Method for reducing the amount of flocculants in gold smelting noble liquid

Abstract

The application discloses a method for reducing flocculants in gold smelting liquid, and belongs to the technical field of water treatment and ore dressing and smelting. In the first step, the pH of the gold smelting liquid is adjusted to 5.5-8.5; in the second step, modified activated carbon is added into the gold smelting liquid at a dosage of 0.4-0.6 g / L, the temperature of the gold smelting liquid is adjusted to 35-45 DEG C, and adsorption is carried out for 4-6 h under stirring. The application solves the problem of flocculant enrichment in ore dressing and smelting water, realizes efficient removal of flocculants in ore dressing and smelting water, has good economic efficiency and environmental protection, and meets the actual application requirements of industry. The application provides a new technical scheme for removing flocculants in ore dressing and smelting water, is suitable for water treatment processes in gold ore dressing and smelting industries, and has a wide industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment and mineral processing, and relates to a method for reducing the amount of flocculants in mineral processing water, especially to a method for treating polyacrylamide flocculants in precious liquid in gold ore dressing and smelting. BACKGROUND

[0002] In the gold ore dressing and smelting industry, flocculants are key additives for realizing solid-liquid separation of ore slurry. Among them, anionic polyacrylamide (PAM) accounts for more than 90% of the application due to its excellent flocculation effect. However, the continuous enrichment of flocculants in leaching precious liquid will cause a series of industry pain points: the filter cloth of the precious liquid purification tank is frequently blocked, leading to a decrease in production efficiency and an increase in equipment maintenance cost; the flocculant film wraps zinc powder and forms a complex with gold ions, reducing gold recovery rate; and it also increases the COD value of wastewater, increasing the difficulty of treatment and environmental pressure.

[0003] Existing flocculant removal technologies have obvious limitations: membrane separation technology has high equipment investment and operation cost, and is prone to membrane pollution; chemical oxidation technology consumes a large amount of oxidizing agent and may produce toxic intermediates such as acrylamide monomer; and biodegradation technology has high requirements for environmental conditions and is inhibited by toxic substances such as heavy metal ions in mineral processing wastewater, making it difficult to be practically applied.

[0004] As a new type of environmental functional material, activated carbon has the advantages of large specific surface area, rich pore structure and low preparation cost. However, existing researches mainly focus on the treatment of conventional pollutants. For example, the Chinese invention patent application with the publication number CN109502933A discloses a treatment method and system for wastewater containing polyacrylamide, which utilizes the physical adsorption function of activated carbon and combines with biological degradation means to reduce the probability of blockage of polyacrylamide wastewater directly into the reactor. However, there are few special studies on specific flocculants in mineral processing water, and the system is not optimized in combination with industrial conditions. SUMMARY

[0005] The technical problem to be solved by the application is to provide a method for reducing the amount of flocculants in precious liquid in gold smelting, to solve the problem of flocculant enrichment in mineral processing water, to realize efficient reduction of flocculants in mineral processing water, and to have good economic and environmental performance to meet the needs of industrial practical application.

[0006] The technical solution of the application is as follows:

[0007] A method for reducing the amount of flocculants in precious liquid in gold smelting, the treatment steps are as follows:

[0008] Step 1, adjust the pH of the precious liquid in gold smelting to 5.5-8.5;

[0009] Second step, adding adsorption: adding modified activated carbon into the gold smelting liquid at a dosage of 0.4-0.6 g / L, adjusting the temperature of the gold smelting liquid to 35-45℃, and adsorbing for 4-6 h under stirring;

[0010] The preparation steps of the modified activated carbon are as follows:

[0011] (1) Preparation of modification liquid: dissolving lauric acid in a methanol aqueous solution and stirring uniformly;

[0012] (2) Modification reaction: adding ordinary activated carbon with a mass of 75-175% of lauric acid into the modification liquid, and stirring at a constant temperature of 70-75℃ for 5-7 h;

[0013] (3) Post-treatment: washing the activated carbon after modification reaction with hexane to remove unreacted lauric acid on the surface, and drying to a constant weight.

[0014] Preferably, in step (2) of the second step, the amount of lauric acid added is 100% of the mass of the ordinary activated carbon.

[0015] Preferably, in step (2) of the second step, the modification reaction temperature is 70℃.

