DD291540A5 - METHOD FOR REMOVING INORGANIC CONTAMINATION FROM FLUIDS - Google Patents

Abstract

The invention relates to a process for the removal of inorganic impurities from liquids, in particular wastewater. The essence of the invention is that it is used to separate coke and / or activated carbon produced from lignite in activated liquids in liquid form. {Inorganic impurities; Sewage / water treatment; Metal / phosphate ions; Coke; Brown coal; Activated carbon}

Description

Field of application of the invention

The process according to the invention relates to the removal of dissolved impurities from liquids, in particular wastewater, by treating them with brown coal cokes and / or activated charcoals from lignite.

Characteristic of the known state of the art

The use of cokes and activated carbons for wastewater treatment has long been known. For example, coke and activated carbon are used as a filter mass for separating finely divided solids into wastewater.

Cokes and activated carbons are also suitable as adsorbents for dissolved organic impurities.

Thus, the use of lignite coke for this purpose is described in "Hordofenkoks aus Brunkohle-conventional applications and future applications" in petroleum, natural gas, coal, 102 pp. 143/144 (1986). According to this publication lignite coke is also very well suited as an additive to biological sewage treatment plants, as compact flocs are formed with the biomass with improved sedimentation properties A particular problem of wastewater treatment is the removal of inorganic impurities, in particular of dissolved metal compounds.

Of the numerous known methods, only a few can be cited by way of example.

Thus, EP 0110240 describes a process according to which wastewater containing copper and zinc is treated with anaerobic sludge. By this method, 92% of copper and 90% of zinc can be removed.

For example, assuming a wastewater with a content of 7 mg / l of copper, the effluent will contain 0.56 mg.

At 70 mg / l, accordingly, 5.6 mg of copper would remain in the wastewater. The same applies to zinc. Accordingly, the desired degree of purification is not achieved with this method.

An interesting method is disclosed in DE-PS 3026430. Here, converter slag from the iron industry in a particle size of ca, 0.15 mm is used.

As can be seen from Table 4 of the patent, 4 mg of mercury can be bound with 1 g of slag. If sufficient amounts of slag are used, Hg can be removed up to the detection limit of <0.001 ppm.

However, Cs is required to work at a pH <2. Accordingly, significant amounts of acid such as HCI or H2SO4 must be used.

The investigations into the removal of Cd, Pb, Cr and arsenic show that, despite the use of said slag amounts, significantly higher concentrations of metals remain in the treated wastewater than in the case of mercury.

Assuming an only slightly contaminated with Hg wastewater containing 10 mg Hg / l of water, as already 11 slag has to be used by this method are a relatively small amount of 1000m ^{3 of} waste water and a correspondingly large amount of acid. Also, the grain size of the slag of 0.15 mm charged the economy of the process. In addition, when using the slag with this grain size, a stirring or other mixing reactor is required.

A further process in which activated carbon pretreated with secondary amines and carbon disulfide is disclosed in DE-OS 3020608.

In DE-OS 3438140 a method is described according to which metals are precipitated by the addition of a Natriumaluminatlösung. In addition, a polyelectrolyte must be added and then the difficult to filter precipitated metal hydroxides must be separated.

EP-A-0 156059 describes the precipitation of metals as metal phosphates.

In view of the development in the field of wastewater, it is becoming more and more urgent to develop improved processes which, in economic and with high selectivity, remove the dissolved impurities which are in part extremely harmful to both plants and animal and human from water in which they are contained , to remove. This can be industrial wastewater as well as surface water par excellence, such as river, pond, sea and also seawater and in particular groundwater. As is well known, landfill leachate has become an increasing risk to groundwater.

Object of the invention

The aim of the invention is to further increase the degree of disposal in the treatment of waste water and / or in the treatment of water.

Explanation of the essence of the invention

The invention has for its object to develop a method with which in a very economical manner dissolved metal and phosphate ions can be separated to the detection limit of industrial wastewater, surface water and groundwater.

According to the invention, the object is achieved by using coke (s) and / or activated carbon (s) produced from lignite for the removal of the ions contained in the liquid.

