RU2353588C2 - Method of sewage water purification from mercury compounds - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical industry and can be used in process of sewage water purification from mercury. In order to realise the method preparation of sorbent - Anionite "ВП-1АП" by modifying it with dichlorantin water suspension is carried out. Sewage water is alkalified, filtered, acidified and ion-exchanging sorption of mercury compounds is carried out by means of prepared sorbent Anionite "ВП-1АП" before being modified with dichloratin is preliminarily converted into chlorine-form by processing with 5% HCl solution. Water suspension with dichloratin is chosen with weight fraction of dichloratine 2%, sorbent processing with suspension being carried out for 5-6 hours. After ion-exchanging sorption of mercury and its compounds from sewage water, purified water is alkalified. Mercury-containing sludge after filtration and waste sorbent after sorption are sent to recycling. Processing of anionite with water suspension containing dichloratin is carried out ensuring foam-extinguishing and even distribution of dichloratin in suspension.

EFFECT: reduction of mercury concentration in purified water to values not exceeding hygienic norm with simultaneous increase of productivity and efficiency of purification from mercury both in ionic and in metallic form.

3 cl, 3 dwg

Description

The invention relates to the chemical industry and can be used in the process of purification of wastewater from mercury compounds.

A known method of treating industrial wastewater from metal ions, including heavy metals, with a sorbent based on crushed manganese nodules (see the description of the patent of the Russian Federation No. 2050973, IPC B01J 20/30, publ. 1995). However, this method does not provide for the purification of water from metallic mercury.

There is also a method of purifying mercury-containing wastewater by the action of sodium sulfide together with calcium chloride, followed by separation of the precipitate formed by sedimentation by acidification with hydrochloric acid to pH 9 (ed. St. USSR No. 343568, class C02F 1/00, publ. 1981). The method requires a long settling time, does not give a high degree of purification of water from mercury, since mercury sulfide is formed in the form of a hydrogel, poorly separated from the liquid. So, after 60 hours of settling, 0.33 mg / l of mercury remains in the waters.

A known method of purifying solutions from mercury by sorption it in the presence of chlorine on anion exchange resin, which is the product of the copolymerization of 2-methyl-5-vinylpyridine with divinylbenzene (see the description to the AS of the USSR No. 633821, class G02F 1/42, publ. 1976 g.).

However, this method is not effective enough for the extraction of mercury in both ionic and metallic form.

A known method of producing a sorbent for the extraction of mercury from solutions, including processing an anion exchange resin (anion exchange resin VP-1AP-alkylated copolymerization product of 2-methyl-5-vinylpyridine with divinylbenzene) modifying reagent - 1,3-dichloro-5,5-dimethylhydantoin (dichlorantin) in the presence of atmospheric oxygen. In this method, the air-dry anion exchange resin VP-1AP is placed in an airlift apparatus, the aqueous suspension with dichlorantin is added, and stirred with air for 7 hours. The solution was drained and the anion exchange resin washed with water. Then, the sorbent obtained in this way is poured into the column and wastewater is passed through it at a rate of 200 ml / h with a pH of about 3, containing 18 mg / L Hg ²⁺ and 5 mg / L Hg ⁰ . After passing 500 volumes of the solution through 1 volume of the sorbent, the concentration of mercury in the effluent is 0.0007 mg / L, in purified water - 0.001 mg / L (see the description of the patent of the Russian Federation No. 2026736, IPC ⁶ B01J 20/22, publ. 20.01 .1995 g.).

The known method is quite effective, but its performance is small.

In addition, according to the hygienic standard GN 2.1.5.1315-03 “Maximum permissible concentrations (MPC) of chemicals in the water of water bodies of domestic, drinking, and domestic water use”, the standard for maximum permissible concentration of mercury in industrial effluents is not more than 0, 0005 mg / l.

Also, according to clause 6 of GOST 17.1.3.13-86 “General requirements for the protection of surface water from pollution” “... discharge into the surface water of sewage causing pollution of water bodies” is not allowed.

The objective and technical result of the claimed invention is to reduce the concentration of mercury in the treated wastewater to values not exceeding the hygienic standard while increasing the productivity and efficiency of purification from mercury in both ionic and metallic forms.

The specified technical result is achieved by the fact that in the method of treating wastewater from mercury compounds using a VP-1AP sorbent anion exchange resin, which includes preparing the sorbent by modifying it with an aqueous suspension of dichlorantin, alkalizing the wastewater, filtering them, acidifying, ion-exchanging sorption of mercury and its compounds from wastewater water with the help of a prepared sorbent, anionite VP-1AP before it is modified with dichlorantin is preliminarily converted to chlorine form by treatment with a 5% HCl solution, while the aqueous suspension with dichlorantino m is selected with a mass fraction of dichlorantin of 2%, and the sorbent is treated with a suspension for 5-6 hours, and after ion-exchange sorption of mercury and its compounds from wastewater, the purified water is made alkaline.

