DE2713684A1 - METHOD FOR TREATMENT OF WASTE WATER - Google Patents

Description

HOFFMANN · EITLE & PARTNER

DR. ING. E. HOFFMANN (1930-1976). Dl PL.-ING. W. E ITLE · D R. RER. NAT. K. H OFFMAN N · D IPL. -1 N G. W. IEH N

DIPL.-ING. K. FDCHSLE DR. RER. NAT. B. HANSEN ARABELLASTRASSE 4 (STERNHAUS) D-8000 MDNCH EN 81 TELEPHONE (089) 911087. TE LE X 05-29619 (PATH E)

29 173 o / wa

SYSTEMS ENGINEERING & MANUFACTURING CORP. d / b / a BAKER BROS., STROUGHTON / USA

Process for the treatment of waste water

In many industrial processes, wastewater with high concentrations of heavy metal ions and other contaminants, how various anions and cations including fluorides, cyanides and hexavalent chromium are generated. Because the high concentrations of heavy metals and others

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Impurities, the water cannot be used in circulation in many industrial processes and beyond it cannot be discharged into the environment either, because of the polluting effects of these heavy metals and / or the other impurities. In the metalworking industry, there were some experimental ones Limits are set for the maximum amounts of heavy metal ions that may remain in the water that is released into the environment. The industry has attempted to address these pollution problems by means of numerous well known and newer methods to cope with. One of the most frequently used processes is metalworking incoming rinse water, which contains heavy metal ions and other impurities, with alkaline or acidic material Treated to adjust the pH to insoluble hydroxides or other precipitates of metals to build. The insoluble hydroxides and other precipitates can then be separated from the wastewater. A The problem with this, however, is that many of the heavy metal ions and other impurities are also in their hydroxide form or in the form of their precipitates are soluble to a certain extent, so that a wastewater that is treated in this way often contains undesirably high amounts of certain metal ions. In more recent developments, ion exchange processes have been used used to remove heavy metal ions and other impurities. Such procedures however, they are often expensive and complicated. Other problems arise when using reverse osmosis technology on. High concentrations and high pressures are part of the operational problems with reverse osmosis

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Reverse osmosis is limited to approximately 2000 parts per million (ppm) concentrations and the effectiveness of the Procedure is inversely proportional to the concentration.

It was previously assumed that heavy metal hydroxides tend to form gelatinous precipitates, which are filter membranes clog by penetrating the filter pores or by building up a gelatinous contiguous Precipitation at the top of the membrane. Therefore, the prior art processes have heavy metal hydroxides in filter processes either removed or avoided at all in order to avoid the known clogging problems.

An important object of the invention is to provide a method for treating wastewater by which effectively removes materials from it, and which enables these materials to be recovered and / or to reuse or discard the water treated in this way.

Another object of the invention is to provide a method according to the preceding object, which can be carried out quickly in technical systems at reasonable costs. Another goal of the The invention is to provide a method which essentially comprises two stages, in which large-part Particles are formed from ions or other particles that are to be removed and then these Materials are removed by effective filtering devices.

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Finally, it is also an object of the invention to show preferred chemicals that contain heavy metal ions and other impurities can be combined to separate these substances from water.

According to the invention, small-sized substances such as heavy metal ions are used and / or other contaminants, removed from wastewater by removing the particulate matter with agents brings together with the formation of soluble and / or insoluble bound substances which have a particle size have that is large enough to allow the wastewater to be filtered while removing the bound material. In a preferred embodiment, the wastewater comes from industrial metal processing plants, such as Metal plating operations, and the combining agent is a metal in its oxide and / or hydroxide form and they are preferably oxides or hydroxides of iron and / or aluminum. A metal hydroxide is preferably used, to remove heavy metal ions from wastewater that is no more than about 4000 parts per million of heavy metal ions and contain impurities. The metal hydroxide used is in concentrations of at least 1700 parts per million are employed in the water to be filtered and preferably in an amount of at least 2000 ppm and in a molar ratio of at least 1: 1 and above in terms of the moles of the to be removed Fabrics.

Preferably the filtration step is by ultrafiltration by means of anisotropic or coated membranes

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η.

carried out at which one has high filtration speeds with small membrane surfaces and with relatively lower pressures achieved.

The process can be carried out batchwise or continuously, with continuous filtration Receives service water, and the concentrates from the filtration can be drawn off where they are for a Release to the environment can be treated or where recovery of the metal ions is possible.

It is a feature of the invention that the process can be carried out economically and reuse or allows the treated wastewater to be discarded. In addition, the removed heavy metal ions and other impurities are concentrated so that these metals can be recovered or discarded is. The invention includes the use of a combining means to determine the size of the substances to be removed to increase so that numerous filtration methods can be used in practice to recover the purified water or discard. The use of combining means in conjunction with filtering devices and preferably an ultrafiltration, has notable advantages because high flow rates with an extremely good separating effect with regard to impurities such as heavy metal ions, are possible, whereby such impurities are reduced to concentrations that are considerably below the concentration that was previously achieved by precipitating agents according to the state of the art. Indeed

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the impurities are diminished to such an extent that that their amount is well below the solubility limits of the material to be removed. Is working one in a continuous system, so can large amounts of water in a closed continuous Circuit can be reused. Becomes such a closed one If a continuous cycle is used, a customary cleaning stage can be built into the cycle will. The volume of waste water that can be disposed of is reduced to an absolute minimum. The focus on Metal ions and / or other impurities that remain after filtration are increased sufficiently to in order to economically extract or destroy these substances. In the case of hexavalent chromium, one one-step mechanical process brought the hexavalent chromium directly together with the combining agent according to the invention. This avoids the need to have chromium from CR. to reduce CR-, as is customary is done in a separate step in the prior art methods.

