MEV 013: Unit 04 - Developments In Environmental Chemistry

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UNIT 4: DEVELOPMENTS IN ENVIRONMENTAL CHEMISTRY

4.0 Introduction

Environmental chemistry continues to evolve to meet urgent global needs such as pollution reduction, sustainable industrial practices, and environmental safety. This unit focuses on the emergence of green chemistry, disasters that shaped environmental policy, eco-friendly materials, and sustainable practices.

4.1 Objectives

By the end of this unit, you should be able to:

  • Understand the origin and need for green chemistry.
  • Recognize the role of major industrial disasters in shaping environmental regulations.
  • Describe principles and applications of green chemistry.
  • Evaluate the use and development of green solvents, plastics, and pesticides.

4.2 Need for Emergence of Green Chemistry

Green Chemistry arose as a preventive approach to pollution, emphasizing the design of products and processes that reduce or eliminate hazardous substances.

4.2.1 Bhopal Gas Tragedy (1984, India)

  • Methyl isocyanate gas leak from Union Carbide pesticide plant.
  • Over 3,000 immediate deaths; long-term health consequences.
  • Highlighted need for safer chemical practices.

4.2.2 Thalidomide Disaster (1950s, Europe)

  • Drug caused birth defects in thousands of infants.
  • Raised awareness about testing, regulation, and chemical safety.

4.2.3 Times Beach, Missouri (1970s–80s, USA)

  • Town contaminated by dioxins from chemical waste sprayed on roads.
  • Resulted in evacuation and complete closure of the town.

4.2.4 Love Canal Disaster (New York, USA)

  • Toxic waste buried under neighborhood seeped into homes and schools.
  • Led to miscarriages, birth defects, cancer.
  • Triggered the Superfund Law for waste cleanup.

4.3 Some Important Laws for Environmental Protection

  • Clean Air Act and Clean Water Act (USA)
  • Environment Protection Act (1986) – India
  • REACH (EU): Registration, Evaluation, Authorization of Chemicals
  • Hazardous Waste Rules, Air and Water Quality Standards

These regulations emphasize prevention, monitoring, and safer alternatives.

4.4 Green Chemistry and Sustainability

  • Aims for sustainable development by designing safer products and reducing energy/waste.
  • Encourages circular economy, renewable resources, and environmental stewardship.

4.5 Concept of Green Chemistry

Green Chemistry focuses on:

  • Preventing waste
  • Using renewable feedstocks
  • Reducing toxicity
  • Designing for degradation

4.5.1 Twelve Principles of Green Chemistry

  1. Prevent waste.
  2. Atom economy.
  3. Less hazardous chemical syntheses.
  4. Safer chemical products.
  5. Safer solvents and auxiliaries.
  6. Energy efficiency.
  7. Renewable feedstocks.
  8. Reduce derivatives.
  9. Catalysis over stoichiometry.
  10. Degradable products.
  11. Real-time pollution monitoring.
  12. Inherently safer chemistry.

4.6 Greener Solvents

Solvents are a major part of chemical waste and hazards. Green chemistry promotes alternatives.

4.6.1 Issues with Traditional Solvents

  • Volatile Organic Compounds (VOCs) → smog, health effects.
  • Toxicity, flammability, non-biodegradability.

4.6.2 Green Solvents

4.6.2.1 Water

  • Abundant, non-toxic, ideal for polar reactions.
  • Limitation: Not all solutes dissolve well.

4.6.2.2 Supercritical Fluids (SCFs)

  • CO₂ at high pressure/temperature becomes a fluid.
  • Excellent solvent for extraction; easily removed.

4.6.2.3 Ionic Liquids

  • Non-volatile, reusable salts.
  • Tailored properties for green synthesis.

4.6.2.4 Liquid Polymers

  • High molecular weight, low vapor pressure.
  • Used in lubricants, coatings.

4.6.2.5 Bio-Based Renewable Solvents

  • Derived from plant sources (e.g., ethanol, limonene).
  • Biodegradable and renewable.

4.7 Earth-Friendly Plastics

4.7.1 Plastics – The Biggest Source of Pollution

  • Non-biodegradable, persistent in land and oceans.
  • Microplastics affect marine life and enter food chains.

4.7.2 Greening of Plastics

  • Bioplastics: Made from renewable sources like starch or corn.
  • Degradable plastics: Break down under specific conditions.
  • Recycling & Upcycling: Reduces environmental footprint.

4.8 Environmentally Benign Pesticides

4.8.1 Effects of Synthetic Pesticides

  • Accumulate in soil, water, food.
  • Linked to cancer, hormonal disruption, biodiversity loss.

4.8.2 Search for Environmentally Friendly Alternatives

  • Focus on target specificity, biodegradability, and low toxicity.

4.8.3 Examples

4.8.3.1 Microbial Pesticides

  • Bacteria (e.g., Bacillus thuringiensis) target specific pests.
  • Safe for humans and non-target species.

4.8.3.2 Plant-Pesticides

  • Neem extracts, pyrethrum: natural pest repellents.

4.8.3.3 Biochemical Pesticides

  • Hormones, pheromones that interfere with pest life cycles.

4.8.3.4 Natural Home-made Solutions

  • Garlic-chili sprays, soap solutions, vinegar sprays for small-scale use.

4.9 Let Us Sum Up

  • Green Chemistry emerged from the need to prevent environmental disasters and promote sustainability.
  • Major incidents like Bhopal and Love Canal led to global environmental regulations.
  • The twelve principles of Green Chemistry guide safe, eco-friendly chemical design.
  • Green solvents, biodegradable plastics, and eco-pesticides are practical advances.
  • These approaches aim to balance human needs with environmental protection.

4.10 Glossary

  • Green Chemistry: Chemistry focused on reducing environmental impact.
  • Supercritical Fluid: A substance above its critical temperature and pressure acting as a solvent.
  • Ionic Liquid: A liquid salt used as a green solvent.
  • Bioplastic: Plastic made from renewable biomass.
  • Biopesticide: Pest control substance derived from natural materials.
  • VOC: Volatile Organic Compound, often toxic or smog-forming.

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