In this research, the process of gold and silver extraction from a refractory gold-silver sulfide ore, sourced from the Gran Chimú Province in the La Libertad department of Peru, was evaluated. The extraction was carried out in two stages, the first being called indirect bio-oxidation, and the second involving conventional cyanidation. In the first stage, an acidic solution from the area was used to cultivate Thiobacillus ferrooxidans bacteria, which was promoted by the addition of salts (9K). The objective of this stage was the transformation of ferrous cations to ferric, which was evidenced by the color change of the acidic water to red. In the second stage, a solution of sodium cyanide and calcium oxide (lime) was used, and the total cyanidation time was 51 hours at an average pH of 10.5 and ambient temperature. The quantification of gold and silver was done through a dry method (fire assay). The evaluated process variables were the concentration of silver salt (0, 0.75, and 1.5) mg/g, mineral particle size (80% passing 100 mesh, 80% passing 200 mesh, and 80% passing 325 mesh), and temperature of indirect bio-oxidation (25, 45, and 65)°C. To evaluate the effect of the bio-oxidation pretreatment, conventional cyanidation tests were conducted, resulting inextraction percentages of 44.61% for gold and 48.98% for silver, using 80% passing 325 mesh particle size. This indicated the need for the mentioned pretreatment to release the gold and silver from the ore. Meanwhile, the extraction percentages using the two stages were 61.44% for gold (80% passing 325 mesh, 65°C, 0.0 mg/g) and 94.24% for silver (80% passing 200 mesh, 65°C, 0.75 mg/g) in the best cases, and 35.98% for gold (80% passing 100 mesh, 45°C, 0.0 mg/g) and 41.44% for silver (80% passing 100 mesh, 25°C, 0.0 mg/g) as the lowest recorded values..
The present research evaluated the influence of the concentration of sodium hydroxide and aminopropyltrimethoxysilane on the thermal stability of the aguaje fibers. The fibers were extracted by manual immersion in water and subsequent separation by manual pressure. The NaOH concentrations were 5%, 10% and 15% w / v; while in the case of the silane coupling agent they were 1% and 1.5% v / v. The chemically treated fibers together with the control samples were subjected to thermogravimetric analysis evaluation, in addition, the variation of the humidity percentage, the chemical variation of the main functional groups of the fibers and the surface physical changes of the fibers were determined in a complementary way. The mercerization - silanization treatments increase the thermal degradation temperature of the aguaje fibers, in the conditions tested this increase was 3.89% in the best of cases (5% NaOH + 1.0 Silane). Regarding untreated fibers, mercerization - silanization treatments decrease the percentage of lost mass or degradation, in the best of cases this decrease in mass percentage was 26.85% (15% NaOH + 1.5 Silane), compared to fibers without treatment. Finally, mercerization-silanization treatments increase the percentages of cellulose present in the aguaje fibers evaluated, while the amount of extractives and lignin decrease, under the chemical treatment conditions carried out in the present research.
The present research work had as study variables the current density of 20, 40 and 80 mA/cm2 and residence times of 10, 20, 40 and 60 minutes, within these evaluation parameters values were taken of pH, conductivity and Fe2+ removal percentage before and after the electrocoagulation process of artisanal acid mine drainage samples (AMD), the amount of AMD sample per test was 350 mL per test, from the results obtained it could be observed that For the current density of 80 mA/cm2 and a time of 40 minutes, the highest percentage of removal was obtained (76.20%), likewise a minimum percentage of removal of 17.97% was obtained at 20 mA/cm2; The removal percentages are attributed to the effect of the current density of the electrocoagulation process, which allows increasing the initial pH values of the effluent, which in turn allows the formation of precipitates and co-precipitates, in this case of Fe2+.
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