DE10160664A1 - Purification of waste waters charged with metal salts, especially heavy metal salts, by treating with magnetic adsorption agent, e.g. magnetic fly ash, then separating adsorbent using magnetic field - Google Patents

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

The invention relates to a method for wastewater treatment, in which for easier Removal of harmful substances, especially for easier removal of Metal salts adsorbents with magnetic properties can be used.

With a large number of chemical processes, such as those in almost all areas of industrial production of capital and consumer goods are carried out, there is waste water. In the course of an ever increasing environmental awareness expects such wastewater to be cleaned prior to being released into the environment are subjected to, among other things, heavy metals from the waste water be removed. Heavy metals are special ingredients in wastewater undesirable because they have a variety of toxic, carcinogenic and mutagenic Properties are awarded.

Especially when processing ore and galvanizing Metal surfaces often produce waste water that is contaminated with heavy metals. The prepares the complete removal of such heavy metals from the wastewater however in practice due to the high solubility of many heavy metal salts Trouble. For removing heavy metals from aqueous solutions For example, precipitation processes, solvent extraction, distillation, Membrane process or ion exchange used. Many of the methods mentioned point However, there are a number of disadvantages, particularly expensive equipment, complicated procedures that can only be operated by trained personnel, Large amounts of waste or large space requirements are to be mentioned. As a suitable and therefore Often used means has been the addition of Adsorbents exposed. Wastewater is often used to remove Heavy metals are therefore treated with adsorbents, the heavy metal ions due to ionic or bind complex interactions.

For example, A.I. Zouboulis and K.A. 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 method of removal soluble ionic metal cations or oxyanions from dilute aqueous Solutions. The method involves treating the solutions with particulate Sorbents whose particle size is in the ultra-fine size range, the Separation of the particles is achieved by a flotation process. Problematic However, in the processes described, the separation has the finest effect Particles by flotation usually do not succeed so completely that the Heavy metal content can be reduced below the detection limit. It also points the foam formed during flotation has a high water content, whereby the Water must be removed from the foam in subsequent processes. The However, flotation usually separates the majority of those in the wastewater suspended matter, which in addition to the adsorbed heavy metals other suspended matter get into the adsorbate to be disposed of as special waste. In addition, flotation is an energy-intensive process.

Ebner et al. describe in "New Magnetic Field-Enhanced Process for the Treatment of Aqueous Wastes ", Separation Science and Technology, 34 (6 & 7), p. 1277-1300, 1999, a process for the separation of plutonium and americium Wastewater. Within the scope of the described method, the removal of the Plutoniums and the Americiums used compounds made from non-porous Ammonia-epichlorohydrin polymer balls with magnetite adhesions exist. The However, the process described is due to the properties of the separated metals not transferable to the separation of heavy metal ions. In addition, the Magnetite content in the systems described is so low that the separation is difficult. Furthermore, the small surface area of the described Polymer particles only have a low specific loading with metal ions.

Lin et al. describe in their 1999 at the recovery, recycling, Reintegration in February 1999 in Geneva presented the removal manuscript 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. A Magnetization of the material is not described.

There was therefore a need for a method of separating Heavy metal ions from wastewater, which has the disadvantages of the prior art does not have known methods. There was also a need for one Process for the separation of heavy metal ions from waste water, in which elaborate filtration steps are either eliminated or at least significantly accelerated become. There was also a need for a process for the separation of Heavy metal ions from wastewater, which has low energy consumption having.

The present invention met the above needs as Based on the task. It has now been found that the use of magnetic adsorbents for the cleaning of heavy metal contaminated wastewater the above solves the tasks mentioned.

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

"Metal salts" in the context of the present invention are metal salts understood that have a water solubility of at least about 0.1 g / l and a suitable adsorbent are adsorbable. As part of a preferred embodiment of the present invention are within the Method according to the invention heavy metal salts from the treated waste water away. "Heavy metals" in the context of the present invention especially the elements lead, cadmium, chrome, cobalt, iron, gold, copper, Manganese, molybdenum, nickel, platinum, mercury, selenium, silver, vanadium, zinc and tin Roger that.

