The branch of chemistry which deals with chemicals and other pollutants in environment This presentation includes atmospheric pollution, water pollution, waste water treatment method and green chemistry.

1. ENVIRONMENTAL
CHEMISTRY
Chapter 23
XII FDC

2. Environmental Chemistry
◦ It is the branch of chemistry which deals
with the chemicals and other pollutants in
the environment resulting directly and
indirectly from human activities.

3. ComponentsofEnvironment
Atmosphere
Hydrosphere
Lithosphere
Biosphere

4. Atmosphere
◦ Our surrounding on earth is called atmosphere. It consists of gases i.e. N2, O2, CO, He, Ne, Kr, Xe,
and water vapors.
◦ Its thickness is about 1000 Km above the surface of earth.
◦ The gases present in atmosphere are very important in the following ways:
◦ These gases absorbs harmful radiations of sun to protect life on earth.
◦ N2 is used by nitrogen fixing bacteria.
◦ O2 is required for respiration.
◦ CO2 is necessary for photosynthesis.
◦ Water vapors are responsible for sustaining life on earth.

5. LayersofAtmosphere
Troposphere
Stratosphere
Mesosphere
Thermosphere

6. Chemistry of Troposphere
◦ Troposphere is very close to the surface of
earth in which we live.
◦ It extends up to 20 Km.
◦ It contains all those gases which are
present in our atmosphere.

7. Smog
◦ It is a combination of smoke and fog.
◦ The smog is of two types:
◦ Reducing smog
◦ Oxidizing smog

8. Types of smog
Reducing smog
◦ This smog contains high contents of SO2.
◦ It is chemically reducing in nature.
◦ For example, the smoke and SO2 produced
from burning of coal can combine with fog
to create industrial smog.
Oxidizing smog
◦ Photochemical smog is termed as oxidizing
smog which consists of higher
concentration of oxidants like ozone.
◦ It is a yellowish, brownish, grey haze which
is formed in the presence of water droplets
and chemical reactions of pollutants in the
air.
◦ It has unpleasant odor because of its
gaseous components.

9. Conditions for photochemical smog
◦ Following conditions are necessary for the
chemical process of photochemical smog:
◦ Sunlight
◦ The production of oxides of nitrogen NOx
◦ The production of Volatile Organic
Compounds VOCs
◦ Temperature greater than 18o C

10. ACID RAIN

11. Acid Rain
SO2 present in air undergoes photolytic and catalytic oxidation to form SO3 which reacts with rainy
water or moisture to form H2SO4
SO3 + H2O  H2SO4
NO2 reacts with rainy water in the presence of O2 and O3 and produces HNO3
4NO2 + 2H2O + O2  4HNO3
CO2 reacts with rain water to form H2CO3
CO2 + H2O  H2CO3
In some countries HCl is released by volcanic eruption.
These acids formed as above come down the atmosphere as acid rain of acid snow.

12. Impacts of Acid Rain
◦ It makes lakes so acidic that they can no longer support fish life.
◦ The yield of agricultural crops is also reduced.
◦ HNO3 acid rain gradually eats up lime stone and marble of buildings and corrodes metals.
◦ It fades the color of fabrics (e.g. cotton, nylon and rayon), leather and paper.
◦ Causes extensive leaf drop in plants.
◦ It is very corrosive and attacks skin.
◦ Acidification of soil and rocks can leach metals like Al, Hg, Pb and Ca and discharge them into
water bodies. Then these heavy metals are eaten by fishes which proves very much dangerous
for those animals and birds which eat these fishes.
◦ It also damages steel, paints, plastic, cement, masonry work and sculptural materials.

13. Greenhouse Effect
◦ The heat causes the atoms in the earth’s
surface to vibrate and radiate heat and
infrared radiations.
◦ CO2 and water vapors in air, by absorbing
infrared radiations, act as an insulating
layer to prevent heat from escaping, this is
often referred to as Greenhouse effect.
◦ The trapping of heat on the surface of
earth by CO2 and water vapors in the
atmosphere is known as Greenhouse effect.

