In the industrial microbial leaching process popularly known as "bioleaching", low grade ore is dumped in a large pile (the leach dump) and a dilute sulfuric acid solution (pH 2) is percolated down through the pile. The liquid coming out at the bottom of the pile, rich in the mineral is collected and transported to a precipitation plant where the metal is reprecipitated and purified. The liquid is then pumped back to the top of the pile and the cycle is repeated. "Acidithiobacillus ferrooxidans" is able to oxidize the Fe2+ in to Fe3+. Chemical oxidation of the copper ore with ferric (Fe3+) ions formed by the microbial oxidation of ferrous ions (derived from the oxidation of pyrite). Three possible reactions for the oxidation of copper ore are:  The copper metal is then recovered by using Fe0 from steel cans:  The temperature inside the leach dump often rises spontaneously as a result of microbial activities. Thus, thermophilic iron-oxidizing chemolithotrophs such as thermophilic "Acidithiobacillus" species and "Leptospirillum" and at even higher temperatures the thermoacidophilic archaeon "Sulfolobus (Metallosphaera sedula)" may become important in the leaching process above 40 °C. Similarly to copper, "Acidithiobacillus ferrooxidans" can oxidize U4+ to U6+ with O2 as electron acceptor. However, it is likely that the uranium leaching process depends more on the chemical oxidation of uranium by Fe3+, with "At. ferrooxidans" contributing mainly through the reoxidation of Fe2+ to Fe3+ as described above. Gold is frequently found in nature associated with minerals containing arsenic and pyrite. In the microbial leaching process "At. ferrooxidans" and relatives are able to attack and solubilize the arsenopyrite minerals, and in the process, releasing the trapped gold (Au):  "Biohydrometallurgy" is an emerging trend in biomining in which commercial mining plants operate continuously stirred tank reactor (STR) and the airlift reactor (ALR) or pneumatic reactor (PR) of the Pachuca type to extract the low concentration mineral resources efficiently. The development of industrial mineral processing using microorganisms has been established now in several countries including South Africa, Brazil and Australia.