SU1738758A1 - Ion-exchange method of cleaning sewage from nickel - Google Patents

Abstract

The invention relates to a method of ion-exchange wastewater treatment from nickel, in particular, cleaning the washing waters of the nickel-plating process, in engineering, metallurgical, electrical, electronic and other enterprises of the industry with the return of purified water and for creating local systems of waste-free technology and allows reduce the cost and speed up the cleaning process, as well as reduce the number of ion-exchangers and reagents used. The method of ion-exchanging wastewater from nickel is carried out by passing water through ion-exchange sorbents with their subsequent regeneration, while a mixture of weakly acidic cation exchanger in hydrogen form and strongly basic anion exchanger in hydroxyl form with ratio 1: 1 is used as ion exchange sorbents. Before regeneration, the mixture of ion exchangers is separated by supplying water in countercurrent at a speed of 3.9 V 1.1 cm / s and is regenerated separately. 3 tab. (Ls

Description

The invention relates to a method for purifying wastewater from nickel, in particular, to ion-exchange methods for purifying wastewater from the process of nickel plating and recycling water supply, can be used for engineering, metallurgical, electrical, electronic and other industries with the return of treated water for creation of local systems of waste-free technology.

There are several methods for treating nickel-containing wastewater: reagent, biological, sorption, and others. It is most expedient to use an ion exchange method for cleaning waste water and extracting nickel in order to return it to the production process.

The essence of the known methods of cleaning wastewater from nickel using ion exchangers consists in passing them through a layer of cation exchanger followed by desorption of nickel with an acid solution.

The closest to the proposed technical essence and the achieved result is a method for extracting nickel from wastewater, including the sequential passage of water through two columns: the first with a weakly acidic cationic KB-4 in sodium form; the second — a mixed action filter — is loaded with a mixture of a strongly acidic cation exchanger KU-2 in

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hydrogen form and strongly basic anionite AB-17 in hydroxyl form.

The disadvantage of this method is the use of weak acid cation in sodium form, which is associated with the additional treatment of the sorbent with sodium hydroxide after its regeneration with acid in order to extract nickel. This increases the cost of the process due to the additional technological operation on the first column (conversion of the ion exchanger into the salt form after acid regeneration) and the additional consumption of expensive sodium hydroxide reagent. In addition, with such a scheme, an equivalent amount of sodium is extracted from the first column of the cation exchanger in the purified water during extraction of nickel, which, in addition to the anion exchanger, must additionally provide for the addition of a strongly acidic cation exchanger or filter of mixed action (FSD).

The aim of the invention is to reduce the cost of the process by eliminating the stage of converting a weakly acidic cation exchanger to the sodium form, reducing the number of ion exchangers and reagents used, reducing the number of filters (ion exchange columns) and cleaning time.

In the process of sewage treatment, nickel extraction and recycling water supply, a mixture of weak acid cation exchanger in the hydrogen form and a strongly basic anion exchanger in the hydroxyl form are used as the sorbent material. Before regeneration, the mixture of ion exchangers is separated by supplying water in countercurrent at a rate of 3.9 - V 1.1 cm / s and is regenerated separately. The proposed method makes it possible to refuse the transfer of the hydrogen form of a weakly acidic cation exchanger to a salt form and to eliminate the column with a strongly acidic cation exchanger for sorption of the released sodium and other monovalent cations. The use of the known method only allows the extraction of nickel from wastewater, in which sodium ion in equivalent quality enters, the accumulation of which makes it difficult to reuse nickel-free wastewater.

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Example. A column with a cross section of 1.0 cm is loaded with a mixture of cation exchanger KB-4 in hydrogen form and anion exchanger AB-17 in hydroxyl form at a ratio of 1: 1 over the exchange capacity with a uniform distribution of both ionites across the height of the layer (3 cm). 1000 ml is passed through the column.

a solution containing 100 mg Ni / l at a rate of 0.3 bpm./min. Sorbents are separated from the bottom with a linear velocity of 5–10 cm / s, the AB-17 anion exchange resin floats up, and the KB-4 cation exchanger spent on nickel remains at the bottom of the column. The KB-4 cation exchanger is regenerated with a 0.5N solution of sulfuric (or hydrochloric) acid, and the separated anion exchanger is regenerated with a 0.5N solution of sodium hydroxide. After regeneration, the sorbents are mixed and reused for water purification,

In tab. Figure 1 shows the results of purification of wash water from nickel at different degrees of purification (one and two orders) on weak acid cation exchanger used in various variants, at a solution passing rate of 60 ml / h, nickel concentration 100 mg / l, sorbent bed height 3.0 cm, column diameter 1.0 cm

From tab. 1 it follows that when using a mixture of weak acid cation exchanger in the hydrogen form and a strongly basic anion exchanger in the hydroxyl form, the volume of purified water increases by 100 times compared to using only the hydrogen form of the cation exchanger and more than doubled when using the sodium form of the cation exchanger under other equal conditions x experiment.

