Metallurgy By Vicky Mayall

Introduction Introduction The majority of the elements on the periodic table are metals. There are numerous applications of metals all around us but for students there is often a disconnect between their use and how we obtain these essential resources. Considering Utah has a variety of metal resources this is also a locally relevant topic. The goal of this document is to identify some basic processes that might enrich students understanding of metals.

Metallurgy Metallurgy Extracting metals from ores Extracting metals from ores Chloride, Oxide and Sulfide ores Chloride, Oxide and Sulfide ores Native Metals found in nature in elemental form Native Metals found in nature in elemental form Reactions Reactions Chloride Ores Chloride Ores Converted to metal by electrolysis Converted to metal by electrolysis 2N aCl ( l )  2Na ( l ) + Cl 2(g) Ox:2Na + + 2e -  2Na Red:2Cl -  Cl 2 + 2e - Sodium chloride abundant in Utah

The sodium chloride must be molten because a electrolysis of aqueous NaCl causes a reaction with water and sodium metal is not obtained. The sodium chloride must be molten because a electrolysis of aqueous NaCl causes a reaction with water and sodium metal is not obtained.

Oxide Ores Oxide Ores Very reactive metal Very reactive metal 2Al 2 O 3(s)  4Al ( l ) + 3O 2(g) Bauxite Reduce by electrolysis

Less active metal Less active metal Most commonly Carbon Most commonly Carbon Three Steps Three Steps 1. Carbon to carbon monoxide 2C (s) + O 2(g)  2CO (g) 2. Reduction of metal Fe 2 O 3(s) + 3CO (g)  2Fe ( l ) + 3CO 2(g) Fe 2 O 3(s) + 3CO (g)  2Fe ( l ) + 3CO 2(g) Hematite – has SiO 2 Chemical reducing agent used

3. Formation of Slag – removing SiO 2 CaCO 3(s)  CaO (s) + CO 2(g) limestone CaO (s) + SiO 2(s)  CaSiO 3( l ) Calcium Silicate (slag) as a Liquid is less dense so will form a top layer above the molten iron

Sulfide Ores Sulfide Ores Ores are “roasted” in air or pure oxygen Ores are “roasted” in air or pure oxygen Active metal Active metal 2ZnS (s) + 3O 2(g)  2ZnO (s) + 3SO 2(g) Sphalerite most Sphalerite most common ore Cinnabar Less active metal Less active metal HgS (s) + O 2(g)  Hg (g) + SO 2(g) Reduce using Carbon Reaction forms an oxide Produces metal directly

Copper very important metal Copper very important metal Most ores are now low in copper Most ores are now low in copper Cu 2 S (s) + O 2(g)  2Cu (s) + SO 2(g) “Floatation” process increases yield from less than 2% up to 20-30% “Floatation” process increases yield from less than 2% up to 20-30% After crushing ore is mixed with water, limestone and xanthates (5 C nonpolar chain with a polar thiocarbonate end) – called a slurry After crushing ore is mixed with water, limestone and xanthates (5 C nonpolar chain with a polar thiocarbonate end) – called a slurry Polar end attracted to ore surrounding it, leaving non-polar hydrophobic end exposed Polar end attracted to ore surrounding it, leaving non-polar hydrophobic end exposed Air bubbles bring ore and xanthates to the surface Air bubbles bring ore and xanthates to the surface Waste rock does not adhere to bubbles and sink Waste rock does not adhere to bubbles and sink

Floatation Process Floatation Process

Kennecott Copper Mine Utah Kennecott Copper Mine Utah One of the largest open pit copper minesin the world One of the largest open pit copper minesin the world By-products include Gold, Silver and Molybdenum By-products include Gold, Silver and Molybdenum

Native Metals Native Metals Very un-reactive metals found in elemental form Very un-reactive metals found in elemental form Mined so much that the percentages are so low a chemical process must be used Mined so much that the percentages are so low a chemical process must be used Cyanide used in the recovery of gold Cyanide used in the recovery of gold Facilitates oxidation and solubilization of Au Facilitates oxidation and solubilization of Au 4Au (s) + 8CN - (aq) + O 2 (g) + H 2 O ( l )  4Au(CN) - 2 (aq) + 4OH - (aq) Cyanide acting as a complexing ligand Cyanide acting as a complexing ligand Recover the metal by adding Zinc Recover the metal by adding Zinc 2Au(CN) - 2(aq) + Zn (s)  Zn(CN) - 4(aq) + 2Au (s) Silver, Ag and Gold, Au Zinc more reactive