Effective methods for gold recovery from mining wastes at placers

Abstract

The authors develop the methods for concentration and recovery of dispersed ultrafine gold, including nanogold, in the mining wastes at gold placers by using laser action and chemical reagents.The problem of gold recovery from mining wastes of placer deposits is currently central due to significant deterioration of mineral material base in most subjects of the Russian Far Eastern Federal District (FEFD). The rich and readily available placers have already been exploited, which adversely affects the economical and social status of the conventional placer gold mining areas. This is a reason for careful study and validation of a need for the active use of placer mining wastes, wherein the gold content is equal or even more than the ore one. In Russia, the total amount of the potential reserves of the gold-containing mining wastes are 5000 t (55-60%).The general feature of the FEFD placers is the accumulation of the gold coarseness classes and morphological forms, which are ignored during geological exploration and left in heaps and tailing dumps. A significant part of such gold involves the difficult-to-recover dispersed ultrafine particles. It is well-known that the main losses under placer and ore gold extraction relate to fine, lamellar, and dust-like gold. Three types of gold are distinguished by the grain size distribution: fine-grained gold with the lower limit of 100 µm (0.1 mm), microscopic gold with the lower limit from 100 to 1 µm, and submicroscopic gold with the lower limit of 1.0 µm. According to the morphological features, such particles are net-shaped and can also be like flakes, ultrafine planes, and dendrites. Though this gold are neglected upon determining the technological losses, many researchers and engineers consider the gold content of the given classes on the gravitational-extracted level, and exactly these metal fractions are presented in the technogenic complex of placers. The question arises of how to recover such gold without the loss under reworking the technogenic objects. Then, there is a need to develop new effective methods for recovering the valuable components of all coarseness classes, which minimize the noble metal loss upon dressing the gold sands on the jigs and concentrate finishing on the schlich-dressing plants.The feature of fine and lamellar gold is its floatability under gravity dressing. It was found that the extraction on the tray during washing the 0.1-mm modal-size gold is no more than 25%.There are several reasons for the loss in fine, dispersed, lamellar, and flaky gold even upon using the advanced gravitational devices. The major reason is the presence of minerals of placer complexes (magnetite, titanomagnetite, ilmenite, cassiterite, sulphides, scheelite, zircon, cinnabar,

Estimation of operating costs and energy consumption in beneficiation of alluvial gold deposits

“…For the extraction of placer gold, jigging machines, centrifugal concentrators, screw separators have been developed and tested at many enterprises, which make it possible to increase the recovery of precious metals with a grain size of less than 0.2 mm, but still in Russia and abroad the main share of placer gold is extracted at washing devices equipped with sluices [7][8][9][10][11].…”