14. Global Warming
◦ The concentration of CO2 in the atmosphere is about 330 PBM but is known to be increasing.
◦ When levels of CO2 increases up to 400 PBM, temperature should rise as much as 1oC.
◦ The mean global temperature at earth’s surface is about 15o C.
◦ Any change in amount of energy absorbed or emitted by earth could affect our climate.
◦ The average Global temperature and concentration of CO2 have fluctuates on a cycle of hundreds of
thousands of years as earth’s position relative to the sun has varied. As a result, ice ages have come
and gone.
◦ Volcanic eruption emits particles that cool down earth’s surface temporarily.
◦ E1 nitro cycle also has temporary effects.
◦ CO2 levels have increased by more than a third since the industrial revolution.
◦ Climate changes are now occurring rapidly.
◦ Eleven of the 12 hottest years are between 1995 and 2006.

15. Automobiles (Pollutants and Converters)
◦ Automobile engines use hydrocarbon
fuels
◦ Fuels have general formula C8H18 so
called Octanes
◦ Incomplete burning of fuel release
carbon particles, CO, CO2 , water vapors
◦ At high temperature N2 and O2 combine
to form NO and NO2
◦ C particles, CO, NO, NO2 all are
pollutants

16. Production of pollutants
◦ The pollutants produced in the internal combustion engine by the use of petrol are CO, NO,
NO2
◦ By incomplete combustion of petrol, some CO, unburnt C particles, CO2, water vapors, some
alcohols and acids are produced.
◦ When petrol burns in a car engine, a very high temperature is produced. At this temperature N2
and O2 in air of the engine combine together to for NO and NO2.

17. Control Measures
1. Use of Pb(C2 H5)4 or TEL
◦ Reduces rate of combustion
◦ Complete combustion
◦ Reduced evolution of C particles and CO
2. Catalytic converters
◦ Attached to vehicle engines
◦ Contain Pt based catalyst
◦ Catalytically complete combustion of C-
particles and CO
2C8H18 + 25O2  16CO2 + 18H2O
2CO + O2  2CO2

18. Chemistry of Stratosphere
◦ Stratosphere is present 20-40 km above
the surface of earth.
◦ Ozone is present at the height of 28 Km.
◦ The concentration of ozone in stratosphere
is 10 ppm.

19. Production of O3 and its toxic effects
◦ Some O3 is produced during combustion taking place in air.
◦ O3 concentration more than 0.1 ppm is toxic and harmful for human being.
◦ O3 also attacks rubber.
◦ It is produced in the upper part of atmosphere by action of sunlight on O2.
3O2  2O3

20. Protective action of O3 layer
◦ Thickest layer of ozone is at a height of 23 Km from the surface of earth.
◦ Ozone in this layer absorbs harmful radiation coming from the sun.
◦ If Ozone layer in the atmosphere disappears completely, then all the harmful UV radiations
coming from the sun would reach the earth and would cause skin cancer in men and animals
and will also damage the plants.

21. Sources of destruction of O3 layer
1. Oxides of Nitrogen:
Oxides of nitrogen decompose O3 into O2 and themselves regenerated. These oxides destroy about 70% of O3
found in the stratosphere. Greater the amount of the oxides in the atmosphere greater is the percentage of O3
which is destroyed.
NO + O3  NO2 + O2
NO + O  NO2
2. Nuclear Tests:
Nuclear tests being conducted in the world generate high temperature. At high temperature, atmosphere nitrogen
is favorably oxidized to NO. NO thus formed destroys ozone layer.
3. Chloro-fluoro Carbons:
Chloro-fluoro carbons are the chloro-fluoro methane like Freon 1 (CFCl3) and Freon 2 (CF2Cl2). These are used as
aerosol spray propellants, refrigerants, firefighting reagent and solvent for cleaning electronic components. When
they enter stratosphere, they absorb UV solar radiations and get broken down into free atomic chlorine. This
atomic chlorine decomposes O3 into O2
Cl + O3  ClO + O2
ClO + O3  Cl + 2O2

22. How to protect the ozone layer?
◦ In order to save the ozone layer, the use of oxides of Nitrogen and chloro-fluoro carbons should
be banned or some new types of substance should be discovered which may be used as aerosol
spray propellants and should not react with O3 layer, so it may be saved.