[0016] Preferably, in step (2) of the second step, the modification time is 7 h.

[0017] Preferably, the preparation steps of the modified activated carbon further comprise:

[0018] (4) Directional modification: immersing the modified activated carbon obtained in step (3) into a 0.5-1.0 mol / L citric acid solution by using the immersion method, heating at 60-80℃ for 4-6 h, and drying after suction filtration to obtain directional modified activated carbon; the mass-volume ratio of the modified activated carbon to the citric acid solution is 1 g:(3-5) mL.

[0019] Preferably, in the first step, the pH of the gold smelting liquid is adjusted to 7.0-8.0.

[0020] Preferably, in the second step, the temperature of the gold smelting liquid is adjusted to 45℃.

[0021] Preferably, in the second step, adsorption is performed for 6 h under stirring.

[0022] Preferably, the ordinary activated carbon is RO3520 activated carbon.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] Firstly, the application selects suitable activated carbon material, the micropore and mesopore of the activated carbon intercepts the PAM macromolecular chain through van der Waals force, and the surface carboxyl and hydroxyl form hydrogen bond with the PAM amide group, which strengthens the selective adsorption, can effectively reduce the adsorption of gold cyanide complex in the noble liquid, and better reduces the loss rate of valuable metals such as gold and silver in the noble liquid. On this basis, the removal rate of the flocculant in the beneficiation water can meet the requirements of industrial scenes, effectively solve the problem of frequent plugging of filter cloth of the noble liquid purification cabinet, and the problem of flocculant film wrapping zinc powder and forming complex with gold ions to reduce the gold recovery rate, and to a certain extent, reduce the COD value of waste water, and increase the difficulty and environmental protection pressure.

[0025] In particular, the special modified activated carbon prepared by the application has a flocculant removal rate of 17.90% in the beneficiation water, and an adsorption capacity of 7.12mg / g, which is better than unmodified activated carbon and conventional adsorption materials, and can more effectively alleviate the filter cloth plugging and improve the gold recovery rate.

[0026] In addition, the application further modifies the special modified activated carbon, adjusts the surface properties of the modified activated carbon, controls the pore structure and surface functional groups, and achieves the selective adsorption of PAM, while weakening the adsorption effect of gold cyanide complex. The activated carbon after directional modification of the application is more suitable for adsorbing and removing flocculants from the noble liquid.

[0027] Secondly, the modified raw material of the application has a wide source and a simple preparation process, and does not need complex equipment; the dosage is only about 0.5g / L, and the material wear rate is only 4.72%, the mechanical stability is good, the indirect cost such as filter cloth replacement and hazardous waste disposal can be reduced, and the economic advantage is significant.

[0028] Thirdly, the adsorption process of the application has no secondary pollution, avoids the risk of generating toxic intermediate products by chemical oxidation technology, and realizes "waste treatment with waste". The regenerating solvent can be recycled and reused, and there is no additional pollutant emission. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a modified activated carbon prepared by different lauric acid addition amounts in embodiment 1 of the application, and the influence line graph of the removal rate of anionic polyacrylamide. The abscissa represents the lauric acid addition amount corresponding to 2g of dry activated carbon raw material.

[0030] Figure 2 is a modified activated carbon prepared by different modification temperatures in embodiment 1 of the application, and the influence line graph of the removal rate of anionic polyacrylamide.

[0031] Figure 3 is a modified activated carbon prepared by different modification reaction times in embodiment 1 of the application, and the influence line graph of the removal rate of anionic polyacrylamide.

[0032] Figure 4 Figure 2 is a graph showing the effect of different activated carbons on the adsorption of anionic polyacrylamide at different adsorption times according to Example 2 of the present application. The graph also shows a comparison of the effect of activated carbons before and after modification on the adsorption of anionic polyacrylamide at different adsorption times.

[0033] Figure 5 Figure 3 is a graph showing the effect of the dosage of modified activated carbon on the adsorption of anionic polyacrylamide according to Example 2 of the present application.

[0034] Figure 6 Figure 4 is a graph showing the effect of modified activated carbon on the adsorption of anionic polyacrylamide at different adsorption reaction temperatures according to Example 2 of the present application. DETAILED DESCRIPTION

[0035] The present application is further illustrated by the following examples, comparative examples and experimental data. It should be noted that the scope of the present application is not limited to the examples described above, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of the present application.

