CN108394950B

CN108394950B - Method for adsorbing noble metal gold ions

Info

Publication number: CN108394950B
Application number: CN201810260624.5A
Authority: CN
Inventors: 唐课文; 许卫凤; 胡呈弘; 张盼良
Original assignee: Hunan Institute of Science and Technology
Current assignee: Hunan Institute of Science and Technology
Priority date: 2018-03-27
Filing date: 2018-03-27
Publication date: 2021-01-15
Anticipated expiration: 2038-03-27
Also published as: CN108394950A

Abstract

The patent introduces a new method for adsorbing Au (III) in an aqueous solution by using a porous material, namely, a zeolite-like imidazole ester material ZIF-8 with the characteristics of high porosity, high specific surface area, strong stability, adjustable pore channels and the like is used as an adsorbent to adsorb Au (III) ions in the aqueous solution. The adsorption quantity of ZIF-8 to Au (III) can be greatly improved by selectively regulating and controlling the pH value, adsorption temperature, gold ion concentration, adsorbent quantity and adsorption time of the aqueous solution, and the maximum adsorption quantity exceeds 1000 mg/g. Compared with other adsorption separation technologies, the synthetic method of the adsorbent is simple, the adsorption capacity is large, materials can be reused, the environmental pollution is small, and a feasible new method is provided for recycling precious metals.

Description

Method for adsorbing noble metal gold ions

Technical Field

The invention belongs to the field of precious metal separation and recovery, and particularly relates to a method for adsorbing and separating Au (III) ions in an aqueous solution by using a zeolite-like imidazole ester material ZIF-8.

Background

The precious metals are low in content and dispersed in nature and are generally intergrown with other deposits, so that the precious metals obtained by the traditional method are mainly obtained from byproducts of some smelting processes, and the yield of the precious metals is difficult to improve. In order to cope with the contradiction between the supply and demand of the precious metal resources, the recovery and recycling of precious metals from secondary resources is a future development direction. Most of the precious metals produced by human beings enter the fields of life and industry, and the recycling market is extremely large. Therefore, there is an increasing interest in the recovery and recycling of precious metals, such as used precious metals from used electronic products, deactivated chemical catalysts, and mineral mining. The method not only can repeatedly use the scarce resources, but also can bring huge economic benefits to the society, play a certain role in environmental protection, be beneficial to building an ecological civilized society and promote the national economic development and scientific and technological progress.

The gold has excellent physical and chemical properties, such as high temperature oxidation resistance, corrosion resistance, electrical resistance, good conductivity, higher catalytic activity, stronger coordination ability and the like. Gold has a wide range of applications in industrial applications, known as industrial vitamins. The commercial value of gold has been greatly expanded by continuing stimulation of supply shortages and high industrial demand.

At present, methods applied to the separation of noble metals include adsorption, chemical precipitation, ion exchange, membrane filtration, electrolysis, biological treatment, and the like. Among the above methods, the adsorption method is widely used for separation of noble metals because of its advantages of low running cost, little influence on environment, simple operation, easy industrialization, etc. Currently, the biological adsorption method is researched mostly, and is an adsorption method with great development potential due to wide sources, low price, environmental protection and cleanness, but the biological adsorbent is weak in adsorption capacity, low in adsorption rate, complex in adsorption process, poor in recycling performance, low in selectivity, easy to be affected by impurities and ineffective, and currently, the biological adsorption method is still basically in a laboratory stage. Therefore, the search for new adsorbent materials with high-efficiency adsorption performance and high-efficiency recycling performance has potential application value and commercial value.

Metal-organic frameworks (MOFs) are porous materials formed by self-assembly of metal ions and organic ligands, have the characteristics of high pore structure, high specific surface area, adjustable pore size and the like, and are receiving increasing attention in various fields such as gas storage, separation, catalysis, drug release and the like, particularly in the field of separation methods. ZIF-8 is a novel zeolite imidazole ester-like metal organic framework porous material, which is formed by self-assembling zinc ions serving as a metal center and 2-methylimidazole. ZIF-8 has many advantages, such as permanence of pore channel, regular structure, high thermal stability, good chemical stability, etc., and thus has received extensive attention and application.

In the research, ZIF-8 is used as a novel precious metal adsorbent to adsorb and separate Au (III) in an aqueous solution. The influence of different factors on the adsorption effect, such as pH value, temperature, adsorption time, initial concentration and the like, is researched, and a new method is provided for the adsorption of the noble metal.

Disclosure of Invention

The invention aims to provide a novel precious metal Au adsorbent with large adsorption capacity, high stability and good regeneration performance, namely a zeolite imidazole ester metal organic framework porous material ZIF-8, and the novel precious metal Au adsorbent is applied to the adsorption separation of Au (III) in an aqueous solution. Aiming at the adsorption process, the influence of various conditions on the adsorption effect is explored.

