RU2798979C1 - Method for making an adsorbent for water purification from nickel (ii) and other heavy metals - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for producing an adsorbent for the extraction of nickel (II) ions and can be used in mining, ore-dressing, electroplating, metallurgical, oil, chemical, petrochemical industries. A method is presented for obtaining an adsorbent for water purification from nickel (II), including modification of a zeolite with an organosilicon compound, characterized in that the calcium heulandite zeolite of a fraction of 0.5-1.0 mm, previously dried at a temperature of 150°C, treated with a 10-12% hydrochloric acid solution at a temperature of 120-150°C for 24 hours, then the resulting suspension is filtered and washed with distilled water until the neutral reaction, the resulting activated calcium heulandite ZH-HCl is dried to constant weight; after that, calcium heulandite is modified with a 1% solution of 1-(3-triethoxysilylpropyl)thiosemicarbazide TSC in hexane when heated to 50°C and stirring for 1 hour, then the resulting modified calcium heulandite ZH-HCl-TSC is filtered off and washed with hexane in an amount of 3.3 ml per 1 g of zeolite, dried in air for 12 hours and then in an oven at 110°C within 1 hour.

EFFECT: increased sorption activity of the adsorbent with respect to nickel ions due to the active functional groups of the modifier, which are soft bases, in accordance with the theory of hard and soft acids and bases.

1 cl, 2 dwg, 2 tbl, 3 ex

Description

The invention relates to methods for producing adsorbents for the extraction of nickel ions (surface and waste water). Can be applied in mining, ore processing, electroplating, metallurgical, oil, chemical, petrochemical industries; leaks of oil and oil products, agricultural fertilizers, solid waste landfills and municipal wastewater.

One of the most important environmental problems is the pollution of waste and surface waters with industrial, agricultural and household wastes containing heavy metal ions. Nickel ions can be distinguished among the main pollutants. Reagent and flotation methods are widely used to remove high concentrations of heavy metals. For fine cleaning, up to SanPin standards, ion-exchange and sorption methods are used.

Promising adsorbents are minerals of the zeolite structure as cheap and available materials. However, natural zeolites are characterized by low sorption capacity and hydrophobicity and need to be modified.

A known method of water purification from heavy metal ions (RU No. 2567650, IPC C02F 1/62, C02F 1/28, B01J 20/14, C02F 101/20, published 11/10/2015), which is designed to remove copper, Nickel, cobalt and zinc in ionic form by treating natural zeolite with a solution of hydrochloric acid at a concentration of 0.5-1 mol/l.

The disadvantage of this method lies in the relatively low adsorption capacity, as well as the need for additional stages of treatment with sodium hydroxide solution, three-stage (preliminary, intermediate and final) calcination of the zeolite at 600-900°C for a long time (45-90 min.).

A common feature of the claimed invention with analogue is the use of hydrochloric acid for pre-treatment of the adsorbent when removing heavy metal ions from aqueous solutions.

As modifiers, nitrogen- and sulfur-containing substances can be used, which form complex compounds with ions of the extracted metals.

A known method of obtaining a sorbent for the purification of aqueous solutions from heavy metal ions (RU No. 2563011, IPC B01J 20/12, B01J 20/30, published 09/10/2015), designed to remove ions of copper, zinc, cadmium and lead, 100 ml 0, 04 M solution of rhodamine B at room temperature, acidic medium for 60 min.

The disadvantage of this method is the insufficient fixation of the modifier on the aluminosilicate material, low hydrophobization and adsorption capacity for metals, the need for preliminary washing of the adsorbent with distilled water to remove water-soluble impurities until a negative reaction to chlorides, drying the finished product for 3 hours at a temperature of 100-105 °C in the oven.

A common feature of the claimed invention with analogue is the use of a nitrogen-containing compound as a modifier in the removal of heavy metal ions from aqueous solutions.

The closest in technical essence and the achieved result to the claimed invention and taken as a prototype is a method for cleaning wastewater from heavy metals by adsorption, a filter material (sorbent) and a method for obtaining a sorbent (RU No. 2524111, IPC B01J 20/10, published on 07/27/2014 ). The zeolite is modified by the action of HMDS in toluene in a mass ratio of 1-1.5 g of HMDS per 100 g of zeolite in toluene at a temperature of 20°C for 30 minutes. The obtained modified zeolite after separation of toluene was dried in the open air and then for 6 hours in a muffle furnace at a temperature of 110°C. The resulting zeolite is used to purify water from nickel(II) and zinc(II).