Lignite is known to originate mainly from the tertiary and are therefore comparatively geologically young coal with a low degree of coalification. They are rich in bituminous substances such as humic acids, which dissolve in caustic soda with deep brown color.

They can contain up to 65% by weight of water and are usually mined on open pit shovels in a very economical way. From lignite one can produce coke in different ways.

Examples are the so-called Grudekoks obtainable by smoldering at about 600 ^° C. By coking at 1000-1200 ° C to obtain the so-called Brain coal high-temperature coke with a specific surface area of about 75-250 mVg.

Another very hard coal coke, due to its hardness and pressure resistance, is the so-called hearth furnace coke with a specific surface area of 250-35 OmVg.

When coking in the hearth furnace finely ground and pre-dried lignite is placed on downpipes on the outer edge of the hearth furnace plate and migrates under the constant rotation and the action of the fixed paddles slowly to the center, from where the finished coke is discharged. During the passage, the volatiles escape from the lignite / coke bed and are partially incinerated while supplying air from outside above the coke bed. The coking process is conducted via this combustion of a portion of the volatiles, that is, it is carried out under air deficiency, so that each burns only such an amount of volatile components, as is needed to maintain the coking temperature, the coking of brown coal in the hearth furnace takes place in generally without supplying water vapor or water from the outside, since the water content of the pre-dried lignite can be adjusted so that coke with the desired properties is obtained. In accordance with the invention it has proved particularly useful to produce hearth furnace coke made from Rhenish lignite. The mentioned lignite coke qualities are exemplary, but not to be regarded as limiting.

Activated carbons or, because of their large surface, also called adsorption charcoal, have often been obtained from wood, but lignite is also a suitable starting material.

There are numerous processes for the production of activated carbons. Examples include sulfur processes followed by treatment with steam, heating of finely divided feedstocks in the presence of oxidizing gases in the fluidized bed, treating charred substance with superheated steam to about 1000 ° C u.a. Activated carbons which are produced by this or other processes from lignite and may also be available on the market are suitable for the process according to the invention.

Before the treatment of the liquid containing the impurities with the coke produced from lignite and / or activated carbon, coke or activated carbon is advantageously degassed, ie the surface or gas adhering to the pores, generally air, is at least partially removed as completely as possible , This is done in a preferred embodiment by evacuation. The evacuation may be carried out by applying vacuum to the containers containing the coke and / or the activated carbon and then allowing the liquid, preferably water, to flow into the coke or activated carbon. However, it is also possible first to wet or cover the coke and / or the activated carbon with the liquid and then to apply a vacuum.

Removal of the gas adhering to the coke or activated carbon is an important preferred embodiment of the present invention, as shown by the experiments carried out, although non-degassed coke gives good results (experiment # 37). Very advantageous may be degassing by treatment with steam or hot water or both,

also in combination with degassing by evacuation. Likewise, the degassing and mixing with water in such a way that finely divided coke or activated carbon are sucked into the water jet of a water jet pump.

Of course, the liquid to be purified is preferably water. It is well known that the removal of certain heavy metal ions from water has become an urgent environmental problem. However, the process of the invention can also be used with advantage for mixtures of water with other water-soluble liquids, such as e.g. B.

with alcohols, ketones, organic acids and other acidic compounds and the like. Finally, the method is also applicable if such or non-water-soluble liquids to be removed from dissolved metal ions.

A particular advantage of lignite coke is its availability and high cost-effectiveness. This is especially true for hearth furnace coke, which is at least a factor of 10 cheaper than activated carbon.

The method is applicable to almost all metal ions. However, it is particularly suitable for the removal of heavy metal ions classified as toxic, e.g. of mercury, cadmium, zinc, copper, lead, chromium, cobalt, nickel, vanadium, tin, gallium, indium and thallium, but also for metal ions such as iron, molybdenum, tungsten, manganese and cations of arsenic, antimony and bismuth and rare earths, radioactive metals and precious metals. The metal ions can be present as individual elements or in a mixture.

The method is also very suitable for the removal of phosphate ions, in particular those which pass through detergents into wastewater or other waters.