The method according to the invention is suitable for removing metal salts wastewater contaminated with such metal salts. Basically you can use Using the method according to the invention, metal salts in any concentration Remove waste water. In a preferred embodiment of the In the present invention, however, the method according to the invention is based on waste water applied, which have a low heavy metal concentration, especially one Heavy metal concentration, which are known from the prior art Remove the process from the wastewater only with great effort or not at all leaves. Suitable heavy metal concentrations are, for example, within one 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 involves the use of a magnetic Adsorbent. The term "magnetic adsorbent" includes in the context of the present invention adsorbents which as such are not magnetic Have properties, but by treatment with appropriate Compounds, in particular by treatment with nanoparticles, with magnetic Properties were provided.

In the context of the present solid particles, "nanoparticles" are understood that have a particle size of about 1 to about 1000 nm, for example about 2 to about 500 nm or about 5 to about 300 nm, e.g. B. about 200 nm or about 30 to about 100 nm, the size refers to the whole of the nanoparticles contained in the adsorbent, with at least 90% by weight the nanoparticles the above Size specifications should meet.

The nanoparticles which can be used in the context of the present invention have magnetic, in particular ferromagnetic properties. In a preferred one The nanoparticles therefore have at least one embodiment of the invention 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 the elements mentioned, oxides of the elements mentioned or ferrites of the elements mentioned, or a mixture of two or more thereof.

For example, the nanoparticles can be magnetite, macchiemite, goethite or a ferrite of the general formula MeOFe ₂ O 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 components of which are iron, cobalt, nickel, aluminum, copper or titanium or mixtures contained two or more of them. Furthermore, alloys made of platinum and gobalt, alloys made of iron, cobalt, vanadium and chromium, ludwigite (Mg ₂ Fe ³⁺ [O ₂ / BO ₃ ]), vonsenite (Fe ₂ ²⁺ Fe ³⁺ [O ₂ / BO ₃ ] ), cobalt nickel gravels of the general formula a ²⁺ B ³⁺ ₂ X ² wherein a _4, cobalt, nickel or copper is iron, B is iron, cobalt, nickel or chromium or a mixture of two or more thereof, and X is 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 ( Macchiemite) 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 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 are permanent e contain magnetic dipoles, where M stands for zinc, cadmium, cobalt, manganese, iron, copper, magnesium and the like, as well as iron itself.

Magnetite or macchiemite nanoparticles can be produced for example by using microemulsion technology. Here, the disperse phase of a microemulsion to limit the size of the particles formed used. A W / O microemulsion contains a metal-containing reagent in the dispersed aqueous phase dissolved. The reagent is then in the disperse Phase converted to a precursor of the desired magnetic compound, the then already has the desired size in the nanometer range. Then, with a careful oxidation step, the metal oxide, in particular Iron oxide in the form of magnetite or macchia. A corresponding one The method is described, for example, in US Pat. No. 5,695,901.

Furthermore, nanoscale magnetic particles of Fe ₃ O ₄ , γ-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 determined by the thermal reaction rate and control the concentration of the iron salt solution. So small diameters of 20-100 nm with time-separated formation of iron (II, III) carbonate Temperatures of 1-50 ° C, preferably 5-10 ° C, and subsequent heating, higher Particles of 100-1000 nm at reaction temperatures of 60-100 ° C and so on 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 (I1) and / or iron (III) complex by adding one or more Complexing agents such. B. ethylenediamine tetraacetic acid, citric acid, tartaric acid or their salts, the subsequent neutralization with moderately basic reagents such as ammonia or alkali carbonates and the precipitation of the iron hydroxides Add strong alkalis such as caustic soda to a pH of 11 also desired magnetic particles. The titration rate at the Alkalization determines the size of the magnetic particles.

Particle configurations suitable according to the invention can also be achieved by the Treatment of an iron (II) and / or iron (III) salt solution with basic Anion exchange resins can be synthesized. These are the iron salt solution in a added such a rate that a constant increase in pH 7-10 is guaranteed. The resulting particle sizes can be determined by the Control selection of different anion exchanger types. This is how the Use of weakly basic anion exchangers, such as z. B. under the Trade names Amberlit IR 45 are known, small particle diameter, with strong basic such as B. Amberlite IRA 420 larger particles.

