Preparation method and application of loofah adsorbent for efficient recovery of gold (III) from electronic waste

Abstract

The present invention discloses a preparation method and application of a loofah adsorbent for efficiently recovering gold (III) from electronic waste, belonging to the fields of hydrometallurgy and precious metal recovery technology. The method of the present invention comprises the following steps: weighing a loofah, washing it with deionized water, and drying it; soaking and modifying 0.1g of the loofah in a 0.05-1g / L modification solution at room temperature; washing, filtering, and drying the modified loofah; and preparing the modified solution by dissolving 0.05-1g of pyridine-2-azo-p-dimethylaniline in 1L of ethanol solution. The method of the present invention can quickly and effectively adsorb gold (III) from the leachate of waste circuit boards, and has the advantages of being simple to operate, rapid and efficient, environmentally friendly, having a high loading capacity, and being inexpensive.

Description

Technical Field

[0001] The invention discloses a preparation method and application of a loofah adsorbent for efficiently recovering gold (III) in electronic waste, belonging to the technical field of hydrometallurgy and precious metal recovery. Background Art

[0002] Gold, a precious metal with unique physical and chemical properties, is widely used in jewelry, electronic equipment, financial investment and other fields. However, with the continuous exploitation of gold resources, gold reserves and grades are decreasing year by year, and the degree of dispersion and difficulty of ore processing are also increasing. To meet the sustainable development of various industries in society, the industry has gradually focused on a renewable secondary gold resource: electronic waste. Common electronic waste includes mobile phone circuit boards, computer circuit boards, computer CPUs, etc. The gold grade in this type of solid waste is much higher than that in natural deposits. Studies have shown that the gold grade in computer components is as high as 900 grams per ton, and the gold grade in mobile phone printed circuit boards is as high as 1,200 grams per ton. At present, high-grade gold mines are only around 10 grams per ton. In addition, with the advancement of science and technology, the consumption of electronic products is increasing day by day, and the speed of updates and iterations is accelerating, which has caused tremendous pressure on environmental protection, but also provided us with a stable and sustainable way to recycle precious metals.

[0003] At present, the main methods for recycling gold from circuit boards include cyanide method, thiourea method, halogen method, thiosulfate method, etc. Among the many gold recovery methods, although the cyanide method has the advantages of high gold leaching efficiency and good economic benefits, the cyanide used in this method is a highly toxic reagent. After gold leaching, a large amount of cyanide-containing waste and wastewater will be generated, posing a threat to the environment and human life safety. Although the thiourea method and thiosulfate method have certain advantages in safety performance and leaching efficiency, both methods have the disadvantages of large reagent consumption and high cost, and cannot be promoted in actual production. Taking into account the raw material cost and leaching efficiency, the halogen method stands out and is considered to be the most effective gold leaching method.

[0004] After leaching, it is necessary to select a suitable method to separate and recover the gold element from the leaching solution; researchers have determined that in the halogen leaching solution, gold is separated as Au. 3+ The ionic form coexists stably with other metal ions in the leachate. Therefore, finding an effective gold recovery method is of great significance for the recovery of gold from electronic waste. Among various separation and enrichment methods such as electrodeposition, extraction, metal replacement, and adsorption, adsorption is widely used due to its simplicity, environmental friendliness, high efficiency, and reusability. In the field of gold recovery, traditional adsorbents such as activated carbon, mesoporous silica, and resins are commonly used, but activated carbon has poor adsorption capacity and is expensive. Mesoporous silica mostly exists in powder form. Although functionalized mesoporous silica has good adsorption effects, its morphology affects its industrial application. Resins are expensive, have poor selectivity, and require stringent elution conditions.

