DD215523A1 - METHOD FOR REMOVING METALIONS FROM WATER - Google Patents

Abstract

The invention relates to a method for the purification of water from interfering metal ions with simultaneous Teilenthaertung zeolitic molecular sieve by ion exchange.

Description

Process for removing metal ions from water Field of application of the invention

The invention relates to the use of zeolitic molecular sieve powder for removing metal cations from water to be used, for example, for drinking water purposes. Suitable molecular sieves are natural or synthetic zeolites. To be removed are the cations of metals, such as lead, cadmium, iron, tin, cobalt, copper, manganese, mercury, nickel, chromium, zinc or titanium, which can significantly affect the water quality even in small amounts.

Characteristic of the known technical solutions

It is known that drinking water quality is impaired by hardness factors and increasingly by a content of metal ions. The latter can cause not only a taste quality reduction, but also represent a health hazard. , '. · ... '. '' ... ''^:; , - '', ';';'''' ^Ύ [: [

As is known, the purification of water can be carried out by treatment with ion exchangers and adsorbents. In this case, preference is given to using organic condensation or polymerization resins based on formaldehyde or styrene with exchange-active cations or anions as ion exchangers.

(DEOS 2 362 860, USP 3,969,244) · These processes usually lead to the complete desalination of the water, which must be brought back to a physiologically necessary minimum content by adding salts. In addition, while the pH of the water is unduly reduced, there are bacterial contamination of the water and often also taste impairments of the Kunstharzaustausehern, which must be removed by other additives, such as activated carbon. Other methods use amorphous aluminosilicates, bleaching earths, bentonites, kieselguhr and granulated synthetic zeolites (DSOS 1 767713, DBOS 2 754 488, USP 3 859 210, USP 4'-116'828). for water softening. Due to their structure, the achievable capacities are low, especially for the amorphous materials, and consequently the required amounts are quite large, in addition to the usually long reaction times and the troublesome turbidity of the water in their application.

DEOS 2 504 688 describes the use of granulated zeolitic molecular sieves for water softening. These are known as crystalline synthetic zeolites of types A, X, Y, mordenite and others of the general composition.

Me ₂ 0 .Al ₂ O ₃ .ZSiO ₂ . Y HgO,

, '~' . '. ''. '. where χ can have a value of 2 to 10, depending on the structure and crystal type of the zeolite. Due to their crystal structure, they have a defined and uniform pore system of 3, 4, 5, 10 angstrom units, which enables them to be selectively adsorbed. The metal ions necessary to compensate for the charge defect resulting from the existing Al atoms are exchangeable. The synthetic zeolites are generally prepared by hydrothermal synthesis and granulated mostly with binders because of their fine crystallinity, (USP 2,882,244, DEAS 1 055 515). In the mentioned use of granulated zeolite molecular sieves for water

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softening (DEOS 2,504,688) the inherently high ion-exchange capacity of the zeolites is reduced again by the addition of 20 to 25 % inert binders, which additionally cause difficult to remove clouding of the water, especially when the reaction in the heat and under Movement is performed. Added to this is the fact that granulated zeolites also require extended reaction times due to their existing secondary porosity and the associated longer ion diffusion paths during exchange.

The mentioned methods therefore fulfill the task only imperfectly and with a high temporal and material expenditure. The use of crystalline zeolitic molecular sieve powders for metal ion separation from water has not previously been described.