From tab. 1 that the effect is achieved by reducing the smearing of the equilibrium nickel front as it moves along the mixed layer of sorbents.

In tab. Figure 2 shows data on the degree of nickel extraction at different ratios of a weakly acid cation exchanger and a strongly basic anion exchanger in the mixture.

From tab. 2 it follows that the ratio of ion exchangers in exchange capacity 1: 1 is optimal, since it ensures the equivalence of exchange. With less than 1: 1, the amount taken in the mixture of anion exchange resin, nickel ion slip into the filtrate is observed: at a ratio of 1: 0.5 C / Co 0.16, at a ratio of 1: 0.75 C / Co 0.03 due to that the capacity of a weak acid cation exchanger is not fully utilized.

At more than 1: 1 amount taken in a mixture of an anion in the column, precipitation of nickel hydroxide is observed. At the same time, the volume of water purified from nickel increases, but the hydrodynamics of the process deteriorates significantly, the ion exchanger layer becomes clogged with nickel hydroxide, and the filtration rate slows down.

After processing the mixed layer of sorbents, they are separated by supplying water

countercurrent with a linear velocity of 3.9 to 1.1 cm / s.

In tab. 3, the rationale for the water supply rate for separation of a mixture of ion exchangers before regeneration is provided.

Separated ion exchangers are regenerated separately: cation exchanger - 0.5 N. sulfuric or hydrochloric acid solutions; anion exchanger — 0.5N sodium hydroxide solution (this method of regeneration is used in ion exchange processes).

Thus, the proposed method by using a mixture of a weak acid cation exchanger in hydrogen form and a strongly basic anion exchanger in hydroxyl form and a special technique for separating the spent ion exchanger mixture before regeneration allows the wastewater to be cleaned of nickel to the required concentration and returned to the wash bath, as well as nickel recovery in the form of a concentrated solution and using it to adjust the nickel baths.

The method makes it possible to exclude the transfer of a weakly acid cation exchanger to the sodium form after acid regeneration; use additionally strong acid

cation exchanger for sodium extraction, thus reducing the cost of wastewater treatment and speeding it up by reducing the number of operations.

Techno-economic advantage of the proposed method is to reduce technological operations and obtaining a larger volume of purified to the necessary degree of water.

Claims (1)

Invention Formula The method of ion exchange wastewater treatment from nickel by passing water through ion exchange sorbents with their subsequent regeneration, characterized in that, in order to reduce the cost and speed up cleaning, reduce the amount of ion exchangers and reagents, a mixture of weakly acidic cation exchanger in hydrogen form is used as ion exchange sorbents and strong base anion exchanger in hydroxyl form at a ratio of 1: 1 for exchange capacity, while before regeneration 5, the ionite mixture is separated by feeding water in countercurrent at a speed of 3.9 - V 1.1 cm / s and is regenerated separately. Table 1 Form of weak acid cation exchanger The volume of water purified from nickel, ml. with C / Co 0.1 0.01 Hydrogen cation exchanger 1.2 ml mixed with inert styrene copolymer and DVB 1.8 ml 1.2 ml cation exchanger in sodium form mixed with inert copolymer of styrene and DVB 1.8 ml Cationite 1/2 ml in the hydrogen form in a mixture with strongly basic anioiite in the hydroxyl form 1.8 ml; ratio of exchange capacity 1: 1 0.1 0.01 11.0 3.6 270.0 160.0 410.0 360,0 Water flow rate, cm / s , one,, 3, 1 1, 4, 4 table 2 Table 3 Behavior of ionites Layer is motionless separation of components The separation of a layer of ionites to cation exchanger in nickel form (at the bottom of the column) and anion exchanger in sulphate form (top of column) Anion exchange ash is observed with a stream of water. Ablation of anion exchanger and cation exchanger