[0005] In recent years, domestic and foreign research teams have also developed a series of new adsorbents, including MOFs materials and various types of nano-adsorbents. However, most of these adsorbents are not suitable for acidic solutions, and the preparation process is complicated, the cost is high, and it is difficult to apply them on a large scale. In addition, the reagents used in existing precious metal recovery methods almost all contain sulfur and phosphorus. After gold leaching, a large amount of sulfur- and phosphorus-containing waste liquid, solid waste, and waste gas is generated, posing risks to the environment and organisms. Based on the above, in order to achieve effective recovery of gold from electronic waste, it is still necessary to find an adsorbent that is fast, efficient, green, low-cost, has a large load capacity, and has good adsorption performance. Summary of the Invention

[0006] The present invention aims to provide a method for preparing a loofah adsorbent, wherein the loofah is modified using pyridine-2-azo-p-dimethylaniline as a modifier, and the modified loofah can significantly improve the adsorption efficiency of gold, thereby providing a green, renewable, rapid, efficient, high-adsorption capacity, and low-cost adsorption method. The method specifically comprises the following steps:

[0007] (1) Weigh a loofah, wash off the surface dust with deionized water, filter, and dry;

[0008] (2) placing the loofah obtained in step (1) in an ethanol solution of pyridine-2-azo-p-dimethylaniline, soaking and modifying the loofah at room temperature, washing, filtering and drying to obtain the modified loofah.

[0009] Preferably, the concentration of the pyridine-2-azo-p-dimethylaniline in the ethanol solution of the present invention is 0.05-1 g / L.

[0010] Preferably, the soaking modification time of the present invention is 4 to 20 hours.

[0011] Another object of the present invention is to provide an application of the loofah adsorbent prepared by the method in the recovery of gold (III) from electronic waste. By modifying the loofah to adsorb gold (III) from the leachate of waste circuit boards, not only the performance of the loofah is regenerated, but also the environmentally friendly recycling of circuit boards is of great significance. The method specifically comprises the following steps:

[0012] (1) Take the waste circuit board, add 1:1 aqua regia and heat on a hot plate to dissolve it. After cooling, filter and take the filtrate for later use.

[0013] (2) Add loofah adsorbent to the filtrate, and the solid-liquid ratio of loofah to modified solution is 1:100 to 2:100, unit: g:mL.

[0014] The electronic waste mentioned in the present invention includes but is not limited to computer CPUs, circuit boards of mobile phones and other electronic products.

[0015] The beneficial effects of the present invention are:

[0016] (1) The modified loofah can significantly improve the adsorption speed and efficiency of gold (III). It can quickly adsorb gold under acidic conditions and has a large adsorption capacity.

[0017] (2) The modified loofah of the present invention is simple to prepare, the reagents used are harmless to the environment and organisms, and the recovery of gold (III) by the modified loofah is environmentally friendly and has good industrial application prospects.

[0018] (3) The modified loofah described in the present invention is a renewable natural agricultural waste with a wide source of raw materials and low cost, which is of great significance to the environmentally friendly recycling of electronic waste. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0020] Example 1

[0021] This embodiment uses 0.05g of modifier-modified loofah to adsorb gold (III) in waste circuit boards, comprising the following steps:

[0022] (1) Take two pieces of waste circuit boards, add 40 mL of 1:1 aqua regia and heat on a 400°C hot plate for 20 minutes. After cooling, filter and dilute to a 500 mL volumetric flask for later use.

[0023] (2) Weigh two portions of 0.1 g of untreated loofah in parallel, wash with deionized water, filter, and dry at 80 °C for 4 h.

[0024] (3) One portion of the loofah obtained in step (2) was placed in the modified solution at a solid-liquid ratio of 1:100 and soaked at room temperature for 8 hours, washed three times with deionized water, filtered, and dried at 60°C for 4 hours to obtain the modified loofah. The other portion was the original loofah.

[0025] The modified solution is prepared as follows: 0.05 g of pyridine-2-azo-p-dimethylaniline is dissolved in 1 L of ethanol solution.

[0026] (4) The modified loofah obtained in step (3) and the original loofah were respectively placed in 100 mL of the solution obtained in step (1) at pH = 2, and stirred for adsorption at the same room temperature; the concentration of gold (III) was 25 mg / L; after 5 hours of adsorption, the adsorption rate of gold (III) by the modified loofah reached 100%, and the loading capacity was 25 kg / t; 20 mg / L of gold remained in the original loofah solution.

