Chemistry · Ch 14 — Environmental Chemistry
Introduction
Introduction
The Cost of Development Without Care
India achieved self-sufficiency in food production in the late 20th century through the use of fertilizers, pesticides, improved farming methods, better seeds and irrigation. But over-exploitation of soil and excessive use of fertilizers and pesticides has, in turn, degraded soil, water and air quality.
What Green Chemistry Actually Means
The answer is not to halt development, but to find methods that reduce environmental deterioration while development continues. Green chemistry is a way of thinking that applies existing chemical knowledge and principles — of chemistry and other sciences — to reduce the adverse impact of chemical processes on the environment.
- A green chemical process aims to produce minimum pollution or environmental deterioration.
- Byproducts that are not put to further use simply become additional pollution — such processes are both environmentally unfriendly and cost-ineffective, since waste generation and its disposal are both economically wasteful.
- The foundation of green chemistry is applying existing knowledge to reduce chemical hazards while still pursuing development.
Designing Cleaner Reactions
A chemical reaction involves reactants, reagents and the medium in which it occurs, and its efficiency depends on physical parameters such as temperature, pressure and catalysts. If reactants are converted almost completely into useful, environmentally friendly products using an environmentally friendly medium, essentially no chemical pollutant is introduced into the environment.
- Synthesis should choose starting materials that can be converted to end products at close to 100% yield, achieved through optimum reaction conditions.
- Carrying out reactions in aqueous medium is often advantageous: water has a high specific heat, low volatility, is cost-effective, non-inflammable and free of carcinogenic effects — unlike toxic organic solvents such as benzene, toluene and carbon tetrachloride, which demand great care in handling.