Green Chemistry and Nanochemistry — Chemistry STD 12 Science — Question

Following the Principles of Green Chemistry:
i. Prevention of waste or by-products: According to this principle of green chemistry, priority is given for the prevention of waste rather than cleaning up and treating waste after it has been generated.
Illustration: To develop zero-waste technology (ZWT). As per ZWT, in chemical synthesis, the waste product should be zero or minimum. It also aims to use the waste product of one system as the raw material for other systems.
For example:
a. The bottom ash of the thermal power station can be used as a raw material for the cement and brick industry.
b. The effluent coming out from the cleansing of machinery parts may be used as coolant water in the thermal power station.
ii. Less hazardous chemical synthesis:
According to this principle of green chemistry, designed chemical reactions and synthesis routes should be as safe as possible to avoid the formation of hazardous waste from chemical processes.
Illustration:
Earlier Dichlorodiphenyltrichloroethane (DDT) was used as an insecticide and was effective in controlling diseases like typhoid and malaria-carrying mosquitoes. It was realized that DDT is harmful to living things. Nowadays, benzene hexachloride (BHC) is used as an insecticide. One of the γ-isomer (gamma) of BHC is called gammexane or lindane.
iii. Designing safer chemicals: This principle of green chemistry aims at developing products that are less toxic or which require less toxic raw materials. Illustration: In chemical industries workers are exposed to a toxic environment. Safer chemicals must be designed in order to prevent workers from exposure to toxicity.
For example:
Adipic acid is widely used in the polymer industry. Benzene is the starting material for the synthesis of adipic acid but benzene is carcinogenic and benzene being a volatile organic compound (VOC) pollutes the air. In green technology developed by Drath and Frost, adipic acid is enzymatically synthesised from glucose.