[0027] Example 2

[0028] This embodiment uses 0.5g of modifier-modified loofah to adsorb gold (III) in waste circuit boards, comprising the following steps:

[0029] (1) Take a piece of waste circuit board, add 30mL of 1:1 aqua regia and heat on a 400℃ hot plate for 20 minutes. After cooling, filter and dilute to a 500mL volumetric flask for later use.

[0030] (2) Weigh two portions of 0.1 g of untreated loofah in parallel, wash with deionized water, filter, and dry at 80 °C for 4 h.

[0031] (3) One portion of the loofah obtained in step (2) was placed in the modified solution at a solid-liquid ratio of 2:100 and soaked at room temperature for 8 hours, washed with deionized water three times and then filtered, and dried at 60°C for 4 hours to obtain the modified loofah. The other portion was the original loofah.

[0032] The modified solution is prepared as follows: 0.5 g of pyridine-2-azo-p-dimethylaniline is dissolved in 1 L of ethanol solution.

[0033] (4) The modified loofah obtained in step (3) and the original loofah were respectively placed in 100 mL of the solution obtained in step (1) at pH = 2, and stirred for adsorption at the same room temperature; the concentration of gold (III) was 10 mg / L; after 2 hours of adsorption, the adsorption rate of gold (III) by the modified loofah reached 91%, and the loading capacity was 9.1 kg / t; 8.11 mg / L of gold remained in the original loofah solution.

[0034] Example 3

[0035] This embodiment uses 1g of modifier-modified loofah to adsorb gold (III) from waste circuit boards, comprising the following steps:

[0036] (1) Take two pieces of waste circuit boards, add 40 mL of 1:1 aqua regia and heat on a 400°C hot plate for 20 minutes. After cooling, filter and dilute to a 500 mL volumetric flask for later use.

[0037] (2) Weigh two portions of 0.1 g of untreated loofah in parallel, wash with deionized water, filter, and dry at 80 °C for 4 h.

[0038] (3) One portion of the loofah obtained in step (2) was placed in the modified solution at a solid-liquid ratio of 1.5:100 and soaked at room temperature for 20 hours, washed three times with deionized water, filtered, and dried at 60°C for 4 hours to obtain the modified loofah, and the other portion was the original loofah.

[0039] The modified solution is prepared as follows: 1 g of pyridine-2-azo-p-dimethylaniline is dissolved in 1 L of ethanol solution.

[0040] (4) The modified loofah obtained in step (3) and the original loofah were respectively placed in 100 mL of the solution obtained in step (1) at pH = 2, and stirred for adsorption at the same room temperature; the concentration of gold (III) was 25 mg / L; after adsorption for 3 hours, the adsorption rate of gold (III) by the modified loofah reached 88%, and the loading capacity was 22 kg / t; the gold remaining in the original loofah solution was 22.07 mg / L.

[0041] Example 4

[0042] This embodiment uses 0.75g of modifier-modified loofah to adsorb gold (III) in waste circuit boards, comprising the following steps:

[0043] (1) Take 5 pieces of waste circuit boards, add 80 mL of 1:1 aqua regia and heat on a 400°C hot plate for 40 minutes. After cooling, filter and dilute to a 500 mL volumetric flask for later use.

[0044] (2) Weigh two portions of 0.1 g of untreated loofah in parallel, wash with deionized water, filter, and dry at 80 °C for 4 h.

[0045] (3) One portion of the loofah obtained in step (2) was placed in the modified solution at a solid-liquid ratio of 1:100 and soaked at room temperature for 16 hours, washed three times with deionized water, filtered, and dried at 60°C for 4 hours to obtain the modified loofah. The other portion was the original loofah.

[0046] The modified solution is prepared as follows: 0.75 g of pyridine-2-azo-p-dimethylaniline is dissolved in 1 L of ethanol solution.

[0047] (4) The modified loofah obtained in step (3) and the original loofah were respectively placed in 100 mL of the solution obtained in step (1) at pH = 2, and stirred for adsorption at the same room temperature; the concentration of gold (III) was 73 mg / L; after 3 hours of adsorption, the adsorption rate of gold (III) by the modified loofah reached 81%, and the loading capacity was 59 kg / t; the gold remaining in the original loofah solution was 65.35 mg / L.

