The Experimental Study and Production Practice of GDA Reagent in the Process of Carbon-in-Pulp Gold Extraction

----selected from the fifth issue of GOLD in 2013

Wu Ge

(Hui Town Hongyuan Mining Limited Liability Company)

Abstract:for the new type gold beneficiation reagent named “GDA”, the experimental study and production practice are conducted. The results indicate that,underthe same process conditions with all-sliming carbon-in-pulp method, the“GDA” can absolutely replace sodium cyanide. The gold leaching rate can reachmore than 90% with remarkable economical benefit.

Keywords: gold beneficiation reagent;sodium cyanide; gold; leaching

CLC Number: TD 952 05-0052-02       Article Number: 1001-1277（2013）

Literature Mark Code: A                      doi：10.11792/hj20130514

0 Introduction

Hui Town Hongyuan Mining Limited Liability Company is a gold mining company with the mining and processing capacity of 300t per day. The ores are of relatively simple compositions, which are ferritization micro-fine particle gold ores, with great degree of oxidation and little injurious ingredient. The ores are easy to be leached. The existence of gold in the ores is native gold. The native gold mainly imbed in the intergranules of limonite granules, quartz granules, calcite granules, and intergranule of limonite granules and quartz granules, totally occupying 90.94%. This part of native gold is easy to be dissociated and leached while the ores are grinded to fine particles; the rest native gold of 9.06 % is micro-fine particles and wrapped by limonite, quartz and calcite, the wrapped native gold is hard to be dissociated and leached even the ores have been grinded to fine particles, which certainly affects the leaching rate.

The processing plant was constructed and put into operation in 2002, and the technological process is all-sliming carbon-in-pulp gold extraction process. The main beneficiation reagent is sodium cyanide which is a highly toxic chemical. The use of this agent in the process brings about great pressure on the safety production and environmental protection of the plant. In order to solve the problem, Hongyuan Company adopts a new low toxic gold beneficiation reagent produced by Senhe High Technology(named “GDA”, general chemistry) to carry out laboratory and industry tests. Andthe ideal processing indicators are reached in the tests. So the test results proves that the reagent can replace sodium cyanide in the gold extraction process of Hongyuan Company. At present, the reagent has been put into normal use.

1. Test

1.1 Laboratory test

According to the existing technological process of the plant, the condition tests of the carbon-in-pulp leaching process were conducted.The test conditions kept the same with thoseof the existing process, namely, the pulp density was 40%, the grinding fineness was 88%, and the pH value was 11~12. The industrial simulation tests were conducted in a special steel vessel, and the working conditions of the leaching tank were simulated in the maximum level. In the first and second tests, air was blown into the pulp with stir. In the third and fourth groups of tests, 83% - 90% oxygen was blown into the pulp with stirring.

Table 1- Test results of the first group

Reagent	Gold grade of Leaching residue /(g·t-1)	Gold grade of tail liquid /(g·m-3)	Grade of carbon    with gold     /(g·t -1)	Gold leaching rate /%	Gold adsorption rate /%	Gold leaching recovery /%
GDA	0.36	0.004	60.26	86.96	99.83	86.81
Sodium cyanide	0.37	0.009	59.16	86.59	99.62	86.27

Note: raw ore grade 2.76 g/t, leaching time 17h, agent concentration 0.05%, carbon density 20g/t.

Table 2- Test results of the second group

Reagent	Gold grade of Leaching residue /(g·t-1)	Gold grade of tail liquid /(g·m-3)	Grade of carbon     with gold      /(g·t -1)	Gold leaching rate /%	Gold adsorption rate /%	Gold leaching recovery /%
GDA	0.32	0.005	94.22	84.24	99.71	83.99
Sodium cyanide	0.34	0.007	99.32	83.25	99.59	82.91

Note: raw ore grade 2.03 g/t, leaching time 17h, agent concentration 0.07%, carbon density 10g/t.According to the test results of the first and second groups, in the condition of airagitation, the test results using “GDA” are very close to that using sodium cyanide.