Surprisingly, it has now been found that through the Using high concentrations of a metal hydroxide combining agent, ultrafiltration can be applied can to achieve a product water flow through the filter that is higher than if you had a low one Concentration of metal hydroxides applies. It is believed that the excess of metal hydroxides leads to the formation of allows essentially crystalline precipitates and does not form the more gelatinous precipitates that

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often cause the filters to clog. You can have a steady stream of product water for a long time Achieve periods of time when using a large excess of the combining agent according to the invention.

The aforementioned and other objectives, advantages and features of the invention are explained in more detail below and shown in the drawing, in which a preferred closed wastewater treatment method according to the invention is sketched.

In the metal processing and coating industry, wash water is used during processing and These wash waters are often not recyclable if they are not treated to remove the contaminants Heavy metal ions and certain other impurities or contaminating ions released from the water during of the procedure. Common heavy metal ions and other anions and cations that Are contained in what wastewater include the following and it also becomes the allowable limits given for the concentrations of these ions within which they can be released into the environment.

Wastewater parameters, mg / 1

Phosphorus aluminum antimony

O, 6th 0, 2 O, 3

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cobalt F Iu or id AS 1.0 copper 0.3 barium iron 0.3 Berylium lead 0.1 boron manganese 0.05 cadmium nickel 0.2 Chromium Cr + 6 silver 0.25 Cr + 3 selenium 0.3 Cr total tin 0.2 zinc 0.5 gold 0.05 ammonia 1.0 mercury 1.0 Cyanide Dest. By Cl- 0.05 Refract. 0.3 total 0.3 0.5 0.3 1.0 0.2 0.03 0.5 0.53 2.0

The term "heavy metal ions" as used in this application and the claims is closed all of the metals listed above in their pure ionic form and / or in bound form, such as with chromates, a. The term "impurities" as used in the

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Description and the claims are used, excludes all non-metallic substances that are listed above, a. In all cases, heavy metal ions and impurities for the purposes of the present invention are included understood all undesirable substances in wastewater caused by the combination agent according to the invention are removable.

Separated rinsing water can be obtained from the rinsing water of a tank cladding and according to the invention Procedures are dealt with. For example, in a gold plating process, the rinse water used may be separated and treated according to the invention to enable the removal of gold ions from the wastewater. In this case, the remaining filtrate has a high concentration of gold ions, without a larger one Number of other contaminants causing a separation of the gold ions from the concentrate according to standard procedures is easy to do. Alternatively, the rinse water, which may come from a variety of metalworking stages, can be combined to form wastewater to win that contains various combinations of the aforementioned heavy metal ions and other impurities. In this case the clear filtrate obtained can be reused and it is often most practical to destroy the heavy metal ions and the other impurities in the concentrate and use them as usual Discard methods.

In most cases, the non-metallic ions and the substances in the rinsing wastewater do not affect this

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Method according to the invention. In some cases you can non-metallic ions such as fluorides, chromates and cyanates along with the heavy metal ions during the be removed according to the invention. In some cases, prevent the non-metallic ions or others Particles don't reuse the wastewater after the heavy metal ions have first been removed are. In some cases, the non-metallic impurities, if any, can be associated with the combining agent are united, forming complexes so that they can be removed in this way. So For example, ammonia can be used with the preferred combining agents combine according to the invention, thereby removing in many cases during the filtration step will.

In the process according to the invention, the heavy metal ions and other impurities that have to be removed, which may belong to the substances listed above, treated with a combining agent to reduce the particle size which is normally a small particle size to increase containing impurities to those sizes that are large enough to filter the undesirable Allow contaminants from the wastewater. The particle size is preferably kept to a minimum of 10 8 and in general the particle size is increased approximately in the range of 10 to 1000 8. The particle size is determined by the fact that the material thus increased in size does not pass through a filter, which has pore sizes below 10 8 or maintains a specific particle size to which the

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Impurities have been increased.

The size of the particles to be removed from the wastewater Contaminants are eliminated through the use of a combining agent or a combination of combining agents that are added to the wastewater or are formed in the wastewater. The combining agent is preferably a metal in the hydroxide form, although it may also be in the oxide form with a large Zeta potential with high absorption or absorption properties. Preferred combining agents are inorganic salts of metals and preferably iron and aluminum educated. It is believed that these inorganic salts, when added to the wastewater, are basic pH has been adjusted to form oxides and probably hydroxides which then act as combining agents. In some cases when the heavy metal ions coexist with non-metals such as cyanides or fluorides the cyanides and fluorides are removed by filtration together with the heavy metal ions. Other inorganic Oxides and hydroxides that form agglomerates that are large enough to be filtered and that are high Absorption and / or absorption properties against heavy metal ions and other contaminants in the wastewater have, due to the electrical potential on the surface, the zeta potential, of hydrogen bonds, van der WaIs see Forces, and other forces, can also be used and include oxides and hydroxides those of tin, copper, zinc, cadmium, nickel, cobalt, silicon, lead, barium, calcium, manganese and chromium.