[0036] Example 1, Preparation of Modified Activated Carbon

[0037] Pretreatment: 300 g of RO3520 activated carbon as ordinary activated carbon was added to 1.5 L of water and stirred at 750 r / min for 2 h. After washing with a 1.00 mm test sieve, the activated carbon was dried at 105°C and screened to remove impurities using a 50 mesh sieve for standby use.

[0038] Preparation of modification liquid: 2.0 g of lauric acid was dissolved in 100 mL of 10% (v / v) methanol aqueous solution and stirred uniformly.

[0039] Modification reaction: 2 g of pretreated RO3520 activated carbon was added to the modification liquid, and constant temperature stirring was performed at 70°C and 150 r / min for 7.0 h. During the reaction, the mixture was stirred for 10 min every 1 h to ensure uniform mixing.

[0040] Post-treatment: After the reaction was completed, the activated carbon was washed with hexane 3 times to remove unreacted lauric acid on the surface, and dried at 60°C until the weight was constant to obtain the modified activated carbon.

[0041] Related parameter selection test and results:

[0042] (1) Effect of modified activated carbon prepared by different lauric acid addition amounts on the removal rate of anionic polyacrylamide.

[0043] Only the lauric acid addition ratio was changed, and the removal rate of anionic polyacrylamide at different ratios was determined, and the results are shown in Table 1. Figure 1

[0044] From​Figure 1 It is known that as the proportion of lauric acid added increases, the removal rate of anionic polyacrylamide by modified activated carbon also increases. When the amount of lauric acid added reaches 100% of the mass of the activated carbon raw material, the removal rate approaches its peak. Therefore, this invention selects the amount of lauric acid added to be 75-175% of the mass of the activated carbon raw material, and further preferably 100%, i.e., 2.0g in this embodiment.

[0045] (II) Effect of modified activated carbon prepared at different modification temperatures on the removal rate of anionic polyacrylamide.

[0046] The removal rate of anionic polyacrylamide was measured at different modification temperatures by only changing the modification temperature. The results are shown in [Figure number missing]. Figure 2 .

[0047] from Figure 2 It is evident that modified activated carbon prepared at different modification temperatures has a significant impact on the removal rate of anionic polyacrylamide. When the modification temperature is below 70℃, the polyacrylamide removal effect is not significant, while above 75℃, the polyacrylamide removal rate decreases rapidly with increasing temperature. Therefore, this invention selects a modification temperature of 70℃~75℃, and further preferably 70℃.

[0048] Experiment on the effect of modified activated carbon prepared with different modification reaction times on the removal rate of anionic polyacrylamide.

[0049] By varying only the modification time, the removal rate of anionic polyacrylamide was measured under different modification reaction times. The results are shown in [Figure Number]. Figure 3 .

[0050] from Figure 3 It is known that when the modification time is less than 5 hours, the removal effect of polyacrylamide is not obvious, and when it exceeds 5 hours, the removal rate of polyacrylamide does not increase significantly with the extension of time. Therefore, the present invention selects a modification time of 5 to 7 hours, and further preferably 7 hours.

[0051] Example 2: Reduction of Flocculant in Precious Gold Smelting Solution (Example 1)

[0052] Target of treatment: Precious liquor containing polyacrylamide flocculant, generated during gold ore beneficiation and smelting. In this example, the wastewater is a leaching precious liquor with the following composition: gold grade 12.1 g / t, silver grade 25.3 g / t, copper grade 0.16%, lead grade 0.0017%, and zinc grade 0.11%. The polyacrylamide flocculant concentration is 20 mg / L. The treatment steps are as follows:

[0053] I. Adjusting the pH of wastewater:

[0054] Adjust the pH of the wastewater to 7.0-8.0 to avoid destroying the surface functional groups of activated carbon at extreme pH, avoid polyacrylamide hydrolysis, or metal hydroxide precipitation, and protect the stability of gold cyanide complexes.

[0055] II. Adding adsorbent:

[0056] Scheme A: Add ordinary activated carbon (RO3520 activated carbon) to the wastewater at a dosage of 0.5 g / L, adjust the wastewater solution temperature to 45°C, and stir at a speed of 150 r / min for 6 h.

[0057] After detection, the adsorption capacity of ordinary activated carbon was 4.32 mg / g, the removal rate of polyacrylamide was 10.79%, and the gold adsorption rate was 98.01%.

