Leaching Hydrometallurgy

1 leaching

1.1 in-situ leaching
1.2 heap leaching
1.3 vat leaching
1.4 tank leaching
1.5 autoclave leaching

leaching

leaching involves use of aqueous solutions extract metal metal bearing materials brought contact material containing valuable metal. lixiviant solution conditions vary in terms of ph, oxidation-reduction potential, presence of chelating agents , temperature, optimize rate, extent , selectivity of dissolution of desired metal component aqueous phase. through use of chelating agents, 1 can selectively extract metals. such chelating agents typically amines of schiff bases.

the 5 basic leaching reactor configurations in-situ, heap, vat, tank , autoclave.

in-situ leaching

in-situ leaching called solution mining. process involves drilling of holes ore deposit. explosives or hydraulic fracturing used create open pathways within deposit solution penetrate into. leaching solution pumped deposit makes contact ore. solution collected , processed. beverley uranium deposit example of in-situ leaching.

heap leaching

in heap leaching processes, crushed (and agglomerated) ore piled in heap lined impervious layer. leach solution sprayed on top of heap, , allowed percolate downward through heap. heap design incorporates collection sumps, allow pregnant leach solution (i.e. solution dissolved valuable metals) pumped further processing. example gold cyanidation, pulverized ores extracted solution of sodium cyanide, which, in presence of air, dissolves gold, leaving behind nonprecious residue.

ball-and-stick model of aurocyanide or dicyanoaurate(i) complex anion, [au(cn)2].




vat leaching

vat leaching, called agitation leaching, involves contacting material, has undergone size reduction , classification, leach solution in large vats.

tank leaching

stirred tank, called agitation leaching, involves contacting material, has undergone size reduction , classification, leach solution in agitated tanks. agitation can enhance reaction kinetics enhancing mass transfer. tanks configured reactors in series.

autoclave leaching

autoclave reactors used reactions @ higher temperatures, can enhance rate of reaction. similarly, autoclaved enable use gaseous reagents in system.