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Non Ferrous Metal Extraction Process Notes | Study Crack Inspire

Non Ferrous Metal Extraction Process Notes

April 03, 2025

Non-Ferrous Metal Extraction - TestUrSelf

Non-Ferrous Metal Extraction

Principles and processes for aluminium, copper and titanium production

Table of Contents

1. Aluminium Extraction

Aluminium is extracted from bauxite ore through the Bayer process followed by the Hall-Héroult electrolytic process.

1.1 Hall-Héroult Process Components

Component Purpose Composition
Cryolite (Na3AlF6) Electrolyte solvent 80-85% of bath
Alumina (Al2O3) Aluminium source 2-8% dissolved
Aluminium Fluoride (AlF3) Lowers melting point 5-12%
Calcium Fluoride (CaF2) Improves conductivity 3-7%

1.2 Bayer Process Parameters

Stage Temperature Pressure Time
Digestion 150-250°C 20-30 atm 1-3 hours
Precipitation 50-70°C Atmospheric 24-48 hours
Calcination 1000-1200°C Atmospheric 1-2 hours

2. Copper Extraction

Copper is extracted from sulfide ores through pyrometallurgical processes or from oxide ores via hydrometallurgy.

2.1 Copper Smelting Reactions

Stage Reaction Temperature
Roasting 2CuFeS2 + 5O2 → 2CuS + 2FeO + 4SO2 500-700°C
Smelting 2CuS + 3O2 → 2Cu2O + 2SO2 1200-1300°C
Converting Cu2S + 2Cu2O → 6Cu + SO2 1150-1250°C

2.2 Hydrometallurgical Parameters

Process Conditions Recovery
Leaching H2SO4 (pH 1.5-2.0), 25-50°C 70-90%
Solvent Extraction LIX reagents, O:A ratio 1:1 to 3:1 95-99%
Electrowinning 2.0-2.5 V, 200-300 A/m2 99.99% pure

3. Titanium Extraction

Titanium is extracted from rutile (TiO2) or ilmenite (FeTiO3) through the Kroll process.

3.1 Kroll Process Parameters

Stage Conditions Duration
Chlorination 900-1000°C with petroleum coke 4-12 hours
Purification Distillation at 136°C 2-4 hours
Reduction 800-850°C, Ar atmosphere 36-50 hours
Vacuum Distillation 1000°C at 0.1-1 mbar 48-72 hours

Aluminium Extraction MCQs

1. What is the primary purpose of cryolite in the Hall-Héroult process?
To provide aluminium ions
To dissolve alumina and lower the melting point
To act as a reducing agent
To prevent oxidation of the aluminium

Correct Answer: To dissolve alumina and lower the melting point

Cryolite (Na3AlF6) serves as a solvent for alumina (Al2O3), allowing electrolysis to occur at 950°C instead of alumina's melting point of 2072°C. This dramatically reduces energy requirements.

2. In the Bayer process, what is the purpose of adding sodium hydroxide (NaOH) to bauxite?
To neutralize acidic impurities
To selectively dissolve aluminium hydroxide
To precipitate iron oxides
To increase the melting point of the mixture

Correct Answer: To selectively dissolve aluminium hydroxide

NaOH reacts with Al(OH)3 in bauxite to form soluble sodium aluminate (NaAlO2), while impurities like Fe2O3 remain insoluble. This selective dissolution is the key separation mechanism in the Bayer process.

Copper Extraction MCQs

1. What is the primary purpose of the converting stage in copper pyrometallurgy?
To remove gangue minerals
To oxidize iron sulfides and produce blister copper
To reduce copper oxides to metallic copper
To dissolve copper minerals in acid

Correct Answer: To oxidize iron sulfides and produce blister copper

The converting stage uses oxygen injection to oxidize remaining FeS in the matte to FeO (which forms slag) and produce blister copper (98.5% Cu) through the reaction: Cu2S + O2 → 2Cu + SO2.

2. In copper hydrometallurgy, what is the purpose of solvent extraction?
To melt the copper concentrate
To selectively transfer copper from leach solution to organic phase
To reduce copper ions to metal
To remove sulfur dioxide emissions

Correct Answer: To selectively transfer copper from leach solution to organic phase

Solvent extraction uses organic reagents like LIX 984N to selectively extract Cu2+ ions from the pregnant leach solution into an organic phase, leaving impurities behind. The copper is then stripped into a high-purity electrolyte for electrowinning.

Titanium Extraction MCQs

1. Why is magnesium used in the Kroll process instead of carbon for titanium reduction?
Magnesium is cheaper than carbon
Carbon would form titanium carbide which contaminates the metal
Magnesium reduces at lower temperatures
Carbon cannot reduce titanium tetrachloride

Correct Answer: Carbon would form titanium carbide which contaminates the metal

Carbon reduction of TiCl4 would produce brittle titanium carbide (TiC) instead of pure titanium. Magnesium is used because it reduces TiCl4 to pure titanium while forming MgCl2 byproduct that can be separated.

2. What is the primary reason the Kroll process is batch rather than continuous?
Lower equipment costs
The need to physically remove titanium sponge from the reactor
Easier temperature control
Government regulations

Correct Answer: The need to physically remove titanium sponge from the reactor

The Kroll process produces titanium in a porous "sponge" form that adheres to reactor walls and must be mechanically removed after each batch. This makes continuous operation impractical, unlike processes that produce molten metals.

Comparative Extraction MCQs

1. Which of these metals is primarily extracted using electrolysis of a molten salt?
Aluminium
Copper
Titanium
All of the above

Correct Answer: Aluminium

Aluminium is produced by electrolysis of alumina dissolved in molten cryolite (Hall-Héroult process). Copper is typically produced by pyrometallurgy or electrowinning from aqueous solutions, while titanium is produced by magnesium reduction (Kroll process).

2. Which extraction process uses chloride chemistry for metal production?
Bayer process (Al)
Flash smelting (Cu)
Kroll process (Ti)
All of the above

Correct Answer: Kroll process (Ti)

The Kroll process converts TiO2 to TiCl4 which is then reduced by Mg. The Bayer process uses hydroxide chemistry, while copper smelting uses sulfide/oxide chemistry.

TestUrSelf

Evaluate your knowledge with these interactive courses

Aluminium Extraction

10 questions covering Bayer process and Hall-Héroult electrolysis

Copper Metallurgy

8 questions on pyrometallurgical and hydrometallurgical routes

Titanium Production

6 questions focusing on Kroll process and alternatives

Comparative Analysis

12 questions comparing all three extraction processes