Study on the Properties of P510 Resin Adsorbing Gold and Desorbing Gold from Gold-Containing Chlorinated Solution

I. Introduction

Since the 1980s, gold extraction faces two major challenges: first, direct cyanidation gold resources dwindling, gold resources to be developed, mostly low grade and impurities of refractory gold ore containing traditional application The cyanidation method has been unable to raise gold effectively; second, countries around the world have put forward higher and stricter requirements on ecological balance and environment. These two challenges have led to efforts to find new methods and processes for gold extraction.

Resin pulping is a relatively advanced and promising process. It uses the ion exchange resin to recover gold directly from the slurry, thereby avoiding liquid-solid separation, reducing the loss of gold in the tailings, and improving the recovery rate of gold. Therefore, the resin slurry method is used to extract gold in the cyanide-free system. It has become a hot spot for metallurgical workers.

At home and abroad, there are many researches on gold extraction from cyanide systems. In 1978, the former Soviet Union used the resin slurry method to apply gold to industrial practice. In 1988, South Africa also built a resin slurry method to raise gold; in the early 1990s Zimbabwe built the first resin gold extraction plant, but the factory was abandoned after the test; other countries, such as the United States, Canada, Romania and other countries have also built intermediate test plants, but none of them have been put into industrial production; late 80s century, our own research and design production of Huoshan County Dongxi gold, silver Square Laiyuan County, Hebei gold, Axi gold are used resin-in-pulp gold extraction process.

With the increasingly strict requirements of environmental protection in various countries around the world, the research and development of cyanide-free immersion gold and non-cyanide gold extraction processes have been greatly promoted. Among them, there are many researches on gold extraction by chlorination. The chlorination method has a high speed of gold extraction, which can make the carbon-containing material adsorbing gold lose its activity. In the chlorination system, the resin pulp method is used for gold extraction. At present, there is no large-scale application in the industry. Most researches in this field at home and abroad are in the experiment. Room stage.

P510 resin is a new type of weakly basic resin synthesized by Beijing Chemical and Metallurgical Research Institute according to user needs. It has been used in industry. In this paper, the properties of P510 resin adsorbing gold and desorbing gold from hydrochloric acid medium were studied, in order to make the resin be applied to the chlorination system resin pulp method to increase gold under the premise of mechanical strength.

Second, the test part

(1) Instruments and reagents

1, the instrument

AA320 atomic absorption spectrophotometer (Shanghai Precision Scientific Instrument Co., Ltd. Analytical Instrument Factory).

2, reagents

P510 resin: particle size 16 to 32 mesh, water content 56%.

Gold standard solution: prepared by dissolving AR-grade reagent AuCl ₃ ·HCl·4H ₂ O in 1.0 mol/L HCl, [H ⁺ ] = 1.0 mol/L, and ρ(AuCl ₄ ^- ) = 0.9570 g/L.

Thiourea solution: ready for use, AR grade.

(2) Test methods

1, resin pretreatment

The resin was thoroughly rinsed with absolute ethanol before use, and then equilibrated with 2.0 mol/L HCl for 24 h. Washed with deionized water until neutral before use, suction-dried and drained.

Conversion of dry and wet resin: accurately measure 10ml of wet resin into a beaker, dry it in a far infrared fast drying oven to the same quality, weigh the dry resin with an electronic balance, and dry the resin. The mass was converted to the volume of the wet resin, and as a result, it was 0.35 g of _{dry resin} /ml of the _{wet resin} .

2, static method

A certain amount of resin is weighed, and under the selected conditions, a gold standard solution is added, and the electromagnetic oscillator is shaken for a certain period of time, and the aqueous phase is taken up to determine the gold concentration in the aqueous phase by atomic absorption spectrophotometry. The static saturated adsorption capacity of the resin was measured, and the effects of time, temperature and acidity on the adsorption of gold were investigated. The influence of the concentration of the desorbent thiourea, the acidity of the solution and the desorption time on the desorption of the gold-loaded resin.