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Are inorganic metal hydroxides or oxides used as combining agents used, they can be added directly to the wastewater to be treated, but is it is preferable to add them to waste water in the form of the inexpensive inorganic metal salts. For example, can to chlorides, fluorides, sulfates, nitrates and the like of one or more of the aforementioned metals Add wastewater. Sulfates such as ferrous sulfate, ferrous sulfate and aluminum sulfate are preferred because of their easy accessibility and value for money.

The pH of the waste water is preferably set to a range between pH 7.1 to pH 14 for the formation of the hydroxides and in particular pH 8 to pH 12 is set. Preferably the pH value is set as close as possible to neutral in order to achieve an effective separation of the impurities. If high pH values are used, the filtered wastewater must be treated with acidic substances in order to adjust the pH value to lower before it is discharged into the environment without contamination by the basic constituents can be. In general, the higher the pH, the better the separation of the undesired impurities is achieved, however, will provide excellent separation and filtration at pH levels that are not are above 9, achieved. The pH can be adjusted in the wastewater to be treated by adding inorganic hydroxides can be set. For example, sodium hydroxide, potassium hydroxide and calcium hydroxide can be used. Calcium hydroxide is preferred because of its ready availability and low cost.

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It is preferable to use a large excess of the combining agent because it is easily filtered by itself and a large excess ensures that a maximum amount of heavy metal ions and the other is bound impurities contained in the wastewater. For example, molar ratios of at least 1: 1 and preferably in the range of 1: 1 to 10: 1 moles of the combining agent with respect to the Moles of the metal salt to be removed can preferably be used. Thus the inorganic salt, when added to the wastewater to form the combining agent, in a molar ratio of at least 1: 1 and preferably higher added. In most cases, molar ratios of 1: 1 are sufficient effect removal of heavy metal ions and impurities, and molar ratios above 10: 1 are unnecessary, although there are no adverse effects from higher molar ratios.

In addition to using the molar ratios given above it is necessary to have a minimal amount of metal hydroxides present in order to be effective Achieve ultrafiltration without blocking the filter. Crystalline precipitates are preferred to a rapid clogging of the filter membrane, as often occurs within a short time with the appearance of gelatinous Precipitation should be avoided. At least about 1700 ppm, and preferably at least about 20OO ppm of the combining agent are used in the aqueous solution to be filtered. There is no upper limit with regard to the concentration of the combining agent,

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except that the solution or suspension must remain pumpable in conventional technical systems.

The combining stage can be within a wide temperature range and can be carried out in a wide time range. In most cases that will find combining and binding the heavy metal ions and other impurities essentially instantaneously at room temperature instead, although the temperature range can be varied very widely, for example in the range from 4.4 to 93.3 ° C, a range that can exist in numerous industrial processes. The period for the combination stage can range from a few seconds with certain continuous circulation processes to hours, in batch processes, although periods of from 30 seconds to 15 minutes are generally sufficient are.

After the combination stage with the subsequent formation of large particles, which are soluble or insoluble can be or can be present in a combination of both, and which are contained in the wash water, can be a conventional filtration to complete the separation and removal of heavy metal ions from the Sewage can be applied. For example, filter paper can be used to remove the insoluble, large particles formed Use substances while using reverse osmosis to remove soluble or insoluble large particles to remove. According to a preferred embodiment of the invention, however, it is preferably used for the separation stage an ultrafiltration.

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The ultrafiltration is a process in which small-scale Particles are retained in a filter medium while the solvent and only certain accompanying, low molecular weight soluble substances pass through. Using the preferred method ultrafiltration with anisotropic or coated (skinned) plastic membranes gives the best results. Such ultrafiltration can take place under low pressures in the range from 0.63 to 70.3 atmospheres or higher and preferably 0.70 to 10.54 Atü can be made. Large flow rates are achieved even at low Pressing achieved. The preferred flow rates are in the range of 113 to 3785 1/929 cm ^ / day (based on the surface of the membrane). It is known that higher pressures give higher flow rates, and that higher Flow rates allow the use of smaller membrane surfaces. Because of the low pressures and the high flow rates that can be achieved with anisotropic or coated membrane can be achieved with technical Process a practical separation of the bound heavy metal ions and other impurities can be achieved. The porosity of the coated (skinned) membrane is designed so that the passage of the enlarged heavy metal ion particles and other impurities are prevented in their bound form. In ultrafiltration The filtration is carried out on the outermost surface of the skin (coating), causing clogging of the filter is avoided and the operation of the filter can be maintained for long periods of time.

In the figure, a system 10 for the

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shown continuous circulation of purified wastewater the method according to the invention in a metal plating process applies. A wash tank 12 is included in the system which holds one or more of the metal ions and other contaminants picked up by the rinse water during rinsing of the workpiece contains. For example, fresh water introduced into the wash tank can be used to to wash plated objects so that the impurities are absorbed by the pure water that this turns into wastewater with a high concentration of unwanted heavy metal ions and / or other impurities. Appropriate lines and pumps or gravity feed devices connect the rinsing tank 12 to a reaction tank 13, which in turn is connected by means of a pump 15 with an ultrafiltration unit 14. The concentrate from the ultrafiltration unit 14 can through the line 23 are fed to a reaction tank 17, where conventional methods are used to remove the impurities to destroy or separate from the concentrate in order to recover the highly concentrated materials present. Alternatively, line 18 can be used to feed the concentrate directly through line 19 in to lead the reaction tank 13. Line 22 allows reagents or more water to be added, if any Water has been delivered to the reaction tank 17. The Lei device 2O receives the purified water filtrate, which then for reuse in the rinse tank 12 can be passed through the line 21 or if desired the environment is emitted.