[0048] Example 5

[0049] This embodiment uses 0.25g of modifier-modified loofah to adsorb gold (III) in waste circuit boards, comprising the following steps:

[0050] (1) Take 3 pieces of waste circuit boards, add 50 mL of 1:1 aqua regia and heat on a 400°C hot plate for 30 minutes. After cooling, filter and dilute to a 500 mL volumetric flask for later use.

[0051] (2) Weigh two portions of 0.1 g of untreated loofah in parallel, wash with deionized water, filter, and dry at 80 °C for 4 h.

[0052] (3) One portion of the loofah obtained in step (2) was placed in the modified solution at a solid-liquid ratio of 2:100 and soaked at room temperature for 12 hours, washed three times with deionized water, filtered, and dried at 60°C for 4 hours to obtain the modified loofah. The other portion was the original loofah.

[0053] The modified solution is prepared as follows: 0.25 g of pyridine-2-azo-p-dimethylaniline is dissolved in 1 L of ethanol solution.

[0054] (4) The modified loofah obtained in step (3) and the original loofah were respectively placed in 100 mL of the solution obtained in step (1) at pH = 1, and stirred for adsorption at the same room temperature; the concentration of gold (III) was 42 mg / L; after 2 hours of adsorption, the adsorption rate of gold (III) by the modified loofah reached 55%, and the loading capacity was 23 kg / t; the gold remaining in the original loofah solution was 37.83 mg / L.

[0055] Example 6

[0056] This embodiment uses 0.1g of modifier-modified loofah to adsorb gold (III) in waste circuit boards, comprising the following steps:

[0057] (1) Take 4 pieces of waste circuit boards, add 50 mL of 1:1 aqua regia and heat on a 400℃ hot plate for 30 minutes. After cooling, filter and dilute to a 500 mL volumetric flask for later use.

[0058] (2) Weigh two portions of 0.1 g of untreated loofah in parallel, wash with deionized water, filter, and dry at 80 °C for 4 h.

[0059] (3) One portion of the loofah obtained in step (2) was placed in the modified solution at a solid-liquid ratio of 2:100, and the modified solution was immersed at room temperature for 20 hours. The modified solution was washed three times with deionized water and then filtered. The modified loofah was dried at 60°C for 4 hours to obtain the modified loofah. The other portion was the original loofah. The modified solution was prepared as follows: 0.1 g of pyridine-2-azodimethylaniline was dissolved in 1 L of ethanol solution.

[0060] (4) The modified loofah obtained in step (3) and the original loofah were respectively placed in 100 mL of the solution obtained in step (1) at pH = 1, and stirred for adsorption at the same room temperature; the concentration of gold (III) was 48 mg / L; after 4 hours of adsorption, the adsorption rate of gold (III) by the modified loofah reached 76%, and the loading capacity was 36 kg / t; the gold remaining in the original loofah solution was 40.25 mg / L.

[0061] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A preparation method of a loofah adsorbent, characterized in that, The specific steps include: (1) Weigh the loofah, wash the surface dust with deionized water, filter, and dry; (2) The loofah obtained in step (1) is placed in an ethanol solution of pyridine-2-azodimethylaniline, and is immersed in the solution at room temperature for modification. The modified loofah is then washed, filtered, and dried to obtain the modified loofah.

2. according to the preparation method of the described loofah adsorbent of claim 1, it is characterized in that: The concentration of the ethanol solution of pyridine-2-azo-p-dimethylaniline is 0.05-1 g / L.

3. according to the preparation method of the described loofah adsorbent of claim 1, it is characterized in that: The soaking modification time is 4~20h.

4. Use of the loofah adsorbent prepared by the method according to claim 1 or 2 in recovering gold (III) from electronic waste.

5. The use according to claim 4, characterized in that: The specific steps include: (1) Take the waste circuit board, add 1:1 aqua regia and heat on a hot plate to dissolve, cool and filter, take the filtrate and set aside; (2) Add loofah adsorbent to the filtrate, and the solid-liquid ratio of loofah to modified solution is 1:100~2:100, unit: g:mL.