3. Calculation formula

Third, the results and discussion

(1) Gold standard curve

The gold concentration in the solution was determined by an atomic absorption spectrophotometer, and the standard curve is shown in FIG.

The linear regression equation is: A = 0.0212C, K = 0.0212, B = 0.000, R = 1.000 (n = 5)

From the standard curve, the gold concentration is in the range of 0 to 10.0 mg/L, and the absorbance and concentration are in accordance with Lambert Beer's law.

Figure 1 gold standard curve

(2) Static saturated adsorption capacity of P510 resin to gold

Measure 2.0ml of pretreated P510 resin, add enough gold standard solution, shake well, measure the gold concentration of the solution at a certain time, until the gold concentration in the solution is unchanged, and obtain the resin in 1.0mol/L HCl medium. The static saturated adsorption capacity for the intermediate feed was 242 mg/ml _{wet resin} , i.e., 691 mg/g _{dry resin} .

(3) Resin adsorption of different gold concentration solutions

Under room temperature conditions (20 ° C), other conditions were fixed, and the initial gold concentration in the solution was changed to: 10.0, 20.0, 30.0, 40.0, 50.0 mg/L, and the adsorption was carried out for 30 min at the same speed, and the gold concentration in the liquid phase was analyzed. The amount of gold adsorbed by the resin was investigated to investigate the effect of the initial gold concentration on the gold adsorption of the resin. The test results are shown in Table 1.

It can be seen from Table 1 that when the saturated adsorption capacity of P510 resin is not reached, the initial gold concentration has little effect on the resin adsorption rate, and the gold adsorption rate is high.

(4) Effect of adsorption time on resin adsorption of gold

At room temperature (20 ° C), the gold concentration of the aqueous solution was fixed, the stirring speed was the same, and the adsorption time was changed: 1.5, 5, 10, 15, 20, 25, 30 min, and the gold concentration in the aqueous phase before and after the adsorption was measured. , calculate the gold adsorption rate. The test results are shown in Figure 2.

Table 1 Effect of initial gold concentration on gold adsorption rate

Figure 2 Effect of adsorption time on the adsorption rate of P510 resin gold

It can be seen from Fig. 2 that the adsorption rate of gold to the resin gradually increases with time. When the adsorption time is longer than 15min, the adsorption rate does not change much, so the adsorption time of 15min is the best.

(5) Effect of acidity of solution on gold adsorption of resin

The mass concentration of the fixed initial solution gold was 50.0 mg/L, the stirring adsorption time was 15 min, and the concentration of hydrochloric acid in the solution was changed to 0.50, 1.00, 1.50, 2.00, 2.50, 3.00 mol/L, and the concentration of gold in the solution before and after adsorption was measured. . The measured results are shown in Figure 3.

Fig. 3 Effect of acidity of solution on the adsorption rate of P510 resin gold

It can be seen from Fig. 3 that the gold adsorption rate decreases with the increase of acidity in the same time. This is because the principle of adsorption of AuCl ₄ ^- by P510 resin can be simply expressed as follows:

As the acidity increases, the weakly basic groups on the resin undergo protonation, which reduces the adsorption groups, resulting in a decrease in the adsorption rate of gold. At the same time, the acidity is enhanced, the chloride ion concentration is increased correspondingly, and the competitive adsorption of the gold chloride complex anion is also caused, and the adsorption rate of gold is also lowered. For this reason, considering the conditions of chlorination of gold, [H ⁺ ] can be selected to be 1.0 mol/L.

(6) Effect of temperature on the adsorption of gold by resin

For the chlorinated aqueous solution with a gold concentration of 50.0 mg/L and [H ⁺ ]=1.0 mol/L, respectively, at a temperature of 20 ° C, 30 ° C, 40 ° C, 50 ° C, 60 ° C, adding resin adsorption: 1 , 2, 5, 10, 15, 20, 25 min, the gold concentration in the aqueous phase was measured, and the gold adsorption rate was calculated. The relationship between gold adsorption rate and time and temperature is shown in Fig. 4. It can be seen from Fig. 4 that the adsorption rate of gold on the resin is very fast, and when the temperature is raised, it is advantageous to increase the gold adsorption rate and shorten the adsorption to reach the equilibrium time. However, the adsorption reaction temperature should not be too high, and the adsorption rate will decrease when it exceeds 60 °C. Because the resin decomposes and decomposes at high temperatures, the adsorption capacity is lowered. At room temperature (10 ~ 30 ° C), the temperature has little effect on the adsorption reaction.

