Water Technology, Engineering Materials, and Green Chemistry Exam Notes

Water Technology

• Quantity and quality of water are important for industries and domestic purposes.

• Hardness of water is the extent of pollution; estimation and removal of hardness are essential.

  • Hard water prevents lathering with soap, forming scum due to the presence of calcium and magnesium salts.
  • Types of hardness: temporary (carbonate) and permanent (non-carbonate).
  • Temporary hardness can be removed by boiling, while permanent hardness requires chemical treatment

• Key Definitions:

  • Soft water readily forms lather with soap.
  • Hard water prevents lathering of soap.
  • Degree of hardness is the total quantity of hardness-causing salts, expressed as $CaCO_3$ equivalent.
  • Formulae for calculating Lime and Soda requirements.
  • Concentrations are expressed in terms of $CaCO_3$ equivalents for hardness measurement.

• Various sources of water (rain, surface, ground) have different impurities.

• Impurities include dissolved salts and gases, suspended impurities, and microbial impurities.

• EDTA titration method is used to estimate hardness by complexing with $Ca^{2+}$ and $Mg^{2+}$ ions using Eriochrome Black T indicator.

  • EDTA forms complex ions with hardness causing $Ca^{2+}$ and $Mg^{2+}$ ions.
  • At the end point, wine red complex disappears and the original blue colour of the dye appears
  • Standardization of EDTA involves titrating against a standard hard water sample.

• Softening methods include Lime Soda process, Zeolite process, and Ion Exchange process.

  • Lime Soda process converts soluble calcium & magnesium salts into insoluble compounds using lime $Ca(OH)<em>2$ and soda $Na</em>2CO_3$.
  • Zeolite (Permutit) process exchanges ions with heavy $Ca$, $Mg$ ions.
  • Ion exchange or Demineralization process: removes ions (both the cations and anions) from a sample of water.

• BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) are parameters used to measure water pollution.

• Sewage treatment involves preliminary, primary, secondary (biological), and tertiary treatments.

  • Preliminary: removes gross solids
  • Primary: removes suspended matter
  • Secondary: filtration and activated sludge process
  • Tertiary: decrease the load of nitrogen and phosphorus compounds

• Biosensors monitor biological and chemical reactions, providing signals proportional to analyte concentration.

Engineering Materials

• Composite materials are engineered materials with two or more constituents with different mechanical properties.

• Composites consist of matrix and dispersed phases.

• Matrix phase binds the dispersed phase and protects it from abrasion or chemical reactions.

• Dispersed phases of composites are fiber, particulates, flakes, or whiskers.

• Different types of matrices (metal, ceramic, polymer) lead to metal matrix composites (MMC), ceramic matrix composites (CMC), and polymer matrix composites (PMC).

• Fibers have high tensile strength and length to diameter ratio.

• The matrix phase is a continuous body that encloses the composite and gives it its bulk form; it should be ductile and corrosion-resistant Metals, ceramics, and polymers are used.

• The dispersed phase determines the internal structure and may be fiber, particulates, flakes, or whiskers

• Classes of Composites: Particle-reinforced, Fiber-reinforced, and Structural Composites

  • Particle-Reinforced: Large Particle and Dispersion-Strengthened
  • Fiber-Reinforced: Continuous (Aligned) and Discontinuous (Aligned or Randomly Oriented)
  • Discontinuous fibers have lower reinforcement efficiency than that for continuous fibers.
  • Structural: Laminates and Sandwich Panels

• Nanomaterials have nanoscale dimensions (1-100 nm) and exhibit unique properties.

  • Nanoclusters: aggregates of atoms or molecules in the nanoscale range.
  • Nanorods: nanoscale rectangular prism one dimension is sized in the nanoscale, other 2 in normal value.
  • Nanotubes: hollow cylindrical structures with nanoscale diameters.
    • Single-Wall Nanotubes (SWNT)
    • Multi-Wall Nanotubes (MWNT)
  • Nanowires: thin elongated structures with nanoscale dimensions.

• Synthesis methods include precipitation and sol-gel processes.

Green Chemistry & Green Engineering

• Green Chemistry is designed to reduce or eliminate hazardous substances.
• There are 12 principles of green chemistry.

1. Prevention.
2. Atom economy.
3. Less hazardous chemical synthesis.
4. Designing safer chemicals.
5. Safer solvents.
6. Design for energy efficiency.
7. Use of renewable feedstocks
8. Reduce derivatives
9. Catalysis.
10. Design for degradation
11. Real-time analysis for pollution prevention
12. Inherently safer chemistry for accident prevention

• Green Chemistry aims to minimize environmental impact.

• Atom economy maximizes incorporation of material from starting materials into the final product.

• Catalysts alter reaction rates without being consumed.

  • Types: Homogeneous and Heterogeneous

• In any chemical synthesis, the requirement of energy should be kept to a minimum.

• Green engineering is designing sustainable solutions that meet present needs without compromising futures

• Green engineering is designing and implementing engineering solutions that aim to minimize environmental impact and promote sustainability.

• Green engineering principles include pollution prevention, resource efficiency, design for the environment, and innovation.