Abstract
This study provides an up to date review of tannins, specifically quebracho, in mineral processing and metallurgical processes. Quebracho is a highly useful reagent in many flotation applications, acting as both a depressant and a dispersant. Three different types of quebracho are mentioned in this study; quebracho “S” or Tupasol ATO, quebracho “O” or Tupafin ATO, and quebracho “A” or Silvafloc. It should be noted that literature often refers simply to “quebracho” without distinguishing a specific type. Quebracho is most commonly used in industry as a method to separate fluorite from calcite, which is traditionally quite challenging as both minerals share a common ion—calcium. Other applications for quebracho in flotation with calcite minerals as the main gangue source include barite and scheelite. In sulfide systems, quebracho is a key reagent in differential flotation of copper, lead, zinc circuits. The use of quebracho in the precipitation of germanium from zinc ores and for the recovery of ultrafine gold is also detailed in this work. This analysis explores the wide range of uses and methodology of quebracho in the extractive metallurgy field and expands on previous research by Iskra and Kitchener at Imperial College entitled, “Quebracho in Mineral Processing”.
Highlights
Tannins are organic, wood derived compounds that have many industrial applications including leather production, chemical and petroleum processes, and froth flotation
The findings of this study showed that the use of tannins in a column flotation scheme as opposed to a traditional flotation circuit improved the overall separation of fluorite from the gangue consisting of CaCO3, SiO2, and P2O5 [16]
This study has explored the role of tannins in extractive metallurgy, flotation and precipitation
Summary
Wood derived compounds that have many industrial applications including leather production, chemical and petroleum processes, and froth flotation. The heartwood is chipped, heated to around 230 °F under pressure and evaporated under a vacuum This produces Tupafin ATO, the most basic form of quebracho, which is soluble in warm water. Quebracho is a member of the condensed tannin group and will not break down to form other compounds in when acids, alkali or enzymes are introduced [3]. The quebracho compounds are made up of phenol and carboxylic groups When ionized, these groups provide the adsorption onto cationic surfaces and with the addition of hydrogen bonding, the mineral surfaces become hydrophilic [2]. Quebracho adsorption occurs in a variety of ways including hydrogen bonding, complex formation between OH groups and cations, charge neutralization with OH- meets a positively charged surface, and from electrostatic attraction between negatively charged quebracho micelles and positively charged mineral surfaces [3]
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