The disadvantage of this method is the low sorption capacity of the resulting adsorbent for heavy metals (99 mg/g nickel and 95 mg/g zinc) and applicability only at low metal concentrations in water (less than 1 mg/l). An increase in the ratio of HMDS:zeolite above 1.5:100 requires a greater consumption of HMDS and reduces the sorption capacity of the resulting zeolite. Reducing the ratio less than 1:100 also leads to a decrease in sorption activity.

A common feature of the claimed invention with the prototype is the use of nitrogen-containing organosilicon compounds, providing good fixing of the modifier on the zeolite and its hydrophobicity; the absence of a stage of pre-drying or calcination of the zeolite containing bound water;

The objective of the claimed invention is to obtain a zeolite-containing adsorbent with a high metal capacity.

The technical result of the claimed invention is to increase the sorption activity of the adsorbent in relation to nickel ions due to the active functional groups of the modifier, which are soft bases, in accordance with the theory of hard and soft acids and bases. The high adsorption capacity of the modified zeolite is associated both with the involvement of pores and active centers of the zeolite and active groups of the immobilized modifier on the surface of the zeolite.

The technical result is achieved by the fact that the zeolite fraction 0.5-1.0 mm, previously dried at a temperature of 150°C, is treated with a 10-12% hydrochloric acid solution at a temperature of 120-150°C for 24 hours, then the resulting suspension filtered and washed with distilled water until neutral, the obtained activated zeolites ZH-HCl are dried to constant weight; after that, the zeolite is modified with a 1% solution of 1-(3-triethoxysilylpropyl)thiosemicarbazide TSC in hexane when heated to 50°C and stirred for 1 hour, then the resulting modified zeolite is filtered off and washed with hexane in an amount of 3.3 ml per 1 g of zeolite, dried in air for 12 hours and then in an oven at 110°C for 1 hour.

The difference from the prototype is also the use as a natural zeolite calcium heulandite (ZH) Kholinsky deposit Ca[Al ₂ Si ₇ O ₁₈ ] ⋅ 6H ₂ O containing 25-30% (wt.) potassium spar KAlSi ₃ O ₈ in the form of an impurity rock , as well as its fractionation and selection of a fraction of 0.5-1.0 mm, which is then pre-treated with a solution of 10-12% hydrochloric acid at a temperature of 120-150 ° C for 24 hours before modification, followed by filtering the suspension, washing the zeolite distilled water until neutral and air dried.

The presence of distinctive features allows us to conclude that the claimed invention complies with the condition of patentability "novelty".

As a result of pre-treatment with hydrochloric acid, aluminum is dissolved (the process of dealumination) and impurities in the pores, Ca ²⁺ ions are partially displaced from the raw zeolite layers, which increases its microporosity and the outer surface area available for the subsequent fixation of the modifier.

The TSC modifier is synthesized from a mixture of 0.1 mol of 1-(3-aminopropyl)-triethoxysilane and thiosemicarbazide in the presence of 0.1 g of catalyst (NH₄)₂SO₄ the condensation reaction indicated in Fig. 1. Synthesis is carried out in a flask at 150°C for 3 hours until the release of ammonia ceases. TSC is a yellowish viscous liquid with a yield of 97%. 1-(3-aminopropyl)-triethoxysilane and thiosemicarbazide are commercial products and have a relatively low cost of $100-150/kg.

Immobilization of TSC on the surface of the zeolite was carried out by adding 3 g of air-dry ZH zeolite to 27 g of hexane. To the mixture in small portions for 10 minutes. 0.27 g TSC was added. The mixture was heated to 50° C. with stirring for 1 hour. The product was filtered and washed with hexane (3.3 ml per 1 g of zeolite) to remove excess free TSC. Then the zeolite with immobilized TSC was dried in air for 12 hours and then in a dryer at 110°C for 1 hour.

The modification of the zeolite is the result of the interaction between the TSC and the hydroxyl groups of the zeolite material and proceeds in several steps shown in FIG. 2, and includes:

- the hydrolysis reaction of TSC, leading to the formation of the corresponding silanol (a);

- condensation reaction of silanol with the hydroxyl group of the zeolite, leading to the formation of silanol intermediate (b);

- condensation reaction of the next silanol molecule, both with the hydroxyl group of the intermediate and with the OH group of the zeolite, leading to the formation of -O-Si-O-Si-O- chains (c).

As a result of the modification, self-assembled functional siloxane layers-films are formed on the surface of the zeolite. The modified zeolite thus obtained is a red-brown solid.