In addition, the mercury-containing sludge after filtration and the spent sorbent after sorption are sent for processing.

In addition, the treatment of the anion exchange resin with an aqueous suspension with dichlorantin is carried out to ensure defoaming and uniform distribution of dichlorantin in the suspension.

The claimed method is illustrated by graphical materials, in which Fig. 1 shows a diagram of the data of experiments obtained by passing wastewater in parallel with a mass concentration of 17 mg / dm ³ Hg ²⁺ and 6 mg / dm ³ Hg ⁰ at pH3 through columns filled with anion exchange resin in chlorine -form and anionite VP-1AP in chlorine form, modified with dichlorantin, FIG. 2 shows a flow chart of a wastewater treatment from mercury compounds, FIG. 3 is a flow chart of a wastewater treatment equipment.

The claimed method is implemented as follows and includes the following stages:

- pre-absorption treatment of ion exchange resins;

- adjustment of the pH value of wastewater;

- ion exchange sorption of mercury;

- alkalization of wastewater;

- neutralization and dechlorination of the spent dichlorant solution.

At the first stage, alkalization of wastewater pH (10 ± 0.5) is carried out to isolate mercury in the form of hydroxide. The following transformations occur:

Fe ³⁺ + 3OH Fe (OH) ₃ Cr ³⁺ + 3OH Cr (OH) ₃ Hg ²⁺ + 3OH Hg (OH) ₂

(Fe ³⁺ and Cr ³⁺ - ions contained in waste water).

Further, the wastewater goes through the stages of sludge and filtration, in which mercury is partially separated in metallic form and in the form of hydroxide. The concentration of mercury in wastewater is reduced to 1 mg / DM ³ .

Then the wastewater is acidified to a pH of 3 ± 0.5, which is optimal for ion-exchange absorption of mercury by VP-IAP anion exchange resin.

NaOH + HCl NaCl + H ₂ O

At the stage of ion-exchange sorption, mercury is absorbed by the VP-IAP anion exchanger in the Cl form modified with dichlorantin.

RCl + HgCl ₂ RHgCl ₃ RCl R ¹ N ₂ Cl + Hg ° RCl R ¹ N ₂ HgCl RCl R ¹ N ₂ Cl + HgCl ₂ RHgCl ₃ RN ₂ Cl

At the stage of alkalization of wastewater, hydrochloric acid is neutralized:

HCl + NaOH NaCl + H ₂ O

The absorption treatment of anion exchange resin consists in its processing with a 5% HCl solution for conversion to the Cl form:

RSO ₄ + HCl RCl + H ₂ SO ₄

and then in the processing of a suspension with a mass fraction of dichlorantin of 2%, during which the following reaction occurs:

2RCl + 2R ¹ N ₂ Cl ₂ + H ₂ O 2RClR ¹ N ₂ Cl + HClO + HCl

To bind the active chlorine resulting from the reaction and neutralize the acid, sodium sulfite and alkali are added to the solution. In this case, the reactions proceed:

HCl + NaOH NaCl + H ₂ O H ₂ SO ₄ + 2NaOH Na ₂ SO ₄ + 2H ₂ O HCl + Na ₂ SO ₃ Na ₂ SO ₄ + HCl

Modified by dichlorantin VP-IAP anion exchange resin, previously converted to the chlorine form, is capable of absorbing mercury present in wastewater at any oxidation state.

Upon sorption of metallic or monovalent mercury, it first oxidizes to divalent mercury and then is absorbed due to complexation with counterions of the VP-IAP anionite. This makes it possible to achieve effective sorption of mercury from solutions (waste water) without its preliminary oxidation.

The experimental data shown in the diagram (Fig. 1) show that the sorbent VP-IAP preliminarily exceeds the sorbent VP-IAP in chlorine form by the degree of effective treatment of wastewater from mercury compounds modified with dichlorantin.

This is due to the fact that as a result of the interaction of VP-IAP anion exchange resin with an aqueous suspension of dichlorantin, the monochlorantin radical is chemisorbed by anion exchange resin, due to which the latter acquires oxidizing properties.

The use of VP-IAP anion exchanger converted to chlorine form and modified with dichlorantin allows one to achieve deep wastewater treatment even of metallic mercury without its preliminary oxidation, which is not achieved using unmodified VP-IAP anion exchanger in chlorine form or modified VP-anion exchanger IAP dichlorantin.

To describe an example of the method and the operation of the technological scheme of production, we will ask some parameters necessary for further calculation and description of the method.

The volume of wastewater requiring treatment is 42 m ³ / h or 382.5 thousand m ³ / year.

The mercury content before treatment is 5 mg / l; after purification, the mercury content in wastewater should not exceed 0,0005 mg / l (standard value for MPC).

Mercury-containing wastewater enters the reactors 1 (installed in cascade for sequential operation) to alkalize to pH (10 ± 0.5) with sodium hydroxide solution from pressure gauge 2 through feeders.

