MINERÍA la mejor puerta de acceso al sector minero MINERÍA / MAYO 2022 / EDICIÓN 536 7 Abstract Cementation systems have played an important role in the world's mining and metallurgical industry since time immemorial, and in some cases continue to do so. They are apparently very simple and spontaneous reactions involving the displacement of a dissolved metallic element by another more reactive solid metal to precipitate the more noble one in the form of a so-called cement and leaving a very low concentration of the latter in the spent solution. The Cu++/Fe0 y Co++, Cu++, AsO 2H/Zn0 cementation systems are the ones that will be analyzed from a chemical kinetic and electrochemical approach with the purpose of knowing how they occur and what knowledge can be extracted from these fundamental studies in order to use them in the design of appropriate reactors for the purposes pursued in each one of them. In the case of copper cementation with iron scrap, chemical and electrochemical approaches have been analyzed, where both have agreed that this reaction is controlled by a phenomenon of molecular diffusion of cupric ions through the immobile liquid film. We also analyze the influence of the tank on the reaction progress taking into account the practical aspects of the operational part. We explain how a cementation reactor should be in order to meet the objectives of industrial practice. On the other hand, the second cementation system to be discussed, which refers to the purification of zinc sulfate solutions, for the removal of cobalt within the zinc electrolytic process, employs activators such as copper, arsenic or antimony, in order to achieve a more efficient cobalt precipitation with a reasonable consumption of zinc powder. Several fundamental studies are discussed with the purpose of understanding the role of activators in cobalt removal reactions. There are different points of view, all of them respectable, that aim to explain the role of activators. A different type of reactor is also presented, which could be the solution to the deficiencies and lack of control suffered by the conventional systems used for the purification of zinc sulfate solutions. At the end, a list of specific references on both cementation systems is presented. Se analizan diversos estudios fundamentales con el propósito de conocer el papel que juegan los activadores en las reacciones de remoción de cobalto. Como veremos, hay diferentes puntos de vista, todos ellos respetables, que apuntan a explicar el rol de los activadores. Se presenta, asimismo, un tipo distinto de reactor que podría ser la solución a las deficiencias y falta de control que adolecen los sistemas convencionales empleados para la purificación de soluciones de sulfato de zinc. Al final, se presenta un listado de referencias específicas sobre ambos sistemas de cementación. Introducción Reacciones de cementación, también conocidas como reacciones de reducción por contacto, son aquellas en las que un metal disuelto menos reactivo, al contactarse, en solución, con un metal sólido más reactivo, precipita sobre este último,