RU2412756C2 - Sorbent for cleaning effluents of lead and cadmium compounds and method to this end - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to treatment of whatever effluents for removal of contaminants, namely, lead and cadmium, and may be used in treatment of effluents produced in electroplating, production of plastic materials and paint-and-varnish industry. White sludge, a product of autoclave removal of silicon from aluminate solutions of alumina production, is used as a sorbent for removal of lead and cadmium compounds from effluents. Lead and cadmium sorption is carried out on mixing liquid phase containing said compounds for 6-32 h.

EFFECT: efficient treatment of effluents by inexpensive sorbent.

2 cl, 6 tbl

Description

The invention relates to the field of industrial ecology, in particular to the treatment of industrial and domestic wastewater from industrial water from contaminants containing lead and cadmium compounds, and can be used, in particular, in mechanical engineering for the treatment of industrial wastewater from galvanic production or the production of materials and products from plastics and paint and varnish production.

Known use as filtering materials for water purification from various substances of natural materials - sorbents: crushed anthracite, diatomite, tripoli, marble, magnomass (Kulsky LA Chemistry and water treatment technology. - Kiev, 1960. - P.225).

On an industrial scale, water and industrial wastewater treatment uses filters loaded with quartz sand, which are pre-washed and sorted by sieving through sieves. (Zhuzhikov V.A. Filtration. - M .: Chemistry, 1968. - 412 p .; Yakovlev S.V., Karelin Y.A., Zhukov A.I., Kolobanov S.K. Sewerage - M .: Stroyizdat , 1976. - 632 s .; Zhukov A.I., Mongayt I.L., Rodziller I.D. Methods for the treatment of industrial wastewater .-- Moscow: Stroyizdat, 1977. - 208 p.)

However, quartz sand is almost everywhere scarce and has a relatively high cost and relatively low dirt capacity, which necessitates the search for cheaper materials or the development of special sorbents with high absorption capacity that could be used for treating water and industrial effluents.

It is known that specially prepared filter materials are used in wastewater treatment schemes — sorbents, in particular granular activated carbon of the SKD-515 brand (TU 922406-001-95) manufactured by Perm SORBENT OJSC, produced by extrusion of fine coal and coal mixtures from fine dust a binder, followed by treatment in a medium of water vapor at a temperature of 800-950 ° C.

With high sorption of heavy metals, this sorbent, a certain limitation of its use is a rather high cost associated with the production technology.

Also known is the adsorbent “GLINT” (TU 2163-001-15191069-2003), developed and used for the treatment of industrial and surface-storm sewage by precipitation of heavy metal cations (Cu, Ni, Zn, Pb, Cd, Cr) and others ( see. Instructions for use. Activated Aluminosilicate Adsorbent. GLINT. CJSC "Quantum Mineral. St. Petersburg. 2007. P. 6).

With a long service life of the adsorbent and the possibility of multiple washing it when used in existing technological schemes for wastewater treatment, some of the disadvantages of the GLINT adsorbent include limitations on the acidity of the treated effluents (pH 7.5 ÷ 8.0), which requires preliminary treatment of effluents ( 2-3-phase treatment), and a limited sorption capacity for heavy metal ions (4.5 ÷ 5.6 kg / m ³ ), which requires frequent flushing when working with highly toxic effluents, and this increases the cost of cleaning industrial effluents.

The objective of the invention is to search for an artificially created sorbent with enhanced sorption, in particular, to compounds of lead and cadmium from industrial effluents, primarily engineering and metallurgical production, not toxic to the environment, convenient to use (in the form of bulk powder), which does not require the manufacture and application of large capital and operating costs, allowing it to be used in existing technological schemes and lines of treatment facilities at enterprises and in nature security laboratories.

The problem is solved in that as a silicon-containing sorbent for the purification of industrial effluents from lead and cadmium compounds, white grade A (BS) sludge is used - a specially processed recycled product of the processing of alumina production waste from an aluminum plant in the form of a powder, while the sorbent is introduced in a mass ratio of 5, 0 ÷ 50: 1 to the number of lead compounds or 5.0 ÷ 10.0: 1 to the number of cadmium compounds contained in wastewater, and the sorption process with stirring is carried out for a period of time from 6 to 32 hours, followed by BSe and water.

Neutralized white sludge (BS) - a loose powder of light brown color, represented by the sulfate form of the aluminosilicate of the sodalite group (noseanodalite) with a mass fraction of 80 to 90%; glandular hydrogarnet with a mass fraction of 8 to 15%; finely divided aluminum hydroxide with a mass fraction of from 1 to 5%; pH 6.0 to 9.0. Not toxic, not combustible.