The process can be carried out in a very simple manner by contacting the water to be purified with the coke and / or charcoal in such a way that coke or activated carbon is arranged as a solid bed and the water flows through it with a certain residence time leaves. Here, the water can be pushed from bottom to top through the bed or flow from top to bottom through the same. Also a migrating fixed bed, a fluidized bed and other forms of contact between liquid and adsorbents are possible, such as in the bed of suspensions. In the purification of metal ions containing water is preferably at a pH of> 4 and more preferably at a pH of> 5 in the worked to be cleaned liquid, especially in water. However, the pH may be lower or higher. The pH in the purified liquid is not retained during the entire cleaning period on these values, but allowed the pH during the ^Re: nigungsbetriebs to higher values such as 8 to increase.

However, higher pH values are possible.

Basically, coke or activated carbon can be used according to the invention with very different particle sizes, such. B.

from> 0 to 100 mm. For technical and economic reasons, however, certain grain sizes are preferred, namely> 0.01 to 20mm and more preferably of> 0.01-10 mm. Usual Feinkokssorten are z. B. between about 1.2-5 mm, Feinstkokssorten between 0.1-1.5 mm. All these grain sizes, including coke dusts are replaceable and provide very good results. It should be noted that grain sizes in shredded and sieved products are Gaussian distribution, i. H. a mean grain size in the specified limits predominates, but in small quantities are also smaller and larger grain sizes.

In practical use, it may be advantageous to use large grain sizes in the lower bed up to 100 mm, but in the upper part small grain sizes. The reverse arrangement may possibly be. Of importance, that a part of the contamination is caught in the upper coarse part and the remaining impurities in the fine-grained lower part.

The residence time of the water or liquid to be purified should be 1-300 min, preferably 5-180 min and more preferably 10-120min. In principle, significantly longer residence times can be applied at the expense of the economy of the process.

Of the lignite cokes, the hearth furnace coke is preferred according to the invention. This is very inexpensive compared to other types of coke and activated carbon and shows excellent adsorption properties for the metals mentioned.

After loading with the metallic or other contaminants, the coke can be dumped or incinerated, and the metals can optionally be recovered from the ash.

Herdofenkoks is generally traded as so-called. Fine coke with a particle size of 1.25-5 mm, as Feinstkoks with a particle size of 0.1-1.5mm and as a coke dust with a particle size of <0.4mm.

All grain sizes can be used according to the invention, as already stated, individually or as mixtures, but with the use of coke dust alone preferably also with the water sine intimate mixing should be done by, for example, stirring.

Loaded coke or loaded activated carbon can, if necessary. Also be regenerated, such. B. in the case of loading with Hg, Cd u. a.

by thermal desorption, but also by chemical reaction.

embodiments

To further explain the present invention, the following tests are used:

(In all purified water samples, the residual content was determined by atomic absorption spectroscopy or ion chromatography.) The hearth furnace coke was a product of Rhenish brown coal.) The experiments summarized in the tables were generally carried out by placing in a glass column (diameter 1, 8cm), which was equipped with a sieve bottom, 1bg r! Erdofenkoks the grain size 0.1-1.5mm were filled (filling height 11cm). The column was filled up with tap water and evacuated at 18-20 mm on a water jet vacuum (evacuation time 15 min). The coke volume was 30cm.

Or the finely divided coke was sucked in by means of a water jet pump and mixed with water. Subsequently, the coke was allowed to settle. Also, the method of hot steam treatment has been used in some cases, especially in the larger devices. So Experiment 7 was carried out in the manner, for example, that the ground water to be purified through a container filled with open-hearth coke container was passed, which contained several m ³ and coke was heated as a pretreatment with steam and then filled with hot water. For the technical implementation of the method according to the invention is in the German patent application no., P 3823127.1 filed by the same Applicant method. Characteristic feature of the present invention, however, is not the implementation of the apparatus, but the use of cokes and lignite-based activated carbon.

A filtered waste water containing 25mg Cd ⁺ * as cadmium acetate per liter and a pH of 5.3 was used for purification. The experiments are carried out at room temperature and normal pressure. The throughput per hour was 30 ml (residence time: 1 hour). After 110-260 hours, the experiment was stopped and the purified water analyzed. After these trial periods, the coke fills were not exhausted. The analyzes were each drawn at the end of the specified maturities, so that the residual concentration of metals in the entire treated wastewater was even lower than indicated in the right column.

