Textile & Environment

 Textile & Environment   

We will able to know

1. Environment Pollution & Social Issue: 

• What is Environment
• Pollutant
• Contaminant
• Sinks
• Receptor
• Speciation
• Dissolved oxygen
• Biological oxygen demand
• Chemical oxygen demand
• Causes of Environmental Pollution
• Environmental Segments
• Composition of the Atmosphere
• Structure of the Atmosphere
• Formation of ozone
• Depletion of ozone
• Global warming
• Green House & it’s mechanism, it’s adverse effects

2. Energy: 

• Conventional & non-conventional sources of energy
• Recovery of waste heat & application

3. Air Pollution: 

• Classification of air pollutant & their effects
• Source & control of different air pollutants
• Acid rain
• Air pollution in industry with special emphasis on Textile Industry & it’s mitigation

4. Water Pollution: 

• Introduction
• Classification & Description of different water pollutants
• Important water quality parameters
• Water required for different textile processing
• Water used for various industries
• Sources and Characteristics of Waste water coming from cotton, silk, wool & synthetic fiber industries

 5. Noise Pollution: 

• Introduction
• Decibel, Noise recording equipment
• Noise control in industrial establishment and effects of Noise pollution

6. Solid Waste Management: 

                                                          

• Introduction
• Classification
• Characteristics & Magnitude

7. Environmental Management:  

• Introduction
• Objectives
• Components
• EIA
• EIS

Reference  Books:

Ø Environmental Chemistry by A. K. De

Ø A Textbook of Environmental Chemistry by  S. S. Dara

Ø Environmental Chemistry by John W. Moore, Elizabeth A. Moore

Ø Guide to the Environmental conservation Act 1995 & Rules 1997. Prepared by Bangladesh centre for Advanced Studies.

Environment pollution

Ø  Environmental chemistry is the multidisciplinary science involving chemistry, physics, life science, agriculture, medical science, public health and sanitary engineering. In broader terms it is the study of the sources, reactions, transport effect and fate of chemical species in air, water, soil and the effect of human activity upon these.

Ø  The objective of environmental education is to enlighten the public, particularly students and social workers, about the importance of protection and conversation of our environment and the need to restrain human activities which lead to indiscriminate release of pollutants into the environment.

               A wave of concern for the environmental swept across the developed countries in the sixties & reached its climax in 1970 with the celebration of earth day under the auspices of the United Nations. Then from 1972 onward with the conclusion of United Nations conference on human environment of Stockholm this wave started sweeping across India & other developing nations. At present there are many environmental issues, which have grown in size & complexity day by day, threading the survival of mankind on earth. However several Japanese killed by eating fish from Minamata  Bay in the sixties. Why did 3000-4000 people die in London in 1952? Why are historic marble status in Greece & Italy getting damaged by rain water?  How did the Mediterranean Sea polluted river in India? Should plutonium breeder reactors be developed? Is saccharin a dangerous food additive? These are some typical chemical issues which can be best handled in their chemical perspective. Of course the issues are linked with ecological, social, political and economic questions which have also to be taken into account.

Nomenclature:

Pollutant

            A substance present in nature, in greater than abundance due to human activity, which ultimately effect on the environment and therefore on living organisms and mankind. E.g. Pb, Hg, SO₂, CO₂ etc.

Contaminant

             A material which does not occur in nature, but is introduced by human activity into the environment, affecting its composition. A contaminant is classified as a pollutants when it exerts a detrimental effect

Receptor

              The medium which is affected by a pollutant. Man is the receptor of photochemical smog causing irritation of the eyes and respiratory tract.

Sinks

              The medium which retain and interacts with a long-lived pollutant. A marble wall will act a sink for atmospheric. The ocean are sinks for atmospheric CO₂ & H₂SO₄ and ultimately damaged H₂SO₄ + CaSO₃  = CaSO₄  + H₂O + SO₂

 

Pathways of pollutant

                    The mechanism by which the pollutant is distributed from its source into the environment segments.

Pb(C₂H₅)₄ ( in gasoline / in automobile petrol)          →         PbCl₂ + PbBr₂(Air)

                                                                                                          ↓                                   

                                                                                               PbCl₂ + PbBr₂ (soil)  

Speciation

                The different chemical forms or species of inorganic, organic or organometallic compounds present in the environment is known as specification. It is important to identify the chemical species of a pollutant since some species are more toxic than others. Thus methyl mercury (CH₃Hg)⁺, (CH₃)₂Hg are deadly poison compared to others species of Hg.

Dissolved oxygen

                     Oxygen is a vitally important species in water. It is consumed by oxidation of organic matter/ reducing agents. It is an important water quality parameter. The optimum value for good water quality is 4-6 mg/L of DO, which ensures healthy aquatic life in water body. Lower DO values indicate water pollution. In natural & waste waters DO levels depend on the physical, chemical & biological activities of the water body.

Chemical oxygen demand (COD)

                       This is an index of the organic content of water (oxygen demanding substances in water) and is important water quality parameter. It is a rapidly measurable parameter for stream, industrial waste studies & control of water treatment plants.

Bio-chemical oxygen demand (BOD)

                         Based on oxidation of organic matter in water. This is also a water quality parameter for organic matter in water, which is empirical in nature. It is measured by the quality of oxygen utilized by suitable aquatic microorganisms during a five-day period.

