component. Polyalkylene oxides, for example, are suitable as the polyol component or at least as part of the polyol component.

If necessary, parts of the polyalkylene oxide can be replaced by other hydrophobic diols containing ether groups, which have molecular weights of 250 to 3,000, preferably 300 to 2,000, in particular 500 to 1,000. Specific examples of such diols are: polypropylene glycol (PPG), polybutylene glycol, polytetrahydrofuran, polybutadiene diol and alkanediols with 4 to 44 carbon atoms. Preferred hydrophobic diols are polypropylene glycol, polytetrahydrofuran with a molecular weight of 500 to 1,000 and 1,10-decanediol, 1,12-dodecanediol, 1, 12-octadecanediol, dimer fatty acid diol, 1, 2-octanediol, 1, 2-dodecanediol, 1, 2 -Hexadecanediol, 1,2-octadecanediol, 1,2-tetradecanediol, 2-butene-1,4-diol, 2-butyne-1,4-diol, 2,4,7,9-tetramethyl-5-decyne-4 , 7-diol and its ethoxylation products, especially with up to 30 moles of ethylene oxide.

In addition to the diols of the polyol component, diisocyanates are essential components of the polyurethane that can be used as a hot melt adhesive. These are compounds of the general structure O = C = N-X-N = C = O, where X is an aliphatic, alicyclic or aromatic radical, preferably an aliphatic or alicyclic radical with 4 to 18 C atoms.

Examples of suitable isocyanates are 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), hydrogenated MDI (H ₁₂ MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 4,4'-diphenyldimethylmethane diisocyanate, di- and tetraalkylene diphenylmethane diisocyanate, 4,4'- Dibenzyl diisocyanate, 1, 3-phenylene diisocyanate, 1, 4-phenylene diisocyanate, the isomers of tolylene diisocyanate (TDI), 1-methyl-2,4-diisocyanato-cyclohexane, 1, 6-diisocyanato-2,2,4-trimethylhexane, 1, 6-diisocyanato-2,4,4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1, 5,5-trimethylcyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-di-isocyanatophenyl perfluoroethane, Tetramethoxybutane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate (HDI), dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene-diisocyanate, phthalic acid-bis-isocyanato-ethyl ester, furthermore Diisocyanates with reactive halogen atoms, such as 1-chloromethylphenyl-2,4-diisocyanate, 1-bromomethylphenyl-2,6-diisocyanate, 3,3-bis-chloromethyl ether-4,4'-diphenyl diisocyanate.

A polyurethane suitable according to the invention is preferably produced in a one-step process. For example, all starting materials are first mixed in the presence of an organic solvent with a water content of less than 0.5% by weight. The mixture is heated to 80 to 200 ° C, in particular to 100 to 180 ° C and preferably to 130 to 170 ° C for about 1 to 30 hours.

The reaction time can be shortened by the presence of catalysts. In particular, tertiary amines are useful, e.g. B. triethylamine, dimethylbenzylamine, bis-dimethylaminoethyl ether and bis-methylaminomethylphenol. 1-Methylimidazole, 2-methyl-1-vinylimidazole, 1-allylimidazole, 1-phenylimidazole, 1,2,4,5-tetramethylimidazole, 1 (3-aminopropyl) imidazole, pyrimidazole, 4-dimethylaminopyridine, 4-pyrrolidinopyridine are particularly suitable , 4-morpholinopyridine, 4-methyl pyridine. However, preference is given to working without a catalyst. The solvent is also expediently omitted. In the context of the present text, “solvents” are understood as meaning inert organic liquid substances with a boiling point of less than 200 ° C. under normal pressure.

For the preparation of the polymers which can be used in the process according to the invention, for example olefinically unsaturated monomers are suitable which are accessible to emulsion polymerization. Suitable polymers are, for example, from monomers such as acrylic acid, methacrylic acid, if appropriate available as copolymers with their esters with primary and secondary saturated monohydric alcohols with 1 to about 28 carbon atoms such as methanol, ethanol, propanol, butanol, 2-ethylhexyl alcohol, cycloaliphatic alcohols such as cyclohexanol, hydroxymethylcyclohexane or hydroxyethylcyclohexane.

