Reduction of Environmental Pollution and Gold Recovery Through Metallurgical Processes Without the Use of The Peruvian Mining Merchand Mercury

The sample that is the subject of research study is a partially oxidized mineral with a calculated head grade of 16.20g/MT; provided by artisanal miners from the province of Canta, department of Lima. The characterization of the sample was carried out in the polarized optical microscope, at the Professional School of Geological Engineering of the UNMSM, where the presence of gold, chalcopyrite, covelite, chalcosite, sphalerite, pyrite, arsenopyrite, magnetite, goethite, rutile and bargains In addition, we find interlaced particles of gold with chalcopyrite and pyrite, the rest of the gold must be within the mineralogical species of the sulphured minerals. This makes the recovery of gold low, due to the amalgamation process, which uses artisanal mining. The best selected preconcentration test, with the Knelson gravimetric concentrator is with a grain size of 67.13%-200 mesh, obtaining 300.20g/MT of concentrate, 33.66% recovery and 51.59 radius of concentration. The best cyanidation test of the tailings of the preconcentration of the Knelson gravimetric concentrator, with the sample not removed, with 24 hours of leaching, granulometry of 52.25% - 200 mesh and 300RPM of agitation, 75.96% gold recovery is obtained with a consumption of sodium cyanide of 1.16Kg / TM. By rewinding the tailings of the preconcentration to a particle size of 87.25% - 200 mesh, 48 hours of leaching and 500 RPM of agitation, a gold recovery of 81.06% is reached with a sodium cyanide consumption of 2.52 Kg/TM. The total recovery of gold from both the preconcentration and cyanidation of the tailed gravimetric preconcentration tailings is 87.44%. The appropriate metallurgical process according to the results of the present research at the laboratory level, for the processing of minerals from artisanal miners in the province of Canta, is a preconcentration with the Knelson gravimetric concentrator, removing the tailings from preconcentration and Perform the cyanidation process, to obtain a total recovery of 87.44% gold, with a consumption of sodium cyanide of 2.52 Kg/TM, without the use of mercury thereby reducing environmental pollution. Abstract


Introduction
He mentions that mercury is a highly toxic metal for minors, since it produces irreversible damage to the central nervous system (brain), and can lead to death in the most severe cases. In artisanal mining, Quimbaleteo or amalgamation is used, where mercury is added manually to the quimbalete's pit, then it is squeezed out, to obtain the amalgam ball.
The exposure to contact with mercury is more evident, since it is fully manual, here we must observe that not only through the skin does the mercury enter the body but also through the nails, through the nail bed, which is the part below The nail. Also in the bulletin they indicate the mechanism of how mercury is introduced through the skin. Mercury is a substance that has a property of liposolubility, that is; in small quantities it crosses the skin barriers, so that in prolonged exposure times the mercury that enters, passes into the bloodstream and travels throughout our body damaging our kidneys, liver and especially our brain. In refueling or burning, it is performed outdoors or worse; Inside a room that is one of the most direct and dangerous forms of poisoning. It is necessary to point out that the rudimentary protection of a handkerchief that covers the mouth or nose does not help at all, since the mercury vapors that produce the burning of amalgam can pass through the tissue of the handkerchief. While the reflux occurs, where the vapor-shaped mercury is found in tiny particles and they travel through our bronchi reaching a very deep part where the breathing process takes place, it is here where the mercury again enters the blood and disperses throughout our body. Likewise, harmful is the dust produced by the permanence of the tailings in the pools when the water evaporates.
Due to the high current prices of gold, the surrounding towns and the communities of the mountains, (as is the case in the province of Canta) find job opportunities abandoning agriculture, because mining activity is more profitable. The research study conducted on the tailings of the amalgamation process of artisanal mining yields worrying results, the gravimetric preconcentration tailings have 3.67 ppm of mercury and the cyanidation tailings have 2.70 ppm of mercury. These values are high, if we compare with the maximum permissible limits that is 0.14 ppm. This means permanent contamination of basins and tailings fields [2][3][4][5]. The study aims to reduce pollution by avoiding the use of mercury and improving productivity in the recovery of gold.

Characterization of the Mineral
The analysis carried out on the sample has allowed determining its mineralogical constituents, the volumetric distributions, of those minerals that have intervened in the modal analysis, their respective degrees of release and the interpretation of the degrees of release for each of the minerals. In the following table the observed minerals and those that have participated in the modal analysis are inserted (Table 1).

Mineralogical Interpretation
Gold Minerals As gold ore is gold.
Copper Minerals. As copper minerals are chalcopyrite, covelite and chalcosite.
Zinciferous minerals. As zinc ore is sphalerite Ferriferous minerals. As iron ores are pyrite, arsenopyrite, magnetite, hematite and goethite Other minerals Within this group are the rutile and bargains.

Volumetric Percentage Distribution and Degrees of Release
The volumetric distribution and the weight in percentage terms, in the same way with respect to the degrees of release; which are provided for all the minerals that have intervened in the modal analysis and can be seen in the following table (Table 2).

Pre-concentration tests with the Knelson Gravimetric Concentrator
To perform preconcentration metallurgical tests with the Knelson gravimetric concentrator, it is important that the sample is representative and that the independent variable is granulometry.

Test Conditions
Sample weight: 5000 g

Source: self-made
In the first stage, which is the preconcentration with the Knelson gravimetric concentrator, the best metallurgical test selected is indicated in (Table 3) (Table 5).    (Table 3). In this stage the free and coarse gold of the sample is recovered and environmental pollution is reduced, because only water is worked without the use of mercury (Figures 1-3).     (Table 5).
d) The total recovery of gold from both preconcentration and cyanidation of the preconcentration tailings is 87.44%, which is the dependent variable. Compared to the work done by artisanal mining that reaches between 40 and 50% gold recovery with the conventional amalgamation process.
e) The appropriate metallurgical process according to the results of the present investigation, for the processing of minerals from artisanal mining in the province of Canta, is a preconcentration with the Knelson gravimetric concentrator, removing the tailings from the preconcentration and carrying out the process of cyanidation, to obtain a total recovery of 87.44% gold, without the use of mercury.

Recommendations
With the results obtained in this research, it is recommended that the metallurgical process studied is an alternative for artisanal gold mining in the province of Canta, because it replaces the conventional amalgamation process, improving the recovery of gold and reducing environmental pollution by the nonuse of mercury.
a) It is recommended that artisanal miners in the province of Canta group and process their ore directly and can be replicated as a model for artisanal mining in general, improving their profitability.
b) It is recommended to carry out tests at the pilot plant level, with the variables obtained from this research work.