White sludge (BS) is made in accordance with RF patent No. 2053688 (A23K 1/16, publ. 02/10/96 Bul. No. 4) by neutralizing the sludge during desiliconization of aluminate solutions of alumina production. BS grade A does not contain additional mineral additives.

The composition of the BS corresponds to TU 1711-127-001941091-96 with the change No. 1 of 03/27/2000 and is presented in table 1.

White sludge (BS), proposed as a silicon-containing sorbent for the purification of industrial effluents from lead and cadmium compounds, was previously developed and used when feeding animals as a mineral additive to increase live weight and preserve animals for fattening at their industrial maintenance, as well as to reduce the level of stress and loss of meat productivity in cattle during transportation (RF Patent No. 2271211, А61К 33/04, publ. 03/10/2006. Bull. No. 7).

Table 1 The composition of the white sludge (BS) produced by the aluminum plant Component Name Mass fraction,% Silica 20-25 Aluminium oxide 25-35 Iron oxide 3-10 Calcium oxide 3-10 Sodium oxide 15-20 Sulfur oxide 3-6 Potassium oxide 0.5-2.0 Free alkali, no more 0.02 Mass fraction of moisture in the product should not exceed 15%

Another well-known area of use of BS is its use in growing crops on soils contaminated with heavy metals, where the use of BS in the amount of 1 ÷ 5% of the mass of the arable layer allows to obtain higher yields and reduce pollution of the products by lead, nickel, chromium and cadmium (RF Patent No. 2189712, АВВ 79/02, published on September 17, 2002. Bull. No. 27).

The novelty of the proposed method for the treatment of industrial effluents from lead and cadmium is the use of white sludge (BS) for a new purpose, as a sorbent for highly efficient wastewater treatment of compounds of lead (Pb) and cadmium (Cd), carried out with a minimum cost of replacing the sorbent reagent in existing systems and cleaning schemes.

The method of purification of industrial effluents from lead and cadmium using the proposed sorbent reagent in the form of a silicon-containing white sludge is carried out in the following order.

A sorbent is introduced into the wastewater to be treated, followed by mixing and separation of the liquid and solid phases, and white sludge is used as the sorbent. Sodium aluminosilicates in the form of nozean or sodalite “act” as elements sorbing Pb and Cd in the white sludge. White sludge is removed in an amount 5.0 to 50.0 times higher than the content of toxicants in the treated wastewater.

The results of a study of the efficiency of laboratory cleaning of solutions of lead and cadmium compounds using the proposed white sludge in various concentrations at various exposures as sorbents are presented in tables 2; four; 5; 6. Research was carried out in the central factory laboratory of the Federal State Unitary Enterprise in the Northern Urals, which has galvanic shops and treatment facilities. Inaccuracies in the results of analyzes do not exceed the permissible ones for research methods.

table 2 Results of sorption of heavy metals on white sludge (BS) No. of solution Concentration in terms of element, g / l solution pH Pb Cd before sorption after sorption before sorption after sorption before sorption after sorption g / l % g / l % one 6.6 0.15 2.27 13,2 0,040 0.30 2,3 5.2 2 6.6 0.13 1.96 6.6 0,045 0.68 2.2 5.3 3 10 0.20 2.0 10 8.52 85,2 1.7 5.7 four 10 4,51 45.1 10 9.89 98.9 2.1 . 5.8

Notes:

1. Sorption time with stirring - 6 hours.

2. Solutions were prepared from heavy metal nitrates; hydrofluoric acid was used as a supplier of fluorine ion.

3. The concentration of white sludge in solutions is 60 g / l.

The results of the reverse extraction with distilled water of compounds Pb and Cd from BS samples after sorption according to table 2 are presented in table 3.

Table 3 The results of the extraction of heavy metals from white slurry BS distilled water BS samples after sorption of metals from solutions No. (Table 2) pH after extraction The concentration of metals in water after extraction, mg / l Pb Cd one 6.2 2.00 30.00 2 6.3 2.00 35.00 3 6.2 3.08 30,0 four 6.3 3.75 27.7

Notes:

1. The total extraction time for each sample is 100 hours, of which 32 hours with stirring.

2. The concentration of white sludge in water is 60 g / l.

The experimental results presented in tables 2 and 3 show that BS actively absorbs Pb and Cd compounds from solutions, converting them into water-insoluble forms (extraction of Pb and Cd with distilled water from samples is practically absent - Table 3).

The following series of experiments on the sorption of Pb and Cd compounds by white mud from solutions with different concentrations of elements in the solution (from 1 to 35 g / l) and extraction exposure (from 6 hours) are presented in Tables 4, 5, 6.

