RU2261757C1 - Method of production of granulated inorganic sorbents on base of oxyhydrates of metals - Google Patents

Abstract

FIELD: methods of production of granulated inorganic sorbents on base of oxyhydrates of metals, mainly trivalent and tetravalent used in metallurgy and chemical industry; treatment of sewage and decontamination of solutions.

SUBSTANCE: proposed method includes precipitation of oxyhydrates of metals, filtration, washing and granulation of sediment; sediment is divided into two parts: larger part is subjected to treatment with sodium chloride solution at concentration of 250-300 g/dm³ NaCl; then sediment is dried and repulped at liquid-to-solid ratio =(5-10): 1; suspension is settled, filtered and washed with water; then it is repeatedly dried; after mixing the remaining moist part of sediment, paste is granulated by extrusion.

EFFECT: increased dynamic capacity of sorbents to "jump" of radio-nuclides into filtrate.

Description

The present invention relates to the field of hydrometallurgy, in particular, to non-ferrous, rare, dispersed and radioactive metals used in metallurgy methods for producing granular inorganic sorbents based on metal oxyhydrates, mainly III-IV valence, used at enterprises of the metallurgical industry for the treatment and neutralization of toxic wastewater metals, for the decontamination of solutions from natural radionuclides, for the selective extraction of waste technological solutions once personal metal ions. The present invention can also be used in the field of technology of inorganic substances, for the processing and disposal of polymetallic waste with obtaining granulated sorbents for various purposes on their basis.

Known (A.S. USSR No. 686168 according to the application No. 2602590 / 23-26 with priority from 04/10/1978, M. cl. B 0 J 1/22; Publish. 04/10/1999; BI, No. 10, p. 512 , 1999) "A method for producing inorganic sorbents based on metal oxyhydrates."

A known method is as follows.

Sublimates of salt titanium chlorinators containing iron, titanium, zirconium, aluminum and other chlorides are dissolved in water or in a solution of hydrochloric acid. The insoluble residue is separated from the solution. The resulting solution is diluted to an iron concentration of 5-50 g / dm ³ . The operations of oxidation and deposition of metal hydroxides are combined. For this, the solution after dilution is brought into contact with continuous stirring with an alkaline solution of sodium hypochlorite with an alkali concentration in the solution of 30-120 g / dm ³ . Then the precipitate of metal hydroxides - the hydrogel is separated from the solution, washed from excess salts (in particular, NaCl) by sequential treatment with reverse washing solutions (i.e., washes from the previous portion of the hydrogel) and water. Washing is carried out to a residual concentration of chlorides in the wastes of 0.5-5.0 g / dm ³ . The washed precipitate is washed on the filter from the mother liquor and sent to granulation. Granulation is carried out by the method of "thermal hardening" - decription. For this, the precipitate of metal oxyhydrates is dried at a temperature of 100-120 ° C for 20-40 hours. The dried hot (100-120 ° C) precipitate is brought into contact with cold (15-25 ° C) water.

The sorbent thus granulated is separated from the solution and again dried in air to constant weight (within 10-50 hours). The resulting sorbents are irregular-shaped grains with a size of 0.1-2 mm. Humidity of the sorbent is 8-9%. The chemical composition of the sorbents according to the main components, wt.%: Iron 10-20, aluminum 2-5, manganese 0.5-2, titanium 0.1-10, zirconium 2-10. Loss on ignition 20-30%.

This method provides the neutralization and disposal of polymetallic production wastes with the receipt of marketable products - granular inorganic sorbents based on metal oxyhydrates (Fe, Al, Ti, Zr, etc.). The disadvantage of this method is unsatisfactory sorption characteristics, operational and consumer properties, which in turn is associated with the formation in the granulation process by the method of "thermal hardening" - decription of granules of irregular shape, polydisperse composition: from 0.1 to 2 mm

Of the known analogues, the closest in technical essence and the achieved result is the known method (A.S. USSR No. 1150024 according to application No. 3627433 / 23-26 with priority from 07.26.1983; B 01 J 20/06; Registration. 04.15.1985 , Bull. No. 14) "A method of producing a granular sorbent based on titanium hydroxide" - adopted as a prototype.

The prototype method is as follows.