[0058] Scheme B: Add modified activated carbon to the wastewater at a dosage of 0.5 g / L, adjust the wastewater solution temperature to 45°C, and stir at a speed of 150 r / min for 6 h.

[0059] After detection, the adsorption capacity of modified activated carbon was 7.12 mg / g, the removal rate of polyacrylamide was 17.80%, and the gold adsorption rate was 73.27%.

[0060] Comparison test of adsorption capacity of scheme A and scheme B.

[0061] Under different adsorption times, the adsorption capacity of anionic polyacrylamide by activated carbon in scheme A and scheme B was detected, and the results are shown in Figure 4 .

[0062] It can be seen from Figure 4 that the adsorption effect of scheme B on anionic polyacrylamide is better than that of scheme A.

[0063] It can also be seen from Figure 4 that in scheme B, the adsorption equilibrium is basically reached at 5 h, the adsorption capacity is 7.12 mg / g, and the removal rate of flocculants is 17.90%. Therefore, the adsorption time is selected to be 4-6 hours, and further preferably 6 hours.

[0064] Scheme B related parameter selection test and results:

[0065] (1) The effect of modified activated carbon dosage on the adsorption capacity of anionic polyacrylamide was tested.

[0066] Only the dosage of modified activated carbon was changed, and the adsorption capacity of anionic polyacrylamide was detected, and the results are shown in Figure 5 .

[0067] From Figure 5It can be seen that when the dosage of the modified activated carbon reaches 0.5 g / L, further increasing the dosage will not continue to increase the adsorption capacity, but will decrease. Therefore, the dosage of the modified activated carbon is selected as 0.4-0.6 g / L, and is further preferably 0.5 g / L.

[0068] (2) The influence test of different adsorption reaction temperatures on the adsorption capacity of anionic polyacrylamide.

[0069] Only the adsorption reaction temperature is changed, and the adsorption capacity of anionic polyacrylamide is detected, and the results are shown in Table 2. Figure 6 .

[0070] It can be seen from Table 2 that the adsorption capacity of the modified activated carbon prepared in the application for anionic polyacrylamide increases with the increase of the adsorption reaction temperature. Figure 6

[0071] Considering the production cost and energy consumption factors, the adsorption reaction temperature is selected as 35-45 DEG C, and is further preferably 45 DEG C.

[0072] Description: The detection method of the adsorption test in Example 2: starch-cadmium iodide method is used to measure the absorbance of the solution at different time points at 585 nm wavelength, and the residual flocculant concentration and the adsorption capacity are calculated.

[0073] Example 3, preparation example of directional modified activated carbon

[0074] The modified activated carbon prepared in Example 1 is immersed in 0.5 mol / L citric acid solution, heated in a water bath at 70 DEG C for 5 h, and dried at 110 DEG C after suction filtration, to obtain the directional modified activated carbon. 5 mL of citric acid solution corresponds to 1 g of modified activated carbon.

[0075] Example 4, second example of reducing the amount of flocculant in gold smelting liquid

[0076] Treatment object: same as Example 2. The treatment steps are as follows:

[0077] I. Adjust the pH of the wastewater: same as Example 2.

[0078] II. Dosage of adsorption:

[0079] Scheme C: The directional modified activated carbon prepared in Example 3 is added to the wastewater at a dosage of 0.5 g / L, the temperature of the wastewater solution is adjusted to 45 DEG C, the stirring speed is 150 r / min, and the adsorption is 6 h.

[0080] After detection, the adsorption capacity of the modified activated carbon is 11.36 mg / g, the removal rate of polyacrylamide is 28.4%, and the gold adsorption rate is 53.3%.

[0081] Example 5, wear performance test example of modified activated carbon​

[0082] Test method: Wear test was carried out according to the gold industry standard "Granular activated carbon for gold production". 40 g of the modified activated carbon prepared in Example 1 and the directional modified activated carbon prepared in Example 3 were weighed, respectively, and 40% slurry (-0.074 mm content 90%) was added, stirred at 450 r / min for 72 h, separated by 0.50 mm test sieve, and dried at 105°C.

[0083] Test results: The wear rate of the modified activated carbon prepared in Example 1 was 4.72%, and the wear rate of the directional modified activated carbon prepared in Example 3 was 5.13%. Both of them could withstand the wear during the industrial slurry stirring process and meet the long-term operation requirements.