The use of water-alcohol solutions of TSC leads to a high rate of hydrolytic polycondensation of TSC, which leads (under solvent conditions alcohol:water=9:1) to the formation of a mechanical mixture of zeolite and modifier polycondensation product. Fixation of the modifier on the surface of the zeolite under these conditions is difficult. When the process is carried out in a hexane environment in the absence of additional moisture, the reactions of hydrolysis and condensation of TSC are realized only on the surface of the zeolite, which leads to the production of the target product - a modified zeolite. This is confirmed by the fact that the solution of TSC in hexane after the end of the modification process remains transparent and does not contain solid products of hydrolytic polycondensation of TSC. The remaining solution of TSC in hexane is stable during long-term storage and, after adjusting for the content of the modifier, can be reused.

Comparison of the proposed technical solution not only with the prototype, but also with other technical solutions in this and related fields did not allow to identify sources containing information about the known totality of all the distinctive features of the proposed technical solution.

A new set of features of the proposed method for producing an adsorbent: the use of calcium heulandite, its fractionation, pretreatment with a solution of hydrochloric acid and modification with a solution in hexane of 1-(3-triethoxysilylpropyl)thiosemicarbazide make it possible to obtain an adsorbent with a nickel sorption capacity of 165.7 mg/g, which 67.4% more than in the prototype. Therefore, we can conclude that the claimed invention meets the condition of patentability "inventive step".

The method is carried out as follows.

Calcium heulandite zeolite Ca[Al ₂ Si ₇ O ₁₈ ] * 6H ₂ O was used as a raw material for obtaining the sorbent. The zeolite was fractionated on sieves, a fraction of 0.5–1.0 mm was taken, which was hydrochloric acid at a temperature of 120-150°C for 24 hours, followed by filtration, washing and air drying of the zeolite. The obtained adsorbent was modified with a 1% solution of 1-(3-triethoxysilylpropyl)thiosemicarbazide (TSC) in hexane at heating to 50°C and stirring for 1 hour. The modified zeolite was filtered off and washed with hexane (3.3 ml per 1 g of zeolite), dried in air for 12 hours and then in an oven at 110°C for 1 hour. The original zeolite was not subjected to preliminary drying, and hexane was not subjected to absolute, the presence of moisture bound in zeolite and hexane is sufficient for the modification process.

The claimed method is illustrated by the following examples

Example 1. Zeolite activation.

A fraction of 0.5-1.0 mm of calcium heulandite (this particle size was chosen because it allows obtaining the maximum adsorption of Ni (II) ions and ensuring the optimal filtration rate in wastewater treatment), preheated to constant weight at a temperature of 150 ° C , treated with a 10-12% hydrochloric acid solution for 24 hours. Take 200 ml of solution per 10 g of zeolite. Then the suspension is filtered and washed with distilled water until neutral. The obtained activated zeolites ZH-HCl are dried to constant weight. The acid concentration of 10-12% hydrochloric acid, the temperature of 120-150°C and the time of 24 hours are chosen because they allow to maximize the textural characteristics of the natural mineral (table 1).

Table 1 - Textural characteristics of lumosilicates Characteristic ZH ZH-HCl Specific surface, m ² /g 33 75 Specific pore volume, cm ³ /g 0.015 0.036 Average pore size, nm 1.8 1.6

From the presented data (table 1) it can be seen that when the zeolite is activated with 10-12% hydrochloric acid at a temperature of 120-150°C, the specific surface area and specific pore volume increase by more than two times. The average pore size is reduced from 1.8 to 1.6 nm.

With an increase in the concentration of hydrochloric acid, temperature and time of treatment with acid, the textural characteristics improve slightly.

The adsorption capacity of the activated zeolite ZH-HCl was studied on model solutions containing Ni(II) ions under static conditions. NiSO ₄ ⋅ 7H ₂ O salt and distilled water were used to prepare model solutions. The content of nickel(II) ions in solutions was determined by standard methods.

The concentration of Ni(II) ions in solutions varied from 1 to 30 mg/L.

The volume of the investigated solutions - 0.1 l.

The weight of the adsorbent sample is 1 g.

Mixing time 120 minutes.

The adsorption value ( A , mg/g) was calculated by the equation:

where c ₀ and c _equals the initial and equilibrium concentrations of the metal in the solution, mg/l; V is the volume of the solution, l; m is the mass of the adsorbent, g.

The maximum adsorption value of Ni(II) ions was obtained with the following indicators:

The initial concentration of Ni(II) is 25.3 mg/l.