Hydroxide - titanium oxyhydrate obtained by hydrolysis of aqueous solutions of titanium salts in the presence of alkali, for example, titanium cake of the process of obtaining vanadium pentoxide from industrial oxytrichloride, is used as the basis for the sorbent. At the first stage, the precipitate of titanium hydroxide-oxyhydrate of titanium (titanium cake) obtained after thickening on a suction filter is repulped in a solution of sodium hydroxide with a concentration of 0.1-0.2 N. at W: T = 8: 12 (stirring 0.5-1.0 h), dehydrated on the filter and re-pulp in a solution of mineral acid (H ₂ SO ₄ , HCl or HNO ₃ ) at an equilibrium value of the suspension pH equal to 2 ÷ 4 W: T = 8 ÷ 12. After stirring the suspension for 1-2 hours, the precipitate is separated from the solution. Then, a precipitate is prepared for granulation by a known extrusion method. First, a retur and a mixture for molding the granules are prepared. To prepare a retura, 50-60 wt.% Wet titanium hydroxide precipitate is dried at 120-140 ° C until the moisture content in the material is 10-15 wt.% And crushed to a size of less than 0.1 mm. Then, the retur with the remaining wet cake is mixed in the mixing reactor until a homogeneous mixture with a moisture content of 37-45 wt.% Is obtained. The prepared mixture is served on the formation of granules. Formation and drying of granules is carried out on a roll granulator, combined with a fluidized bed dryer. Granulation is carried out with a molding force of 5-8 kg / cm ² , a temperature in the fluidized bed zone of 120-140 ° C, a drying time of 0.5-1.0 hours. The dried granular material is placed in baking sheets in a calcining furnace, where it is kept at 150- 180 ° C for 4-6 hours. The calcined material is a finished sorbent product for the absorption of arsenic.

The prototype method provides sorbents with high mechanical strength and physico-chemical stability in multi-cycle processes for the extraction of arsenic.

The disadvantage of the prototype method is unsatisfactory sorption and operational characteristics in the processing of radioactive chloride solutions, in particular in the decontamination and purification of chloride solutions and wastewater from natural radionuclides - decay products of thorium and / or uranium.

The task of the invention is to increase the operational characteristics of sorbents in the processing of radioactive chloride solutions containing natural radionuclides.

The technical result that can be obtained by implementing the invention is to increase the dynamic capacity to the “slip” of radionuclides in the filtrate.

The problem is solved with the achievement of the above technical result by the proposed method for producing granular inorganic sorbents based on metal oxyhydrates, including the deposition of metal oxyhydrates, filtering the pulp, washing the oxyhydrate precipitate and granulating it.

The difference between the proposed method and the known one is that the oxyhydrate precipitate is divided into two parts in a proportion of 10-20% and 80-90%, with 80-90% of the precipitate being treated with a solution of sodium chloride with a concentration of 250-300 g / dm ³ NaCl, then they are dried, repulped at W: T = (5 ÷ 10): 1, the suspension is defended, filtered, washed with water, re-dried, and after mixing with the remaining wet part of the precipitate, the paste is granulated by extrusion.

It has been experimentally established that the combination of the above distinguishing features of the claimed invention is necessary and sufficient to achieve a technical result according to the invention, which consists in increasing the dynamic capacity of sorbents to “leak” of radionuclides into the filtrate, and improving the operational properties of the obtained sorbents. Those. between the features of the claimed invention and the achieved technical result there is a well-defined cause-and-effect relationship, not explicitly following from the existing level of technology.

It was experimentally established that preliminary washing of an 80-90% oxyhydrate precipitate with a solution of sodium chloride with a concentration of 250-300 g / dm ³ and its subsequent drying at 80-120 ° C lead, ceteris paribus, to obtain almost uniform monodisperse particles - primary granules metal oxyhydrates, very convenient for carrying out the following operations according to the claimed invention: repulpation, washing (washing from NaCl), drying and granulation by extrusion - subject to preliminary mixing of 80-90% of the dried precipitate with 10-20% moisture oxyhydrate sediment - a hydrogel, which in this case plays the role of a binder (not inert) material.

The diameter of the holes (dies) during the extrusion and granulation of a pasty oxyhydrate mixture (2 or 3 or 4 or 5 mm) and the heating temperature of the paste during extrusion (80 ÷ 120 ° C) are selected according to the proposed method, depending on the conditions of the subsequent operation, one-time sorbent loading into the column, the required filtration rate of the initial working solutions through the column, etc.

An analysis of the book, journal and patent literature indicates that the proposed invention — a new sequence of actions (operations) and their modes previously — is not described in known sources of information, and the technical result achieved in this way does not explicitly follow for specialists from the previously described methods for obtaining granular inorganic sorbents based on metal oxyhydrates.

Information confirming the possibility of practical implementation of the claimed method with the achievement of the above technical result is shown in the example.

Example

As raw materials for the production of granular sorbents based on valence metal oxyhydrates III-IV, various non-utilizable polymetallic production wastes were used:

- waste products of titanium tetrachloride production: spent melts and sublimates of titanium chlorinators;

- spent pickling solutions, for example, tube production;

- waste generated during the processing of zircon concentrates, titanomagnetites (tailings of wet magnetic separation);

- red helmets of aluminum production;

- Waste from the integrated processing of slag from ferro-tungsten production, etc.

The main components of this waste were iron, chromium, manganese, titanium, zirconium (hafnium), aluminum, and others. The vast majority of metallurgical waste contained a small amount of thorium and its decay products.

To obtain the initial (working) solution, the above production wastes and intermediate products from their processing were leached (dissolved) in water, circulating washing solutions and / or solutions of mineral acids, after which the resulting solutions were deactivated by coprecipitation of thorium, radium, etc., with various sorbents collectors, mainly with precipitation of barium sulfate and iron oxysulfate. Insoluble residues and collectors with sorbed radionuclides were separated from the solution, which was directly used to obtain granular inorganic sorbents based on metal oxyhydrates.