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In the system 10, the continuous revolving is represented as follows. Waste water is drawn from the wash tank 12 obtained and passes through the reaction tank, for example, at a rate of 3 4.8 l / min. Of the Reaction tank has a reservoir volume of approximately 3030 1. The wastewater contains high concentrations, such as 100 parts / million, of contaminating heavy metal ions. The reagent used to form the combining agent along with pH adjusters such as iron sulfate and calcium hydroxide added to the reaction tank, with the iron sulfate in a large excess, such as an input concentration is present in the tank 13 of 5%, and there at least in a molar ratio of 1: 1 opposite the metal ions and other impurities present. The pH is adjusted to pH 9 and monitored by adding more calcium hydroxide, if necessary to maintain the pH at 9 is. The reaction tank preferably contains a mixer to ensure thorough mixing of the reactants with the wastewater, although a continuous flow is often sufficient for a thorough one Mix. The impurities and heavy metal ions react with the combining agent in the Reaction tank and can by means of the pump 15, the ultrafiltration unit 14 can be supplied in an amount of 2660 l / min with a pressure of about 3.5 Atü. Purified Water passes through the coated membrane of the ultrafiltration unit at a speed of 37.8 l / min and is fed back to the wash tank 12. That

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Concentrate is returned to the reaction tank 13 in an amount of 2612 l / min through the pipes 18 and 19, allowing reuse of the reagent is used. For example, if the rinse water contains 100 parts / million of heavy metals, so are to treat 1,514,000 liters of water after 660 hours of continuous operation. At this time the concentration of the concentrate obtained, which flows through the line 18, is 5% and it can then through the line 23 are dispensed and replaced with fresh water and reagent. Treatment of 1,514,000 l of rinsing water produces only 2,650 l of concentrate. If a separate rinse water is used that contains only one or a few impurities, it is relatively easy to remove the contaminating substances to win and regain. Alternatively, conventional methods can be used to make the concentrate obtained in a non-harmful form so that it can be discarded.

Alternatively, the system can be operated in such a way that it is continuous Water, calcium hydroxide and reagents such as iron sulfate can be added while continuously the concentrate through line 23 during the continuous Operating mode of the system is released. So you can work continuously without> closing the system interrupt, even if high concentrations of impurities in the tank 13 are reached. Since the levy through the line 23 constitutes only a small amount, such amounts of concentrate can be discarded or

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treated for extraction over long periods of time.

Examples of the invention are given below. They are only meant to be descriptive and not limiting.

example 1

200 ml of a 0.01 molar (2980 ppm) aqueous sodium bicarbonate solution are mixed with 200 ml of water in a reaction tank so that the chromate concentration 1510 ppm. By adding calcium hydroxide it becomes the pH increased to 9. The solution is filtered through Whatman No. 2 filter paper and analyzed. One poses found that the filtrate contains 1510 ppm bichromate. No metal was thus removed.

In a modification of this example, 200 ml of a 0.01 molar sodium dichromate solution with 200 ml of an aqueous Iron sulfate solution mixed and the pH adjusted to 9 with calcium hydroxide, a combining agent made which is believed to be iron hydroxide. The iron sulphate is added in an amount sufficient to to bring the total solution to 0.0025 moles of iron sulfate. The solution is left at room temperature (25 ° C.) 5 React for minutes and then filter through Whatman # 2 filter paper. Analysis shows that chromium (Cr) is present in the filtrate in an amount of 490 ppm, equivalent to a bichromate value of 1510 ppm.

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The above steps are repeated with the exception that the final concentration of iron sulfate reagent in solution is increased giving the following results for the indicated molar amounts:

0.025 m reagent - 55 ppm Cr- * 170 ppm bichromate 0.037 m "- 0.075 ppm Cr -» 0.23 ppm bichromate 0.05 m "- 0.03 ppm Cr ■» 0.009 ppm bichromate

This means that a reagent to impurity molar ratio 5: 1 and above is sufficient to remove the impurities.

Example 2

0.01 mol of aluminum sulfate in water is treated at room temperature. The pH is adjusted to 9 with sodium hydroxide and iron sulfate is added as a reagent. If the Eisensulfatreagenz in a molar ratio of 1: 5 contaminating aluminum sulfate ^f Eisensul given atreagenz, so 2 filter paper is obtained on filtering through a Whatman No. a filtrate containing more than 0.2 ppm of aluminum.. If iron sulfate is added in a molar ratio of 1:10, the concentration of aluminum in the filtrate water is 0.018 ppm.

Example 3

In this example the reactions are at room temperature

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performed for a period of 5 minutes under Stir to ensure thorough mixing of the materials used. 100 ml of 0.01 molar zinc chloride in water are mixed with calcium hydroxide to bring the pH to 11. This is done with 100 ml of iron sulfate in aqueous solution added in a molar amount of 0.005 and the aqueous solution is passed through a Whatman No. 2 filter paper filtered and analyzed. It is found that the filtrate contains 0.27 ppm of zinc.

