Airlift Reactors: Characterization And Applications In Biohydrometallurgy

Abstract

Over the last decade biooxidation for the pretreatment of refractory sulfidic gold concentrates and the bioleaching of copper have been applied with increasing frequency. In addition to heap-leach facilities for the bioleaching of copper, several biotank oxidation plants are also operational for the pretreatment stage in the processing of refractory gold ores in large-scale operations (Brierley, 1997; Acevedo, 2000; Rossi, 2001). The application of commercial biooxidation plants using bioreactors started in South Africa and expanded first into Africa and then Australia, South America and, more recently, into China (Morin et al., 2005). These commercial operations show that bioleaching/biooxidation processes can be viable options for the mining industry. Moreover, there is currently a great deal of interest in improving tank technologies for use in the recovery of other metals, such as Cu, Ni, Zn and Co (Brierley & Brierley, 1999; Okibe et al., 2003; Morin et al., 2005; Acevedo & Gentina, 2005; Sand & Gehrke, 2006). The reactors most commonly employed in biohydrometallurgy are the Stirred Tank Reactor (STR), the Bubble Column (BCR) and the Airlift Reactor (ALR). Additionally, cylindrical vessels with a conical bottom known as Pachuca tanks have traditionally been used in biomining. Furthermore, new reactor designs have recently been developed: the Low Energy Bioreactor, the Delft Inclined Plate Bioreactor and the Revolving Drum Bioreactor (Biorotor) (Rossi, 2001). Numerous different papers have been published on bioleaching-biooxidation processes using ALRs and Pachuca tanks (Atkins et al., 1986; Acevedo et al., 1987; Roy et al., 2000; Acevedo, 2000; Rossi, 2001; Mousavi et al., 2005; Shi & Fang, 2005); however, there is limited knowledge on the applications and characterization