With a molar ratio of the iron (II) / iron (III) salt solution of 1: 2, the ferrimagnetic Fe ₃ O ₄ (magnetite) forms during alkalization. Its mild oxidation also results in ferrimagnetic γ-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 made of double oxides or hydroxides of the two or trivalent iron with divalent or trivalent metals or mixtures of the Oxides or hydroxides mentioned can also be according to the above Processes are made by a solution of salts of the divalent or trivalent Iron and divalent 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) were synthesized using divalent iron trivalent metal ions such as Cr (III), Gd (III), Dy (III) or Sm (III).

The magnetic particles thus produced are filtered, ultrafiltered, Dialysis or magnetic separation of foreign ions cleaned, if necessary concentrated and are available for further processing.

According to the invention, very small superparamagnetic particles can pass through Precipitation from a saturated organic solvent containing Iron salt solutions can be prepared with alkalis.

It was found that almost monodisperse superparamagnetic Have particles made very easily by adding an iron salt solution to it Water-miscible solvent, such as acetone, ethyl methyl ketone or dioxane, is added until the first beginning turbidity is just by stirring dissolves again. The superparamagnetic particles can be made from such a solution z. B. be precipitated 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 get. 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 by conventional precipitation reactions as they are generally known to the person skilled in the art are known.

It has been found, however, that in the context of the invention Processed magnetic adsorbent particularly good Have properties with regard to their separability in the magnetic field if the Precipitation reaction carried out in the presence of the adsorbent to be used becomes. This procedure is explained in more detail in the further text.

Basically all adsorbents are suitable as adsorbents Removal of metal salts, especially heavy metal salts from waste water are suitable. For the purposes of the present invention, organic are, for example and inorganic adsorbents.

Hollow bodies, for example, are suitable as inorganic adsorbents Silicate base, for example those with a spherical structure.

According to a further embodiment of the method according to the invention such a silicate material, for example, essentially closed Hollow body included.

Suitable silicate-based materials have a diameter of, for example less than about 200 microns, especially less than about 100 microns. suitable Particles with a diameter of approx. 50 µm usually have a wall thickness of approx. 1 µm while smaller particles with a diameter of about 1 µm have a wall thickness of approximately 0.1 µm. The specified particle sizes refer to the diameter of the individual particles.

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

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

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

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

In the context of a preferred embodiment of the present invention, as inorganic adsorbent fly ash used. Under "fly ash" is in the frame of the present invention a predominantly made of glassy beads existing, powdery material of light to dark gray color Roger that. Fly ash is preferred in the context of the present invention used as it arises from the combustion of hard coal (Coal fly ash). The main components of the coal fly ash silicon, aluminum and Iron oxide from the accompanying minerals of coal. There are also small quantities unburned coal particles as so-called flying coke or loss on ignition. The in Hard coal fly ash used in the context of the present invention preferably comes from a combustion process in which the coal is in Coal mills are ground to grain sizes of less than about 90 µm and into one Boiler is blown. Depending on the coal used, 5 to 35% will not flammable, mineral bedrock with blown into the boiler, which as ash remains. If this procedure is carried out in dry combustion plants, the ash is not liquid due to low temperatures of around 1200 ° C. The Non-combustible mineral components are only used in this process melted on the surface and when blowing into the boiler with the Flue gas flow entrained. The majority of this ash is in the Flue gas stream cools quickly and forms spherical, mostly amorphous particles. to Separation of those used in the present process Bituminous coal fly ash, the flue gas stream is passed through multi-stage electrostatic precipitators, of which from which the fly ash is discharged.

Fly ash preferably used in the process according to the invention has a loss on ignition of 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 a preferred embodiment, the fly ash has the present carbon content of at most about 30 wt .-%, for example at most about 20% by weight or at most about 10 or 5% by weight.

Instead of or in addition to the above-mentioned inorganic adsorbents can in the process of the invention and inorganic Adsorbents are used. Suitable organic adsorbents are In the context of the present invention, organic compounds which are natural or can be of synthetic origin. It has been within the scope of the present Invention found that organic adsorbents in particular Within the scope of the present invention are well suited if they are either water-soluble are or, if they have no water solubility, a porous structure exhibit. In particular, essentially spherical particles are preferred.

These include organic adsorbents of natural origin for example adsorbents based on alginate, cellulose or starch. Particularly suitable are water-soluble or water-dispersible starch and / or starch derivatives or cellulose derivatives, especially cellulose ethers.