For this, a solution of sodium hydroxide (20-120 g / dm ³ ) was precipitated from the solution with the sum of metal oxyhydrates (Fe, Al, Ti, Zr, etc.) mainly at pH 7 ± 2; the pulp was filtered on a vacuum suction filter. A wet precipitate of metal oxyhydrates (humidity 60-80%) was divided into 2 parts: 10-20% of the precipitate was washed with water, washed from the mother liquor and left for the subsequent operation of granulation of sorbents by extrusion; 80-90% of the precipitate was washed on the filter with a NaCl solution with a concentration of 250-300 g / dm ³ in the amount of 2-3 volumes of solution per 1 volume of wet sediment. Washed with a saline solution (almost saturated with NaCl), a wet (65 ± 5%) precipitate of metal oxyhydrates was dried in a vacuum oven at 100 ± 10 ° C for 4 ± 2 hours. In this case, the formation of a certain oxyhydrate structure [MeO-OH] precipitate agglomeration and sintering of the particles of the precipitate was not observed.

Apparently, the presence of a salt background - a very concentrated (250-300 g / dm ³ ) NaCl solution in the composition of the mother liquor, the amount of which (≈65%) is almost 2 times the intrinsic weight of the oxyhydrate precipitate (≈35%) by some in a way (until it is not completely clear how) it affects the processes of structure formation, polymerization and polycondensation of the sum of metal oxyhydrates, which results in the formation of primary sorbent granules of uniform size in the drying process (in the presence of an electrolyte).

After drying, the precipitate (a mixture of NaCl crystals and metal oxyhydrates [MeO (OH) _x ]) was repulpated at 20 ± 5 ° C and W: T = 8: 1 in water, with complete dissolution of NaCl. The suspension was defended, the thickened part (20-25%) was filtered on a vacuum filter, washed with 3-5 volumes of water and dried either in air or at 100 ± 10 ° С. The dried precipitate (primary granules of metal oxyhydrates) was mixed with the remaining (10-20%) part of the hydrogel - a wet water-washed precipitate of the amount of metal oxyhydrates (not subjected to preliminary drying), the resulting paste was granulated by extrusion with simultaneous heat treatment of the paste at 100 ± 10 ° С , with obtaining strong granules in the form of cylinders with d = 5 mm and h = 4 ÷ 6 mm

Thus, the claimed method of producing granular inorganic sorbents based on metal oxyhydrates, on the one hand, makes it possible to neutralize highly toxic polymetallic wastes, utilize them, and obtain high-quality inorganic sorbents of the oxyhydrate type based on the use of various wastes and industrial products. To compare the effectiveness of the known (prototype) and the present invention, comparative tests of sorbents obtained by various methods in the processing and deactivation of radioactive chloride solutions resulting from the chlorination of loparite concentrates were carried out. In particular, the sorbents obtained by the known and proposed methods were tested for purification - in the second stage of decontamination of radioactive (10-50 Bq / kg) chloride solutions (up to 250 g / dm ³ ∑ KCl, NaCl). Such solutions are formed after the first stage of decontamination of solutions and pulps from the hydraulic erosion of spent melts of the salt irrigation filter of loparite chlorinators.

As a result of tests, it was found that during operation in radioactive chloride solutions there is a private peptization of sorbents obtained by a known method. In connection with peptization, fine particles of the sorbent, saturated with radionuclides, are “taken out” into the solution, which entails secondary contamination of deactivated solutions with radionuclides (Ra-224, Ra-228, etc.).

When using sorbents obtained by the proposed method, peptization was not observed even when passing through the sorption column more than 10,000 volumes of radioactive chloride solutions.

The results of comparative tests also showed that the dynamic capacity before the “slip” (<6 Bq / kg) of radionuclides into the filtrate of sorption columns filled with sorbents obtained by the proposed method is 5 times greater than for sorption columns filled with sorbents obtained by known (prototype) method.

Thus, the results of comparative tests showed that the invention provides a solution to the problem with the achievement of the above technical result. The present invention provides, in particular, the production of non-recyclable waste products of high-quality granular inorganic sorbents based on metal oxyhydrates with enhanced performance characteristics in the processing of radioactive chloride solutions. At the same time, a technical result is achieved consisting in increasing the dynamic capacity to a “breakthrough” (less than 6 Bq / kg) of natural radionuclides in the filtrate.

Claims (1)

A method of producing granular inorganic sorbents based on metal oxyhydrates, including the deposition of metal oxyhydrates, filtering the pulp, washing the oxyhydrate precipitate and granulating it, characterized in that the oxyhydrate precipitate is divided into two parts in a ratio of 10-20% and 80-90%, with 80- 90% of the precipitate is subjected to treatment with a solution of sodium chloride with a concentration of 250-300 g / dm ³ NaCl, then dried, repulpated at W: T = (5 ÷ 10): 1, the suspension is defended, filtered, washed with water, re-dried, and after mixing with the remaining power hydrochloric portion precipitate paste was granulated by extrusion.