Also suitable as comonomers are simple ethylenically unsaturated hydrocarbons such as ethylene or α-olefins having about 3 to about 28 carbon atoms, for example propylene, butylene, styrene, vinyl toluene, vinyl xylene and halogenated unsaturated aliphatic hydrocarbons such as vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride and the like ,

Multi-ethylenically unsaturated monomers, for example, can also be used as comonomers. Examples of such monomers are diallyl phthalates, diallyl maleinate, triallyl cyanurate, tetraallyloxyethane, divinylbenzene, butanediol-1, 4-dimethacrylate, triethylene glycol dimethacrylate, divinyl adipate, allyl acrylate, allyl methacrylate or vinyl crotonate, pentylene bisacrylamide or hexa diacrylate, polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyacrylate triethyl acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate or polyalkylene acrylate. Such comonomers ensure crosslinking of the polymers.

Also suitable as monomers or comonomers are ethylenically unsaturated compounds with N-functional groups. These include for example acrylamide, methacrylamide, allyl carbamate, acrylonitrile, N-methylolacrylamide, N-methylolmethacrylamide, N-methylolallyl carbamate and the N-methylol esters, alkyl ethers or Mannich bases of N-methylolacrylamide or N-methylolmethacrylamide or N-Methylolallylcarbamats, acrylamidoglycolic acid, Acrylamidomethoxyssigsäuremethylester, N - (2,2-Dimethoxy-1-hydroxyethyl) acrylamide, N-dimethylaminopropylacrylamide, N-dimethylaminopropylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-butylacrylamide, N-butylmethacrylamide, N-cyclohexylacrylamide, N-cyclohexylmethacrylamide, N - Dodecyl acrylamide, N-dodecyl methacrylamide, ethyl imidazolidone methacrylate, N-vinyl formamide, N-vinyl pyrrolidone and the like. In order to be usable in the context of the present invention, the corresponding adsorbents must have magnetic properties. However, adsorbents which are suitable in the context of the present invention do not have such magnetic properties as the original substance property, but the magnetic properties are imparted to the adsorbents which can be used according to the invention by mixing the adsorbents with magnetic compounds.

It has been shown that magnetic nanoparticles, as have already been described in the context of the present text, are suitable for transferring their magnetic properties to a corresponding adsorbent.

In principle, all methods are suitable for transferring the magnetic properties to a corresponding adsorbent, by means of which magnetic particles can be combined with an appropriate adsorbent in such a way that the connection between adsorbent and magnetic particles in the aqueous environment is so stable that the method according to the invention can be carried out , For this it is necessary that the adsorbent particles have magnetic properties or at least be magnetizable. In the context of a preferred embodiment of the present invention, absorbent particles are therefore used to carry out the method according to the invention which are connected to magnetic particles either physically as inclusion compounds, ionically, covalently or via dipolar interactions.

Magnetized adsorbents which can be used in the context of a method according to the invention can in principle be produced by any method which leads to the binding of magnetic particles to the adsorbents. For example, it is possible to provide adsorbents with magnetic properties by mixing the adsorbents with a suspension of magnetic particles in a suitable solvent. The suspension medium can then be drawn off and the mixture of adsorbent and magnetic particles can be washed, for example. It is also possible to functionalize the magnetic particles on their surface in such a way that they form a covalent bond with the adsorbent. For this purpose, the surface of the nanoparticles are modified in such a way that a reaction with a functional group of an organic natural or synthetic polymer is subsequently possible, or the modified nanoparticle can be incorporated into an organic synthetic polymer.

The surface of the magnetic particles can be modified, for example, with silanes. If oxides are used as magnetic particles, these oxides generally carry superficial OH groups which can react with silanes or halosilanes to form a covalent Si-O bond. If the silanes themselves have a suitable functional group that enables the silanes to be attached to a polymer later, the modified magnetic particles can be covalently attached to the polymers. Suitable functional groups are, for example, olefinically unsaturated double bonds or protected OH or NH groups. A suitable possibility for modifying the surface of nanoparticles with silane compounds is described, for example, in US Pat. No. 5,695,901.

Other suitable methods for functionalizing magnetic particles are known to the person skilled in the art.

However, it has been shown that, as already described above, particularly good magnetic adsorbents result if the production of the magnetic particles is carried out in the presence of the adsorbent.

For this purpose, the production of the magnetic particles, as described above in the context of the present text, is modified in such a way that inorganic and or organic adsorbents which can be used in the context of the present invention are present in the corresponding salt solutions leading to the magnetic particles. In the context of a preferred embodiment of the present invention, the magnetic adsorbents are therefore used in processes in which the formation of a microemulsion is avoided.