If in the process of the invention as an organic Adsorbent starch is used, so is preferred Embodiment of the present invention used water-swellable modified starch. Partially degraded starch or swelling starch are suitable, for example. If Starch derivatives are used, for example starch esters or Starch ethers, especially carboxylated, alkoxylated or in some other way Improved their properties as reagents binding heavy metals Strengthen. All of them are suitable as carboxylated or alkoxylated starches modified natural starch types from potatoes, corn, wheat, rice, milo, Tapioca and the like, starch derivatives based on potatoes or Corn starch is preferred. Suitable starch derivatives have, for example Degree of carboxylation from about 0.1 to about 2.0 (DS) or degree of alkoxylation from 0.05 to 1.5 (MS).

Starch or cellulose ethers include starch or cellulose derivatives understood by partial or full substitution of hydrogen atoms Hydroxy groups of starch or cellulose by alkyl and / or (ar) alkyl groups getting produced. The alkyl and / or (ar) alkyl groups preferably carry additionally non-ionic, anionic or cationic groups. Here are the Single molecules usually substituted differently, so that their degree of substitution Is mean.

The etherification of the starch or cellulose is generally by exposure of (ar) alkyl halides, for example methyl, ethyl and / or benzyl chloride, 2- Chloroethyldiethylamine or chloroacetic acid, and / or epoxides, e.g. B. ethylene, Propylene and / or butylene oxide, glycidyltrimethylammonium chloride, and / or activated olefin, for example acrylonitrile, acrylamide or vinyl sulfonic acid with bases, usually with aqueous sodium hydroxide solution, activated cellulose. 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 methyl hydroxyethyl or - hydroxypropyl cellulose, carboxymethyl hydroxyethyl 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) Hydroxyethyl ethyl cellulose (HEEC), hydroxypropyl cellulose (HPC), Hydroxypropyl carboxymethyl cellulose (HPCMC), hydroxypropyl methyl cellulose (HPMC), hydroxyethylethyl cellulose (HEMC) methyl hydroxyethyl cellulose (MHEC), hydroxyethyl methyl cellulose (HEMC) methyl hydroxyethyl cellulose (MHEC), methyl cellulose (MC) and propyl cellulose (PC), where Carboxymethyl cellulose, methyl cellulose, methyl hydroxyethyl cellulose or Methyl hydroxypropyl cellulose and optionally alkoxylated, in particular ethoxylated methyl cellulose are preferred. Also within the scope of the present Derivatives of the compounds mentioned, which are used for to improve their adsorption capabilities against heavy metals were modified.

Described derivatives of other polysaccharides or their degradation products, such as Dextran, carrageenan, agar, tragacanth, gatti gum, karaya gum, guar gum, Tara gum, alginates, pectin or chitin are also considered organic Adsorbents can be used. Derivatives of proteins like casein, collagen or gelatin as well their degradation products also meet the requirements of the invention.

Are also suitable for use in the process according to the invention synthetic organic compounds. To the within the synthetic organic compounds suitable according to the method of the invention for example the organic synthetic polymers.

Suitable organic polymers in the context of the present process for example, polymers that can be produced by polycondensation or polyaddition, such as Polyester, polyether, polyamide or polyurethane or by polymerization producible polymers 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. Preferably polyesters are used in the process according to the invention which modified so that their absorbency for heavy metals to carry out of the method according to the invention is at least sufficient. Are suitable for this for example polyesters which have a sufficient number of ionic centers.

Suitable polyesters can be produced, for example, by polycondensation. So can 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 of them, or their reactive derivatives, are condensed to polyester polyols. Suitable dicarboxylic acids are, for example, succinic acid and its higher ones Homologues with up to 44 carbon atoms, also unsaturated dicarboxylic acids such as Maleic acid or fumaric acid and aromatic dicarboxylic acids, especially those isomeric phthalic acids such as phthalic acid, isophthalic acid or terephthalic acid. As Tricarboxylic acids are, for example, citric acid or trimellitic acid. in the Polyester polyols of at least one are particularly suitable in the context of the invention of said dicarboxylic acids and glycerin, which have a residual OH group exhibit. Particularly suitable alcohols are hexanediol, ethylene glycol, Diethylene glycol or neopentyl glycol or mixtures of two or more of them.

