A method for efficiently recovering gold from waste gold catalysts

Abstract

This invention belongs to the field of precious metal metallurgy technology, specifically relating to a highly efficient method for reducing gold from waste gold catalysts. The invention includes the following steps: Step 1, dissolving the waste gold catalyst; Step 2, reducing sponge gold. This invention optimizes existing methods for reducing gold from waste gold catalysts by using a buffer solution, eliminating the complex pH adjustment process.

Description

Technical Field

[0001] This invention belongs to the field of precious metal metallurgy technology, specifically relating to a method for efficiently reducing gold from waste gold catalysts. Background Technology

[0002] Gold catalysts have attracted much attention due to their large specific surface area and numerous active sites, and their demand has been increasing year by year. Given the dwindling domestic gold mining resources, the efficient recovery of gold resources from waste gold catalysts is of paramount importance.

[0003] Currently, the mainstream method for reducing gold from waste gold catalysts is the oxalic acid reduction method. However, this method has a low reaction rate and is very sensitive to pH values, requiring constant monitoring and adjustment of the pH value of the system, making it difficult to operate.

[0004] Therefore, it is crucial to provide an efficient method for reducing gold from waste gold catalysts. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art and propose a highly efficient method for reducing gold from waste gold catalysts. This invention optimizes existing methods for reducing gold from waste gold catalysts by using a buffer solution, eliminating the need for complex pH adjustment.

[0006] A method for efficiently reducing gold from waste gold catalysts specifically includes the following steps:

[0007] Step 1: Dissolution of waste gold catalyst:

[0008] Take 250-500g of degraded waste gold catalyst and place it in a beaker. Add aqua regia until the catalyst is submerged. Then place the beaker on an electric furnace and heat it at 150℃-250℃ until the solid is completely dissolved. Continue to concentrate the volume until small and dense bubbles appear on the surface of the solution. At this point, slowly add 80-150mL of concentrated hydrochloric acid to the solution to remove nitrate ions from the system. Repeat this process 5-10 times. If there are insoluble substances in the solution, filtration is required; otherwise, this step is unnecessary.

[0009] Step 2, reduction of sponge gold:

[0010] Dilute the solution obtained in step 1 with deionized water to 1500-2500 mL, add saturated sodium hydroxide solution until the pH is weakly acidic, then add an appropriate amount of buffer solution to adjust the pH to between 5 and 6. Place the beaker on an electric furnace and heat at 150℃-250℃ for 0.5-1 hour. Then slowly add saturated potassium oxalate solution to the solution while heating and stirring continuously until no sponge gold is formed when potassium oxalate solution is added. Continue heating the solution to boiling until the solution becomes clear and transparent. Wash and filter the resulting solid to obtain sponge gold.

[0011] Furthermore, in step 2, the buffer solution is an acetate-sodium acetate buffer, a potassium hydrogen phthalate-hydrochloric acid buffer, or a hexamethylenetetramine-hydrochloric acid buffer.

[0012] Further, the method for preparing the acetate-sodium acetate buffer solution is as follows: take 41 mL of 0.2 mol / L acetic acid solution and 9 mL of 0.2 mol / L sodium acetate solution, mix them evenly, and dilute with deionized water to 100 mL.

[0013] Further, the potassium hydrogen phthalate-hydrochloric acid buffer solution is prepared by mixing 25 mL of 0.2 mol / L potassium hydrogen phthalate solution and 6 mL of 0.1 mol / L hydrochloric acid evenly, and then diluting with deionized water to 100 mL.

[0014] Furthermore, the preparation method of the hexamethylenetetramine-hydrochloric acid buffer is as follows: take 4g of hexamethylenetetramine, add 20mL of deionized water and 1mL of hydrochloric acid, and dilute with deionized water to 100mL.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0016] 1. By using a buffer solution, the complex process of adjusting the pH value of the system is eliminated, making the entire reduction process more convenient and efficient.

[0017] 2. Using potassium oxalate as a reducing agent reduces costs and produces no toxic or harmful substances.

[0018] 3. It improves the reaction rate and saves one day or more compared with existing methods.

[0019] 4. The direct recovery rate of sponge gold is ≥99.97%, while the current technology is around 99.95%.

[0020] 5. The purity of sponge gold is ≥99.98%, while the existing technology is ≥99.95%. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] A method for efficiently reducing gold from waste gold catalysts specifically includes the following steps:

[0023] Step 1: Dissolution of waste gold catalyst:

[0024] Take 250-500g of degraded waste gold catalyst and place it in a beaker. Add aqua regia until the catalyst is submerged. Then place the beaker on an electric furnace and heat it at 150℃-250℃ until the solid is completely dissolved. Continue to concentrate the volume until small and dense bubbles appear on the surface of the solution. At this point, slowly add 80-150mL of concentrated hydrochloric acid to the solution to remove nitrate ions from the system. Repeat this process 5-10 times. If there are insoluble substances in the solution, filtration is required; otherwise, this step is unnecessary.

