ore leaching

Examples of ore leaching in the following topics:

• Microbial Ore Leaching

  • Microbial ore leaching is the process in which microorganisms are used to extract metals from ores.
  • Microbial ore leaching (bioleaching) is the process of extracting metals from ores with the use of microorganisms.
  • very efficiently extract metals when their concentration in the ore is low.
  • Bacteria perform the key reaction of regenerating the major ore oxidizer which in most cases is ferric iron as well as further ore oxidation.
  • When fungi are used, the leaching mechanism is different.

• Oligotrophs

  • Oligotrophic environments include deep oceanic sediments, caves, glacial and polar ice, deep subsurface soil, aquifers, ocean waters, and leached soils.
  • An ecosystem or environment is said to be oligotrophic if it offers little to sustain life.
  • The term is commonly utilized to describe environments of water, ice, air, rock or soil with very low nutrient levels.

• Metallurgy

  • Hydrometallurgy describes the process of extracting metals from ores using aqueous solutions.
  • The most common hydrometallurgical process is leaching, which involves the dissolution of the valuable metals into the aqueous solution.
  • Here, the coordination chemistry and solubility of the compound can become very important, as one attempts to precipitate a mineral (metal) of interest over the other metals in the solution or attempts to selectively leach one desired mineral over the others present in the sample.
  • Solids containing valuable metals are reacted to form intermediate compounds for further processing or converted into their elemental or metallic state.
  • Electrowinning is an electrolysis process used to recover metals in aqueous solution, usually as the result of an ore having undergone one or more hydrometallurgical processes.

• Extractive Metallurgy

  • The grade or concentration of an ore mineral, or metal, as well as its form of occurrence, will directly affect the costs associated with mining it.
  • The process of ore formation is called ore genesis.
  • In order to convert a metal oxide or sulfide to a purer metal, the ore must be reduced physically, chemically, or electrolytically.
  • After mining, large pieces of the ore feed are broken through crushing and/or grinding.
  • The most common hydrometallurgical process is leaching, which involves dissolution of the valuable metals into the aqueous solution.

• Prokaryotes and Environmental Bioremediation

  • Microbial bioremediation is the use of prokaryotes (or microbial metabolism) to remove pollutants.
  • Bioremediation has been used to remove agricultural chemicals (pesticides, fertilizers) that leach from soil into groundwater and the subsurface.

• The Carbon Cycle

  • The most efficient type of respiration, aerobic respiration, requires oxygen obtained from the atmosphere or dissolved in water.
  • On land, carbon is stored in soil as a result of the decomposition of living organisms or the weathering of terrestrial rock and minerals.
  • This carbon can be leached into the water reservoirs by surface runoff.
  • A non-renewable resource is either regenerated very slowly or not at all.
  • Carbon is released as carbon dioxide when a volcano erupts or from volcanic hydrothermal vents.

• Biogeochemical Cycles

  • Energy flows directionally through ecosystems, entering as sunlight (or inorganic molecules for chemoautotrophs) and leaving as heat during the many transfers between trophic levels.
  • Water can be liquid on the surface and beneath the surface or frozen (rivers, lakes, oceans, groundwater, polar ice caps, and glaciers) or exist as water vapor in the atmosphere .
  • For example, the movement of water is critical for the leaching of nitrogen and phosphate into rivers, lakes, and oceans.
  • Thus, mineral nutrients are cycled, either rapidly or slowly, through the entire biosphere, from one living organism to another, and between the biotic and abiotic world.
  • It is important for leaching certain components of organic matter into rivers, lakes, and oceans, and is a reservoir for carbon.

• The Phosphorus Cycle

  • In addition to phosphate runoff as a result of human activity, natural surface runoff occurs when it is leached from phosphate-containing rock by weathering, thus sending phosphates into rivers, lakes, and the ocean.
  • A dead zone is an area within a freshwater or marine ecosystem where large areas are depleted of their normal flora and fauna.

• Calcium and Phosphate Balance Regulation

  • Ninety-nine percent or more is deposited in bone and the remainder plays a vital role in nerve conduction, muscle contraction, hormone release and cell signalling.
  • This hormone also causes phosphate to leach out of bone.

• Soaps & Detergents

  • Such molecules are termed amphiphilic (Gk. amphi = both) or amphipathic.
  • Fatty acids made up of ten or more carbon atoms are nearly insoluble in water, and because of their lower density, float on the surface when mixed with water.
  • To summarize, the presence of a soap or a detergent in water facilitates the wetting of all parts of the object to be cleaned, and removes water-insoluble dirt by incorporation in micelles.
  • Before sodium hydroxide was commercially available, a boiling solution of potassium carbonate leached from wood ashes was used.
  • These problems have been alleviated by the development of synthetic amphiphiles called detergents (or syndets).