Metals and Metallurgy

Minerals

Most metals are found in solid inorganic compounds known as minerals.

Minerals are named by common names and not chemical names.

Minerals

• Most important metals are found in minerals as oxides, sulfides, orb tcarbonates.

Metallurgy

The science and technology of extracting metalsfrom their natural sources and preparing themp p gfor practical use.

Involves:Involves:

– Mining

– Concentrating ores

– Reducing ores to obtain freemetals

– Purifying metals

– Mixing metals to form alloysthat have the propertiesdesired

Pyrometallurgy

The thermal treatment of minerals and metallurgical ores and concentrates.

The use of high temperature to alter or reduce minerals.

The process brings about physical and chemical transformations in thematerials to enable recovery of valuable metals.

Pyrometallurgical processes are generally grouped into one ormore of the following categories:

o Drying

o Calcining

o Roastingo Roasting

o Smelting

o Refining

i) Drying

Thermal removal of liquid moisture (not chemicallybound) from a material.bou d) o a ate a

Drying temperature is usually above the H2O bp. >120 °C.

Drying of moist solids is carried out using industrialdryers, such as rotary dryers, fluidized bed dryers, flashdryers or spray dryersdryers or spray dryers.

ii) Calcination

Heating an ore to bring about its decomposition and Heating an ore to bring about its decomposition andelimination of a volatile product.

PbCO3(s) PbO(s) + CO2(g)PbCO3(s) PbO(s) + CO2(g)

Normally takes place at Temp below the Mp. of the product.

iii) Roasting A thermal reaction between ore and the furnace

atmosphere (O2).

2 MoS2(s) + 7 O2(g) 2 MoO3(s) + 4 SO2(g)

HgS(s) + O2(g) Hg(g) + SO2(g)

iv) Smelting

2 2

A melting process in which materials formedduring reactions separate into two or more layers.

v) Refiningv) Refining

The treatment of a crude, relatively impure metal toimprove its purity and better define its compositionimprove its purity and better define its composition.

Reduction of Iron

Hematite (Fe2O3), magnetite(Fe3O4), and other iron oxidesare reduced in blast furnaces.

Purified iron exits the furnaceat the bottom.

Steel

ll i ti tl f i ith b an alloy consisting mostly of iron, with a carboncontent between 0.2% and 2.1% by weight.

Crude molten iron contains many impurities: Silicon;Manganese; Phosphorus; Sulfur; Carbon.

The impurities are oxidized by O2 (exceptphosphorus, which reacts with CaO) to compounds

il t d f th lt ieasily separated from the molten iron.

Hydrometallurgyy gy

These are techniques in which metal is extracted from ore via theuse of aqueous reactions.

Leaching

Electrometallurgy

Leaching

• Process in which metal-containing compound is selectivelyProcess in which metal containing compound is selectivelydissolved.

• Can use water if metal-containing compound is water soluble but• Can use water if metal-containing compound is water soluble, butmore often must use acid, base, or a salt solution.

Gold cyanidation

4 Au(s) + 8 CN−(aq) + O2(g) + 2 H2O(l) 4 Au(CN)2

−(aq) + 4 OH−

(aq)

2 Au(CN)2−

(aq) + Zn(s) Zn(CN)42−

(aq) + 2 Au(s)

Electrometallurgy

The reduction of metal ores or refining of metals by use of electricity.

Example: Copper• Active metal impurities oxidized at anode.

– Cu2+ water‐soluble and more easily reduced at the cathode

• Less active metals deposit asLess active metals deposit assludge below anode.