Polyols that can be used as the polyol component for the production of the polyester are, for example, diethylene glycol or higher polyethylene glycols with a molecular weight (M _n ) of approximately 100 to approximately 22,000, for example approximately 200 to approximately 15,000 or approximately 300 to approximately 10,000, in particular approximately 500 to approximately 2,000.

Polyurethanes as can be used in the process according to the invention, are usually obtained by reacting at least one polyisocyanate, preferably a diisocyanate, and a polyol component, preferably consists predominantly of diols. The polyol component can only be a polyol contain, but it can also be a mixture of two or more different Polyols are used as the polyol component. As a polyol component or at least as For example, polyalkylene oxides are suitable components of the polyol component.

If necessary, parts of the polyalkylene oxide can be replaced by others containing ether groups Hydrophobic diols are replaced, the molecular weights of 250 to 3,000, preferred Have 300 to 2,000, in particular from 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 building blocks of Polyurethane that can be used as a hot melt adhesive. It refers to Compounds of the general structure O = C = N-X-N = C = O, where X is an aliphatic, is an alicyclic or aromatic radical, preferably an aliphatic or alicyclic radical with 4 to 18 carbon 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 tetra-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-isocyanatophenylperfluoroethane, 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, also diisocyanates with reactive halogen atoms, such as 1-chloromethylphenyl-2,4-di isocyanate, 1-bromomethylphenyl-2,6-diisocyanate, 3,3-bis-chloromethyl ether-4,4'-diphenyl diisocyanate.

A polyurethane suitable according to the invention is preferably in a one-stage Process manufactured. For example, all starting materials are Presence of an organic solvent with a water content of less than 0.5% by weight mixed. The mixture is at 80 to 200 ° C, especially at 100 to 180 ° C and preferably heated 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. Particularly suitable are 1-methylimidazole, 2-methyl-1-vinylimidazole, 1-allylimidazole, 1-phenylimidazole, 1-methylimidazole, 2-methyl-1-vinylimidazole, 1-allylimidazole, 1-phenylimidazole, 1,2,4,5-tetramethylimidazole, 1 (3-aminopropyl) imidazole, pyrimidazole, 4- Dimethylaminopyridine, 4-pyrrolidinopyridine, 4-morpholinopyridine, 4-methylpyridine. However, preference is given to working without a catalyst. The solvent too conveniently omitted. Under "solvents" within the scope of the present text inert organic liquids with a boiling point of less than 200 ° C understood at normal pressure.

To produce those which can be used in the process according to the invention Polymers are, for example, olefinically unsaturated monomers that are accessible to an emulsion polymerization. Suitable polymers are for example from monomers such as acrylic acid, methacrylic acid, optionally as Copolymers with their esters with primary and secondary saturated monovalent Alcohols with 1 to about 28 carbon atoms such as methanol, ethanol, propanol, butanol, 2- Ethylhexyl alcohol, cycloaliphatic alcohols such as cyclohexanol, Hydroxymethylcyclohexane or Hydroxyethylcyclohexan accessible.

Simple ethylenically unsaturated are also suitable as comonomers Hydrocarbons such as ethylene or α-olefins with 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.

Also usable as comonomers are, for example, multiple ethylenic unsaturated monomers. Examples of such monomers are diallyl phthalates, Diallyl maleate, triallyl cyanurate, tetraallyloxyethane, divinylbenzene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, divinyl adipate, allyl acrylate, Allyl methacrylate, vinyl crotonate, methylenebisacrylamide, hexanediodiacrylate, Pentaerythrol diacrylate or trimethylolpropane triacrylate or mixtures of two or more from that. 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- Methylol methacrylamide, N-methyl olallyl carbamate and the N-methyl esters, alkyl ether or Mannich bases of N-methylolacrylamide or N- Methylol methacrylamide or N-methylolallyl carbamate, acrylamidoglycolic acid, Acrylamidomethoxyacetic acid methyl ester, N- (2,2-dimethoxy-1- hydroxyethyl) acrylamide, N-dimethylaminopropylacrylamide, N- Dimethylaminopropyl methacrylamide, N-methyl acrylamide, N-methyl methacrylamide, N-butyl acrylamide, N-butyl methacrylamide, N-cyclohexyl acrylamide, N- Cyclohexyl methacrylamide, N-dodecyl acrylamide, N-dodecyl methacrylamide, Ethylimidazolidone methacrylate, N-vinylformamide, N-vinylpyrrolidone and the like.