[0025] Step 2, reduction of sponge gold:

[0026] Dilute the solution obtained in step 1 with deionized water to 1500-2500 mL, add saturated sodium hydroxide solution until the pH is weakly acidic, then add an appropriate amount of buffer solution to adjust the pH to between 5 and 6. Place the beaker on an electric furnace and heat at 150℃-250℃ for 0.5-1 hour. Then slowly add saturated potassium oxalate solution to the solution while heating and stirring continuously until no sponge gold is formed when potassium oxalate solution is added. Continue heating the solution to boiling until the solution becomes clear and transparent. Wash and filter the resulting solid to obtain sponge gold.

[0027] Furthermore, in step 2, the buffer solution is an acetate-sodium acetate buffer, a potassium hydrogen phthalate-hydrochloric acid buffer, or a hexamethylenetetramine-hydrochloric acid buffer.

[0028] Further, the method for preparing the acetate-sodium acetate buffer solution is as follows: take 41 mL of 0.2 mol / L acetic acid solution and 9 mL of 0.2 mol / L sodium acetate solution, mix them evenly, and dilute with deionized water to 100 mL.

[0029] Further, the potassium hydrogen phthalate-hydrochloric acid buffer solution is prepared by mixing 25 mL of 0.2 mol / L potassium hydrogen phthalate solution and 6 mL of 0.1 mol / L hydrochloric acid evenly, and then diluting with deionized water to 100 mL.

[0030] Furthermore, the preparation method of the hexamethylenetetramine-hydrochloric acid buffer is as follows: take 4g of hexamethylenetetramine, add 20mL of deionized water and 1mL of hydrochloric acid, and dilute with deionized water to 100mL.

[0031] Example 1.

[0032] Take 250g of degraded waste gold catalyst and place it in a beaker. Add 1000mL of aqua regia and place the beaker on an electric stove. Heat it at 200℃ until the solid is completely dissolved. Continue to concentrate the volume until small and dense bubbles appear on the surface of the solution. At this point, slowly add 100mL of concentrated hydrochloric acid to the solution to remove nitrate ions from the system. Repeat this process 8 times. If there are insoluble substances in the solution, filtration is required. Otherwise, this step is unnecessary.

[0033] Dilute the above solution to 2000 mL with deionized water, add a saturated sodium hydroxide solution until the pH reaches 5, then add an appropriate amount of acetate-sodium acetate buffer solution to adjust the pH to 6. Place the beaker on an electric furnace and heat at 150°C for 30 min. Then slowly add a saturated potassium oxalate solution to the solution while continuously heating and stirring until no gold sponge forms upon addition of the potassium oxalate solution. Continue heating the solution to boiling and until the solution becomes clear and transparent; wash and filter the resulting solid to obtain gold sponge.

[0034] result:

[0035] Sponge gold direct recovery rate: 99.97%;

[0036] Time required to recycle sponge gold: 5 hours;

[0037] The purity of sponge gold is 99.99%.

[0038] Example 2.

[0039] Take 250g of degraded waste gold catalyst and place it in a beaker. Add 1000mL of aqua regia and place the beaker on an electric stove. Heat it at 200℃ until the solid is completely dissolved. Continue to concentrate the volume until small and dense bubbles appear on the surface of the solution. At this point, slowly add 100mL of concentrated hydrochloric acid to the solution to remove nitrate ions from the system. Repeat this process 8 times. If there are insoluble substances in the solution, filtration is required. Otherwise, this step is unnecessary.

[0040] Dilute the above solution to 2000 mL with deionized water, add saturated sodium hydroxide solution until the pH reaches 5, then add an appropriate amount of potassium hydrogen phthalate-hydrochloric acid buffer solution to precisely adjust the pH to 6. Place the beaker on an electric furnace and heat at 150°C for 30 min. Then slowly add saturated potassium oxalate solution to the solution while continuously heating and stirring until no sponge gold is formed upon addition of potassium oxalate solution. Continue heating the solution to boiling and until the solution becomes clear and transparent; wash and filter the resulting solid to obtain sponge gold.

[0041] result:

[0042] Sponge gold direct recovery rate: 99.97%;

[0043] Time required to recycle the painting sponge: 5 hours;

[0044] The purity of sponge gold is 99.98%.

[0045] Example 3.

[0046] Take 250g of degraded waste gold catalyst and place it in a beaker. Add 1000mL of aqua regia and place the beaker on an electric stove. Heat it at 200℃ until the solid is completely dissolved. Continue to concentrate the volume until small and dense bubbles appear on the surface of the solution. At this point, slowly add 100mL of concentrated hydrochloric acid to the solution to remove nitrate ions from the system. Repeat this process 8 times. If there are insoluble substances in the solution, filtration is required. Otherwise, this step is unnecessary.

