Studies on uranium recovery from a U-bearing Radoniów Dump

This work reports the possibility of uranium recovery from a post-mining uranium ore dump in Poland by a bioleaching method. The studies were conducted on the dump leaching model with the mass of 570 kg of uranium bearing mineral material from Radoniów pile and in the periodic bioreactor with a work volume of 80 dm3 and with mechanical mixing and aeration of the charge. The uranium concentration in the examined material was about 800 ppm. In this process, the consortium of microorganisms isolated from former mines was used. It was composed of the following microorganisms: Bacillius, Pseudomonas, Sphingomonas, Thiobacillus, Halothiobacillus, Thiomonas, and Geothrix. The efficiency of the uranium bioleaching process was 98% in the reactor, and a yield of 70% was obtained in the dump leaching model. The post-leaching solution contained significant amounts of uranium ions that were separated in two stages: (1) by ion chromatography and then (2) by a two-step precipitation method. The resulting solution was a source of ammonium diuranate, the precursor of yellowcake (uranium oxides).

Unravelling the Complexity of Heap Bioleaching

Heap and dump leaching of sulphide minerals have become well-established techniques for the processing of low grade ores, especially of copper, over the past 30 years. The oxidative dissolution of sulphides in heaps can be significantly enhanced by microbial colonies, but the complexities of the heap leach process overall often counteract the potential advantages, or prevent microbial colonisation and bioleaching in the first place. This overview discusses the multiple layers of complexities that govern percolation leaching processes, such as the interactions between mineral grains, particle pores and leach solution, microbial responses to solution chemistry typical of heaps, solution and solute transport in heterogeneous unsaturated ore beds, as well as heap aeration and microbial response to CO2 supply. It becomes clear that economically successful heap bioleaching hinges on careful engineering and operation of the heap process as a whole to create an environment in which microbial colonies can thrive and the value metal is released sufficiently rapidly into solution.

Research on Reinforcing Acid Leaching of a Refractory Copper Oxide Ore with High Content of Slime and Iron Minerals

The characteristics of Yangla copper oxide ore and acid leaching of this copper ore were investigated. The results indicate direct dump acid leaching of raw ore is not feasible for the treatment of this copper ore in practice. Sieve sizing-warming-stirring-acid leaching process was employed for the treatment of the fine grain materials below 1m, while 66.19% copper leaching efficiency and10.92 t H2SO4 consumption for per ton are obtained. Dump acid leaching process was employed for the treatment of the coarse grain materials above 1 mm, while 68.65% copper leaching efficiency and 15.43 t H2SO4 consumption for per ton copper are obtained. Key techniques are that sieve sizing process strictly controls the content of fine grain materials in dump leaching process and the searches ability of H2SO4 for the internal copper ore is improved, while warming-stirring-acid leaching process reinforces the copper leaching efficiency of fine grain materials. The proposed in this paper will be of benefit to the utilization of similar refractory copper oxide ore with high content of slime and iron minerals.

Changes in an Ore Dump during a 40-Year Period of Commercial-Scale and Spontaneous Natural Bioleaching

A dump located in the proximity of the Vlaikov Vrah mine, Bulgaria, and containing about 120 000 tons of run-of-mine mining wastes (low-grade ores and rock mass), since 1968 was subjected initially to spontaneous natural bioleaching based on the rains as irrigating leach solutions, then from 1972 to 2003 to commercial-scale bioleaching by means of irrigation with acidified leach solutions, and since 2004- again to spontaneous natural bioleaching. The monitoring of these processes during this 40-year period revealed considerable changes in the composition, geotechnical and acid-base properties of the dump material, as well as in the diversity, number and activity of its microflora.The data obtained during this study were used to stimulate the bioleaching process in the huge commercial-scale copper dump leaching operation at Vlaikov Vrah mine in which about forty million tons of such mining wastes were treated.