Figure 4 Effect of temperature on the adsorption rate of resin gold

(VII) Effect of chloride ion concentration on resin adsorption of gold

The acidity of the solution was fixed with H ₂ SO ₄ [H ⁺ ]=1.0 mol/L, the gold concentration was 50.0 mg/L, and different amounts of NaCl were added to adjust the concentration of chloride ions, and the gold concentration of the aqueous phase after adsorption equilibrium was determined. The relationship between the chloride ion concentration and the gold adsorption rate is shown in Table 2.

Table 2 Effect of chloride ion concentration on resin adsorption of gold

It can be seen from Table 2 that as the concentration of chloride ions increases, the gold adsorption rate starts to increase slightly, and then decreases slowly. The chloride ion concentration in the system should be maintained at 0.1-0.5 mol/L. This is because chloride ions play a complex coordination role and compete for adsorption of gold chloride anions.

When the chloride ion concentration is too high, the adsorption of the gold chloride complex anion is reduced due to its own adsorption competition; when the chloride ion concentration is too low, the stability of the gold chloride anion is lowered.

(8) Effect of thiourea concentration on the desorption rate of P510 resin gold

The gold-loaded resin was washed with distilled water until neutral, and then added to the mass fraction: 1.0%, 3.0%, 4.0%, 5.0%, 7.0%, 9.0% thiourea solution, 10.0 ml of desorbed resin, and the desorption time was 15 min. The gold concentration in the solution after desorption was measured to investigate the effect of thiourea concentration on gold desorption. The test results are shown in Figure 5.

Figure 5 Effect of thiourea concentration on desorption rate of P510 resin

It can be seen from Fig. 5 that with the increase of thiourea concentration, the gold desorption rate first increases and then decreases. When the thiourea mass fraction is 3.0%, the desorption rate of P510 resin has the maximum value. When the thiourea mass fraction exceeds 4%, the solution will be turbid. This is because thiourea is easily oxidized to form oxidation products such as sulfur in an acidic solution at room temperature. When the concentration of thiourea is high, unreacted thiourea is easily oxidized in the solution to cause turbidity of the solution, without affecting the desorption rate. Under the premise, a mass concentration of 3% thiourea is used as a desorption solution.

(9) Effect of desorption time on desorption rate of P510 resin

The gold-loaded resin was washed with distilled water to neutrality, and 10.0 ml of a thiourea solution having a mass fraction of 3.0% was added to the gold adsorbed on the desorbed resin, and the desorption time was changed to 15, 20, 30, 40 min, respectively. The test results are shown in Figure 6.

Figure 6 Effect of time on the desorption rate of P510 resin

It can be seen from Fig. 6 that when the thiourea mass fraction is 3.0% and the desorption time is changed, the gold desorption rate increases with time before 30 min; the desorption rate decreases slightly after 30 min. That is, when the time is 30 min, the gold desorption rate is the largest, and 30 min is selected as the optimal desorption time.

Fourth, the conclusion

P510 resin is suitable for extracting gold from gold-containing solution of chlorination system. The adsorption rate of gold can reach 99.28% under the condition of adsorption time of 15 min and hydrochloric acid concentration of 1.0 mol/L. The gold static saturated adsorption capacity of the resin was 691 mg/g dry resin. The gold on the resin is desorbed with thiourea to make [Au(CS(NH ₂ ) ₂ ) ₂ ] ⁺ , in a neutral or weakly alkaline medium, the thiourea mass fraction is 3.0%, stirred and desorbed for 30 min, the gold desorption rate can be It reached 99.85%.

The effects of mechanical strength and particle size of P510 resin on the gold adsorption of the resin can be further studied. The performance of the resin in the chlorination system for resin pulping is studied.

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