[0084] Example 6, modified activated carbon regeneration performance test example

[0085] Test conditions: 5 g of the modified activated carbon prepared in Example 1 and the directional modified activated carbon prepared in Example 3 were saturated with adsorption, respectively, and 50 mL of petroleum ether was added. Desorption was carried out at 60°C and 120 r / min stirring for 2 h, respectively. After desorption, each was washed with deionized water for 3 times, dried at 60°C, and then the adsorption performance test of Example 2 was repeated. The cumulative regeneration was 5 times.

[0086] Test results: (1) The modified activated carbon prepared in Example 1: the adsorption capacity after the first regeneration was 6.89 mg / g, after the third regeneration was 6.23 mg / g, and after the fifth regeneration was 6.05 mg / g, still maintaining more than 85% of the initial adsorption capacity, and the regeneration effect was good. (2) The directional modified activated carbon prepared in Example 3: the adsorption capacity after the first regeneration was 11.07 mg / g, after the third regeneration was 10.85 mg / g, and after the fifth regeneration was 10.01 mg / g, still maintaining more than 85% of the initial adsorption capacity, and the regeneration effect was good.

[0087] Explanation: Since the modified activated carbon or the directional modified activated carbon still inevitably adsorbs part of the gold while adsorbing the flocculant, the modified activated carbon or the directional modified activated carbon saturated with adsorption usually needs to be treated for gold desorption. The general treatment method is: the saturated carbon is sent into a gold carbon desorption column, and a traditional medium-temperature cyanide-free desorption process is used for desorption. The poor carbon after desorption is regenerated and reused.

Claims

1. A method for reducing the amount of flocculant in precious metal smelting solutions for gold refining, characterized in that... The processing steps are as follows: Step 1: Adjust the pH of the gold smelting solution: Adjust the pH of the gold smelting solution to 5.5-8.5; Step 2, adsorption: Add modified activated carbon to the gold smelting solution at a dosage of 0.4 ~ 0.6 g / L, adjust the temperature of the gold smelting solution to 35 ~ 45℃, and adsorb for 4 ~ 6 hours with stirring; The modified activated carbon is prepared in the following steps: (1) Preparation of modified solution: Dissolve lauric acid in methanol aqueous solution and stir until homogeneous; (2) Modification reaction: Add 75-175% of ordinary activated carbon by weight of lauric acid to the modification solution and stir at a constant temperature of 70℃-75℃ for 5-7 h; (3) Post-treatment: Wash the modified activated carbon with hexane to remove unreacted lauric acid on the surface, and dry to constant weight; (4) Directional modification: The modified activated carbon obtained in step (3) is immersed in a 0.5~1.0 mol / L citric acid solution by impregnation, heated at 60~80℃ for 4~6 h, filtered and dried to obtain directional modified activated carbon; The mass-to-volume ratio of the modified activated carbon to the citric acid solution is 1 g: (3-5) mL.

2. The method for reducing the amount of flocculant in precious gold smelting liquid as described in claim 1, characterized in that: In step (2) of the second step, the amount of lauric acid added is 100% of the mass of ordinary activated carbon.

3. The method for reducing the amount of flocculant in precious gold smelting liquid as described in claim 1, characterized in that: In step (2) of the second step, the modification reaction temperature is 70℃.

4. The method for reducing the amount of flocculant in precious gold smelting liquid as described in claim 1, characterized in that: In step (2) of the second step, the modification time is 7 hours.

5. The method for reducing the amount of flocculant in precious metal smelting liquid as described in any one of claims 1 to 4, characterized in that: In the first step, the pH of the gold smelting solution is adjusted to 7.0-8.

0.

6. The method for reducing the amount of flocculant in precious gold smelting liquid as described in any one of claims 1 to 4, characterized in that: In the second step, the temperature of the gold smelting solution is adjusted to 45℃.

7. The method for reducing the amount of flocculant in precious metal smelting liquid as described in any one of claims 1 to 4, characterized in that: In the second step, adsorption is carried out for 6 hours with stirring.

8. The method for reducing the amount of flocculant in precious gold smelting liquid as described in any one of claims 1 to 4, characterized in that: The ordinary activated carbon is RO3520 activated carbon.

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