This example is repeated without the addition of iron sulfate reagent or using higher molar Concentrations of the reagent, the following results are obtained:

Concentration of zinc in the filtrate

no reagent 0.8 ppm

0.01 mole reagent 0.37 ppm

0.05 moles of reagent 0.12 ppm

0.1 mole reagent 0 ppm

Example 4

In a series of experiments, which was carried out at room temperature, a 50 ml chromium sulfate solution in water with 1000 ppm chromium mixed with various amounts of an aqueous iron sulfate solution and water became

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added to give equal volumes for all experiments and the solutions obtained were made with sodium hydroxide solution made alkaline. In each experiment, the solution was passed through Whatman No. 2 filter paper filtered and the chromium concentration was determined. The following results were obtained.

ml iron (II) sulfate ml water Chromium concentration in the filtrate

10,000 ppm added (ppm) at pH

ben 8 9 11

35 5 15th 5 0 , 03 0 , 03 > o, 5 32, 17, 0 , 13 1 ,8th 3, 2 30th 20th 0 , 29 2 ,8th 5 25th 25th 4th 38 5, 2

Example 5

Example 4 was repeated with the exception that 50 ml an aqueous solution of aluminum sulfate with a concentration of 1000 ppm is used in place of the chromium sulfate and the results shown below were obtained in the filtrate.

ml iron (III) sulfate ml water aluminum concentration in the 10,000 ppm added filtrate (ppm) at pH ben

9 11

35 15 0.005 0

32.5 17.5 0.022 0.029

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30th

20th 0 , 018 0 , 069 25th 0 , 035 0 , 075 50 70 , 2

Example 6

In this example the continuous system 10 of the figure was used. The ultrafiltration unit is a commercial Abcor unit HFA 300 (FEG tubes) manufactured by Abcor Corporation, Cambridge, Massachusetts, UNITED STATES. The unit contains four ultrafiltration tubular membranes 2.54 cm in diameter and 2.54 cm in length 150 cm. The water supplied to the reaction tank contains heavy metal ion impurities as indicated below. The pH is adjusted to 9 through lines 22 and 19 by adding sodium hydroxide and ferrous sulfate will be in large excess (about 25.00 parts / million) admitted. The solution is through the ultrafiltration tubes

at a pressure of 3.5 kg / cm and the pure water is collected and with the results shown below analyzed:

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"5Γ

Analysis of the "pure water"

Supply in ppm "pure water" in ppm Aluminum 3 50 0.02 Iron 1000 0.01 Copper 1500 0.025 Zinc 30 0.08 Chrome 70 0.01

In this example, the flow rate of pure water from line 20 is 700 ml / min, accordingly 35 ml / min / 0.31 cm tube length of the ultrafiltration device. The filtrate from pure water was drawn off and analyzed directly, and the concentrate was directly dem Tank 17 supplied so that the system was not operated continuously in the circulation process, but only a single passage of the wastewater through the ultrafiltration unit took place.

Example 7

In this specific example, the system 10 of the figure is used. The line 21 is connected to a number of Metal plating baths connected, in which the flowing back Pure water from washing water is used. A versatile system collects the wash water from each of the baths and leads it to tank 12 so that the system

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forms a closed loop. In this example, an Abcor unit from Example 6 was used again as an ultrafiltration unit, and the flow rate was set at 37.9 1 / hour from tank 12 to the Tank 13 set and 227 l / min were with a

Pressure of 3.50 kg / cm from tank 13 of the ultrafiltration system fed. It becomes 37.9 1 / hour. of the filtrate is collected in line 20 and continuously passed through the line 21 fed to the metal plating washers. 13,588 1 / hour of concentrate are fed through lines 18 and 19 passed back to reaction tank 13. Tank 13 is a 946 liter tank containing 757 liter of the starting flush water. At the beginning of the system is calcium hydroxide and ferrous sulfate through line 19 in an amount added to the volume of waste water in tank 13 to a pH 9 and a content of 8,400 ppm iron (II) sulfate bring.

The system is operated continuously at room temperature for a period of 8 hours and then switched off and through the line 23 the concentrate is fed to the tank 17, this concentrate having a concentration of 3% impurities, compared to an initial total concentration of metal salts of 0.5%. Will the system Operated 16 hours before it is turned off, the concentration in the concentrate in the tank 17 is 6%.

The following table shows the composition of the initial rinse water, combined with the iron (II) sulfate reagent, that was added to the tank 13, and the concentration of impurities in the filtrate water that

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behind the ultrafiltration unit in line 20 ent was taken:

Tank solution: Na ₃ Cr ₂ O ₇ 27 5 ppm

NiSO ₄ 275 ppm

Al 2 (SO.) 2 100 ppm

CuSO ₄ 27 5 ppm

ZnCl ₂ 27 5 ppm

FeSO ₄ 8400 ppm

Analysis of the purified water:

pH = 8.7 Na ₂ Cr ₃ O ₇ 0.002 ppm

321 1 NiSO ₄ 0.03 ppm

Al ₃ (SO ₄ J ₃ O, O1 ppm

CoSO ₄ 0.04 ppm

ZnCl ₂ 0.06 ppm

FeSO-0.07 ppm

Example 8

In a series of experiments, 100 ml of an aqueous iron (II) sulfate solution were mixed with 100 ml of an aqueous sodium dichromate solution (concentration 2 ppm). Concentrated sodium hydroxide was added until the pH ¹ S changed to 9. The combined solutions were filtered through Whatman No. 2 filter paper. The analysis of the filtrate obtained shows the specified ppm amounts

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of the iron (II) sulfate solution in each case achieved results on:

200 ppm FeSO ₄ 0.002 ppm Na ₂ Cr-O ₇

20 ppm FeSO ₄ 0.36 ppm Na ₃ Cr ₂ O ₇

10 ppm FeSO 1 ppm Na.Cr 0.

