Environmental chemistry


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Environmental chemistry

  2. 2. pollution noun [puh-loo-shuhn] The act or process of polluting or the state of being polluted, especially the contamination of soil, water, or the atmosphere by the discharge of harmful substances.
  3. 3. Soil pollution or soil contamination is caused by the presence of xenobiotic(human made) chemicals or other alterations in the natural soil environment. Causes :  Waste Dumping  Mining Agrochemicals Urbanization
  4. 4. WASTE DUMPING :  Industrial solid wastes and sludge are the major sources of soil pollution  Industrial emissions such as fly ash from thermal power plants can contaminate the surrounding soil Particles of industrial emissions from the tall chimney comes down to the surface of the earth, sooner or later  Nuclear testing laboratories and the increased number of radioactive nuclear reactions can contaminate the soil Radioactive materials are thriving in the soil for long periods of time, since they often have a long half-life. Strontium-90, for example, has a half life of 28 years, and half-life of cesium-137 is 30 years
  5. 5. MUNICIPAL WASTES :  Municipal waste includes household waste, kitchen waste, medical waste, waste from livestock, poultry slaughterhouse waste, metals, glass and ceramic waste, etc.  Non-biodegradable materials used to transport, polythene bags, waste plastic sheeting, PET bottles, etc., remain in soil for long periods  Hospital waste contains organic matter, chemicals, metal pins, plastic and glass bottles, which could also contaminate.  Dumping of sewage waste and organic waste from hospitals pollute the environment with a wide range of pathogens that will seriously affect human health. MUNICIPAL WASTES :
  6. 6. MINING :  Modern mining projects leave behind disrupted communities, damaged landscapes, and polluted water.  Mining also affects ground and surface waters, the aquatic life, vegetation, soils, animals, and the human health.  Acid mine drainage can cause damage to streams which in return can kill aquatic life.  The vast variety of toxic chemicals released by mining activities can harm animals and aquatic life as well as their habitat.  Mining gas and petroleum also pollutes the land. Petroleum extraction and manufacturing contaminates the soil with bitumen, gasoline, kerosene and mining brine solutions.  Opencast mining, which is a process where the surface of the earth is dug open to bring out the underground mineral deposits, destroys the topsoil and contaminates the area with toxic metals and chemicals.
  7. 7. AGROCHEMICALS :  Many of the chemicals used in pesticides are persistent soil contaminants, which adversely affect soil conservation  The use of pesticides decreases the general biodiversity in the soil.  The insecticides DDT, methyl parathion and especially pentachlorophenol have been shown to interfere with legume-rhizobium chemical signaling. Reduction of this symbiotic chemical signaling results in reduced nitrogen fixation and thus reduced crop yields.  Animals may be poisoned by pesticide residues that remain on food after spraying, for example when wild animals enter sprayed fields or nearby areas shortly after spraying  Widespread application of pesticides can eliminate food sources that certain types of animals need, causing the animals to relocate, change their diet, or starve. Poisoning from pesticides can travel up the food chain and bioacculmulate
  8. 8. URBANIZATION : Construction uses up forestland. More constructions means increase in demand for raw materials like timber. This leads to the exploitation and destruction of forests. There is more demand for water. Reservoirs are built leading to the loss of land and valuable soil
  9. 9. STRATEGIES TO CONTROL ENVIRONMENTAL DAMAGE : The public is becoming increasingly aware that the natural environment is fragile. The news media have reported on many instances of environmental changes affecting animal life, often as a result of pollutants from human activities. Recent reports have focused on –  Deaths and population declines of birds and fish because of the large oil spills  Deaths of porpoises and whales along the coasts as a result of pollutants and disease;  Fish contaminated with polychlorinated biphenyls (PCBs)  Contamination of rivers and lakes by dioxin and other pollutants that may cause cancer and reproductive disorders
  10. 10. These events may be omens that other forms of life, including people, could become threatened if environmental conditions continue to worsen. But how much worse must conditions be before wildlife and human life are in danger? Or are they in danger already? Clearly, better methods are needed to predict the probability of future environmental and health problems based on present evidence. Such information could guide environmental regulators and decision makers in taking actions in time to minimize damage to the environment and human health. And an important strategy to control such environmental damage is : Waste Management
  11. 11. WASTE MANAGEMENT : Waste management is the collection, transport, processing or disposal, managing and monitoring of waste materials. The term usually relates to materials produced by human activity, and is generally undertaken to reduce their effect on health, the environment or aesthetics. Waste management is a distinct practice from resource recovery which focuses on delaying the rate of consumption of natural resources. The management of wastes treats all materials as a single class whether solid, liquid, gaseous or radioactive substances, and tried to reduce the harmful environmental impacts of each through different methods. The two major concepts which are widely used for waste management are :  Waste Hierarchy  Polluter Pays Principle
  12. 12. Waste Hierarchy : The waste hierarchy refers to the "3 Rs“ reduce, reuse and recycle, which classify waste management strategies according to their desirability in terms of waste minimization. The waste hierarchy remains the cornerstone of most waste minimization strategies. The aim of waste hierarchy is to extract the maximum practical benefits from products and to generate the minimum amount of waste. Polluter Pays Principle : The Polluter Pays Principle is a principle where the polluting party pays for the impact caused to the environment. With respect to waste management, this generally refers to the requirement for a waste generator to pay for appropriate disposal of the waste.