Equilibrium concentration of Ni(II) ions 13.7 mg/l

The adsorption value of Ni(II) ions was 11.6 mg/g.

A further increase in the concentration of Ni(II) ions does not lead to an increase in adsorption.

Example 2 Modification of a zeolite.

Zeolite, fractions of 0.5–1.0 mm calcium heulandite, were modified with a 10% solution of TSC in hexane when heated to 50°C (this temperature was chosen because it allows the most complete dissolution of TSC in hexane and prevents them from boiling away) and stirring for 1 hour. The mixing time was chosen as such, because it allows to achieve maximum coverage of the zeolite with a layer of modifier. With its increase, the degree of coverage changes slightly. The modified zeolite was filtered off and washed with hexane (3.3 ml per 1 g of zeolite allows free TSC to be washed off), air dried for 12 hours and then in an oven at 110° C. for 1 hour. Drying time and temperature is sufficient to remove moisture and hexane vapor from the zeolite. The adsorption capacity of the modified AS-TSC zeolite was determined on model solutions analogously to Example 1. The initially chosen high TSC concentration of 10% does not provide an acceptable adsorption of Ni(II) ions, because leads to excessive aggregation of zeolite particles.

The concentration of Ni(II) ions in solutions varied from 5 to 50 mg/l.

The volume of the investigated solutions - 0.1 l.

The weight of the adsorbent sample is 0.2 g.

Mixing time 120 minutes.

The maximum adsorption value of Ni(II) ions was obtained with the following indicators:

The initial concentration of Ni(II) is 49.7 mg/l.

Equilibrium concentration of Ni(II) ions 16.5 mg/l

The adsorption value of Ni(II) ions was 16.6 mg/g.

A further increase in the concentration of Ni(II) ions does not lead to an increase in adsorption.

Example 3 Modification of activated zeolite.

The adsorbent activated according to example 1 was modified with 0.5 (1.0; 1.8; 3.5; 4.5; 5.8) % TSC solution in hexane when heated to 50°C and stirred for 1 hour. The modified zeolite was filtered off and washed with hexane (3.3 ml per 1 g of zeolite), dried in air for 12 hours and then in an oven at 110°C for 1 hour. The adsorption capacity of the obtained zeolite ZH-HCl-TSC was determined on model solutions similarly to example 1, the data obtained are presented in table 2.

The concentration of Ni(II) ions in solutions varied from 5 to 400 mg/L.

The volume of the test solution is 0.1 l.

The weight of the adsorbent sample is 0.2 g.

Mixing time 120 minutes.

Table 2. Adsorption results Concentration
TSC modifier, % Maximum adsorption value, mg/g 0.5 120.6 1.0 165.7 1.8 135.2 3.5 86.5 4.5 51.1 5.8 35.2

The maximum adsorption value of Ni(II) ions was obtained with the following indicators:

TSC Modifier Concentration 1%

The initial concentration of Ni(II) is 400 mg/l.

Equilibrium concentration of Ni(II) ions 68.6 mg/l

The adsorption value of Ni(II) ions was 165.7 mg/g.

A further increase in the concentration of Ni(II) ions does not lead to an increase in adsorption.

The use of the claimed method makes it possible to increase the sorption capacity of the adsorbent fraction with respect to nickel ions due to the use of 1-(3-triethoxysilylpropyl)thiosemicarbazide as a modifier and pre-treatment of the zeolite with hydrochloric acid, providing good adsorption capacity. The modifier is produced on the basis of available reagents by a simple and technological reaction with high yield, which can serve as a cost-effective and effective surface modifier, in particular, heulandite zeolite. The adsorption value of nickel (II) ions is 165.7 mg/g.

Claims (1)

A method for producing an adsorbent for water purification from nickel (II), including modifying the zeolite with an organosilicon compound, characterized in that the calcium heulandite zeolite of a fraction of 0.5-1.0 mm, previously dried at a temperature of 150 ° C, is treated with 10-12% hydrochloric acid solution at a temperature of 120-150 ° C for 24 hours, then the resulting suspension is filtered and washed with distilled water until neutral, the resulting activated calcium heulandite ZH-HCl is dried to constant weight; after that, calcium heulandite is modified with a 1% solution of 1-(3-triethoxysilylpropyl)thiosemicarbazide TSC in hexane when heated to 50 °C and stirred for 1 hour, then the resulting modified calcium heulandite ZН-HCl-TSC is filtered off and washed with hexane in in an amount of 3.3 ml per 1 g of zeolite, dried in air for 12 hours and then in an oven at 110°C for 1 hour.

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