In order to be used in the context of the present invention, the corresponding adsorbent have magnetic properties. As part of the Adsorbents suitable for the present invention have such magnetic ones Properties, however, not as the original substance property, but the Magnetic properties are those that can be used according to the invention Adsorbents by mixing the adsorbent with magnetic compounds awarded.

It has been shown that magnetic nanoparticles as described in the this text have already been described, for the transfer of their magnetic properties are suitable on an appropriate adsorbent.

To transfer the magnetic properties to a corresponding one Adsorbents are basically suitable for all processes with which magnetic Allow particles to be combined with an appropriate adsorbent so that the Connection between adsorbent and magnetic particles in aqueous Environment is so stable that the inventive method can be carried out. For this it is necessary that the adsorbent particles have magnetic properties have or are at least magnetizable. As part of a preferred Embodiment of the present invention are therefore for performing the Method used absorbent particles according to the invention with magnetic Particles either physically as inclusion compounds, ionic, covalent or via dipolar interactions are connected.

Magnetized which can be used in the context of a method according to the invention Basically, adsorbents can be produced by any method a bond of magnetic particles to the adsorbent. That's the way it is possible, for example, adsorbent with magnetic properties to provide that the adsorbent with a suspension of magnetic particles in be mixed with a suitable solvent. Then that can Suspended medium deducted and the mixture of adsorbent and magnetic Particles can be washed, for example. It is also possible that functionalize magnetic particles on their surface so that they with the Adsorbents enter into a covalent bond. For this, the nanoparticles superficially modified in such a way that a reaction with a functional group of an organic natural or synthetic polymer is possible or the incorporation of the modified nanoparticle in an organic synthetic polymer can be made.

The surface of the magnetic particles can be modified, for example, with Silanes take place. If oxides are used as magnetic particles, they carry them Oxides usually have superficial OH groups with silanes or halosilanes can react to form a covalent Si-O bond. If the silanes in turn have a suitable functional group, a later one Attachment of the silanes to a polymer enables so that covalently attach modified magnetic particles to polymers. suitable Functional groups are, for example, olefinically unsaturated double bonds or protected OH or NH groups. A suitable way to modify the Surface of nanoparticles with silane compounds is, for example, in the US A 5,695,901.

Other suitable methods for functionalizing magnetic particles are known to the expert.

However, it has been shown that, as already described above, it is particularly good leads to magnetic adsorbents when producing the magnetic Particle is carried out in the presence of the adsorbent.

For this purpose, the production of the magnetic particles as described in the present text has been described above, modified so that in the corresponding salt solutions leading to the magnetic particles within the scope of the inorganic and / or organic usable in the present invention Adsorbents are present. In the context of a preferred embodiment of the present Invention are therefore used to manufacture the magnetic adsorbents Processes used in which the formation of a microemulsion is avoided.

In the context of a preferred embodiment, the present invention relates to Implementation of the inventive method for inorganic magnetic Adsorbents used. It has been shown that cleaning with metal salts contaminated waste water when using such inorganic magnetic Adsorbents leads to particularly good results.

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

The term "containing magnetic particles" is within the scope of the present To interpret the text so that the adsorbent itself is not magnetic Has properties and in particular a particle diameter of more than has about 1 µm.

An adsorbent according to the invention contains as magnetic particles preferably 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 above elements, oxides of the above Elements or ferrites of the elements mentioned (except iron), or a mixture of two or more of them.

To carry out the method according to the invention, it is necessary to clean the waste water with the magnetic used in accordance with the invention Mix adsorbent. This can be done either batchwise or continuously respectively. 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 for a sufficiently long time with the magnetic adsorbent in contact, for example for a period of about 1 s to about 1 h, in particular about 10 s to about 30 min or about 5 to about 20 min. is the mixture of waste water and magnetic adsorbent conducted a magnetic field. For example, the mixture of wastewater and magnetic adsorbent passed through a tube, the outside of a appropriate magnetic field is penetrated or through the inside of the tube arranged magnets is generated.

