Green Chemistry, Pollution, Food Adulteration & E-waste
1. Twelve principles of green chemistry (condensed)
- Prevent waste rather than clean it. 2. Maximize atom economy (reactant atoms in product). 3. Less hazardous synthesis. 4. Safer products. 5. Safer solvents (water/scCO₂). 6. Energy efficiency (ambient T/P). 7. Renewable feedstocks. 8. Fewer derivatization steps. 9. Catalysis over stoichiometric reagents. 10. Design for degradation. 11. Real-time analysis/prevention. 12. Inherently safer chemistry.
Atom economy . Example: Diels–Alder ~100% (addition); Grignard with workup much lower.
2. Air and water pollution (engineering view)
- Air: particulates (PM2.5/PM10), (acid rain), (smog), CO (carboxyhaemoglobin), ozone (ground-level oxidant), lead/VOCs. Control: ESPs, scrubbers, catalytic converters, BHEL/stack norms.
- Water: organic load (BOD/COD), nutrients (eutrophication by N/P), heavy metals (Hg/Minamata, As, Pb), oil, thermal discharge. Control: ETP with primary (settling) → secondary (activated sludge) → tertiary (chlorination/RO) treatment; Zero Liquid Discharge in textile/tannery clusters.
- Standards route: CPCB/SPCB limits, EIA before projects.
3. Food adulteration — tests asked in syllabus
| Food | Adulterant | Simple detection test |
|---|---|---|
| Ghee/butter (fat) | vanaspati, starch, mashed potato | Baudouin test (pink with furfural-HCl for vanaspati); iodine → blue for starch |
| Sugar | chalk powder, washing soda | dissolves: chalk leaves white residue; soda turns red litmus blue / effervesces with acid |
| Turmeric powder | metanil yellow (banned dye), chalk, lead chromate | HCl + drop: pink/red = metanil yellow; dip paper in extract — persistent yellow stain |
| Chilli powder | brick powder, Sudan dye, starch | water settling: brick grit sinks; acetone extract red = Sudan dye; iodine blue = starch |
Health effects: liver/kidney damage (dyes, lead), GI disorders, carcinogenic risk. Prevention: FSSAI standards, AGMARK, consumer test kits.
4. E-waste management
E-waste = discarded phones, PCs, batteries, CFLs, PCBs — contains Au/Ag/Pd/Cu (urban mine) plus Pb, Hg, Cd, brominated flame retardants.
- Hazards: informal burning/acid leaching poisons air, soil, groundwater; CRT lead, battery Cd, mercury switches.
- Management hierarchy: reduce → reuse/refurbish → recycle (dismantle → segregate → metal recovery by smelting/hydrometallurgy) → scientific disposal (TSDF landfill/incineration).
- India: E-Waste (Management) Rules — EPR (producer must collect back), authorized dismantlers only, deposit-refund schemes; consumer duty: don't mix with household waste, hand to collection centres.
Exam Points
- Any 6 green-chemistry principles + atom-economy formula (3–5 marks).
- Air vs water pollutant lists + one control device each (3 marks).
- Adulteration table for the four named foods with one test each (5 marks favourite); E-waste hazards + EPR/management steps (3 marks).