1 ppm FeSO ₄ 1 ppm Na Cr ₃ O ₇

Example 9

Example 8 is repeated using 100 ml of an aqueous copper sulfate solution (concentration 2 ppm) instead of sodium dichromate as in Example 8. Similar Results are achieved by making the copper effective at concentrations above 10 ppm concentration of the Iron (II) sulfate solution is removed.

Example 10

100 ml of a 0.1 M manganese sulfate solution in water were with 100 ml of an aqueous solution of 0.01 M sodium dichromate mixed at room temperature. By adding 2 ml of sodium hydroxide the pH was changed to 9. The entire solution was filtered through Whatman No. 2 filter paper. at the analysis of the filtrate showed 0.008 ppm sodium dichromate.

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as

Example 11

In this example, a system 10 according to the figure used. However, the rinse tank was connected to the reaction tank 13 by a single pipe and the pipes 18 and 19 returned the concentrate to the reaction tank 13 and clear filtered water was passed through the line 20 withdrawn for discharge to the environment. A 56.8 liter sample of the wash water was added to tank 12 given. This sample contained the following heavy metal ions:

Fe 4O 6th ppm Ni 27 ppm Zn 0, ppm

Cr 108 ppm

For this purpose 110 g FeSO. given. After 20 minutes, the pH was adjusted to 9.2 by adding 56 ml of 50% strength NaOH. The mixture was then returned to the reaction tank 13 and passed through the filtration unit 14 with a Pressure from 0.7 to 1.05 kg / cm ^ passed. The analysis of the outflowing water was the following:

Fe 0.035 ppm

Zn 0.04 ppm

Cr 0.01 ppm

Ni negligible

The water flow through the ultrafiltration membrane

2
was 10000 ml / min / 0.059 m membrane surface area accordingly

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Th

2 2

500 gf d (gallons χ ft per day). After the water level in tank 13 was low, another 56.7 became 1 Wash water containing 12.2 ppm aluminum was added. That Water obtained in line 20 then contained 0.04 ppm Al.

Example 12

The system of Example 11 was used. 340 1 of a combined wash water containing

Fe 1300 ppm

Ni 27 ppm

Cu 300 ppm

Al 300 ppm

Cr 300 ppm

Zn 38 ppm

were added to the wash tank.

The pH of the rinse water was adjusted to 9.3 by adding 50% sodium hydroxide solution. This solution was fed in an amount of 1000 ml / min to a 95 l circulation tank 13, which contained 57 l of an aqueous solution 2000 ppm Fe in the form of iron hydroxide at a pH of 8.7 to 9.2. The solution was passed through an ultrafiltration membrane tube 91 cm in length and 2.4 cm in diameter in a filtration unit, as indicated in 14, passed, at a rate of 87 l / min. The river on

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Product water was 1000 ml / min and was collected, after the largest amount of 340 liters had passed through the filter, the amount of sludge in the recirculation tank was 37.9 1 and the water obtained was analyzed with the following result:

Fe 0.02 ppm

Ni negligible

Cu 0.06 ppm

Al 0.018 ppm

Cr 0.008 ppm

Zn 0.05 ppm

It should be noted here that although the initial rinse water or wastewater less than 3000 ppm of impurities and heavy metal ions to be removed contained, amounts that were significantly above these amounts accumulated in the reaction tank because the water was removed and the concentrate was returned to the reaction tank 13 through lines 18 and 19.

Example 13

In a recirculation tank containing 100 ppm Fe ions and 60 ppm Zn ions in aqueous solution are added to sodium hydroxide to adjust the pH to 9. The solution will be is pumped through a filtration unit 14 at a rate of 100 ml / min at a pressure of 0.91 kg / cm. Man notes that the flow rate is on

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280 ml / min drops after 1400 minutes.

The same system is used, except that the concentration of iron ions is set to 2000 ppm the water flow rate is 1260 ml / min at the beginning and 1400 ml / min after 1300 minutes. In both cases it was fraudulent the analysis of the purified water downstream of the line 20:

0.02 ppm Fe 0.06 ppm Zn

The ratio between the original Fe ion concentration and the product water flow is given below, using the conditions of the previous example. It became a number of different Iron ion concentrations used:

Fe ion concentration according to product water flow ml / min

24 hours through the ultrafilter

100 ppm 280

1000 ppm 3 50

12 50 ppm 400

1,500 ppm 5OO

17 50 ppm 670

2000 ppm 1400

It should be noted here that for quantities below 1500 ppm of iron combining agent is the product water flow

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considerably within 24 hours to a level that is no longer acceptable for large-scale technical work sank. On the other hand, the product water flow at 200 ppm and above is economically satisfactory after 24 hours and suitable for practical use. The limiting feature seems to be that you can do more than Must use 1,700 parts / million of combining agent to produce a product water flow of at least 600 ml / min after 24 hours of use.

Example 14

The same system is used as in Example 11, 20OO ppm of Cr are present in the reaction tank 13 in the form of chromium hydroxide. A pressure of 1.05 kg / cm is applied, whereby a water flow in the tank 13 to the filtration unit 14 of 120 ml / min is achieved. Will the The concentration of the chromium increased to 5000 ppm in the reaction tank 13, due to the return of the concentrate through the lines 18 and 19, the flow rate is im Filter 880 ml / min and drops to 600 ml / min after 72 hours of operation. The purified water obtained contains no measurable amounts of Cr ions. Contaminant iron ions are added to the tank 13 in one concentration of 200 ppm, the purified water in line 20 contains 0.04 ppm Fe after a single pass the ultrafiltration membrane.

