Sandioss, an alternative reactive to NaCN for the Au leaching process by agitation for an oxide type mineral

The influence of the Sandioss reagent was studied as an alternative for the gold’s leaching by agitation of a mineral-type oxide. The evaluated variables were: the hydrogen potential (pH) with levels 7, 9 and 11, the concentration of Sandioss leach at 250 ppm, 500 ppm and 750 ppm, and the leaching time at 12, 24 and 48 hours. For each concentration of the leaching agent, a test was conducted in parallel with sodium cyanide at a pH = 11 to prevent the volatilization of cyanide. The solutions taken were analyzed by atomic absorption to determine the gold content in solution and tails were analyzed by fire assay. From the result of the leaching tests it can be concluded that for a better gold extraction with the Sandioss leaching, it is obtained at a concentration of 750 ppm of Sandioss, pH of 11 and time of 48 hours, obtained 79.15% extraction. Finally, the variance analysis at a level of 95% confidence shows that the variables studied significantly influence the extraction of gold and is presented as an alternative to the use of NaCN


Introduction
The Sodium cyanide allows us a good recovery of gold and silver, but it also has effects on the pollution of the environment (biodiversity, water resources and human health, being one of the consequences of mining practice.To avoid these consequences in the practice of mining researchers have determined through studies other reagents that can be used as a leaching agent and obtain a good recovery percentage of gold and silver, such as Golmax, Jin zhibao, Sandioss, among others.The aim is to evaluate the leaching with Sandioss at different pH, concentrations and time until 48 hours by agitation, maintaining the control parameters similar to sodium cyanide, in order to obtain a better percentage of gold extraction and decrease the costs of the reagents used in the gold leaching process.It was determined the influence of hydrogen potential (pH), the concentration of Sandioss and the leaching time in the percentage of gold's extraction from a type oxide mineral by leaching in agitation.
Please cite this article as: Heras M., Quispe N., Vega J., Sandioss, an alternative reactive to NaCN for the Au leaching process by agitation for an oxide type mineral, Journal of Sciences and Engineering, vol.2, no 1, 2018, pp.1-6.

Object of study
The object of the study was an oxide-type gold ore from the province of Pataz, department La Libertad, which presents, according to chemical analysis, an average gold grade of 13.30 g/MT.
The ore was treated using leaching by agitation, to do the gold's extraction and its relationship with the hydrogen potential (pH), concentration of Sandioss leach and the leaching time.

Methods and techniques
To carry out the leaching tests with Sandioss of gold ore, the constant monitoring of each one of the variables to be controlled during 48 hours was taken into account, since it is the duration of each experimental test.1000 kg of gold ore from the province of Pataz was sampled, the ore was dried at 110 ° C + -5 ° C in an oven for 12 hours (ASTM D-2216), then the mechanical preparation of the ore was done in order to obtain the release of valuable particle (Bustamante et al., 2008), the respective quartering was performed to obtain the representative sample, 250 g was sprayed during 5 minutes until obtaining the granulometry of the required mineral.A chemical analysis of the ore was made to obtain head law using the fire test method.Then the alkalinity test was performed to determine the natural pH of mineral.Then the bottles were prepared and each one was added mineral and water in a ratio of 33% solid and 67% liquid (1 to 2).For this case study it was used 500 g of mineral and 1L of water for each bottle and the test was run for 48 hours The study tests was carried out by leaching the bottle with sodium cyanide, with a pH of 11 for each concentration of 250ppm, 500ppm and 750ppm used to be the standard sample, since the Sandioss does not have a defined chemical composition.Therefore, the replenishment control of leaching reagent was made based on the consumption of sodium cyanide.Each test that was carried out at different concentrations of Sandioss was titrated and analyzed by atomic absorption equipment, for which 25 mL of solution was removed 12, 24 and 48 hours after the start of the test, while the sacrifice test (leaching with sodium cyanide) helped determine the consumption of the leach.Finally was proceeded to make the respective metallurgical balance based on the head law, the solution's laws and the laws of the respective tailings, to determine the percentage of gold extraction.Data processing is carried out with the Minitab 17 program.The experimental design to be used for the analysis of the results of the experimental tests will be a trifactorial design with 3 independent variables (leaching time, concentration of Sandioss leach and hydrogen potential (pH), with three levels for each variable and applied to a single dependent variable (percentage of gold extraction).The number of experimental tests were 54 taking into account that the number of repetitions will be 2 for each variable.

Characterization of sample
The values of the chemical composition in gold obtained by fire test for gold are shown in Table 1.The relationship of Sandioss leach concentration vs. % Au extraction is shown in Figure 1.

Table 1 .
Chemical composition of sample

Main effect of the concentration of Sandioss on the percentage of gold extraction.
The gold extraction values are shown as a function of the concentration of the water-soluble leach In Table2.From the statistical analysis carried out, it was determined that the concentration of the Sandioss lixiviant (ppm) has a significant effect on the percentage of gold extraction, showing a higher value at a concentration of 750 ppm, with a gold extraction percentage of 49.17%.

Table 2 .
Sandioss concentration and gold extraction