RU2790159C1 - Method for production of saponite sorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods for chemical modification of natural clay materials for the production of sorbent for purification of aqueous solutions from heavy metal ions, biogenic substances, microelements, detergents, and other environmentally harmful substances. A method for the production of saponite sorbent is presented, including processing of clay rocks with chemical reagents to obtain plastic mass, clay rock is processed with an acidic reagent, after which it is neutralized with an alkaline reagent with simultaneous introduction of peptizing additives, wherein saponite clay-plastic mass is used as clay rocks, sulfuric acid is used as an acidic reagent, cement is used as an alkaline reagent, iron (III) chloride is used as a peptizing additive. Next, sorbent is molded in an extruder to obtain granules with a length from 0.5 to 1 cm, granules are unloaded and dried at a room temperature, then sorbent granules are placed in a muffle furnace, and thermal processing is carried out at a temperature from 500 to 600°C to obtain clay saponite sorbent.

EFFECT: invention provides an increase in adsorption activity relatively to heavy metal cations.

1 cl, 1 tbl, 6 ex

Description

The invention relates to methods for the chemical modification of natural clay materials in order to obtain a sorbent for purification of aqueous solutions from heavy metal ions, biogenic substances, microelements, detergents and other environmentally harmful (hazardous) substances.

A known method of obtaining a sorbent for purification of aqueous solutions from heavy metal ions and a sorbent (RF Patent No. 2563011, publ. 2015.09.10), where 20 g of clay is treated with 100 ml of 0.04 M solution of rhodamine B (C ₂₈ H ₃₁ ClN ₂ O ₃ , M = 479.02) at a temperature of 20 to 22°C, pH 2 for 60 min, then the solid phase filtered from the solution is washed with 40 ml of distilled water and dried for 3 hours at a temperature of 100 to 105°C in a drying oven. closet.

The disadvantage of this method is that rhodamine B used to obtain the sorbent is characterized by increased toxicity and causes serious irritation of the skin and mucous membranes, and its use in the food industry is generally prohibited, as a result of which the area of use of the sorbent treated with rhodamine B is sharply reduced.

A known method for producing a sorbent based on natural bentonite (RF Patent No. 2714077, publ. 2020.02.11), which includes mixing an aqueous suspension of bentonite in a 20% sodium metasilicate solution, taken from the calculation of the mass ratio of SiO ₂ present in the sodium metasilicate solution, to bentonite, equal to 0.8:1. The modified bentonite is washed with water, treated with a 10% sulfuric acid solution and subjected to heat treatment at 200°C.

The disadvantage of this method is the formation of water-alkaline runoff from washing the modified sorbent with sodium metasilicate.

A known method for producing a clay adsorbent (USSR author's certificate No. SU 1327956, publ. 24.03.1987), which is carried out as follows, montmorillonite is treated with sulfuric or hydrochloric acid when heated, phosphoric acid is added to the ratio P ₂ O ₅ : (FeAl) ₂ O ₃ in hydrogel (0.7-1):1, after which the pulp is neutralized with an ammonia solution, and the precipitate is washed and dried.

The disadvantage of this method is that during the acid activation of the clay mineral, it is necessary to strictly adhere to a certain concentration of phosphoric acid in the solution used to wash the clay, since with a noticeable increase in the concentration of phosphoric acid, an irreversible change occurs in the structure of montmorillonite with leaching of Ca ²⁺ ions from the crystal lattice , Na ⁺ , K ⁺ and destruction of adsorption exchange centers, which can lead to a noticeable decrease in the efficiency of the adsorption properties of the resulting sorbent.

A method of obtaining an alkaline aluminosilicate sorbent is known (RF Patent No. 2409417, publ. 20.11.2011). The method for obtaining a sorbent involves processing coarsely ground clay rock of natural moisture with lime or a mixture of lime with sodium carbonate at a weight ratio of clay rock to lime equal to from 1: 0.25 to 1: 1, with continuous stirring until the dry mixture is homogeneous. Holding the resulting dry mixture for 1 to 3 hours to ensure the flow of the exothermic reaction and cooling.

The disadvantage of this method is the duration of the cooling process before the process of molding the sorbent from the alkali-activated clay rock after the exothermic reaction.

