RU2495830C1 - Method of extracting ions of heavy metals from aqueous solutions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used to improve membrane and sorption techniques, in water treatment, in techniques for recycling ions of heavy metals from aqueous solutions and waste water. The method is realised by contacting aqueous solutions for 1-20 minutes with cellulose-based polymer sorbents which are modified with microwave radiation with power of 300 W and frequency of 2.45 GHz, with solution/sorbent ratio of 50-200. The sorbents are modified by pre-immersion in aqueous caprolactam solution or caprolactam distillation residue with concentration of 2-20 g/l with modulus of 15-50, followed by pressing and microwave exposure for 1-5 minutes at temperature of 150-200°C. The modified sorbents are brought into contact with aqueous solutions at solution pH 3-7.

EFFECT: method increases degree of extraction of heavy metal ions from weakly acidic solution with pH below 5 by about 20%, while maintaining a high degree of extraction of heavy metal ions from neutral aqueous solutions, and also increases sorbent stability when stored on open air to one year and reduces the number of steps when modifying sorbents.

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Description

FIELD OF TECHNOLOGY

The invention relates to methods for the extraction of heavy metal ions by sorption on natural cellulose-containing sorbents, from solutions of various compositions resulting from a variety of technological processes, and can be used to improve membrane and sorption technologies, in water treatment, in the development of technologies for the disposal of heavy metal ions from water solutions and wastewater of various nature.

BACKGROUND

There is a method of wastewater treatment of industrial enterprises from heavy metals, in particular from copper ions, by sorption on sawdust treated with 4-methyl-8-oxo-5-azadecadiene-3,9-OH-2 with a sawdust-reagent mass ratio of 1 : 0.05 ÷ 0.1 [A.S. 1819669 USSR, MKI ⁵ V 01020/22. A method of producing a sorbent for wastewater treatment of copper // Timofeeva S.S., Kukharev B.F., Stankevich V.K., Klimenko G.R. - No. 4911863/05; Claim 05/15/91; Publ. June 7, 93, Bull. No. 21.].

However, this method of modifying sawdust is uneconomical, since it implies the use of an expensive reagent in an amount of 5-10% by weight of the sorbent, and also leads to environmental pollution.

There is a method of extracting heavy metal ions from aqueous solutions by contacting them at room temperature with modified polymer sorbents with a solution / sorbent module of 50-200, which are secondary products of the processing of oilseeds - meal or meal, pre-treated in an aqueous solution containing sodium salt of monochloracetic acid in an amount of 1-10% by weight of the sorbent and soda or alkali to create a pH of 8-12, with a solution / sorbent module of 5-50 for 30-60 minutes in a boiling water bath, last why add a dilute solution of a strong mineral acid (HCl or H ₂ SO ₄ ) to a pH of 4-7, and the contacting of the modified sorbent is carried out for 0.5-1.5 hours [T. Nikiforova, VA Kozlov, Rodionova M.V. The method of extraction of heavy metal ions from aqueous solutions. RF patent No. 2329098. Publ. in BI No. 20 of July 20, 2008].

However, this method of extraction of heavy metal ions from aqueous solutions involves a long sorption time (0.5-1.5 hours).

The closest in technical essence and the achieved result, that is, the prototype, is a method of extracting heavy metal ions from aqueous solutions by contacting them at room temperature with modified polymer sorbents based on cellulose with a solution / sorbent module of 50-200, in which the modification of sorbents carried out by interacting with an oxidizing agent under microwave irradiation with a power of 300 W with a frequency of 2.45 GHz and a temperature of 25-70 ° C for 5-15 minutes, followed by washing with water and processing th sodium bisulfite, while the contacting of the modified sorbent is carried out for 1-20 minutes The interaction of sorbents with an oxidizing agent is carried out in a solution with a concentration of 0.1-0.3 M at a pH of 2.5-4.5, and treatment with sodium bisulfite is carried out in a solution with a concentration of 0.5-5% at a pH of 2-4.5 V for 0.5-1 hours at room temperature. Sodium metaperiodate, iodic acid or sodium hypochlorite are used as an oxidizing agent, and cotton or wood pulp, short flax fiber or wood sawdust are used as polymeric sorbents [Nikiforova TE, Kozlov VA, Titarenko NA, Zimin D.M. The method of extraction of heavy metal ions from aqueous solutions. RF patent No. 2438995. Publ. in BI No. 1 dated January 10, 2012].

The disadvantages of the prototype are:

- insufficiently high degree of extraction of heavy metal ions from weakly acidic solutions (with pH <5);

- polymer sorbent is unstable when stored in the open air (retains its properties for no more than 3 months).

