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Abstract
Chemical industry represents a highly successful sector of manufacturing and a vital part of the economy in many industrialized and developing countries. The range of chemical industry is vast which makes an invaluable contribution to the quality of our lives. However, the manufacture of chemical products also leads to enormous quantities of environmentally harmful waste and the health of the environment is declining rapidly. Despite the great success and importance of chemistry to our society its public image has deteriorated. A major reason is that the industry is perceived as being polluting and causing significant environmental damage. Green chemistry is an effort of terminating or reducing the use and generation of hazardous chemicals in the design, manufacture and applications of chemical products. Green chemistry efficiently utilizes renewable raw materials, eliminates waste and avoids the use of toxic and/or hazardous reagents in the manufacture and applications of chemical products thereby it plays an important role for pollution control and sustainable development & conservation of environment and Biodiversity.
Introduction
Society has been very much benefitted from Chemical products synthesized. Chemical industry represents a highly successful sector of manufacturing and a vital part of the economy in many industrialized and developing countries. The range of chemical industry is vast which makes an invaluable contribution to the quality of our lives. However, the manufacture of chemical products also leads to enormous quantities of environmentally harmful waste and the health of the environment is declining rapidly.
Atmospheric air is polluted by exhaust gases from chemical industries which seriously affect Biodiversity. Lower life forms are more affected e.g. Lichens, Bryophytes, Fungi. On land, Plants are more prone than animals. It is also observed that due to air pollution some species declines but some expand to full fill space of declined species. Contamination of soil by anything is called Soil Pollution. It occurs when pollutants in the soil reduce soil quality and make it inhabitable to organisms such as insects. In recent decades, the use of inorganic fertilizers has increased dramatically. Chemical runoff from pesticides and fertilizers can degrade soil quality. Industrial development has been associated with both physical degradation and chemical contamination of soils. The industry is also responsible for dumping industrial chemicals and heavy metals (such as mercury) onto soil and thus polluting it. Soil pollution can lead to the lack of biodiversity in an ecosystem. The life of bird, insect, mammal and reptile species who live in the soil can get affected by pollution. The soil is an important habitat. When it rains, surface run-off carries contaminated soil into water sources causing water pollution. The contaminated water is thus unfit for both animal and human consumption. It will also affect aquatic life since the organisms that live in these water bodies will find their habitats inhabitable.
From all the described species of biodiversity, 6% belongs to fresh water. Effluent from Chemical Industry drastically affects the aquatic life and thus affecting the biodiversity.
The pesticides are used to kill fungal or animal pests. As they are sprayed across the entire agricultural field affects lives of many species. Also, most of the pesticides after their use remains in the environment get transferred through food chain and causes many serious problems related to reproduction rates.
Major problems in chemical production are handling of waste, the search for environmentally tolerable procedures, the preservation of resources, and the increase in the efficiency. Industry is increasingly realizing that environmental standards are a lifeline to profitability in the highly competitive global and community markets that exist today. The so-called triple bottom line, which seeks simultaneous economic, environmental and societal benefits, is seen as a realistic evolutionary goal in chemical manufacturing. This has led to the development of eco-friendly chemical processes to replace the current hazardous processes. Hence, the drive is towards so-called Green Chemistry or Cleaner Technology.
Results and Discussion
Green chemistry is an effort of terminating or reducing the use and generation of hazardous chemicals in the design, manufacture and applications of chemical products. The concept of green chemistry was formulated by Paul Anastas at the US Environmental Protection Agency (EPA) to address the environmental issues of both chemical products and the processes by which they are produced. The guiding principle is the design of environmentally benign products and processes, which is embedded in the 12 principles of Green chemistry, which in short can be narrowed down as: Green chemistry efficiently utilizes renewable raw materials, eliminates waste and avoids the use of toxic and/or hazardous reagents in the manufacture and applications of chemical products. Green chemistry eliminates waste at source, i.e. it is primarily pollution prevention than waste remediation.
Principles of Green Chemistry
These principles provides a frame work for learning about the green Chemistry and designing or improving materials, products, processes and systems.
- Prevention : It is better to prevent waste than to treat or clean up waste after it has been created.
- Atom Economy: Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
- Less Hazardous Chemical Synthesis: Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
- Designing safer Chemicals: Chemical products should be designed to affect their desired function while minimizing their toxicity.
- Safer solvents and auxiliaries: The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.
- Design for Energy Efficiency: Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.
- Use of renewable feedstock: A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.
- Avoid Derivatization: Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.
- Catalytic Reagents: Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
- Design for degradation: Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.
- Real-time analysis for Pollution Prevention: Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
- Inherently Safer Chemistry for Accident Prevention: Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires.
It is now generally accepted that the two most useful measures or Green Metrics of the environmental acceptability of chemical processes are the E factor and the atom efficiency. One of the major goals of green chemistry is to demonstrate that adoption of the principles, by the industry, can create a competitive advantage.
E Factor: E factor is defined as the mass ratio of waste to the desired product. It takes the chemical yield into account and includes reagents, solvent loss, all process aids and in principle even fuel; excluding water. Higher E factor means more waste and consequently greater negative environmental impact; ideal E factor being zero. So, Chemical synthesis should be developed such that there is minimum E factor.
The concept of atom economy – Among the progenitors of Green Chemistry is Stanford Chemistry Professor Barry Trost, who first proposed the concept of atom economy in 1973. The atom economy of a process is calculated by dividing the molecular mass of the desired product by the sum of the molecular masses of all substances produced in the stoichiometric equation.
Molecular masses of substances produced
Simply, when all the raw chemicals/materials are completely converted into the desired product, there will be no waste generated that is no pollution and there is less effect on environment and biodiversity. Hence, chemical synthesis should be developed in such way that almost all the starting material is converted to product.
Conclusion
Green chemistry will be one of the most important fields in the future. Scientists, Biologist, engineers and industrialists should work together to promote the development of this field. There is no doubt that the development and implementation of green chemistry will contribute greatly to pollution prevention and thus will play an important role in Conservation of Environment and Biodiversity.
References
- Poliakoff, M.; Fitzpatrick, J. M.; Farren, T. R.; Anastas P. T. (2002), Green Chemistry: Science and Politics of Change , Science, Vol. 297, pp. 807-810.
- Sheldon, R. A. Chemtech., (1994), Consider the environmental quotient , 3, pp.38-47.
- Sheldon, R. A.; Arends, I. W. C. E.; Hanefeld, U.(2007), Green Chemistry and Catalysis , Wiley-VCH, Weinheim
- Anastas, P. T.; Heine, L. G.; Williamson, T. C. (2000), Green Chemical Syntheses and Processes , ACS, Washington DC.
- Anastas, P. T.; Warner, J. C. (1998), Green Chemistry: Theory and Practice , Oxford University Press, Oxford.
- Tundo, P.; Anastas, P.; Black, D. S.; Breen, J.; Collins, T.; Memoli, S.; Miyamoto, J.; Polyakoff, M.; Tumas, W., (2000), Synthetic pathways and processes in green chemistry. Introductory overview Pure Appl. Chem. Vol. 72, pp 1207-1228.
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