A sodium hydroxide solution with a mass fraction of NaOH of 10% is prepared in vessel 3 using a pump from a solution of sodium hydroxide with a mass fraction of NaOH of 44% and wastewater purified from mercury. By the same pump, the prepared sodium hydroxide solution is fed into the pressure gauge 2.

Alkaline wastewater is discharged into a clarifier 4.

The suspension from collectors clarifiers 4 is periodically poured into a container with mixers 5.

With a pump, the suspension is fed for filtering into cartridge filters 6, where the wastewater is further purified from mercury and hydrate compounds. Two filters can be installed (one in filtering mode, the other in accumulation mode).

Sludge from the filters 6 is discharged directly into the container 7. The container 7 is installed in a special cabinet 8, equipped with a local suction. The gases are sent to the ventilation system.

Sludge with a mass fraction of mercury of at least 0.5% in containers 7 is sent for thermal regeneration to the mercury plant.

The clarified part from the clarifier collectors 4 is poured into the intermediate collector 9, from where it is sent by a pump to the filter 10 for filtering.

The filtrate is sent to the reactor 11 for a two-stage acidification to pH (3 ± 0.5) with a solution of hydrochloric acid with a mass fraction of HCl of 5%.

The ion exchange resin (VP-1AP anion exchange resin) is subjected to special treatment in a regeneration column 13 before being loaded into adsorbers 12.

The manufacturer supplies the VP-1AP resin in the HSO ₄ form. Therefore, before loading it into adsorbers 12, it is treated with a solution of hydrochloric acid in order to convert it to the chlorine form in the regeneration column 13. The purified water is collected in a collector 14, sent for further treatment to a second adsorber (not shown) to a mercury content of 0.0005 mg / l

After purification, the purified water is made basic in the reactor 15.

Purified to a mass concentration of mercury of 0.005 mg / L, wastewater with a pH of (9.4 ± 0.5) is discharged into a collection tank and pumped to a post-treatment unit to a mass concentration of 0.0005 mg / L.

The anion exchange resin is prepared in the regeneration column 11, where the resin is poured and the calculated volume of hydrochloric acid with a mass fraction of HCl of 5% is poured. The resin is treated with hydrochloric acid for two hours with stirring.

In the same column, the resin is treated with dichlorantin. For this, the calculated mass of dichlorantin and the calculated volume of water are poured into the column (mass fraction of DCA in the suspension should be 2%). Turn on the air supply and with stirring the resin is treated with dichlorantin for five hours. Then the air supply is turned off and the spent regeneration solution with a mass concentration of active chlorine up to 5 g / dm ^{3 is} poured into the reactor.

The resin thus prepared is washed twice with pure water with stirring for 15-30 minutes (T: W = 1: 5). Wash water is drained into the reactor.

As the mercury is saturated, the spent (saturated with mercury up to 20 mg per 1 g of air-dry resin) from adsorber 12 by hydraulic transport, the resin is discharged through a cut-off chamber into a container 7 and sent to a mercury plant for regeneration.

A fresh portion of the resin is loaded into the adsorber hopper from the regeneration column 13 by hydraulic transport.

The claimed method allows to obtain the mercury content in wastewater at an initial value of 5 mg / l after purification of 0.005 mg / l, with after-treatment, 0.0005 mg / l.

Dichlorantin (1,3-dichloro-5,5-dimethylhydantoin) according to TU-U 6-04689381.01-98 is used as an active ingredient in the preparation of disinfectants, as well as a disinfectant for:

- disinfection of water in swimming pools;

- sanitization of technological equipment;

- disinfection of premises.

(It is made at JSC Plant Orgsintez Oka, Russia).

Thus, the claimed invention, due to the fame of the processes and substances used therein, up to the priority date satisfies the patentability condition “industrial applicability”.

Claims (3)

1. A method of treating wastewater from mercury compounds using a VP-1AP sorbent-anion exchanger, including preparing the sorbent by modifying it with an aqueous suspension of dichlorantin, alkalizing the wastewater, filtering them, acidifying, ion-exchanging sorption of mercury and its compounds from wastewater using a prepared sorbent, characterized in that the VP-1AP anion exchange resin is preliminarily converted into the chlorine form by treatment with a 5% HCl solution before being modified with dichlorantin, and the aqueous suspension with dichlorantin is selected with a mass fraction of dichlo Rantin is 2%, and the sorbent is treated with a suspension for 5-6 hours, and after ion-exchange sorption of mercury and its compounds from wastewater, the purified water is alkalinized. 2. The method according to claim 1, characterized in that the mercury-containing sludge after filtering and the spent sorbent after sorption is sent for processing. 3. The method according to claim 1, characterized in that the treatment of the anion exchange resin with an aqueous suspension with dichlorantin is performed to ensure defoaming and uniform distribution of dichlorantin in the suspension.

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