While specific examples of the present invention have been shown herein, these examples are intended to illustrate the invention

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not restrict. Other filtration units can be used. In fact, other filtration methods are included a reverse osmosis is applicable in some cases, as long as the particle size to which the contaminating Ions are increased, is large enough not to go through the filter. One can, however, have problems such as clogging, low flow rates and the like, depending on the particle size present and the filtration system used. The ultrafiltration through the coated membrane results in a remarkable one improved effectiveness where fast filter times and continuous systems are desired.

Although metal processing, such as plating and etching and the resulting waste water are discussed here have been, other wastewater can according to the invention or other contaminated wastewater are treated. For example metallic impurities in polluted waterways can be removed according to the invention will.

The combining agent formed can be insoluble or soluble in the wastewater to be treated. In the same Way can do that by reacting with the heavy metal ions and the other impurities that are removed formed product should be soluble or insoluble or a combination of both. An important The feature of the invention is that the combining agent in the method according to the invention serves to To remove heavy metal ions and other contaminants below the solubility of these materials. So

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- 3S -

ΜΛ

The present invention enables the reduction of residual metal concentrations in wastewater below the solubility of the corresponding metal hydroxide in water at the corresponding pH values.

If inorganic metal salts are tried as reagents, they can be added directly to the waste water as a powder or preferably can be added as aqueous solutions. The reagent can be used before, simultaneously or after the pH adjustment of the wastewater are added. In some cases it is not necessary to adjust the pH value, if that is to be treated Wastewater already has the preferred pH.

Iron (II) sulfate is extremely effective as an additive among Formation of the combining means for the removal of metal ions from wastewater, which one or more of the The following impurities at the specified pH values have:

Aluminum sulfate (pH 9)

Zinc chloride (pH 11) Copper sulfate (pH 9) Chromium sulfate (pH 9) Sodium dichromate (pH 9) Nickel sulfate (pH 9)

Iron (III) sulfate is extremely effective as an additive to form the combining agent for removing metal ions from wastewater, which one or more of the impurities listed below have the specified pH values:

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Nickel sulfate (pH 9)
Nickel chloride (pH 9)
Zinc chloride (pH 11)

Aluminum sulfate is effective as an additive to formation of the combining agent for the removal of metal ions from waste water, which one or more of the following specified Impurities at the specified pH values have:

Nickel sulfate (pH 9)
Nickel chloride (pH 9)
Chromium sulfate (pH 9)

Manganese sulfate is effective as an additive to form the combining agent for removing bichromate from wastewater.

All of these reactants and combining agents according to Invention are, however, if they are used in large excess, namely above the minimum molar Ver ratio of 1: 1, suitable for removing one or more heavy metal ions and / or other impurities, as they have been listed in the description, taking into account concentrations of heavy metal ions and / or receives other impurities in a filtrate which are at or below the concentrations as experimental limits to be striven for were given at the beginning of the description. In most cases it will be Concentration of heavy metal ions or other impurities emerging from the water prior to treatment according to

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of the invention are to be removed, about 1 part / million or more. At concentrations in the wastewater below 1 part / million of impurities it is sometimes necessary to increase the molar ratio above 1: 1 to achieve a very effective removal. Effective removal can be achieved with highly concentrated wastewater and also for those in which the concentration is below the solubility of the metal ions or the other Impurities occur. Waste water from most common metalworking and plating processes usually contain no more than about 4000 ppm and often less than 2000 ppm of such ions and impurities. Of course, when operating a system according to Example 7 of the present invention or in other cases where the concentrate from the ultrafilter is returned to the reaction tank, the concentration of heavy metal ions and impurities in the reaction tank immediately before ultrafiltration high and can easily get above 4000 ppm over the course of normal system operation. In some cases the metal ions to be removed are present in the wastewater in dissolved form and in other cases, e.g. At basic pH values, the metal ions can be partly in solution and partly in suspension. the Combination agents according to the invention enable the removal of the metal ions, which are both in suspension as well as in dissolved form. Partial or complete removal can be done, depending on the case conditions used, for example the reagent, the molar ratio, the pH, the filtration and the like. In some cases, the filtered water gets out

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line 20 is further purified, e.g., by passing it through an ion exchanger for removal of alkaline salts.

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Claims (24)