Table 1

Experiments with degassed Herdofenkoks from brown coal influence of grain size and coke volume

Verse. CD** Konzen Koksvolumen coke grain size Stay pH experiment Conc. No. (Cd (Oac) ₂ ) tration ml G mm time / min duration to Cd ⁺ * mg / l H cleaning (Cd (OaC) ₂ ) ppm 1 CD** 25 30 15 0.1-1.5 60 5.3 110 <0.002 ppm (Cd (OaC) ₂ ) 2 25 30 15 1.25 to 5 60 5.3 110 <0.002 ppm 3 Cd ⁺ * 25 30 15 30wt .-% 60 5.3 110 <0.001 ppm (Cd (Oac) ₂ ) 1.25 to 5 40 wt .-% <0.4 4 25 10000 5000 1.25 to 5 40 5.3 240 <0.002 ppm

Table 2

Influence of the metal ion species (furnace furnace coke degassed)

verse Cd ⁺ * Konzen Koksvolumen groundwater 30 kc No. (Cd (Oac) ₂ ) tration ml 25 G Zn ** mg / l 30 5 (ZnCl ₂ ) 25 30 25 15 Zn ⁺ * 30 6 (ZnCl ₂ ) 62 60 110 30 30 7 Cu ⁺ * 16inverun- 30 32 15 (CuCl ₂ ) reinigtem 30 Pb ⁺ * 16 8th (Pb (OaC) ₂ ) 30 15 Hg ⁺ * 25 9 (Hg (OaC) ₂ ) 30 15 Hg ⁺ * 25 10 (Hg (Oac) ₂ ) 30 15 : D ** 30 11 (CdCl ₂ ) 30 15 Pb ⁺ * 34 12 (Pb (OaC) ₂ ) 30 15 Ni ⁺ * 25 13 (Ni (OaC) ₂ ) 30 15 Cr *** 27 14 (CrCI ₃ ) 30 15 44 15 (VCI ₃ ) 15 Co ⁺ * 16 (CoCI ₂ ) 15 Sn ⁺ * 17 (SnCI ₂ ) 15 In*** 18 (InCI ₃ ) 15 19 15

Coke quantity Particle size dwell pH mm time / min

Experimental Conc. Duration after

h cleaning

ppm

0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60 0.1-1.5 60

5.3 120 <0.002

5.6 120 <0.1

6.0 120 <1

5.6 120 <0.1 5.6 120 <0.01 5.7 6.0 120 140 140 <0.0005 <0.0005 5.7 140 <0.0005 5.7 140 <0.002 5.6 120 <0.1 5.6 120 <0.1 5.6 120 <0.01 6.1 120 <0.1 5.9 120 <0.01 5.9 120 <0.1

UO ₂ (NO,) ₂ -6H ₂ O I Konzen Koksvolumen coke grain size Stay pH -5 - 291 540 As *** tration ml G mm time / min Table 2 (cont (Ascia / HCl) mg / l experiment Conc. Verse. Mo ⁺ ** duration to No. (M0CI3 / HCl) 15 30 15 0.1-1.5 60 6.0 H cleaning Ce *** 23 30 15 0.1-1.5 60 6.0 ppm (CeCl ₃ ) 120 <0.001 20 Ag * 26 30 15 0.1-1.5 60 6.0 120 <0.001 21 Mn ⁺ * (MnCl ₂ -4H ₂ O) 44 30 15 0.1-1.5 60 5.7 120 <0.1 22 21 30 15 0.1-1.5 60 5.8 120 <0.001 23 40 30 15 0.1-1.5 60 5.3 120 <0.001 24 120 <0.001 24 a

The results given in Table 1 show that the grain size of the used Herdofenkokses only a small

Has influence on the test result.

Table 2 summarizes experiments with numerous metal ions in aqueous solution.

It was worked in almost all experiments for a better comparison with a residence time of 1 hour.

The results show that the inventive method is applicable to a very wide extent, the indicated

Try not to be considered limiting.

