UPSC Prelims 2025Question 50Environment

Consider the following statements:
Statement I: Activated carbon is a good and an attractive tool to remove pollutants from effluent streams and to remediate contaminants from various industries.
Statement II: Activated carbon exhibits a large surface area and a strong potential for adsorbing heavy metals.
Statement III: Activated carbon can be easily synthesized from environmental wastes with high carbon content.
Which one of the following is correct in respect of the above statements?

Options

(a)Both Statement II and Statement III are correct and both of them explain Statement I
(b)Both Statement II and Statement III are correct but only one of them explains Statement I
(c)Only one of the Statements II and III is correct and that explains Statement I
(d)Neither Statement II nor Statement III is correct

Correct answer: a

Decision rule

Two independent properties can both explain one use: performance explains why a material works, cheap feedstock explains why it is attractive.

Explanation

Correct Answer:

(a) Both Statement II and Statement III are correct and both of them explain Statement I

Explanation of the Correct Answer:

Let’s break down and verify each statement:

Statement I:
- Correct. Activated carbon is widely used in industrial effluent treatment due to its excellent adsorption properties.
- It helps remove pollutants such as organic compounds, heavy metals, dyes, and other contaminants from water and gas streams.
Statement II:
- Correct. Activated carbon has an exceptionally large surface area (500–1500 m²/g) and contains numerous pores and functional groups, enabling strong adsorption of heavy metals like lead, cadmium, mercury, etc.
Statement III:
- Correct. Activated carbon can indeed be easily synthesized from biomass waste like coconut shells, sawdust, rice husk, sugarcane bagasse, etc.
- These materials have high carbon content and are cost-effective, making them ideal for sustainable production of activated carbon.
Do both II and III explain Statement I?
- Yes:
  - Statement II explains why activated carbon is effective at removing pollutants (due to its adsorption capacity).
  - Statement III explains why it is an attractive tool (because it can be sustainably and cheaply produced).

Why Other Options Are Incorrect:

(b) Both are correct but only one explains Statement I – Incorrect: Both II and III explain Statement I.
(c) Only one is correct and explains Statement I – Incorrect: Both are correct.
(d) Neither is correct – Incorrect: Both are correct and scientifically valid.

Relevant Supplementary Information

Table: Evaluation of the Statements

Statement	Content	Correct?	Explanation
I	Activated carbon is useful for pollutant removal and industrial remediation	Yes	Widely used in water and air purification, especially in industrial effluent
II	Has large surface area and can adsorb heavy metals	Yes	Surface area enables strong adsorption of metals and organic pollutants
III	Can be made from environmental wastes with high carbon content	Yes	Used in green manufacturing from waste biomass like coconut shells, etc.

Related Concepts:

Concept	Explanation
Adsorption	Surface-based process where pollutants adhere to the activated carbon's surface
Activated Carbon	Carbonaceous material with high porosity and surface area
Heavy Metal Removal	Effective against Pb²⁺, Hg²⁺, Cd²⁺, etc., from wastewater
Biomass-Derived Carbon	Conversion of agri-waste into activated carbon using thermal/chemical activation

Current Relevance:

Activated carbon is key to India’s Namami Gange and other water treatment programs.
Circular economy initiatives promote activated carbon from agricultural waste.
Global demand for low-cost and effective adsorbents is increasing in environmental remediation.

Table: Key Concepts Related to Activated Carbon

Concept	Explanation	Examples / Applications	Relevance
Activated Carbon	A form of carbon processed to have high porosity and surface area, enabling strong adsorption	Water filters, air purifiers, industrial effluent treatment	Widely used in environmental remediation and pollution control
Surface Area and Porosity	Activated carbon typically has 500–1500 m²/g of surface area with micro- and mesopores	High capacity for adsorbing heavy metals, dyes, organic compounds	Explains its effectiveness in removing pollutants
Adsorption (Not Absorption)	The adherence of molecules to a surface, rather than uptake into a volume	Heavy metals like Pb²⁺, Hg²⁺, organic pollutants like benzene	Central mechanism behind activated carbon’s pollutant removal ability
Heavy Metal Adsorption	Binding of metal ions to the carbon surface through electrostatic attraction, chelation, or physical adsorption	Lead, cadmium, arsenic, chromium	Important in treating industrial wastewater
Biomass-Derived Activated Carbon	Produced from agricultural or industrial waste with high carbon content	Coconut shells, rice husk, sawdust, bagasse	Enables low-cost and sustainable production
Effluent Treatment	Use of activated carbon in treating contaminated industrial discharge	Textile, pharmaceutical, chemical industries	Part of environmental compliance and water safety regulations
Carbon Activation Methods	Methods used to create porous structure—physical (steam) or chemical (acid/base)	KOH, ZnCl₂, CO₂, steam	Determines surface area and pore size distribution

Related Environmental Goals and Applications

Application Area	Role of Activated Carbon	Policy/Program Relevance
Water purification	Removes taste, odor, chlorine, heavy metals	Used in municipal and domestic filtration systems
Air purification	Captures VOCs, odors, harmful gases	Used in gas masks, air purifiers, industrial scrubbers
Soil remediation	Immobilizes organic pollutants like pesticides and hydrocarbons	Applicable in land reclamation
Circular economy	Converts agro-waste into valuable material	Aligns with sustainable development and waste-to-wealth models

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