Table 3- Test results of the third group

Reagent	Gold grade of Leaching residue /(g·t-1)	Gold grade of tail liquid /(g·m-3)	Grade of carbon    with gold     /(g·t -1)	Gold leaching rate /%	Gold adsorption rate /%	Gold leaching recovery /%
GDA	0.48	0.022	116.74	78.95	98.78	77.98
Sodium cyanide	0.41	0.011	137.22	82.08	99.41	81.54

Note: raw ore grade 2.28 g/t, leaching time 17h, agent concentration 0.03%, carbon density 10g/t, oxygen enrichment agitation(with little flow).

Table 4- Test results of the fourth group

Reagent	Gold grade of Leaching residue /(g·t-1)	Gold grade of tail liquid /(g·m-3)	Grade of carbon    with gold     /(g·t -1)	Gold leaching rate /%	Gold adsorption rate /%	Gold leaching recovery /%
GDA	0.34	0.006	107.52	85.09	99.69	84.82
Sodium cyanide	0.22	0.003	136.20	90.35	99.85	90.22

Note: raw ore grade 2.28 g/t, leaching time 17h, agent concentration 0.03%, carbon density 10g/t, oxygen enrichment agitation(with large flow).

According to the test results of the third and fourth groups, in the condition of oxygen enrichment, the leaching effectiveness of “GDA” is inferior to the leaching effectiveness of sodium cyanide. The reason may be that the thiocarbamide which is the main effective constituent of “GDA” is aerobic degradation by high concentration of oxygen. So the leaching capacity of “GDA” is reduced. The test results indicated that “GDA” was suitable for leaching gold from the ores.

But it was not suitable for leaching gold in the condition of oxygen enrichment.

1.2 Industrial application practice

Based on the results of laboratory tests, the processing plant of Hongyuan Company carried out industrial tests under the conditions of the existing industrial process(the air was blown to the leaching tank), and the test results were compared with the indicators from the production using sodium cyanide. The comparison of the production indexes are shown in Table 5.

Table 5 - The comparison of the production indexes

Date	Raw ore Gold grade /(g·t-1 ）	Tailing gold grade	Gold grade of tail liquid /(g·m-3)	(Grin ding fineness -200mesh )/%	Pulp Concen tration /%	Pulp pH value	Gold leaching rate/%	Gold adsorption rate /%	Gold leachin g recove ry /%）	Reagent consumption/(g· trawore-1）
2012 -08	3.88	0.34	0.005	90.2	40-42	10-11	91.29	99.80	91.11	260
2012 -09	4.04	0.35	0.005	88.1	40-42	10-11	91.25	99.78	91.05	240
2012 -10	3.82	0.34	0.005	89.7	40-42	10-11	91.08	99.8	90.90	230
2011 -08	3.14	0.35	0.005	87.8	40-42	10-11	88.86	99.75	88.64	220
2011 -09	3.20	0.34	0.005	87.8	40-42	10-11	89.26	99.76	89.04	240
2011 -10	3.36	0.34	0.005	88.0	40-42	10-11	89.90	99.77	89.70	200

Note: the used reagent was “GDA”in 2012, whilethe used reagent was sodium cyanide in 2011.According to the comparison, the environment friendly gold beneficiation reagent named “GDA” can sufficiently replace sodium cyanide in the same conditions and technological process. And “GDA” is more economic than sodium cyanide at the premise of the local price at present.

3. Conclusions

1) For the ores from Hui Town Hongyuan Mining Limited Liability Company, the effectiveness of gold extraction of “GDA” shall be affirmed. Compared with sodium cyanide, there is obvious advantage in gold recovery and reagent consumption.

2) Since there is no stable and mature agent to measure the concentration of “GDA” solution, the measurement of the concentration of “GDA” solution has not been well solved in the operation.

3) Because of the patent factors of the company, the compositions of “GDA” are unknown, so the gold extraction theory needs further study.

4) For the requirements of our state on safety production and environmental protection, it deserves to generalize “GDA” replacing sodium cyanide in the chemical gold extraction industry.

References

[1] Lei Siwei, Yu Jianming, Gao Banglao, etc. Gold beneficiation test report, Tongtianping, Hui town, Gansu province [R]. Baiyin city, Gansu province: Northwest Research Institute of Mining and Metallurgy, 2001.

[2] The production monthly report of Hui Town Hongyuan Mining Limited Liability Company. Hui town, Gansu province: Hongyuan Mining Limited Liability Company,2012.