RU2417952C1 - Method of extracting cadmium from waste and natural water - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to analytical chemistry, chemical engineering and ecology and can be used to detect trace amounts of cadmium in waste and natural water. In order to implement the method of extracting cadmium ions, a polystyrene-azo-rhodanine polymer chelating sorbent is added to the solution and the sorption process is carried out at room temperature and pH 7-9, and the solution is stirred for 20 minutes. The eluent used is 2M HCl solution.

EFFECT: method enables selective concentration of cadmium ions in a neutral medium in the presence of cobalt, nickel and vanadium ions by increasing sensitivity and high sorption capacity of the sorbent with respect to cadmium ions, where the detection limit is equal to 10^-3 mg/l.

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Description

The invention relates to the field of analytical chemistry, chemical technology and ecology and can be used to determine small amounts of cadmium in wastewater and natural waters.

A known method of group extraction of elements from natural and wastewater [1]. The method includes sorption of Cu, Pb, Co, Cd, Mn, Fe, Zn, Ni, Cr on a polymeric chelating sorbent polystyrene-azo-2-hydroxy-3-methylene iminodiacetic acid, while sorption is carried out at pH 1.5-3.0 repeated at pH 5.0-7.5 for 120 minutes.

The disadvantages of this method are the low selectivity to a particular metal, the complexity and the main disadvantage is the duration of the analysis.

There is also known a method of group extraction of Cu, Cd, Zn from aqueous solutions [2]. The method involves the extraction of heavy metal ions from aqueous solutions by contacting them with modified active chlorotriazine dyes with cellulose-containing sorbents for 5-30 minutes at room temperature.

The disadvantages are non-selectivity, low degree of extraction, the complexity and duration of the analysis.

The closest in technical essence is the method of group extraction of Nickel, cobalt, cadmium and vanadium from solutions [3]. The method includes introducing polystyrene-azo-4-hydroxy-3-arsonobenzene into a solution of a polymeric chelate sorbent and sorption is carried out at pH 4.5-6.0, room temperature and the solution is mixed for 10-15 minutes.

The disadvantage of this method is the indiscriminate concentration of cadmium ions in contrast to the proposed method.

The objective of the invention is the expansion of a number of sorbents with more selective functional-analytical groups (FAG) to cadmium ions and the study of their sorption properties.

The technical result is achieved by creating effective mobile phases for the extraction of cadmium ions by introducing a polystyrene-azo-rhodanine polymer sorbent into a solution of a chelating sorbent and performing a sorption process at room temperature, pH 7-9 and a solution mixing time of 20 minutes, and the process of extracting cadmium ions from waste and natural waters includes the use of a sorbent, the elution of sorbed ions and their determination by the AAS method, while polystyrene-azo-rhodanine is used as a sorbent, and 2M solution is used as an eluent HCl creat.

The extraction of cadmium ions from wastewater and natural waters is carried out using a sorbent, and sorbed ions are eluted using a 2M HCl solution and determined by atomic absorption. As the sorbent, polystyrene-azo-rhodanine is used, which, according to Pearson's theory, has a phage for cadmium ions, and this sorbent works as a sorbent for the concentration of Cd.

To assess the ability of the sorbent to concentrate, we considered the completeness of sorption of cadmium ions, the influence of the matrix composition of the solution, and an increase in the background signal during detection.

Concrete example

As objects of analysis were taken the waters of the Caspian Sea, in areas of industrial effluents.

To determine the active (ionic) forms of cadmium, 2000 ml of the sample (previously prepared) was filtered through a blue ribbon filter paper, adjusted to pH 9.0, 0.1 g of sorbent was added, and stirred on a magnetic stirrer for 20 minutes at room temperature. Then, water with a sorbent was passed through a chromatographic column, the sorbent was washed several times with distilled water, and a detectable element was eluted with 10 ml of a 2M HCl solution. In parallel, a blank experiment was conducted. In the obtained eluate solutions, the cadmium content was determined by the AAS method. To build a calibration graph used standard solutions. The correctness of the results obtained is proved on model solutions, which were prepared by introducing into the bidistillate matrix elements (Na, K, Ca, Mg, Ba, Sr, Zn, Cr, Mn, Co, Fe, Ni, Cu, Al, Pb) contained in marine water, in concentrations varying on average in them, and the introduction of a standard solution of Cd. The results of the determination of cadmium in model solutions are shown in table 1, and in water - in table 2.

Reproducibility was defined as the value of the relative standard deviation S _r .

The developed technique for the concentration of cadmium with a polymeric chelating sorbent polystyrene-azo-rhodanine made it possible to determine with high accuracy (Sr = 0.03-0.04) the content of this ion with concentrations of the order of 10 ^-3 mg / L in large volumes of test water with a complex background composition.

Table 1 The correctness of the sorption-atomic absorption determination of cadmium in model solutions (n = 8; P = 0.95) The name of the sorbent Element Introduced, mcg / L Found, mcg / l R% Sr Polystyrene-azo-rhodanine Cd 10.00 9.88 ± 0.28 99.3 0,03

table 2 Verification of the correctness of the sorption-atomic absorption determination of cadmium in the water sample of the Caspian Sea by the additive method (n = 8; P = 0.95) The name of the sorbent Element The initial content, mcg / l Supplement method Sr Introduced, mcg / L The total content, mcg / l Polystyrene-azo-rhodanine Cd 6.90 ± 0.26 7.00 14.10 ± 0.42 0.04

The advantages of the proposed method are:

1. The ability to selectively concentrate cadmium ions in the presence of cobalt, nickel and vanadium ions.

2. An increase in the sensitivity of the sorbent to cadmium ions (limit of sensitivity of the order of 10 ^-3 mg / l).

3. High sorption capacity of the sorbent for cadmium ion (8.6 times higher than that of the prototype).

4. The possibility of sorption in a neutral environment.

Information sources

1. NN Basargin, N.V. Chernova, Yu.G. Rozovsky, patent No. 1792923 - publ. 02/07/93, Bull. No. 5.

2. T.E. Nikiforova, V. A. Kozlov, O. I. Odintsova, M. I. Krotova, patent No. 2351548 - publ. 04/10/2009.

3. NN Basargin, I.E. Kiseleva, Yu.G. Rozovsky, patent No. 1678872 - publ. 09/23/93, Bull. Number 35.

Claims (1)

The method of extraction of cadmium ions from natural and waste waters, including the use of a sorbent, the elution of sorbed ions, characterized in that polystyrene-azo-rhodanine is used as a sorbent, a 2M HCl solution is used as an eluent, and the sorption process is carried out at room temperature, pH 7 -9 and stirring the solution for 20 minutes.