In the context of a preferred embodiment of the present invention, inorganic magnetic adsorbents are used to carry out the method according to the invention. It has been shown that the cleaning of wastewater contaminated with metal salts leads to particularly good results when such inorganic magnetic adsorbents are used.

The present invention therefore also relates to a magnetic inorganic adsorbent containing magnetic particles, preferably nanoparticles.

The term "containing magnetic particles" is to be interpreted in the context of the present text so that the adsorbent itself has no magnetic properties and in particular has a particle diameter of more than about 1 μm.

An adsorbent according to the invention preferably contains at least one compound selected from the group consisting of Fe, Co, Ni, Cr, Mo, W, V, Nb, Ta, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb as magnetic particles , Dy, Ho, Er, Tm, Yb, Lu, alloys of two or more of the said elements, oxides of the said elements or ferrites of the said elements (except iron), or a mixture of two or more thereof.

To carry out the method according to the invention, it is necessary to mix the waste water to be cleaned with the magnetic adsorbent used according to the invention. This can be done either batchwise or continuously. In the context of a preferred embodiment of the present invention, the magnetic adsorbent is continuously mixed with the waste water.

After the wastewater to be cleaned has been in contact with the magnetic adsorbent for a sufficiently long time, for example for one Period of about 1s to about 1h, in particular about 10 s to about 30 min or about 5 to about 20 min, the mixture of waste water and magnetic adsorbent is passed through a magnetic field. For example, the mixture of waste water and magnetic adsorbent is passed through a tube which is penetrated from the outside by a corresponding magnetic field or which is generated by magnets arranged inside the tube.

In a preferred embodiment of the present invention, however, the mixture of waste water and magnetic adsorbent is passed through a magnetic filter.

In the context of the present invention, a “magnetic filter” is understood to mean an arrangement in which a filter arrangement, which consists of a magnetic or magnetizable material, is located within the volume through which the mixture of waste water and magnetic adsorbent flows.

In this case, it is possible, for example, for there to be a filter section, preferably defined by magnetic rods, in the interior of the flowed-through tube. The length of the filter section can be varied by the number and / or length of the rods.

Furthermore, it is possible to generate a magnetic filter in the sense of the present invention by means of a magnetic field applied to the filter arrangement from the outside, the magnetic field in the interior of the filter arrangement being reinforced by corresponding materials which reinforce the magnetic field.

The term "filter" is to be interpreted in the context of the present text in such a way that the inventions of such a "filter" are so great that they allow both the waste water and the particles of the magnetic adsorbent contained therein to pass unless a magnetic field is applied to the arrangement is applied and the filter material itself has no magnetic properties. A "filter" is preferably in the sense of the present invention constructed that the total filtration distance is as long as possible, but the filter itself generates the lowest possible pressure drop.

In principle, all materials can be used as the filter material that can transmit or amplify an external magnetic field in their interior and in particular increase the field line density in the interior of the tube. Iron chips, grids made of magnetizable material or steel wool are suitable for this.

Steel wool has proven to be particularly suitable in the context of the present invention. The steel wool is preferably made of stainless steel.

The strength of the magnetic field to be applied can essentially vary within wide limits. Suitable magnetic fields have a magnetic field strength of approximately 0.05 to approximately 3 Tesla, in particular approximately 0.5 to approximately 2 Tesla.

The invention is explained in more detail below by examples.

Examples

Example 1: Production of a magnetic fly ash educts: 20 g fly ash

20 g FeCI ₃ * 6 H ₂ O

7.36 g FeCI ₂ * 4 H ₂ O

50 ml deionized water

13.3 g NaOH cookies

200 ml of deionized water

The iron salts were dissolved in 50 ml of deionized water. Another solution was made from 200 ml deionized water, 13.3 g NaOH cookies and 20 g filter ash. The iron salt solution was poured into the sodium hydroxide solution with vigorous stirring, stirred for a further 15 minutes and filtered off. The precipitate was washed twice with 400 ml of deionized water. The powder thus obtained was dried overnight in a vacuum drying cabinet at 50 ° C.

Example 2: Preparation of a magnetic organic adsorbent

6.48 g of anhydrous FeCI ₃ were dissolved in 40 g of deionized water. 3.97 grams of FeCI ₂ * 4 H ₂ O were dissolved in a mixture of 8 ml of deionized water and 2 ml of 37% hydrochloric acid. Shortly before the solutions were used in the precipitation process, the two solutions were combined to form a mixture.