23. Alternatives to Chloro-Fluoro Carbons
◦ The first CIFC substitutes to be introduced were HCIFCs such as CF3CHCl2 and CHF2Cl
compounds that have fewer chlorine atoms than other CIFCs.
◦ HCFCs break down more readily in the atmosphere than CIFCs and thus are less likely to reach
the stratosphere.
◦ Much better substitutes for ClFCs are Hydrofluoro carbons which contains no chlorine. CF3CH2F
has been used successfully as a refrigerant and since 1994 has replaced Freon in nearly all car air
conditioners.
◦ In electronic industries, soapy water followed by rinsed and air drying is now used instead of
ClFCs to clean micro circuits.

24. WATER
POLLUTION
AND
WATER
TREATMENT

25. Water pollution
◦ The contamination of water with the
substances which have adverse effects on
human beings, animals and plants is called
water pollution and the substance whose
presence in the water makes it polluted are
called pollutants.

26. Types of Water pollution
Suspended solids and sediments
Oil spillage
Live-stock waste
Industrial waste
Leather industries
Dissolved solids
Detergents
Pesticides
Chemical fertilizers
Thermal pollution

27. A- Suspended solid and sediments:
These are wastes which are not completely
soluble but suspended in the water. These
wastes includes:
1. Oil spillage
2. Live-stock waste
3. Industrial waste
4. Leather tanneries

28. 1. Oil spillage
◦ Petroleum is a complex mixture of many
compounds which are mainly
hydrocarbons. It is transported from one
place to another through sea.
◦ Petroleum products are used as:
◦ Fuel
◦ Lubricants
◦ Plastics
◦ Electrical appliances
◦ Synthetic rubber
◦ Detergents
◦ Manufacture of petrochemicals

29. Pollution of water by petroleum
◦ Water gets polluted by:
1. Accidental oil spills
2. Leakage from cargo oil tankers in sea
3. Tanker trucks
4. Pipelines leakage during offshore
exploration
5. Leakage of underground storage tanks

30. Oil spillage and animal life
◦ Petroleum products are poisonous and
create serious problems to humans,
animals and aquatic life.
◦ Polycyclic hydrocarbons are carcinogenic
even at very low concentration.
◦ Marine animals are seriously affected by
soluble aromatic fractions of oil.
◦ The spilled oil damages the feather of the
birds or fur of animals and sometimes
causes their deaths.

31. Petroleum and under water plants
◦ When oil is spilled on the surface of sea
then the light transmission is affected.
◦ The process of photosynthesis of plant
does not remain much efficient moreover,
the concentration of oxygen in water is
decreased.

32. 2. Live-stock waste
◦ Livestock waste is damped on open land.
◦ Sometimes it is discharged into sewage, canals of rivers.
◦ This practice pollutes the surface and ground water.
◦ In this way serious problem are created for the population.
◦ Bacteria are present in the livestock waste. It contaminates the surface and ground water.
◦ This caused diseases like:
◦ Dysentery
◦ Typhoid
◦ Hepatitis

33. 3. Industrial Wastes
- Source
◦ Industries which produce large quantities
of industrial effluents are leather/tanneries,
fertilizers, oil refineries, petrochemicals,
textiles, foods, sugar, paper/pulp, paper
board, rubber products etc.
◦ The waste products may be waste heat,
smoke, solid or water effluent.

34. - Pollutants
◦ The industrial pollutants are highly toxic
organic compounds and heavy metals like
Pb, Cd, Cr, Hg, As, Sb etc.
◦ Oil grease, mineral acids are also released
in small quantities.
◦ These pollutants result in contamination of
water and make it unsuitable for irrigation
and drinking purposes.

35. - Effects of industrial pollutants
◦ Heavy metal particles are highly toxic and
do not have any safe limits.
◦ When they are continuously ingested
through food or water they get
accumulated in the organisms and cause
serious health problems like anemia, kidney
diseases, nervous disorder, high blood
pressure etc.

36. 4. Leather Tanneries
◦ Leather industries use chromium salts
which have Cr (VI).
◦ Cr(VI) salts are highly toxic and cause
cancer.
◦ Waste treatment can be done by reducing
Cr(VI) to Cr(III).
◦ Cr(III) is precipitated as Cr(OH)3.