Object of the invention

The aim of the invention is the simple and effective improvement of the quality of water for household, pleasure or special chemical engineering applications by removal of metal ions such as lead, cadmium, iron, tin, cobalt, copper, manganese, mercury, zinc, nickel, chromium , Titanium by treatment with crystalline zeolite molecular sieve powder without remaining water turbidity, without taste impairment and without introducing traces of organic substances from the ion exchange material into the water. ,

Explanation of the essence of the invention

It has now been found that with crystalline Zeolithischea molecular sieve powder even in low concentration of water in a very short time, the above-mentioned metal ions can be partially removed to below the chemical detection limit by ion exchange. It is sufficient

bringing a relatively small amount of zeolite powder into contact with the water for 1 to 2 minutes while agitating or stirring. As a guideline for the required amount of molecular sieve powder, depending on the impurity level of the water, 1 to 2 g of zeolite powder per liter of water can be assumed. The reaction can be carried out under all conditions of the presence of liquid water. As zeolites, all the known types can be used, preferably the types A, X, Y, i ^1, mordenite, erionite, ZSM-types and silicalite in the loading with monovalent cations or mixtures thereof technically the cheapest available. Metallions are preferably removed:

Lead, cadmium, manganese, zinc, copper, chromium, iron, tin, hickeys, mercury

in initial concentrations, in some cases up to 100 mg / l of water.

The metals mentioned and their concentration ranges are those which, in practice, most frequently form the cause of drinking water contamination, without wishing to restrict the ion exchange action of the zeolites.

The separation of the zeolite powder is carried out after the reaction time by settling and / or subsequent filtration or decantation, the separation can be carried out quantitatively, since the Zeoiithkristalle to high proportions in the size range of 5 to 30 microns and the low applied amounts of 1 to 2 g present per 1 1 of water.

In addition to the described removal of metaplate, a reduction in the degree of hardness of the applied water is achieved by an average of 20 ⁰ CiH in the inventive method, as well as the subsequent embodiments identify. Since the zeolite powders are free of organic substances, there is no risk of introducing organic substances into the treated water in the process according to the invention.

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Sine further combination of the method according to the invention with anionic exchange resins for the already known removal of, for example, humic acids is possible without complications, as well as a combination with other adsorbents such as Α-carbon or SiIikagel to remove any organic substances present.

Ausführunffsbeispiele:

The following examples of use are intended to illustrate but not limit the process according to the invention.

1. The starting material was 1 1 well water with. an iron content of 8.23 mg / l, 28.4 ° dH and p _H * 6.75 * 1.3 g of zeolite 4A powder (anhydrous) was added to this water and stirred at 295 K for 1 to 2 minutes. Thereafter, the zeolite was filtered off; the water obtained has a residual iron content of 0.15 mg / l, 13.2 ° dH and p _H = 7.3.

2. Well water of the composition mentioned below in Table 1, column 1 was treated as in Example 1, but in a departure therefrom with 1.3 g of zeolite powder of the 13X type. The parameters of the well water treated in this way are shown in column 2 of the same table.

Table 1

1 home water 2 treated

'; Water , .. '.'

Pb ⁺⁺ (mg / l) 3.7 0.69

P _H 7.7 7.8

Hardness ° dH 20.9 8

3. Source water of the starting quality as mentioned in column 1 of Table 2, treated with 1.3 g of zeolite powder of the type 4A as explained in Example 1, achieved the quality listed in column 2.

Table 2

1 Auagangswaaser 2 treated. _. water

Ca ⁺⁺ (mg / l) 1.0 0.37

P _H .. '. 7.6 · 8.4

Hardness ° dH. 21.7 5.2

4. Quality well water as listed in Table 3 column and treated as described in Example 1

with 1.3 g 13Xj, the parameters according to the column reached the same table. -,.,. ·

Table 3

, 1 Auagangswasser 2 treated water

3n ⁺⁺ (mg / l) 50 0.4

P _H 7,4. ·· 7,8

Hardness ° dH 21.2 8.4

Claims (1)

invention claim Process for the removal of metal ions from water for household or pleasure purposes or special chemical-technical-veische applications by treatment with crystalline zeolitic molecular sieve powders, preferably those of the zeolite type A, Y, F, mordenite, erionite and ZSM- and SiIikalit types, characterized in that the molecular sieve powder used has 80 % crystallite size of 2 to 30 μm, is brought into contact with the water to be treated with at least temporary movement or stirring, and the amount of molecular sieve powder used per liter of water is at least 0.2 g ·