A known method for the production of a sorbent of heavy metals and other pollutants based on clay rocks (RF Patent No. 2096081, publ. 11/20/1997), adopted as a prototype, which is as follows, the aluminosilicate rock is treated with an acidic reagent for 0.5 to 1 hour, after which it is neutralized with an alkaline reagent to pH = 12-14 with the simultaneous introduction of peptizing additives. At the same time, the treatment with acidic and alkaline reagents is carried out at normal or elevated temperatures up to 150°C and pressure up to 5 atm.

The disadvantage of this method is that for the preparation of the sorbent, the Cambrian clay of the Leningrad deposit was taken as the basis, the plasticity of which is 22.9%. However, to maintain a given form of the sorbent, this value will be small, and the exchange capacity of Cambrian clay, which belongs to the hydromica class, is inferior to clays from the montmorillonite class.

The technical result is an increase in adsorption activity in relation to heavy metal cations.

The technical result is achieved by the fact that saponite clay-plastic mass is used as a raw material, sulfuric acid is used as an acidic reagent, cement is used as an alkaline reagent, iron (III) chloride is used as a peptizing additive, then the sorbent is molded in an extruder, with obtaining granules with a length of 0.5 to 1 cm, the granules are unloaded and dried at room temperature, then the sorbent granules are placed in a muffle furnace and heat treatment is carried out at a temperature of 500 to 600°C, to obtain a clay saponite sorbent.

The method is carried out as follows. The feedstock is a saponite clay-plastic mass with a career moisture content of 36 to 42%, which contains wt. %: SiO ₂ - 52.3; MgO - 22.12; Fe ₂ O ₃ - 9.9%; Al ₂ O ₃ - 5.7; CaO - 4.6; other - 5.38. The specific surface area of saponite is S _beats = 35-40 m ² /g, pore volume V _por.total. =0.40 cm ³ /g, the plasticity of the clay is 28.4%, the mechanical crushing strength of the thermally untreated sorbent granules is 4.13 kgf/cm ² .

The feedstock is loaded into a specialized stationary mixer with further acid activation with sulfuric acid with a concentration of 0.1 to 0.2 M in an amount of 25 to 35 wt. % depending on the weight of the taken clay rock. After adding the acid, a mixing process takes place for 2 to 5 minutes. Next, the saponite clay-plastic mass is left alone at room temperature for 1 hour, while acid activation occurs. This treatment maximizes the specific surface area of the sorbent. After acid activation, alkaline neutralization of the saponite clay-plastic mass is carried out with cement in an amount of 23 to 26 wt. % depending on the weight of the taken clay rock. A peptizing additive was introduced into the acid-base saponite clay-plastic mass, which was used as iron (III) chloride in an amount of from 0.05 to 0.06 wt. % depending on the weight of the taken clay rock to impart lyophilic properties to the sorbent. The molding of the sorbent is carried out in an extruder by forming granules with a length of 0.5 to 1 cm. Then the molded clay-saponite sorbent was unloaded and dried for at least 24 hours at room temperature. Next, the sorbent is placed in a muffle furnace and heat treatment is carried out at a temperature of 500 to 600°C. A clayey saponite sorbent is obtained, which has an increased sorption capacity with respect to Cu ²⁺ cations.

The method is illustrated by the following examples.

The textural characteristics of the sorbent were calculated based on nitrogen adsorption isotherms obtained on a Quantachrome NovaWin1000 volumetric unit at 73 K. The total pore content in water was determined according to GOST 17219-71, the radial crushing strength of extrudates according to ASTM D6175.

The sorption capacity of the clay sorbent was studied using the adsorption of the Cu ²⁺ cation as an example, the content of which in the model solution was determined by the spectrometric method on a PE-5400UF spectrophotometer according to the method recommended by GOST 4388-72 “Drinking water. Methods for determining the mass concentration of copper. A sorbent weighed in a ratio of 1/50 was added to a 100 ml flask filled with a model solution. As a model solution, a copper sulfate solution with concentrations from 0.25 mg/dm ³ to 2.1 mg/dm ³ was used.

Sorbents were intensively mixed for 20 min with a model solution, then left in a static state for 30 min with periodic shaking for 1 to 2 min. Time of adsorption experiment - 50 min. The degree of purification of the model solution E _ad was determined by the known relation:

E _hell \u003d [(∑ C _ref - ∑ C _con ) / ∑ C _ref ] 100%,

where E _hell is the degree of purification (adsorption value);

∑С _ref - total concentration of pollutants in the initial solution, mg/dm ³ ; ∑С _con - total concentration of pollutants in the purified solution, mg/dm ³ .