  13. 13. Methods Of Waste Management :  LANDFILL Disposing of waste in a landfill involves burying the waste, and this remains a common practice in most countries. Landfills are often established in abandoned or unused quarries, mining voids or borrow pits. A properly designed and well-managed landfill can be a hygienic and relatively inexpensive method of disposing of waste materials. Older, poorly designed or poorly managed landfills can create a number of adverse environmental impacts such as wind-blown litter, attraction of vermin, and generation of liquid leachate. Design characteristics of a modern landfill include methods to contain leachate such as clay or plastic lining material. Deposited waste is normally compacted to increase its density and stability, and covered to prevent attracting vermin. Many landfills also have landfill gas extraction systems installed to extract the landfill gas. Gas is pumped out of the landfill using perforated pipes and flared off or burnt in a gas engine to generate electricity.
  14. 14.  INCINERATION : Incineration is a disposal method in which solid organic wastes are subjected to combustion so as to convert them into residue and gaseous products. This method is useful for disposal of residue of both solid waste management and solid residue from waste water management. This process reduces the volumes of solid waste to 20 to 30 percent of the original volume. Incineration is also described as "thermal treatment". Incinerators convert waste materials into heat, gas, steam and ash. Incineration is carried out both on a small scale by individuals and on a large scale by industry. It is recognized as a practical method of disposing of certain hazardous waste materials (such as biological medical waste). Incineration is a controversial method of waste disposal, due to issues such as emission of gaseous pollutants like dioxins, furans and PAHs. Incineration is common in countries such as Japan where land is more scarce, as these facilities generally do not require as much area as landfills. Waste-to-energy (WtE) or energy- from-waste (EfW) are broad terms for facilities that burn waste in a furnace or boiler to generate heat, steam or electricity.
  15. 15.  ENERGY RECOVERY : The energy content of waste products can be harnessed directly by using them as a direct combustion fuel, or indirectly by processing them into another type of fuel. Thermal treatment ranges from using waste as a fuel source for cooking or heating and the use of the gas fuel, to fuel for boilers to generate steam and electricity in a turbine. The process usually occurs in a sealed vessel under high pressure. Two related forms of thermal treatment :  Pyrolysis : Pyrolysis of solid waste converts the material into solid, liquid and gas products. The liquid and gas can be burnt to produce energy or refined into other chemical products (chemical refinery). The solid residue (char) can further refined into products such as activated carbon.  Gasification : Gasification is used to convert organic materials directly into a synthetic gas (syngas) composed of carbon monoxide and hydrogen. The gas is then burnt to produce electricity and steam.
  16. 16.  AVOIDANCE & REDUCTION METHODS : An important method of waste management is the prevention of waste material being created, also known as waste reduction. Methods of avoidance include : - Reuse of second-hand products - Repairing broken items instead of buying new - Designing products to be refillable or reusable (such as cotton instead of plastic shopping bags) - Encouraging consumers to avoid using disposable products (such as disposable cutlery) - Removing any food/liquid remains from cans - Designing products that use less material to achieve the same purpose (for example, light weighting of beverage cans) Jute bags
  17. 17. green chemistry noun [grēn ′kem·ə·strē] The use of chemical products and processes that reduce or eliminate substances hazardous to human health or the environment
  18. 18. Green chemistry, also called sustainable chemistry, is a philosophy of chemical research and engineering that encourages the design of products and processes that minimize the use and generation of hazardous substances. While environmental chemistry is the chemistry of the natural environment, and of pollutant chemicals in nature, green chemistry seeks to reduce and prevent pollution at its source. As a chemical philosophy, green chemistry applies to organic chemistry, inorganic chemistry, biochemistry, analytical chemistry, and even physical chemistry. Click chemistry is often cited as a style of chemical synthesis that is consistent with the goals of green chemistry. The focus is on minimizing the hazard and maximizing the efficiency of any chemical choice. The year 2005 witnessed three key developments in the field of green chemistry: - use of supercritical carbon dioxide as green solvent - aqueous hydrogen peroxide for clean oxidations - use of hydrogen in asymmetric synthesis Examples of applied green chemistry are : Supercritical water oxidation On water reactions Dry media reactions The term "Green Chemistry" was coined by Paul Anastas in 1991, who is renowned worldwide as “The Father of Chemistry”.
  19. 19. GREEN CHEMISTRY IN DAY-TO-DAY LIFE : Dry Cleaning Of Clothes: Tetra chloroethene (Cl2C=CCl2) was earlier used as solvent for dry cleaning. The compound contaminates the ground water and is also a suspected carcinogen. The process using this compound is now being replaced by a process, where liquefied carbon dioxide, with a suitable detergent is used. Replacement of halogenated solvent by liquid CO2 will result in less harm to ground water. These days hydrogen peroxide(H2O2) is used for the purpose of bleaching clothes in the process of laundry, which gives better results and makes use of lesser amount of water.
  20. 20. Bleaching of Paper: Chlorine gas was used earlier for bleaching paper. These days, hydrogen peroxide (H2O2) with suitable catalyst, which promotes the bleaching action of hydrogen peroxide, is used.
  21. 21. Synthesis Of Chemicals: Ethanal(CH3CHO) is now commercially prepared by one step oxidation of ethene in the presence of ionic catalyst in aqueous medium with a yield of 90%. CH2=CH2  O2 CH3CHO (90%) ethene ethanal Catalyst Pd(II)/Cu(II)[in water]