SUMMARY OF THE INVENTION

The objective of the invention is to provide a method for the extraction of heavy metal ions from aqueous solutions, allowing:

- increase the degree of extraction of heavy metal ions from weakly acidic solutions (with pH <5) while maintaining a high degree of extraction of heavy metal ions from neutral aqueous solutions;

- increase the stability of the sorbent during storage in the open air, that is, increase the time during which the sorbent retains its properties.

The problem is solved by creating a method for the extraction of heavy metal ions from aqueous solutions by contacting them at room temperature for 1-20 minutes with polymer sorbents based on cellulose, modified by microwave irradiation with a power of 300 W at a frequency of 2.45 GHz with a solution / sorbent module equal to 50-200, in which the modification of the sorbents is carried out by preliminary immersion in an aqueous solution of caprolactam or distillation residue of caprolactam with a concentration of 2-20 g / l with a module of 15-50 followed by a dehydration and microwave irradiation for 1-5 minutes at a temperature of 150-200 ° C, and contacting the modified sorbents with aqueous solutions is carried out at pH 3-7 solution.

Sorbents are immersed in an aqueous solution of caprolactam or still bottoms distillation of caprolactam is carried out for 30-60 seconds to impregnate them with a solution and applying caprolactam or caprolactam oligomers to them.

As the polymer sorbents used:

- short flax fiber, which is a secondary product of processing the flax industry of the following composition,%: cellulose (75 ... 78), hemicellulose (9.4 ... 11.9), lignin (3.8), pectin substances (2.9 ... 3 , 2), waxy substances (2.7), nitrogen-containing substances per protein (1.9 ... 2.1), minerals (1.3 ... 2.8) [Krichevsky G.E., Korchagin M.V. ., Senakhov A.V. Chemical technology of textile materials. M., 1985. 640 p.];

- sawdust - waste from the woodworking industry (composition,% of absolutely dry wood: cellulose - 31.0-52.5; lignin - 19.5-30.9; pentosans - 5.3-28.3; mannan - 1, 3-11.3; galactan - 0.7-14.4; uronic acids - 2.9-8.6; substances extracted with hot water - 1.4-22.6; substances extracted with ethyl ether - 0.7 -4.6; ash - 0.2-1.0) [Nikitin V.M., Obolenskaya A.V. Schegolev V.P. Chemistry of wood and cellulose. M .: Forest industry, 1978. - 368 p.];

- cotton cellulose [GOST 595-79 "Cotton cellulose. Specifications.];

- wood pulp [GOST 11208-82. Wood pulp (coniferous) sulfate unbleached. Specifications.].

As modifying agents used:

- caprolactam: [GOST 7850-86 Caprolactam. Specifications]. Caprolactam is a cyclic amide of ε-aminocaproic acid. Formula: C ₆ H ₁₁ NO). Represents white crystals, well soluble in water, alcohol, ether, benzene.

- distillation residue of caprolactam distillation - solid waste in the production of caprone, which is a mixture of oligomers and caprolactam monomer. The average composition, wt.%:

oligomer 85-90;

caprolactam 10-15.

The general formula for cyclic oligomers is: (C ₆ H ₁₁ NO) _n , where n = 1-5. Under ordinary conditions, KODK is a waxy substance with a density of 1302 kg / m ³ with a softening temperature of 85-90 ° C, the color is buffy [Tarasova GI, Tarasov VV Distillation residues of caprolactam distillation. Properties, modification, applications // Science - production. M .: NTP "Virage Center". 2001. p. 35.].

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

Example 1

10 g of wood sawdust for 30 s is immersed in 200 ml of an aqueous solution of caprolactam (module 20) with a concentration of 15 g / l, squeezed and subjected to microwave irradiation with a power of 300 W at a frequency of 2.45 GHz and a temperature of 150 ° C for 5 min, then the mass is dried.

The treated sorbent is poured into 0.5 l of an aqueous solution at room temperature (module 50), pH 5, containing 1.5 mmol / l of copper ions. After 1 min, the solution was filtered off and the content of Cu (II) ions was determined in the filtrate. The concentration of copper ions in the solution after contacting with the sorbent was 0.332 mmol / L (the degree of extraction of 77.9%).

Example 2

10 g of cotton pulp for 40 s is immersed in 400 ml of an aqueous solution of distillation residue of caprolactam distillation (module 40) with a concentration of 10 g / l and subjected to microwave irradiation with a power of 300 W at a frequency of 2.45 GHz and a temperature of 200 ° C for 1 min, then the mass is squeezed and dried.

