Consider the following statements:Statement I: Activated carbon is a good and attractive tool to rem

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UPSC Prelims is a competitive examination conducted in India. This question is from the 2025 UPSC Prelims Environment & Ecology paper.

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This UPSC Prelims 2025 Environment & Ecology question has a medium difficulty level.

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Question

Consider the following statements:Statement I: Activated carbon is a good and 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?

Accepted Answer

Correct Answer: B - Both Statement II and Statement III are correct but only one of them explains Statement IStep-by-step Solution:Statement I (Claim): Activated carbon is an effective tool for removing pollutants from effluent streams and remediating industrial contaminants. This is a well-established fact in environmental engineering and water treatment.Evaluating Statement II: Activated carbon possesses an extraordinarily large surface area - typically 500 to 1500 m²/g - due to its highly porous structure. This large surface area provides abundant adsorption sites. Heavy metals such as lead, cadmium, mercury, and arsenic can be adsorbed onto activated carbon surfaces. This statement is correct. Furthermore, it explains Statement I because the mechanism by which activated carbon removes pollutants is precisely its large surface area enabling strong adsorption. ✓ (Explains Statement I)Evaluating Statement III: Activated carbon can indeed be produced from various carbon-rich waste materials including agricultural wastes (rice husk, coconut shell, sugarcane bagasse), sewage sludge, and industrial byproducts through pyrolysis and activation processes. This statement is correct. However, while this fact establishes that activated carbon is economically and environmentally sustainable to produce, it does not explain why activated carbon is effective at removing pollutants (which is what Statement I is about). It addresses the source/production, not the mechanism of pollutant removal. ✓ (Does NOT explain Statement I)Therefore, both II and III are correct, but only Statement II (large surface area and adsorption capacity) explains Statement I (effectiveness in pollutant removal).Why other options are incorrect:Option A: Incorrect. While both II and III are correct, only Statement II explains Statement I. Statement III explains the production sustainability, not the pollutant removal mechanism.Option C: Incorrect. Both Statement II and Statement III are correct, not just one of them.Option D: Incorrect. Both statements are factually accurate.Key Concept: Activated carbon (activated charcoal) is produced by carbonising carbon-rich organic material (coal, wood, coconut shell) followed by activation using steam, CO₂, or chemical agents (ZnCl₂, H₃PO₄), which creates a highly porous structure. Applications: Water purification; Air/gas filtration (gas masks, industrial exhaust); Soil remediation; Pharmaceutical detoxification (treatment of poisoning); Groundwater remediation (removal of VOCs, pesticides, heavy metals). India uses activated carbon extensively in effluent treatment plants (ETPs) in industries such as pharmaceuticals, textiles, and chemicals.

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