Microbial pretreatment of microfine-grained low-grade zinnwaldite tailings for enhanced flotation to recover lithium and rubidium resources

Abstract

• A new method of mineral cleavage by microbial pretreatment was proposed. • “LM-1” was proved to be an efficient silicate bacterium to release potassium and desilication. • Erosion targeting the potassium-bearing cleavage plane of silicate minerals . • The adsorption mechanism of the mixed OPS/A CO was investigated. • Microbial pretreatment could achieve efficient flotation separation of zinnwaldite from tailings. The accumulation of large amounts of refractory zinnwaldite in tailings pond in Hunan (China) implies a waste of the rare lithium and rubidium resources and also induces serious environmental problems. In the present study, the microbial pretreatment was introduced prior to the desliming and flotation processes. The silicate bacteria “LM-1”, isolated from deep-sea sediments, was used to decompose and erode the minerals. This procedure will solve the problem of difficult sorting of the tailings in a more efficient and environmentally friendly way. Through flotation tests and mineral surface analysis, we derived the optimum pretreatment and flotation solution and we discuss application processes that will enhance the flotation effectiveness. The test results showed that the pretreatment with “LM-1” caused an enlargement of the cleavage plane {0 0 1} on the surface of the ore grains and an increase of the content of the cleavage plane {0 0 1} throughout the raw ore. Therefore, the adsorption capacity of the collector increased, and the selectivity was enhanced, which largely improved the floatability of the zinnwaldite. A good index of 2.89% Li 2 O grade with 71.68% recovery and 0.59% Rb 2 O grade with 80.42% recovery was obtained for the concentrate. Compared to conventional flotation processes, the more efficient release of potassium and desilication through “LM-1” not only avoids the high energy consumption and serious sliming caused by fine grinding of minerals, but also effectively improves the separation results.