Table 3

Influence of coke or activated carbon 25mg Cu ⁺⁺ / I (CuCl ₂ ) (degassed)

Verse. furnace coke Koksvolumen grain size Stay- experiment Conc. After No. (Lignite) ml mm time / min Time / h cleaning 25 spec. surface 30 0.1-1.5 60 260 <0.1 ppm 250-35OmVg coke spec. surface 26 5-25 mVg 30 0.1-1.5 60 20 Rise up Activated charcoal (wooden) 7.6 mg /! spec. surface 14hO, 2mgCu ⁺⁺ / l 27 1200-180OmVg 30 0.1-1.5 60 26 5 mg / l Activated carbon / Hydraffin (AusBraunkohle / Fa. 28 Lurgi) spec. Surface. 30 0.1-1.5 60 90 <0.1 ppm 600-120OmVg High-temperature brown coke coke spaz. 29 Surface 200-25OmVg 30 0.1-1.5 CO 120 <1 ppm Low temperature (DDR- Coke spec. Surface. 30 20-12OmVg 30 0.1-1.5 30 120 <1 ppm

The tests in Table 3 were carried out as the experiments indicated in Tables 1 and 2, but were

various types of coke or activated carbons used.

It was a CuCI _2- containing wastewater with 25mg Cu ** / I used.

Experiment 25 with hearth furnace coke from Rhenish brown coal gave after 260 hours running time a Cu "amount in the purified wastewater of <0.1 ppm.

Coal coke (trial 26) gave 0.2 mg / l after 14 h and a rapid increase to 7.6 mg / l at 20 h. The experiment was stopped after 20h.

For high-temperature lignite coke (DDR), a value of <1 ppm was obtained for up to 120 hours. The same result was obtained with low temperature coke (DDR) (runs 29 and 30).

Very good results were obtained with a Lurgi activated carbon based on lignite. Only after 90 h test duration, an increase to> 0.1 ppm was detected. Significantly worse results were, however, with a wood-based activated carbon

obtained (experiment 27). After 26h, a breakthrough to 5mg / l took place.

The results show the very good properties of lignite cokes and activated charcoal and among them the

outstanding characteristics of hearth furnace coke from Rhenish lignite.

-6- 291 S40

Table 4

Influence of the pretreatment on hearth furnace coke, degassed 25mg Cu ²⁺ (CuCl 2), grain size 0.1-1.5 mm, residence time 60 min

attempt Evacuate 'Concentration after duration of test No. then water addition Cleaning, ppm H 31 Evacuate <0.1 260 underwater , 32 Steaming with steam <0.1 260 at ⁰ C 33 Treatment with boiling <0.1 260 water 34 Aspirate and mix <0.1 with water by means of a 35 Water jet pump <0.1 260 without pretreatment 36 <0.1 110 6.8 (3.0) Cu 3.0 ppm 152 6.8 ppm 170

Table 4 shows the influence of the pretreatment on the residual content of metals in the purified water.

It turns out that both evacuation and treatment with steam and hot water lead to very good results, as well as the suction of fine coke and mixing by means of a water jet pump.

This is of considerable practical importance, since in large cleaning equipment, steaming and soaking are likely to be the easiest to perform pretreatments.

Without pretreatment, the residual concentration rises to 3.0 ppm after 152 h and to 6.8 ppm after 170 h.

Table 5

Influence of the residence time when using degassed hearth furnace coke 25mg Cd ⁺⁺ (CdCl ₂ ) grain size 0.1-1.5mm

attempt dwell Concentration after duration of test No. min Cleaning in ppm H 37 60 <0.002 2 mg / 1 120 38 120 <0.001 120 39 30 <0.002 120 40 10 <0.02 120

Table 5 shows that only for short residence times of about 10 minutes, a significant increase in the residual content of metal ions in the purified water is detectable.