The technical scheme adopted by the invention is as follows:

(1) synthesis of ZIF-8: a certain amount of zinc nitrate hexahydrate and 2-methylimidazole are mixed and completely dissolved in a certain amount of DMF solution (the molar ratio is 1:3:3), the reaction temperature is 140 ℃, and the reaction time is 24 hours. And after the reaction is finished, cooling to room temperature, performing suction filtration to obtain synthesized solid powder, washing with methanol for three times, and drying in a vacuum drying oven at 80 ℃ overnight to obtain the ZIF-8 product. According to XRD characterization, as shown in an attached figure 1 of the specification, the crystal structure of the prepared ZIF-8 is consistent with that of a standard card of the ZIF-8, and the ZIF-8 which is a zeolite-like imidazole ester metal organic framework material is successfully prepared. (2) Preparing Au (III) solution with a certain concentration, adjusting different pH values, adding a certain amount of ZIF-8 as an adsorbent, placing the solution in a constant-temperature water bath oscillator at a certain temperature, fully stirring for a certain time, taking a certain amount of samples after adsorption is finished, performing concentration determination before and after adsorption by using an atomic absorption spectrometer, and calculating the adsorption capacity and the adsorption rate. (3) Adding a certain amount of adsorbed ZIF-8 material into a certain amount of organic solvent, placing the mixture in a constant-temperature water area oscillator at a certain temperature, fully stirring for a certain time, filtering and drying after desorption, and carrying out next adsorption.

Compared with the prior art, the invention has the following advantages:

(1) the ZIF-8 material has larger specific surface area and higher adsorption capacity, can effectively adsorb Au (III) ions in an aqueous solution, and the adsorption capacity reaches over 1000 mg/g. (2) The ZIF-8 material can be repeatedly recycled after desorption, is an economical material, can reduce waste pollution and brings higher economic benefit. (3) The novel adsorbent ZIF-8 has the advantages of mild synthesis conditions, simple method and low raw material cost.

[ description of the drawings ]

Fig. 1 is an XRD characterization pattern.

[ detailed description ] according to the present embodiment

Preparation of mono, ZIF-8

380 mg of zinc nitrate hexahydrate and 315 mg of 2-methylimidazole are added into a 500 mL three-neck flask, 300 mL of DMF solvent is added, and the mixture is stirred until the mixture is completely dissolved; the three-neck flask is placed in an oil bath pot for heating, the reaction temperature is 140 ℃, and the reaction time is 24 hours. After the reaction is finished, cooling to room temperature, performing suction filtration to obtain synthesized solid powder, washing with 30 mL of methanol solvent for three times, and performing suction filtration; and (3) drying the solid in a vacuum drying oven at 80 ℃ overnight to obtain the ZIF-8 product.

Second, adsorption experiment and adsorbent cyclic utilization experiment

(1) Adsorption experiment: preparing Au (III) solution (10-1000 mg/L) with a certain concentration by using gold trichloride with the purity of 98%, adjusting the pH (2.5-12) of the aqueous solution by using sodium hydroxide or HCl with the concentration of 0.1 mol/L, adding a certain volume of the solution into a centrifuge tube or a conical flask, adding a certain amount of ZIF-8 serving as an adsorbent (0.2-1 mg/mL), placing the solution in a constant-temperature water bath oscillator at a certain temperature (5-80 ℃) for fully stirring for a certain time (5-2880 min), after adsorption is finished, taking a certain amount of samples, measuring the concentrations of the original solution and the residual solution after adsorption by using an atomic absorption spectrometer, and calculating the adsorption capacity and the adsorption rate. (2) Adsorbent recycle experiment: adding a certain volume (10-50 mL) of polar organic solvent (methanol or ethanol or acetonitrile or thiourea) into a 50 mL centrifuge tube as a desorption agent, adding 10 mg of adsorbed ZIF-8 material, placing the mixture in a constant-temperature water bath oscillator for oscillating desorption, setting a certain temperature (15-55 ℃) for 1-45 h, filtering and drying, and adsorbing the desorbed ZIF-8 material again.

Third, testing and analyzing

In the embodiment of the invention, the concentration of Au in the solution is analyzed by adopting an AA-6880 atomic absorption spectrophotometer Japan. The related calculation formulas of the adsorption quantity and the adsorption rate are as follows:

wherein the content of the first and second substances,qdenotes the amount of adsorption, subscript 0 denotes the initial value, and subscript t denotes time t.

Second, example

Example 1

Preparing Au (III) solution with the concentration of 300 mg/L by using gold trichloride with the purity of 98%, adding 100 mL of the solution into a 250 mL conical flask, adjusting the pH to 2.5 by using 0.1 mol/L HCl, adding 50 mg of ZIF-8 material as an adsorbent, placing the solution into a constant-temperature water bath oscillator for oscillating and adsorbing, setting the temperature to be 25 ℃, performing fixed-point sampling detection, measuring the concentrations of the original solution and the residual solution after adsorption by using an atomic absorption spectrometer, and after 42 hours, obtaining the adsorption capacity of 434 mg/L and the adsorption rate of 68%.