Notes:

1. The process was carried out with constant stirring during the shift.

2. The volume of the solution is 0.2 l.

3. The mass of the sample sorbent BSH - 20 g.

4. The concentration of BS in solutions is 100 g / l.

Table 5 The results of the sorption of cadmium on white sludge (BS) The initial concentration of the element in solution, g / l The initial amount of element in solution, g The contact time of the solution with the sorbent, hour The final concentration of the element in the solution, The final amount of element in solution, g g / l % 10 2 6 0.5000 5,0 0.1000 eighteen 0.1000 1,0 0,0200 26 0,0550 0.55 0.0110 32 0,0500 0.50 0,0100 fifteen 3 6 2,3000 15.33 0.4600 eighteen 1,1000 7.33 0.2200 26 0.8000 5.33 0.1600 32 0.2200 1.46 0.0440 twenty four 6 7,8000 39 1,5600 eighteen 4,9000 24.5 0,9900 26 4,6000 23.0 0.9200 32 4,4000 22.0 0.8800

Notes:

1. The process was carried out with constant stirring during the shift.

2. The volume of the solution is 0.2 l.

3. The mass of the sample sorbent BSH - 20 g.

4. The concentration of BS in solutions is 100 g / l.

Notes:

1. The process was carried out for 500 hours with periodic stirring 1 time per shift.

2. The volume of the solution is 0.2 l.

3. The mass of the sample sorbent 10 g.

4. The concentration of BS in solutions of 50 g / l.

An unobvious effect of using silicon-containing white sludge as a sorbent for the purification of industrial effluents from lead and cadmium compounds is that, using the proposed BS sorbent in a wide range of ratios of the mass of the sorbent to the mass of toxic compounds in the effluents, at various exposures it is possible without re-equipment of production at minimal cost to carry out almost complete purification of highly toxic acid effluents without first neutralizing them with a degree of purification up to 99.1 ÷ 99.9%, which is high m technical and technological achievement.

Data tables 2; four; 6 show that at the initial concentration of Pb in solutions from 1 to 20 g / l, the residual concentration after BS adsorption is in the range from 0.009 to 0.82%, with the degree of purification of solutions from 99.18% to 99.9% at a mass ratio BS to Pb 5.0 ÷ 50: 1, although at a concentration of 35 g / l Pb and a mass ratio of BS to Pb equal to 2.85, the degree of purification is 71.4-65.8%.

For cadmium (table 5), the final concentration in solutions is from 0.5 to 24.5% with the initial from 10 to 20 g / l, which corresponds to the degree of purification of solutions from 99.5% at a sorption time of 32 hours and an initial concentration of 10 g / l to 75.5% at an initial concentration of 20 g / l and a mass ratio of BS to Cd of 5.0 ÷ 10.0: 1.

From the above examples (tables 2; 4; 5; 6) it can be seen that the cleaning of solutions from lead and cadmium compounds in all experiments is carried out effectively if the sorbent is introduced in an amount exceeding 5 ÷ 50 times the amount of toxicant contained in solutions, t. e. in the mass ratio (5.0 ÷ 50.0): 1.

Thus, the use in the method of wastewater treatment from Pb and Cd of white sludge from alumina production as a sorbent reagent is obviously highly effective and has the following advantages:

- simplification of treatment technology, due to the exclusion of neutralization of effluents before treatment to a limited pH;

- cheaper cleaning, due to the cheapness and availability of white sludge as a by-product of alumina production, manufactured by order of agriculture.

The proposed method is simple to use, does not require large additional capital investments in the conversion of treatment facilities and special training for personnel, and can be used in engineering and metallurgical enterprises that cause environmental pollution by lead and cadmium, as well as in enterprises repairing automotive vehicles and treatment plants constructions of cities and towns by using white sludge (BS) as a filter load of pressure and non-pressure filters in one hundred treatment systems GOVERNMENTAL waters.

Claims (2)

1. Sorbent for the purification of industrial effluents from lead and cadmium compounds, including silicon compounds, characterized in that they use a silicon-containing white sludge, neutralized A-product grade, formed by autoclave removal of silicon from aluminate solutions of alumina production, in the form of a powder containing wt.% :
silica 20-25 aluminium oxide 25-35 with a mass fraction of moisture no more than 15 2. The method of purification of industrial effluents from lead and cadmium by introducing a sorbent into the effluent, followed by mixing and separation of the liquid and solid phases, characterized in that the silicon-containing white sludge used as the sorbent is 20-25% silica and alumina 25-35 when the mass fraction of moisture is not more than 15%, they are introduced in a mass ratio (5.0-50): 1 to the number of lead compounds or (5.0-10): 1 to the number of cadmium compounds contained in wastewater, while the sorption process with mixing is carried out over a period of 6 to 32 hours