Home › PYQs › Environment › All questions › 2021 · Copper smelting
UPSC Prelims 2021 · Environment · Pollution Files
Why is there a concern about copper smelting plants? Select the correct answer using the codes given below.
- They may release lethal quantities of carbon monoxide into the environment.
- The copper slag can cause the leaching of some heavy metals into the environment.
- They may release sulphur dioxide as a pollutant.
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Show the answer and explanation
Answer: (d) 1, 2 and 3
CO, slag leaching and SO₂ are all concerns.
Statement by statement
1. ✓ YES Poor combustion in smelters can release dangerous amounts of carbon monoxide.
2. ✓ YES Copper slag can leach heavy metals (arsenic, lead) into soil and water.
3. ✓ YES Copper ores are sulphides, so smelting releases SO₂.
The idea
Most copper ore is a sulphide: copper and iron joined with sulphur. To get the metal the sulphur has to be burnt off, and it leaves as sulphur dioxide. What remains after the copper is taken out is slag, which carries arsenic, lead and other metals from the ore.
Copper sulphide ore is roasted → Sulphur burns → sulphur dioxide → Molten copper is separated → Slag is left over → Rain on slag heaps leaches heavy metals into soil and water
The trap
CO sounds like a vehicle pollutant, but smelters burn a lot of fuel too.
Elimination technique
All three are soft claims (“may release”, “can cause”) with no absolute word. Plain claims of this kind are usually true in Environment PYQs, which points to all three.
Also know
A well-run smelter captures the sulphur dioxide and turns it into sulphuric acid for sale. The Sterlite copper smelter at Thoothukudi (Tamil Nadu) was closed in 2018 after protests over pollution; India then turned from an exporter of refined copper into an importer.
🔒 Copper smelting: SO₂, heavy-metal slag, CO. Sterlite (Thoothukudi) closed 2018.