37. B- Dissolved Solids
◦ These are wastes which are
dissolved/soluble in water completely.
◦ These waste include:
◦ Detergents
◦ Pesticides
◦ Chemical fertilizers

38. 1. Detergents
◦ The amount of detergents in water bodies
is increasing day be day.
◦ The waste water containing detergents
goes into rivers and finally reaches the
ocean; which is harmful for life in seas.
◦ The detergents bound heavy metal ions
like Pb, Cd and Hg and transport it from
sediments into water.

39. 2. Pesticides
◦ Pesticides are both toxic and persistent.
◦ Analysis of polluted water has shown that it
contains pesticides which are toxic to fish.
◦ Endrin, even in traces, is reported to be
toxic for catfish and other varieties of fish.
◦ DDT affects the central nervous system of
fish.
◦ Toxaphene has been reported to cause
bone degeneration in fish.

40. 3. Chemical Fertilizers
◦ Nitrate/Phosphate salts are generally used
as fertilizers, to increase the yield of the
crops.
◦ When these fertilizers are used in excess,
some of their unused quantity is washed
away from the agriculture lands into the
ponds, lakes and river with rain water and
thus pollute the water.
◦ The waste water coming from the fertilizer
industries also contain
nitrogenous/phosphatic fertilizers.

41. Harmful effects of chemical fertilizers in
waste water:
a) The presence of the fertilizers in the polluted water increases the growth of algae and other
aquatic plants, which later on undergo decomposition and produce disagreeable odor. These
plants also deplete the amount of O2 dissolved in water and hence the survival of aquatic life
becomes difficult.
b) After a long period the lakes and slow moving water which contain plant nutrients are
converted into swamps and marshes.
o A swamp is an area of very wet land with wild plants growing in it.
o A marsh is an area of land which is very wet and muddy.
c) The water containing nitrate salt is not fit for drinking by human being. This polluted water
cannot be purified for drinking purposes.

42. C- Thermal Pollution
◦ Many electric generating companies use
water in the process of cooling their
generators.
◦ This heated water is then released into the
system by causing a warming trend of the
surface water.
◦ Thermal pollution results when a heated
effluent is released into poorly flushed
system.
◦ In these cases permanent temperature
increase often result, which tend to
decrease the solubility of dissolved oxygen.

43. Thermal pollution
◦ When heated water gets released into large, well-flushed marine systems there is little if any
permanent temperature rise.
◦ Seaweeds tends to corrode the cooling pipes, which are generally constructed of copper-nickel
alloy termed monel.
◦ These metals readily dissolved in the heated seawater and are then released into marine
environment together with the heated effluent.
◦ This increase the concentration of Cu and Ni.
◦ The screen covering the water intake pipes rapidly foul with marine organism, which decrease
the flow of water into the plant.
◦ The screen are cleaned by using concentrated detergent solution or copper sulfate,
◦ The cleaning materials have been then released into the contaminated waters in surrounding.

44. WASTE
WATER
TREATMENT

45. Analysis of water
◦ Industrial wastewater treatment covers the mechanisms and processes used to treat waters that
have been contaminated in some way be industrial or commercial activities prior to its release
into the environment or its re-use.

46. Treatment of industrial wastewater
1. Solid Removal • Sedimentation techniques
2. Oil & greases
• Skimming Devices
• Emulsified components require further treatment
3. Soft organics
• Biological materials
• Conventional wastewater treatment
4. Hard organics
• Synthetic organic materials
• Specific methods
• Distillation, adsorption, nitrification, incineration, landfill disposal
5. Acids & Alkalis
• Neutralization under control conditions
• Precipitate may form
• Evolution of gases may occur
Toxic materials
• Organic materials, metals, arsenic, selenium etc.
• Precipitation of metals by change in pH or chemical treatment
• Followed by Land filling or recycling