Within the scope of a preferred embodiment of the present invention the mixture of waste water and magnetic adsorbent, however, by a magnetic filter.

A "magnetic filter" is used in the context of the present Invention understood an arrangement in which within the mixture Waste water and magnetic adsorbent flowed through a volume Filter assembly is made of a magnetic or magnetizable material consists.

It is possible, for example, that the inside of the flowed tube a filter section is preferably defined by magnetic rods. The The length of the filter section can vary by the number and / or length of the rods become.

It is also possible to use a magnetic filter in the sense of the present invention generate a magnetic field applied to the outside of the filter arrangement, the Magnetic field inside the filter arrangement by corresponding the magnetic field reinforcing materials is reinforced.

The term "filter" is to be interpreted in the context of the present text so that the inventions of such a "filter" are so great that they both wastewater as well as the particles of the magnetic adsorbent contained therein let pass if no magnetic field is applied to the arrangement and that Filter material itself has no magnetic properties. Preferably a "filter" in the sense of the present invention so constructed that the filtration section overall is as long as possible, but the filter itself is as low as possible Pressure drop generated.

Basically, all materials that can be used as filter material transmit or amplify the magnetic field applied from the inside can and in particular increase the field line density inside the tube. For this purpose, iron shavings, grids made of magnetizable material are suitable or steel wool.

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

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

The invention is explained in more detail below by examples.

Examples example 1 Production of a magnetic fly ash reactants

20 g fly ash

20 g FeCl

₃

6H

₂

O

7.36 g FeCl

₂

.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 made. The iron salt solution was stirred into the Poured sodium hydroxide solution, stirred for a further 15 minutes and filtered off. The precipitation 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 Production of a magnetic organic adsorbent

6.48 g of anhydrous FeCl ₃ were dissolved in 40 g of deionized water. 3.97 grams of FeCl ₂ .4H 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% strength were placed in a separate beaker Ammonia solution combined and with 5 g of polyacrylic acid with a Molecular weight of about 2000 stirred.

Subsequently, the iron salt solutions at room temperature under strong Stir poured to the ammoniacal template, which with the Polyacrylic acid-coated iron oxide was kept dispersively in solution. excess Ammonia was distilled off and the product was then removed for several days dialyzed by Fe ions. The product so obtained was in deionized water subjected to magnetic deposition for excess, not to remove magnetized polymer. The magnetic deposition was like the wastewater treatment, but deionized as the carrier medium Water was used. The magnetic deposited on the magnetic filter Polymer particles were removed from the magnetic filter after the magnetic field was switched off rinsed. The product was then removed by removing the water Concentrated rotary evaporator. The cleaning was carried out by means of dialysis lasting several days of the product which was then dried into powder.

Example 3 Cleaning a solution containing nickel

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

Example 4

Cleaning heavy metal solutions with magnetized fly ash

Of ZnSO ₄ · 7H ₂ O, NiSO ₄ .6H ₂ O and K ₂ CrO ₄ were each prepared with deionized water solutions with a content of 50 mg / l of the respective metal ions. 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 of strength being attached to the glass tube by permanent magnets (permanent magnets made of neodymium iron boron, from IBS Magnet, Berlin, model NeoDelta magnet ND 7550) 1 Tesla was created. The flow rate was 50 ml / s. The water purified in this way 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 (12)

1. Process for the purification of waste water contaminated with metal salts, at which mixes a magnetic adsorbent with the waste water and the adsorbent after the adsorption of metal salts from the Waste water is separated from waste water in a magnetic field. 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 adsorbent contain magnetic nanoparticles. 7. The method according to claim 6, characterized in that the Adsorbents as nanoparticles selected from the compound 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 elements mentioned (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 for 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 Particle. 10. Magnetic adsorbent according to claim 9, characterized in that it contains nanoparticles as magnetic particles. 11. A magnetic adsorbent according to claim 9 or 10, characterized characterized in that it contains fly ash as an adsorbent. 12. Adsorbent according to one of claims 9 to 11, characterized characterized in that it selected at least one compound as magnetic particles 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 elements mentioned, oxides of the elements mentioned or ferrites of said elements (except iron), or a mixture of two or more of which contains.