Pyrite microencapsulation technologies: Principles and potential field application

Protocolo de valoracion de la efectividad de productos protectores de pizarras para cubiertas

“…La solución más común a este problema propone añadir piedra caliza a la escombrera, lo que aumenta el pH e inhibe la alteración. Otra propuesta sugiere recubrir la superficie de la pirita (10)(11)(12), o pirrotina (13), mediante lixiviación del material con una solución de silicato sódico (Na 2 SiO 3 ) o fosfato potásico (KH 2 PO 4 ). El oleato de sodio también crea una capa hidrofóbica que protege la superficie del sulfuro de hierro evitando el contacto con el oxígeno del agua (14).…”

“…Assuming a weathering with constant conditions and pH values ranging from 2.2 to 3.5, the empiric oxidation rate from Fe 2+ to Fe 3+ shows an average time of 15 years (21). In the case of pH values below 4, the oxidation rate increases together with the come up of bacteria such as Thiobacillus Ferrooxidans or Leptospirillum Ferrooxidans (11), being the bio-induced oxidation very important in pH acid conditions. Two different mechanisms of bacteriogenic oxidation can be appreciated: (1) Direct oxidation, in which both the organism and the mineral surface are joined and (2) Indirect oxidation in which the organism produces Fe 3+ in the environment without physical contact with the iron-sulphide surface.…”

Oxidación de sulfuros en pizarra ornamental: tratamientos protectores con siloxanos

“…El estudio de los mecanismos de oxidación de minerales de sulfuro ha sido y es objeto de numerosos trabajos, tanto de enfoque teórico (5-7) como aplicado; entre éstos destacan aquellos enfocados a minimizar el riesgo de aguas ácidas, en los cuales se estudia la eficacia de distintos compuestos en frenar la oxidación de los sulfuros en condiciones de laboratorio (8)(9)(10)(11)(12). Aunque estos trabajos constituyen una excelente base de conocimiento para abordar la investigación de productos protectores de la corrosión de pizarra para techar, carecen de un enfoque aplicado orientado a optimizar procesos anticorrosivos de los sulfuros en las propias plantas de producción.…”

“…A number of studies have been made of sulphide oxidation mechanisms, whether from a theoretical (5)(6)(7) or practical perspective; among the latter are studies, aimed at minimizing the risk implied by acid rain, that assessed the effectiveness of different compounds in halting sulphide oxidation in laboratory conditions (8)(9)(10)(11)(12). Although these studies are an excellent knowledge base for tackling research into anti-corrosion agents for roofing slate, they are lacking in terms of an applied focus aimed at optimizing sulphide anti-corrosion processes in the production plant.…”

Suppression of floatability of pyrite in coal processing by carrier microencapsulation

“…To suppress pyrite floatability in flotation, the use of depressants such as sodium sulfide, potassium dichromate, potassium permanganate, ferrous/ferric sulfate, aluminum and ferric chlorides, and sodium cyanide [6,9], bacteria like Acidithiobacillus ferroxidans [8,10], as well as several preconditioning techniques [11][12] have been reported. For controlling AMD formation, application of nonpermeable liners (e.g., clay or plastic liner in the tailing dam) and techniques to make a protective coating on pyrite to suppress oxidation were reported [13][14][15][16]. However, a single technique to overcome both problems simultaneously has not yet been developed.…”