PATENT CLAIMS (V) Process for removing fine particles in the form of heavy metal ions and impurities Wastewater resulting from metalworking and plating processes containing no more than about 4000 ppm of heavy metal ions and impurities, characterized in that the bringing together fine particles with a combining agent at a pH between 7.1-14 Formation of a bound material with a particle size of at least 10 8 that the combining agent is an inorganic meta-hydroxide, where the Metal is selected from the group consisting essentially of iron, aluminum, tin, copper, Zinc, cadmium, nickel, cobalt, silicon, lead, barium, calcium, manganese and chromium that the combining agent in an amount of at least 1700 ppm and in a molar ratio of 1: 1 and more with respect to the Moles of small particles are present, but in such an amount that the sewage can still be pumped and that then the wastewater is filtered through an ultrafiltration membrane filtering device with a flow rate of at least 113 1/929 cm membrane surface / day, with one Pressure of at least 0.63 atmospheres with separation of the bound material from the waste water. 2. The method according to claim 1, characterized in that the pH is in the basic range that the 809840/0228 ORIGINAL INSPECTED Wastewater after filtering a lot of fine particles Contains material that is below the water solubility limits of the particulate material, that the small-sized material consists essentially of heavy metal ions contained in wastewater which contain no more than about 4000 ppm of heavy metal ions, and that the ultrafiltration pressure is in the range of 0.63 to 10.5 kg / cm overpressure. 3. The method according to claim 2, characterized in that the pH is in the range from 8 to lies. 4. The method according to claim 3, characterized in that the small-part material in the consists essentially of contaminating heavy metal ions that originate from metalworking processes, wherein the combination is made with a combination agent in a reaction tank, and that Wastewater is filtered in an ultrafiltration system, with the formation of a concentrate from the Ultrafiltration system, this concentrate being returned to the reaction tank, and a Receives filtrate from the filtration unit and this filtrate is fed back to the metalworking process and directing the effluent from the process to the reaction tank, all stages being continuous be carried out in a closed circuit. 5. The method according to claim 1, characterized in that the small-sized material 8098AO / 0228 a mixture of at least two different ones
Is heavy metal ions. 6. The method according to claim 3, characterized in that the combining means is formed is made by adding a large excess of iron (III) sulfate to the wastewater. 7. The method according to claim 3, characterized in that the small-part material a mixture of at least two different heavy metals ions is. 8. The method according to claim 3, characterized in that the combining agent is iron hydroxide and / or aluminum hydroxide. 9. The method according to claim 2, characterized in that the small-scale material in the wastewater is initially present in an amount above 1 ppm and the fine-particle material essentially comes from contaminating heavy metal ions from metal processing plants, and that the combining agent is iron hydroxide and / or aluminum hydroxide. 10. The method according to claim 9, characterized in that the combining means by Addition of iron (III) sulfate in large excess to which wastewater is formed. 809840/0228 _ 44 - 11. The method according to claim 3, characterized in that the combining stage in one Reaction tank is carried out, and that the filtration of the waste water in an ultrafiltration unit is carried out that one obtains a concentrate from the ultrafiltration unit, and that one recover a filtrate from the filtration unit and return this filtrate to the metalworking stage and returning the waste water from metal processing to the reaction tank. 12. The method according to claim 11, characterized in that g e k e η η - It is true that the combining agent is iron hydroxide and / or aluminum hydroxide. 13. The method according to claim 4, characterized in that the combining agent is iron hydroxide and / or aluminum hydroxide. 14. The method according to claim 1, characterized in that the inorganic metal hydroxide Is iron hydroxide. 15. The method according to claim 1, characterized in that the metal hydroxide is aluminum hydroxide is. 16. The method according to claim 1, characterized in that the waste water is concentrated so that the combining agent is combined with the heavy metal ions in said wastewater, 809840/0228 when the concentration of heavy metal ions is above 2OOO ppm. 17. The method according to claim 12, characterized in that the combining means in is present in the wastewater in an amount of at least 2000 ppm. 18. The method according to claim 17, characterized in that a reaction tank is used in which the combining agent and the supplied wastewater are in the form of a reaction mixture, that the reaction mixture passes through an ultra-filtration membrane is passed through, the FiI-entered collected and the concentrate in the said Reaction tank is continuously returned. 19. The method according to claim 1, characterized in that the combination in one first tank is made to form an aqueous reaction mixture that one said The reaction mixture is transferred to a second tank that the wastewater is transferred to an ultrafiltration system filtered and a concentrate obtained from the ultrafiltration system and this concentrate in the second Tank recirculates and that the filtrate is continuously recovered from the filtration unit. 20. Procedure for removing small particles in the form of heavy metal ions and impurities below 809840/0228 Wastewater from metalworking and plating processes originate, with this wastewater no more than about 4000 ppm of the heavy metal ions mentioned and contain impurities, characterized in that one has the small-scale Materials with a combining agent in one pH from 7.1 to 14 to form a bound material having a particle size of at least 10 Å brings together that the combining agent is an inorganic Metal hydroxide of a metal from the group iron, aluminum, tin, copper, zinc, cadmium, nickel, Cobalt, silicon, lead, barium, calcium, manganese and / or chromium is that combining agent in a molar Ratio of 1: 1 and above, based on the moles of small-sized material, but in one Amount that enables the wastewater to be pumped and then to pass the wastewater through a Ultrafiltration membrane with a flow rate 2 at least 113 1/929 cm / day for one Pressure of at least 0.63 kg / cm overpressure for separation of the bound material from the wastewater passes through. 21. The method according to claim 20, characterized in that the combining means by Addition of metal ions of the type mentioned in claim 20 is formed. 22. The method according to claim 1, characterized in that the combining means by 809840/0228 - 44 - Addition of metallics from those mentioned in claim 1 Ions is formed. 23. Process for removing heavy metal ions from aqueous solutions resulting from metal processing and plating process, characterized in that one uses a metal hydroxide brings together the metal ions of said solution at a pH of 8 to 12, said metal of the metal hydroxide is present in the solution in a concentration of at least 1700 ppm and the aforesaid Metal hydroxide in the solution mentioned in a ratio of at least 1: 1, based on the heavy metal ions is present, and a bound material is formed that the combined solutions through an ultrafiltration membrane with a flow rate 2 at least 113 1/929 cm / day for one Filtered pressure of at least 0.63 kg / cm gauge to separate the bound material from the solution. 24. The method according to claim 23, characterized in that said metal hydroxide by adding a large excess of iron (III) sulfate to the aqueous solution is formed. 809840/0228