Por: Huguez Ames Ramírez y Sergio Rojas Rimachi, docentes en Tecsup y Cristian Márquez Sarmiento, gerente de Procesos I+D+I en Proyectos de Desarrollo Metalúrgicos y Medioambientales, Consorcio Stockholm Mining.

Abstract

Among the multiple technologies that exist today to remove cyanide and heavy metals from mining-metallurgical effluents, there is the so-called natural degradation that many mining companies that have the necessary space to contain high volumes of water can take advantage of and, although it always seems to be an ideal treatment in some cases or situations, it may not be so convenient.

When cyanide and heavy metals are present, several stable complexes are formed that can be removed with conventional oxidative methods and advanced oxidation, but others such as iron complexes resist such oxidative attack prevailing and preventing the removal of cyanide especially when the purpose is to use the treated water for irrigation or, discharge to water bodies of ecological protection i.e., categories 3 and 4 respectively, according to DS 004-2017-MINAM. In these effluents, the treatment seeks to precipitate the iron complexes by adding salts that allow such removal.

This paper aims to study the chemical behavior of water from tailings of polymetallic ores loaded with cyanides and heavy metals, among others, in order to demonstrate that there is an interesting natural degradation over time, which in general improves the cost-effectiveness of the treatment.

The study also shows that the degradation of cyanide generates ammonia and, together with this, complexes formed by heavy metals and organometallic compounds, which has repercussions on the reduction of the kinetics of chemical removal of cyanide by oxidation, making the process more expensive due to the use of more reagents and/or a tertiary treatment such as reverse osmosis, so an alternative treatment for effluents with these conditions has also been evaluated.

The Research and Development of Chemical and Metallurgical Processes at Tecsup - Lima, allied with the company Stockholm Mining, has tested different effluents from copper and polymetallic metallurgy in terms of their cyanide strength over time, as well as the concentration of heavy metals to then make balances of pollutants that allow us to see the variations of the main parameters over time and adjust the proposed treatment on that basis.