DD158025A1 - METHOD FOR THE CLEANING OF ANIONIC WATER-SOLUBLE DYES CONTAINING WASTEWATER - Google Patents

Abstract

The invention relates to a method for the treatment of gefaerbtem wastewater. The object of the invention is the replacement of hydrolyzable salts of iron and aluminum, which are used for the removal of dyes in wastewater treatment, by cheap waste products and domestic raw materials. The task was to realize this goal without significant additional effort. It has been found that Mg (OH) 2, in combination with swelling three-layer minerals (such as montmorillonite), can effectively remove anionic dyes by precipitation and adsorption processes. Two variants of the Mg (OH) deep 2 production are indicated. The two possibilities differ in that in variant a, a high loading of the adsorbent is desired, while in variant b, the removal of the loaded adsorbent from the wastewater is paramount. The addition of the clay mineral components is required, on the one hand, to improve the sedimentation and sludge properties of Mg (OH) 2 and, on the other hand, to increase the loading of the adsorbent.

Description

Title of the invention

Process for the purification of waste water containing anionic water-soluble dyes

Application area of the invention

The invention relates to a process for the treatment of colored waste water.

Characteristic of the known te chnic solutions

It is known that organic dyestuffs in wastewaters can be removed mainly by addition of hydrolyzing flocculants, in particular salts of iron and aluminum (ferrous sulphate, ferric chloride, aluminum sulphate) (Rüb ^ F, Technique industrial wastewater treatment, Mainz 1974, p. 328, BRD-OS 1 517 709).

Described are also methods of adsorption with various types of activated carbon, Oxy dationsverfahren with bleaching solution (technical hypochlorite solution) (Randolf, R.: Sewerage and wastewater treatment, VEB Verlag für Bauwesen Berlin 1970, p 431), ion exchange process, extraction process with various organic solvents (Swiss chard, K.-Hj Kaeding, J., - Lorenz, K., Schuster, H .: wastewater treatment, VEB German publishing house for basic industry Leipzig 1973, P. 189) as well as' thermal and biological water treatment methods (author collective, waste water purification process of the material-converting industry, VEB German · Publisher for basic industry, Leipzig 1976, S, 61).

Hachteile the above methods are the high Ohemikalienkosten and often considerable technical and energy costs. In the case of the conventional inorganic flocculants, the degree of decolorization is sometimes only slight. These substances are substantially useful only for the removal in water of dispersed or suspended coloring substances or water-insoluble dyes. The process with hydrolyzing metal salt flocculants is also very pH dependent. The optimum pH value is difficult to adjust due to the constant fluctuations in the quality and quantity of the wastewater.

Methods are also described in which organic polymers (eg polyacrylamide) are used (BRD-AS 2 503 1β9ί BRD-AS 2 321 509). The polymers are used either alone or in combination with inorganic flocculants (BRD-AS 2 428 928). However, like the inorganic flocculants, such organic flocculants are predominantly used for the removal of water-insoluble dyes, but not for water-soluble coloring substances.

Goal of. invention

The object of the invention is to replace the known inorganic flocculants (iron and aluminum salts) for organic dyes with low-cost, readily available waste products or domestic raw materials. The method should also be easy to handle and require only minimal expenses. , ,

Presentation _ι ctes nature of Erf indung

The object of the invention is to develop a process by means of which anionic water-soluble dyes, such as acid dyes, reactive dyes and direct dyes, can be eliminated by suitable substances which are readily available and which are available to a sufficient extent.

According to the invention, the object is achieved by using magnesium hydroxide as the adsorbent. In the processing of carnallitic crude salts, a high magnesium chloride-containing final solution is readily formed from the magnesium hydroxide (Mg (OH) p) by precipitation with an alkaline component (eg calcium hydroxide) can be prepared · Mg (OH) p has good adsorption and flocculation properties and is therefore of interest for this task · A clay mineral (bentonite) was used to improve the sedimentation and sludge properties of Mg (OH) ₂ · bentonite contains montmorillonite as its main constituent, a swellable three-layer mineral · 'The use of this adsorbent combination of Mg (OH) ρ and a swellable three-layer mineral is advantageous because the swellable three-layer mineral also has adsorption and ion exchange properties and thus can make a significant contribution to the elimination of dyes ·

Exe ction s ρ i e1

The invention will be explained in more detail in the following examples.