[0047] Dilute the above solution to 2000 mL with deionized water, add a saturated sodium hydroxide solution until the pH reaches 5, then add an appropriate amount of hexamethylenetetramine-hydrochloric acid buffer solution to precisely adjust the pH to 6. Place the beaker on an electric stove and heat at 150°C for 30 min. Then slowly add a saturated potassium oxalate solution to the solution while continuously heating and stirring until no sponge gold is formed upon addition of the potassium oxalate solution. Continue heating the solution to boiling and until the solution becomes clear and transparent; wash and filter the resulting solid to obtain sponge gold.

[0048] result:

[0049] Sponge gold direct recovery rate: 99.97%;

[0050] Time to recycle sponge gold: 6 hours;

[0051] The purity of sponge gold is 99.99%.

[0052] Comparative Example 1.

[0053] Take 250g of degraded waste gold catalyst and place it in a beaker. Add 1000mL of aqua regia and place the beaker on an electric stove. Heat it at 200℃ until the solid is completely dissolved. Continue to concentrate the volume until small and dense bubbles appear on the surface of the solution. At this point, slowly add 100mL of concentrated hydrochloric acid to the solution to remove nitrate ions from the system. Repeat this process 8 times. If there are insoluble substances in the solution, filtration is required. Otherwise, this step is unnecessary.

[0054] The above solution was diluted to 2000 mL with deionized water, and a saturated sodium hydroxide solution was added to precisely adjust the pH to 2. The beaker was placed on an electric stove and heated at 150°C for 30 minutes. Subsequently, oxalic acid solution was slowly added to the solution in multiple batches, while continuously heating and stirring. During this process, the pH of the solution needed to be monitored continuously, and the pH of the system was adjusted to maintain 2 using 1:1 hydrochloric acid. When no sponge gold was formed upon adding oxalic acid solution, the solution was continued to be heated to boiling until it became clear and transparent. The resulting solid was washed and filtered to obtain sponge gold.

[0055] result:

[0056] Sponge gold direct recovery rate: 99.95%;

[0057] Time required to recycle sponge gold: 10 hours;

[0058] The purity of sponge gold is 99.95%.

[0059] Compared to the method mentioned in this scheme, the traditional oxalic acid reduction method has a longer reaction time, requires constant adjustment of the pH value of the system, and is cumbersome to operate.

Claims

1. A method for efficiently reducing gold from waste gold catalysts, characterized in that, Specifically, the following steps are included: Step 1: Dissolution of waste gold catalyst: Place 250-500g of degraded waste gold catalyst in a beaker, add aqua regia until the catalyst is submerged, then place the beaker on an electric furnace and heat at 150℃-250℃ until the solid is completely dissolved; continue to concentrate the volume until small and dense bubbles appear on the surface of the solution. At this point, slowly add 80-150mL of concentrated hydrochloric acid to the solution to remove nitrate ions from the system. Repeat this process 5-10 times. If there are insoluble substances in the solution, filtration is required; otherwise, this step is unnecessary. Step 2, reduction of sponge gold: Dilute the solution obtained in step 1 with deionized water to 1500-2500 mL, add saturated sodium hydroxide solution until the pH is weakly acidic, then add an appropriate amount of buffer solution to adjust the pH to between 5 and 6. Place the beaker on an electric furnace and heat at 150℃-250℃ for 0.5-1 hour. Then slowly add saturated potassium oxalate solution to the solution while continuously heating and stirring until no sponge gold is formed when the potassium oxalate solution is added. Continue heating the solution to boiling until the solution becomes clear and transparent. Wash and filter the resulting solid to obtain sponge gold. In step 2, the buffer solution is an acetate-sodium acetate buffer, a potassium hydrogen phthalate-hydrochloric acid buffer, or a hexamethylenetetramine-hydrochloric acid buffer.

2. The method for efficiently reducing gold from waste gold catalysts according to claim 1, characterized in that, The method for preparing the acetate-sodium acetate buffer solution is as follows: take 41 mL of 0.2 mol / L acetic acid solution and 9 mL of 0.2 mol / L sodium acetate solution, mix them evenly, and dilute with deionized water to 100 mL.

3. The method for efficiently reducing gold from waste gold catalysts according to claim 1, characterized in that, The potassium hydrogen phthalate-hydrochloric acid buffer solution is prepared as follows: 25 mL of 0.2 mol / L potassium hydrogen phthalate solution and 6 mL of 0.1 mol / L hydrochloric acid are mixed evenly and then diluted with deionized water to 100 mL.

4. The method for efficiently reducing gold from waste gold catalysts according to claim 1, characterized in that, The preparation method of the hexamethylenetetramine-hydrochloric acid buffer is as follows: take 4g of hexamethylenetetramine, add 20mL of deionized water and 1mL of hydrochloric acid, and dilute with deionized water to 100mL.