47. Water Quality parameters
Parameter Significance Level
DO (Dissolved
Oxygen)
Source of O2 for respiration Min 4-5 mg/L
10-15 mg/L for reproduction of
desirable fish
TSS (Total
Suspended
Solids)
Clog fish gills, bury eggs, reduce light penetration,
increase heat absorption
Dependent on location
TDS (Total
Dissolved
Solids)
Total mineral content Max 400 mg/L
BOD (Biological
Oxygen
Demand)
Amount of DO removed during organic decomposition Very Clean 1mg/L
Clean 2 mg/L
Fairly clean 3 mg/L
Doubtful 5 mg/L
Contamination 10 mg/L

48. Parameter Significance Level
COD (Chemical
Oxygen Demand)
Amount of DO removed during chemical
oxidation
0 – 5 mg/L
pH Amount of acids or base Depends on actual system
Iron Clog fish gills, indicates drainage from iron-
bearing sediments, mines, industries
Max 1 mg/L
Copper Indicates drainage from Copper-bearing
sediments, mines, plating, industries
0.02 – 0.1 mg/L
Zinc Mine drainage or industrial input 1 mg/L
Heavy metals Industrial input 1 mg/L
Nitrate Promote excessive plant growth, major sources
are fertilizers, sludge and sewage
Phosphate Detergents, fertilizers, sewage 0.03 – 0.04 mg/L

49. GREEN
CHEMISTRY

50. Green Chemistry
◦ The design of chemical products and
processes that reduce or eliminate the
use and generation of hazardous
substances.
◦ Green Chemistry emphasizes the
design and creation of chemicals that
are not hazardous to people or the
environment.

51. Why Green Chemistry
Green chemistry is important due to
◦ Reducing chemical hazard
◦ Meeting cheaper and profitable
environmental goals
◦ Making companies to comply with law
for environment safety
◦ Can be applied to all kinds of
environmental issues

52. Advances in Green Chemistry
Sinopsad an example of Green Insecticide
◦ Manufactured from naturally occurring soil microbes
◦ Low toxicity for mammals and birds
◦ It does not
− Bio accumulate
− Leach
− Volatilize
− Persist in environment

53. How does Green Chemistry works?
Green chemistry works by
◦ Reducing chemical impact on health
◦ Searching alternative environment
friendly reaction media
◦ Striving to achieve increased reaction
rates at lower temperatures
◦ Innovating scientific solutions to solve
environmental issues

54. The 12 Principles of Green Chemistry
◦ Developed by Paul T. Anastas and John
C. Warner
◦ Focus on reduction in chemical use &
pollution prevention
◦ Can broadly be categorized as
− Risks reduction
− Minimizing environmental
footprints

55. Reducing Risks in the Laboratory
1. Use Safer Chemicals: Utilize performance chemicals that have the lowest levels of
toxicity
2. Design less hazardous synthesis methods: Where feasible, make use of synthetic
or biosynthetic methods that pose little or no toxicity to human health and
environment
3. Use safer solvents and reaction conditions: Search for information on green
solvents that will optimize your process and provide a safer working environment
4. Accident prevention: Select substances that minimizes the potential for explosions,
fires and chemical releases into the environment

56. Minimizing the Environmental Footprints
5. Waste minimization and prevention: Develop synthesis techniques which reduce or
prevent waste
6. Use of catalysts instead of stoichiometric quantities: Catalytic reactions inherently
use smaller quantities of chemicals to carry out a specified transformation
7. Reduce the use of chemical derivatives: The use of protecting groups or other
forms of temporarily modification of a functionality adds to the total waste incurred in a
synthetic route
8. Synthetic efficiency (Atom Economy): An efficient chemical process ensures the
maximum amount of your starting materials is used in the final product so that no atom
is wasted

57. 9. Taking advantage of chemicals designed for degradation: Reduce the effect on
the environment by using chemicals that are designed to be biodegradable
10. Establishment of In process controls for pollution prevention: to avoid the
formation of hazardous substances, adopt real-time analysis and in process monitoring
during synthesis
11. Use of renewable feedbacks: Use raw materials or renewable feedstocks ( waste
from other processes or products derived from agricultural stream) whenever
technically or economically feasible
12. Encourage energy efficiency: The realization of economical and environmental
impact of energy use in a chemical process and the development of alternative means
to reduce the impact.
Minimizing the Environmental Footprints

58. END OF LESSON
sidra.javedali@gmail.com