The wastewater sample to be treated contained 50 mg / l of a water-soluble anionic azo dye. The following hydrodynamic conditions were selected for the experiment:

- mixed phase:

After addition of the chemicals, the dosing conditions of which are described below, the wastewater

- 1

sample stirred for 10 seconds at a stirrer speed ** for 100 minutes,

- Adsorption phase: '.. ·'

The wastewater sample was subsequently moved at a reduced stirring speed (40 min). The adsorption phase is ended after about 10 x 15 min.

After the conclusion of the adsorption phase, the separation of the dye precipitates can be carried out by known processes, such as, for example, sedimentation or filtration.

To 1 liter of the waste water sample, the clay mineral (50 mg) (bentonite "K") was added first. " The effectiveness of the Tonminera component depends essentially on the swelling state of the clay. Therefore, a swelling time of 24 hours must be maintained to produce the clay mineral suspension (5 g / l) to be dosed. After addition of the clay mineral, the dosage or precipitation of the magnesium hydroxide is carried out according to the variants listed below.

It is known that the properties of Mg (OH) _{2 are} essentially determined by its precipitation conditions. The following two variants of Mg (OH) "precipitation were tested:

Use of pre-precipitated Mg (OH) ₂ (external precipitation)

50 mg Mg / Γ was converted to Mg (OH) ₂ by adding the stoichiometric amounts of hydroxide ions. The MgCl ₀ corresponds stock solution (use of MgCl · β ₀ H ₀ O)

ά ρ, d C.

kept 10 mg Mg / ml * For complete precipitation of the hydroxide, it is necessary to add an excess of 2.5 mmol OH ~ / 1 * As the alkaline component was used for accurate pH adjustment sodium hydroxide · With calcium hydroxide, which in the technical Realization should be used, the same results were achieved as with sodium hydroxide.

The thus-prepared Mg (OH) ₀ s was stirred before addition to the wastewater sample 30 »

y ^ ariante b: Use of Mg (OH) _o - _s in the Presence of

(Internal precipitation) In the wastewater sample, which already contains the clay mineral component, the alkaline component (stoichiometric

trical amount Hydroxididnen + excess of hydroxide ions as' added in variant a. Thereafter, the under variant a

ρ ·

metered amount of Mg ions.

The cleaning performance of the adsorbent combination of Mg (OH) ₂ clay mineral is demonstrated on the following two dyes (see Table 1). .

Table 1: Cleaning performance of the adsorbent combination Mg (OH) ρ - clay mineral

Discoloration {%) loading ¹ ^ (%)

^ _{i juj} Dye 1 -Fa rbstoff_2 Dye 1 Dye qff_g_

Variation a 84.0 97.8 24.7 28.8

Variant b 44.5 78.4 13.0 23.1

• The loading refers to solid Mg (OH) ₂ + clay mineral

Dye 1: Solamine light orange 2 GL Dye 2: Solaminlichtblau B 2 R

From Table 1 it can be seen that with pre-precipitated Mg (0H) p (external precipitation) a much higher decolorization or loading of the adsorbent was achieved than with "internally precipitated hydroxide"

For the use of the adsorbent combination Mg (OH) ₂ - clay mineral in the wastewater treatment, a high sedimentation rate of the flakes formed and a low sludge build-up is essential «Table 2 gives the values for the two listed variants«

Table 2J ₁ Average sedimentation velocity and final sediment volume of the adsorbent combination Mg (OH) ₂ clay mineral

mean sedimentation end sediment velocity volume (cm / min) · .. ^ _j (/

Variant a 1.0 9.5

Variant b 2,15. 14.5

From Table 2 it can be seen that in variant a, a very small sediment volume is achieved, but the average sedimentation is relatively low »Variant b, however, has a higher sedimentation speed auf5 but with a larger amount of sludge ·

Claims (4)

Srfindungsanspruch 1. A process for the removal of water-soluble anionic dyes, characterized in that magnesium hydroxide is used in combination with clay minerals. 2 * Process according to item 1, characterized in that on the one hand pre-precipitated Mg (OH) ₂ or, on the other hand, a Mg (OH) ₂ formed in the wastewater to be purified is used « 3 * Method according to item 1, characterized in that the magnesium cilorid-containing final solution from the processing of carnallitic crude salts is used as precipitant or * adsorbent for Mg (OH) "production" 'o 4 »Method according to • kt · 1, characterized in that swellable three-layer minerals are used as the clay mineral components *.