The treated sorbent is poured into 1.5 L of an aqueous solution at room temperature (module 150), pH 3, containing 0.15 mmol / L of nickel ions. After 20 minutes, the solution is filtered off and the Ni (II) ion content is determined in the filtrate. The concentration of nickel ions in the solution after contacting with the sorbent was 0.3615 mmol / L (the degree of extraction of 75.9%).

Example 3

10 g of short flax fiber for 45 s is immersed in 150 ml of an aqueous solution of distillation caprolactam distillation residue (module 15) with a concentration of 20 g / l and subjected to microwave irradiation with a power of 300 W at a frequency of 2.45 GHz and a temperature of 180 ° C for 2 min , then the mass is squeezed and dried.

The treated sorbent is poured into 2 L of an aqueous solution at room temperature (module 200), pH 6, containing 1.5 mmol / L of zinc ions. After 5 minutes, the solution is filtered off and the content of Zn (II) ions is determined in the filtrate. The concentration of zinc ions in the solution after contacting with the sorbent was 0.3855 mmol / L (recovery rate 74.3%).

Example 4

10 g of wood pulp for 50 s is immersed in 500 ml of an aqueous solution of caprolactam (module 50) with a concentration of 2 g / l and subjected to microwave irradiation with a power of 300 W at a frequency of 2.45 GHz and a temperature of 170 ° C for 3 min, then squeeze the mass and dried.

The treated sorbent is poured into 1 l of an aqueous solution at room temperature (module 100), pH 7, containing 1.5 mmol / l of cadmium ions. After 10 min, the solution was filtered off and the content of Cd (II) ions was determined in the filtrate. The concentration of cadmium ions in the solution after contacting with the sorbent was 0.4035 mmol / L (the degree of extraction of Cd (II) ions was 73.1%).

Example 5

10 g of sawdust for 60 s is immersed in 300 ml of an aqueous solution of caprolactam (module 30) with a concentration of 5 g / l and subjected to microwave irradiation with a power of 300 W at a frequency of 2.45 GHz and a temperature of 160 ° C for 4 min, then squeeze the mass and dried.

The treated sorbent is poured into 0.75 l of an aqueous solution at room temperature (module 75), pH 4, containing 1.5 mmol / l of copper, nickel, zinc and cadmium ions in a ratio of 1: 1: 1: 1. After 15 minutes, the solution was filtered and the content of metal ions was determined in the filtrate. The concentration of Cu (II), Ni (II), Zn (II) and Cd (II) ions in solution after contacting with the sorbent was 0.3615; 0.3885; 0.4005 and 0.4245 mmol / L, respectively (degree of extraction of 75.9; 74.1; 73.3 and 71.7%).

To assess the effectiveness of the method described in the prototype, experiments were conducted on the extraction of heavy metal ions from weakly acidic solutions with a pH of 3-5, with the same concentration of heavy metal ions as in the present method, that is, 1.5 mmol / l, using the same sorbents (cotton cellulose, wood pulp, short flax fiber and sawdust), modified according to the prototype.

The results of the experiments are presented in the table.

Thus, it follows from the data in the table that the inventive method allows to solve the problem, namely:

- increase the degree of extraction of heavy metal ions from weakly acidic solutions (with pH <5) by about 20% while maintaining a high degree of extraction of heavy metal ions from neutral aqueous solutions;

- increase the stability of the sorbent during storage in the open air from three months to one year.

In addition, the inventive method allows to reduce the number of stages in the process of modifying sorbents.

Table EXAMPLES The degree of extraction,% pH Storage stability, month Cu ²⁺ Ni ²⁺ Zn ²⁺ Cd ²⁺ one. 77.9 - - - 5 12 2. - 75.9 - - 3 12 3. - - 74.3 - 6 12 four. - - - 73.1 7 12 5. 75.9 74.1 73.3 71.7 four 12 PROTOTYPE 53.5 - - - 3 3 - 56.3 - - four 3 - - 54.9 - 3,5 3 - - - 59.8 4,5 3 55.9 53.7 52.8 51.5 5 3

Claims (1)

The method of extraction of heavy metal ions from aqueous solutions by contacting them at room temperature for 1-20 minutes with cellulose-based polymer sorbents modified by microwave irradiation with a power of 300 W at a frequency of 2.45 GHz with a solution / sorbent module of 50-200 characterized in that the modification of the sorbents is carried out by preliminary immersion in an aqueous solution of caprolactam or distillation residue of caprolactam with a concentration of 2-20 g / l with a module of 15-50, followed by extraction and microwave new irradiation for 1-5 minutes at a temperature of 150-200 ° C, and the contacting of the modified sorbents with aqueous solutions is carried out at a solution pH of 3-7.