Example 2

Preparing Au (III) solution with the concentration of 300 mg/L by using gold trichloride with the purity of 98%, adding 20 mL of the solution into a 50 mL centrifuge tube, adjusting the pH to 5 by using 0.1 mol/L HCl, adding 10 mg of ZIF-8 material as an adsorbent, placing the solution into a constant-temperature water bath oscillator for oscillating adsorption, setting the temperature to be 25 ℃, and after 42 hours, taking a certain amount of sample, and measuring the concentrations of the original solution and the residual solution after adsorption by using an atomic absorption spectrometer, wherein the adsorption amount is 208 mg/L, and the adsorption rate is 42%.

Example 3

Preparing Au (III) solution with the concentration of 400 mg/L by using gold trichloride with the purity of 98%, adding 20 mL of the Au (III) solution into a 50 mL centrifuge tube, adjusting the pH to 2.5 by using 0.1 mol/L HCl, adding 10 mg of ZIF-8 material as an adsorbent, placing the solution into a constant-temperature water bath oscillator for oscillating adsorption, setting the temperature to be 45 ℃, and after 42 hours, taking a certain amount of sample, and measuring the concentrations of the original solution and the residual solution after adsorption by using an atomic absorption spectrometer, wherein the adsorption amount is 580 mg/L, and the adsorption rate is 68%.

Example 4

Preparing an Au (III) solution with the concentration of 900 mg/L by using gold trichloride with the purity of 98%, adding 20 mL of the Au (III) solution into a 50 mL centrifuge tube, adjusting the pH to 2.5 by using 0.1 mol/L HCl, adding 10 mg of ZIF-8 material as an adsorbent, placing the solution into a constant-temperature water bath oscillator for oscillating adsorption, setting the temperature to be 25 ℃, taking a certain amount of sample after 42 h, and measuring the concentrations of the original solution and the residual solution after adsorption by using an atomic absorption spectrometer, wherein the adsorption amount is 1192 mg/L, and the adsorption rate is 66%.

Example 5

Adding 20 mL of acetonitrile into a 50 mL centrifuge tube as a desorption agent, adding 10 mg of the adsorbed ZIF-8 material, placing the mixture in a constant-temperature water bath oscillator for oscillating desorption, setting the temperature at 25 ℃, filtering and drying after 42 hours, and adsorbing the desorbed ZIF-8 material again. After repeated use twice, the adsorption capacity is reduced from 317.38 mg/g to 271.92 mg/g.

The above examples merely express several embodiments of the present invention, and the description thereof is more specific and detailed, but the technical scope thereof is not limited to the above embodiments. It will be apparent to those skilled in the art that various modifications and embodiments can be made without departing from the spirit of the invention, and these are within the scope of the invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A method for adsorbing Au (III) in an aqueous solution by utilizing a zeolite-like imidazole ester metal organic framework material ZIF-8 is characterized in that the method for adsorbing and separating Au in the aqueous solution by adopting the ZIF-8 as an adsorbent is firstly proposed, and comprises the following operations: preparing Au (III) solution with a certain concentration by using gold trichloride with the purity of 98%, adjusting the pH value of the aqueous solution by using 0.1 mol/L sodium hydroxide or HCl, adding a certain volume of the solution into a centrifuge tube or a conical flask, adding a certain amount of ZIF-8 serving as an adsorbent, placing the solution into a constant-temperature water bath oscillator at a certain temperature, fully stirring for a certain time, taking a certain amount of sample after adsorption is finished, measuring the concentrations of the original solution and the residual solution after adsorption by using an atomic absorption spectrometer, and calculating the adsorption capacity and the adsorption rate; and an organic solvent is used as a desorption agent, the repeated performance of the ZIF-8 is researched, a certain volume of polar organic solvent is added into a 50 mL centrifugal tube to be used as the desorption agent, 10 mg of adsorbed ZIF-8 material is added, the mixture is placed in a constant-temperature water bath oscillator to be oscillated and desorbed, a certain temperature is set, after a certain time, the mixture is filtered and dried, and the desorbed ZIF-8 material is adsorbed again.

2. The method of claim 1, wherein the Au concentration is configured to be 10-1000 mg/L.

3. The method of claim 1, wherein the pH of the solution is set to 2.5 to 12.

4. The method of claim 1, wherein the amount of adsorbent is 0.1 to 1 mg per ml of solution.

5. The process of claim 1, wherein the adsorption temperature is 5 to 80 ℃.

6. The process according to claim 1, wherein the adsorption time is 5 to 2880 min.

7. The method of claim 1, wherein the desorption solvent is selected from ethanol, methanol, acetonitrile, and thiourea.

8. The method of claim 1, wherein the volume of the desorption solvent is 10-50 mL.

9. The process of claim 1, wherein the desorption time is 1 to 45 hours.

10. The process of claim 1, wherein the desorption temperature is 15 to 55 ℃.