Example 1. For the production of a sorbent, saponite waste from the Arkhangelsk deposit was used, in terms of mineral composition serpentine-saponite with a plasticity number of 28.4, containing physical clay equal to 49.4%. The clay base in the form of a paste with a moisture content of 36 to 42% is treated with 13 to 16 wt. % 0.1 N hydrochloric acid, stirred for 2 to 5 minutes, the acid activation time is 1 hour. Then, after acid activation, the paste was subjected to alkaline hydrolysis with the addition of cement in an amount of 23 to 26 wt. %, with the introduction of from 0.05 to 0.06 wt. % peptizer - iron chloride (III). The sorbent was molded by the extrusion method; the raw sorbent was dried at room temperature for 24 hours. Next, the material was subjected to heat treatment in a muffle furnace at T=350°C. The specific surface area of the obtained sorbent is S _yd =36.65 m ² /g, the pore volume V _pore.gen. =0.37 cm ³ /g.

The clarified liquid was subjected to chemical analysis to determine the content of the Cu ²⁺ cation in it and to calculate the percentage of metal removal from the purified liquid.

Example 2. For the production of a sorbent, saponite waste from the Arkhangelsk deposit was used, in terms of mineral composition serpentine-saponite with a plasticity number of 28.4, containing physical clay equal to 49.4%. The clay base in the form of a paste with a moisture content of 36 to 42% is treated with 13 to 16 wt. % 0.1 N hydrochloric acid, stirred for 2-5 min, the acid activation time is 1 hour. Then, after acid activation, the paste was subjected to alkaline hydrolysis with the addition of cement in an amount of 23 to 26 wt. %, with the introduction of from 0.05 to 0.06 wt. % peptizer - iron chloride (III). The sorbent was molded by the extrusion method; the raw sorbent was dried at room temperature for 24 hours. Next, the material was subjected to heat treatment in a muffle furnace at T=400°C. The specific surface area of the obtained sorbent is S _yd =39.36 m ² /g, pore volume V _por.total. =0.42 cm ³ /g.

The clarified liquid was subjected to chemical analysis to determine the content of the Cu ²⁺ cation in it and to calculate the percentage of metal removal from the purified liquid.

Example 3. For the production of sorbent was used saponite waste from the Arkhangelsk deposit, in terms of mineral composition serpentine-saponite with a plasticity number of 28.4, containing physical clay 49.4%. The clay base in the form of a paste with a moisture content of 36 to 42% is treated with 13 to 16 wt. % 0.1 N hydrochloric acid, stirred for 2-5 min at room temperature, the acid activation time is 1 hour. Then, after acid activation, the paste was subjected to alkaline hydrolysis with the addition of cement in an amount of 23 to 26 wt. %, with the introduction of from 0.05 to 0.06 wt. % peptizer - iron chloride (III). The sorbent was molded by the extrusion method; the raw sorbent was dried at room temperature for 24 hours. Next, the material was subjected to heat treatment in a muffle furnace at T=500°C. The specific surface area of the resulting sorbent is S _yd =16.90 m ² /g, pore volume V _por.total. \u003d 0.28 cm ³ /g.

The clarified liquid was subjected to chemical analysis to determine the content of the Cu ²⁺ cation in it and to calculate the percentage of metal removal from the purified liquid.

Example 4. For the production of sorbent was used saponite waste from the Arkhangelsk deposit, in terms of mineral composition serpentine-saponite with a plasticity number of 28.4, containing physical clay 49.4%. The clay base in the form of a paste with a moisture content of 36 to 42% is treated with 13 to 16 wt. % 0.1 N hydrochloric acid, stirred for 2-5 min at room temperature, the acid activation time is 1 hour. Then, after acid activation, the paste was subjected to alkaline hydrolysis with the addition of cement in an amount of 23 to 26 wt. %, with the introduction of from 0.05 to 0.06 wt. % peptizer - iron chloride (III). The sorbent was molded by the extrusion method; the raw sorbent was dried at room temperature for 24 hours. Next, the material was subjected to heat treatment in a muffle furnace at T=550°C. The specific surface area of the resulting sorbent is S _yd =16.59 m ² /g, pore volume V _por.total. \u003d 0.31 cm ³ /g.

The clarified liquid was subjected to chemical analysis to determine the content of the Cu ²⁺ cation in it and to calculate the percentage of metal removal from the purified liquid.