Table β Influence of the solvent when using degassed hearth furnace coke 25mg Cd ⁺ * (CdCl ₂ ) grain size 1.25-5mm, residence time 60min

attempt Wt .-% Concentration after No. Cleaning in ppm 41 lOOWasser <0.002 42 50 water <0.002 50 methanol 43 50 water <0.002 50 acetone 44 30 water <0.002 70 ethanol 45 100 methanol <0.002 46 50 benzene <0.02 50 ethanol

Table 7

Influence of the pH in the wastewater used when using degassed hearth furnace coke and 25 mg Cu ⁺⁺ , particle size 0.1-1.5 mm, residence time 60 min

Experiment No.

pH concentration after

Cleaning ppm

Test duration h

3 4 7 9

180> 260 at least 260 at least 260

From Table 6 shows that even with solvents or solvent mixtures containing no water, good to very good results are obtained.

Table 7 shows that the pH in the water to be used is within wide limits without any appreciable influence on the results according to the invention.

Although it is known that lignite, coke and activated carbons contain basic components, the impurities remaining according to the invention are surprisingly far below the solubility products of the corresponding metal hydroxides, at relatively high pH. (At lower pH, the solubility products of the metal hydroxides are even higher.) Table 8 gives some information on the metal ion concentrations remaining in the water due to the solubility products.

Table 8 attempt metal ion pH remaining in the wastewater No. Metal ion concentration mg / l 51 Cd ⁺⁺ 8th 55 52 Ni ⁺⁺ 8.5 30 53 Zn * ⁺ 8th 6 54 Pb ⁺⁺ 8th 37

Table 9 summarizes results for the removal of phosphate ions, in particular detergent phosphates.

Table 9

Removal of phosphate from aqueous solution using degassed coke from lignite, grain size 0.1-1.5mm, residence time 60 min. -

attempt P-Conc. in the P-Conc. Koksart No. use of water after cleaning 55 8mg / lalsPO < ³ ~ <1 mg furnace coke in landfill leachate 56 like 55 <1.5 mg Hochtemperaturkoks 57 16 mg as a wash <1 mg furnace coke medium-phosphate 58 16 mg as a wash <1mg Herdofenkoksohne medium-phosphate previous degassing 59 16mgalsWasch- 12mg coke medium-phosphate

Experiments 51 to 53 show that phosphates can be largely removed by the process according to the invention.

The Einsaulösung in experiment 53 was prepared by dissolving detergent in water.

Experiment 54 shows that even without prior degassing phosphates can be removed with lignite coke with very good results, while coal coke leads to no significant removal of the phosphates.

The applicant's investigations have also shown that, as is generally known, temperature increases do not favorably influence the effectiveness of the cokes and / or activated carbons according to the invention, while the pressure is without significant influence.

The discussion makes it clear that the invention provides a new, useful and very effective method of solving in an outstanding manner the ever more urgent problem of the liberation of waste water from impurities, in particular metal and phosphate impurities.

Claims (12)

A process for separating ions dissolved in liquids with coke and / or activated carbon, characterized in that lignite coke (s) and / or activated carbon (s) are used to remove ions contained in the liquid. 2. The method according to claim 1, characterized in that the liquid is water. 3. Process according to claims 1 and 2, characterized in that the coke and / or the activated carbon are degassed before use. 4. The method according to the Anspiüchen 1-3, characterized in that the degassing by suction of finely divided coke or before. Activated carbon takes place in the water jet of a water jet pump. 5. Process according to claims 1-3, characterized in that the degassing is carried out by treatment with hot water and / or with steam. 6. Process according to claims 1-5, characterized in that one works with a residence time of 1-300min, preferably from 5-180 min, more preferably from 10-120min. 7. Process according to claims 1-6, characterized in that the cokes used and / or activated carbons have a particle size of> 0-100mm, preferably of> 0.01-20mm and more preferably of> 0.01-10mm. 8. Process according to claims 1-7, characterized in that lignite-produced coke is used. 9. Process according to claims 1-8, characterized in that from lignite produced Herdofenkoks is used. 10. The method according to claims 1-9, characterized in that the purification of water takes place, which contains at least one metal from the group Hg, Cd, Zn, Cu, Pb, Cr, Co, Ni, V and Mn as cations, these cations are removed. 11. The method according to claims 1-10, characterized in that a pH> 4, preferably> 5 is present in the liquid to be purified. 12. The method according to claims 1-9, characterized in that the purification of water is carried out containing phosphate ions, in particular detergent-phosphate ions, wherein these ions are removed.