320 g of deionized water and 80 ml of 25% ammonia solution were combined in a separate beaker and stirred with 5 g of polyacrylic acid with a molecular weight of about 2000.

The iron salt solutions were then poured into the ammoniacal receiver at room temperature with vigorous stirring, the iron oxide coated with the polyacrylic acid being kept dispersively in solution. Excess ammonia was distilled off and the product was then dialyzed for several days to remove Fe ions. The product so obtained was subjected to magnetic deposition in deionized water remove excess, non-magnetized polymer. The magnetic separation was carried out in the same way as for wastewater treatment, but deionized water was used as the carrier medium. The magnetic polymer particles deposited on the magnetic filter were rinsed off the magnetic filter after the magnetic field was switched off. The product was then concentrated by removing the water on a rotary evaporator. The product was cleaned by means of dialysis for several days and then dried to a powder.

Example 3: Cleaning a solution containing nickel

500 mg of the magnetic polymer powder from Example 2 were added to a solution of 50 mg of nickel in 1 liter of water at pH 7 at room temperature. The water was then passed through a glass tube filled with steel wool (diameter 2 cm), a magnetic field with a strength of 1 Tesla being attached to the glass tube by permanent magnets (permanent magnets made of neodymium iron boron, from IBS Magnet, Berlin, model NeoDeltaMagnet ND 7550) was created. The flow rate was 50 ml / s. The nickel content of the water purified in this way was less than 0.01 mg / l (detection limit by AAS).

Example 4: Cleaning of solutions containing heavy metals by magnetized fly ash

From ZnSO * 7 H ₂ O, NiSO * 6 H ₂ O and K ₂ CrO, solutions with a content of 50 mg / l of the respective metal ions were prepared with deionized water. 10 g of the magnetized filter ash from Example 1 were added to the solutions. The water was then passed through a glass tube filled with steel wool (diameter 2 cm), a magnetic field with a strength of 1 Tesla being attached to the glass tube by permanent magnets (permanent magnets made of neodymium iron boron, from IBS Magnet, Berlin, model NeoDeltaMagnet ND 7550) was created. The flow rate was 50 ml / s. The water thus purified was less than 0.05 mg / l Zn ions (detection limit for zinc by AAS) and less than 0.01 mg / l Ni or Cr ions (detection limit for copper and chromium by AAS) ,

Claims

claims

1. A process for the purification of waste water contaminated with metal salts, in which a magnetic adsorbent is mixed with the waste water and the adsorbent is separated from the waste water in a magnetic field after the adsorption of metal salts from the waste water.

2. The method according to claim 1, characterized in that the waste water contains at least one heavy metal salt.

3. The method according to any one of claims 1 or 2, characterized in that an organic adsorbent is used as the adsorbent.

4. The method according to any one of claims 1 or 2, characterized in that an inorganic adsorbent is used as the adsorbent.

5. The method according to any one of claims 1, 2 or 4, characterized in that fly ash is used as the adsorbent.

6. The method according to any one of claims 1 to 5, characterized in that the adsorbents contain magnetic nanoparticles.

7. The method according to claim 6, characterized in that the adsorbent as nanoparticles at least one compound selected from the group consisting of Fe, Co, Ni, Cr, Mo, W, V, Nb, Ta, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, alloys of two or more of the said elements, oxides of the said elements or ferrites of the said elements (except iron), or a mixture of two or more of which, included.

8. The method according to claim 6 or 7, characterized in that the nanoparticles magnetite, macchiemite, goethite or a ferrite of the general Formula MeOFe ₂ O ₃ , where Me represents an element selected from the group consisting of Mn, Co, Ni, Cu, Zn, Mg or Cd, or a mixture of two or more thereof.

9. Magnetic inorganic adsorbent containing magnetic particles.

10. Magnetic adsorbent according to claim 9, characterized in that it contains nanoparticles as magnetic particles.

11. Magnetic adsorbent according to claim 9 or 10, characterized in that it contains fly ash as an adsorbent.

12. Adsorbent according to one of claims 9 to 11, characterized in that it contains as magnetic particles at least one compound selected from the group consisting of Fe, Co, Ni, Cr, Mo, W, V, Nb, Ta, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, alloys of two or more of the said elements, oxides of the said elements or ferrites of the said elements (except iron), or a mixture of two or more of them.