Example 5. For the production of a sorbent, saponite waste from the Arkhangelsk deposit was used, in terms of mineral composition serpentine-saponite with a plasticity number of 28.4, containing physical clay equal to 49.4%. The clay base in the form of a paste with a moisture content of 36 to 42% is treated with 13 to 16 wt. % 0.1 N hydrochloric acid, stirred for 2-5 min, the acid activation time is 1 hour. Then, after acid activation, the paste was subjected to alkaline hydrolysis with the addition of cement in an amount of 23 to 26 wt. %, with the introduction of from 0.05 to 0.06 wt. % peptizer - iron chloride (III). The sorbent was molded by the extrusion method; the raw sorbent was dried at room temperature for 24 hours. Next, the material was subjected to heat treatment in a muffle furnace at T=600°C. The specific surface area of the resulting sorbent is S _yd =16.59 m ² /g, pore volume V _por.total. \u003d 0.31 cm ³ /g.

The clarified liquid was subjected to chemical analysis to determine the content of the Cu ²⁺ cation in it and to calculate the percentage of metal removal from the purified liquid.

Example 6. For the production of a sorbent, saponite waste from the Arkhangelsk deposit was used, in terms of mineral composition serpentine-saponite with a plasticity number of 28.4, containing physical clay equal to 49.4%. The clay base in the form of a paste with a moisture content of 36 to 42% is treated with 13 to 16 wt. % 0.1 N hydrochloric acid, stirred for 2-5 min, the acid activation time is 1 hour. Then, after acid activation, the paste was subjected to alkaline hydrolysis with the addition of cement in an amount of 23 to 26 wt. %, with the introduction of from 0.05 to 0.06 wt. % peptizer - iron chloride (III). The sorbent was molded by the extrusion method; the raw sorbent was dried at room temperature for 24 hours. Next, the material was subjected to heat treatment in a muffle furnace at T=650°C. The specific surface area of the resulting sorbent is S _yd =9,59 m ² /g, pore volume V _por.total. =0.11 cm ³ /g.

The clarified liquid was subjected to chemical analysis to determine the content of the Cu ²⁺ cation in it and to calculate the percentage of metal removal from the purified liquid.

Table 1 presents data on the relationship between the adsorption capacity of the resulting sorbents in relation to the Cu ²⁺ cation and the conditions of heat treatment of the sorbent.

Table 1 - Results of adsorption capacity.

Cu ²⁺ cation concentration, mg/dm ³ E _{hell cf} ,% pH Mechanical crushing strength, kgf / cm ² 0.25 0.5 1.25 1.75 2.1 Sample No. 1, T=350°С There is no mechanical strength of the granules in contact with water Sample No. 2, T=400°C There is no mechanical strength of the granules in contact with water - 4.85 Sample No. 3, T=500°C 0.01 0.03 0.07 0.17 0.23 92.8 10.3 5.1 An increase in the turbidity of the model solution is observed due to the low strength of the granules in contact with water. Sample No. 4, T=550°С 0.04 0.05 0.075 0.12 0.48 87.6 8.3 6.9 Sample No. 5, T=600°C 0.04 0.05 0.075 0.12 0.48 87.6 8.3 6.9 Sample No. 6, T=650°C 0.01 0.01 0.032 0.04 0.15 43.3 7.1 7.3

It can be seen from the table that the optimal firing temperature of the saponite base is from 500 to 600°C, since at lower firing temperatures, sorbent samples do not gain sufficient mechanical strength, and heat treatment at temperatures above 600°C is impractical.

Saponite granules effectively sorb heavy metal ions from water. Sorption capacity in relation to copper is 88% without preliminary heat treatment of the clay base.

As a basis for molding saponite clay sorbent without autoclave treatment of the clay base, it can significantly simplify the technology for obtaining the sorbent without adversely affecting the sorption capacity of clay for the heavy metal cation.

Claims (1)

A method for producing a saponite sorbent, including the treatment of clay rocks with chemical reagents to obtain a plastic mass, the clay rock is treated with an acidic reagent, after which it is neutralized with an alkaline reagent with the simultaneous introduction of peptizing additives, characterized in that saponite clay-plastic mass is used as clay rocks, in sulfuric acid is used as an acidic reagent, cement is used as an alkaline reagent, iron (III) chloride is used as a peptizing additive, then the sorbent is molded in an extruder to obtain granules 0.5 to 1 cm long, the granules are unloaded and dried at room temperature , then the granules of the sorbent are placed in a muffle furnace and heat treatment is carried out at a temperature of from 500 to 600°C to obtain a clay saponite sorbent.