Threshold limit value (TLV)

                              This indicates the permissible level of a toxic pollutant in atmosphere to which a healthy industrial worker is exposed during an eight hour day without any adverse effect. TLV values for Be,Zn, are 0.002 and 1.000 mg/ m³ respectively.

Environmental segments

Environment consists of four segments- atmosphere, hydrosphere, lithosphere and biosphere.

 

 

Atmosphere

                 It is the protective blanket of gasses surrounding the earth, which contains life on earth and saves it from the hostile environment of outer space. It absorbs most of the cosmic rays, major portion of the electromagnetic radiation from the sun. It transmits only neat ultraviolet, visible, infrared radiation (300-2500 nm) and radio waves (0.10-40µ) while filtering out tissue- damaging ultraviolet radiation below about 300 nm.

 

Hydrosphere

This means all types of water resources-oceans, seas, rivers, lakes, stream, reservoirs etc.

Lithosphere

This is the outer mantle of the solid earth, consisting minerals occurring in the earth crust & the soil.

 Biosphere

This denotes the realm of the living organisms & there interactions with environment.

                                        Environmental pollution

 

  Air pollution                     water pollution                   Land pollution

      Surface water               Underground water               Marine water

          Pollution                         Pollution                                Pollution

  

Air Pollution

There are five primary pollutants which together contribute more than 20% of global air pollution. These are

(i)                  CO

(ii)                NOx (Nitrogen oxides)

(iii)               HC (Hydrocarbon)

(iv)              Sox (Sulphur oxides)

(v)                Particulates, part.

 

 

CO

 It is a colorless, odourless and tasteless gas, It is 96.5% as heavy as air and is not soluble in water.

 

The basic chemical reactions yielding CO are-

Incomplete combustion of fuel or C- containing compounds.

                        2C + O₂  2CO₂

Reaction between CO₂  and carbon–containing materials at elevated temps. in industrial process e.g. in blast furnace.

                       CO₂ + C     2CO

Dissociations of  CO₂ at high temperatures.

                       CO₂             CO + O

 

Natural process, e .g. volcanic action, Natural gas emission, electrical discharge during storm & seed germination, marsh-gas production etc. contribute CO in the atmosphere. The significant contribution is from human activities.

a)      Transportations contribution about 64%

b)       Misc sources (Agricultural burning , forest fires etc) 16.9 %

c)        Industrial processes. 9.6 %

Control of CO pollution

·         Modification of internal contribution engines to reduce the amount of pollutants formed during fuel combustion.

·         Development of exhaust system reactors which will complete the combustion process.

·         Development substitute fuels for gasoline.

·         Development of pollution – free power sources to replace the internal engine.

·         Use of catalytic converters in two stages helps in eliminating pollutants for exhaust gases before they are discharged into the atmosphere.

·         Gasoline containing pb(C₂H₅)₄   is the major  source  of Pb  pollution in the environment. Pb–free gasoline should be introduced.

                 The possible approach to CO pollution is a substitute fuel for gasoline. May be compressed natural gas (CNG) & Liquefied natural gas (LNG).

 

 

Nitrogen oxides NOx

NOx represents composite atmospheric gases, nitric oxides & nitrogen dioxide, which are primarily involved in air pollution. NO is colorless, odorless gas but   NO₂ has a reddish – Brown-color and pungent suffocating odor. The basic chemical reaction leading to Formation  of NO & NO₂ are

                    N₂ + O₂         ^{1210-1765 º C}             2NO

 

                  2NO + O₂              2NO₂

 

          The  2^nd   reaction Is also  favored  at temps. About  1100⁰C

              

          The distribution of NOx from natural sources is more or less uniform on a global basic lent man- made sources varies depending Urban / rural areas. In Urban atmospheres, NOx is 10-100 times greater than in rural areas.

The end product in HNO₃. A possible mechanism for the formation of HNO₃ is show below in which O₃ plays an important role.

     O₃ + NO₂             NO₃ + O₂

     NO₃ + NO₂          N₂O₅

     N₂O₅ + H₂0         2HNO₃

1.     Before day light NO & NO₂ levels remain fruity stable at concentration slightly higher than the daily minimum.

2.     As the traffic rush begins & increases (6-8 am), the level of NO increases & becomes maximum.

3.      At mid-morning with increased ultraviolet light, the NO₂ level increases due to conversion of NO into NO₂.

4.     O₃ build up as NO level drops below 0.1 ppm.

5.     In the evening the No level again goes up during the evening traffic rush.

6.     O₃ accumulated during day times, reacts with NO during night with the result that NO₂ concentration goes slightly up & O₃ level drops.                                                                            Busy cities heavy automobile traffic has revealed that the maximum values of NO & NO₂ levels are 1-2 and 0.5 ppm, respectively.

Sources of NOx pollution

·        Natural bacteria action discharges.

·        Man-made source release 50*10⁷ tons of NOx .man made some in combustion of coal, oil, natural gas & gasoline.

·        By photo chemical reaction.

Control of NOx pollution

a)     The use of catalytic converts for control of automobile emissions provides for removals of ( NO)x.

b)    Power plants emit about 50-1000 ppm of (NO)x. Such emission can be reduced to 90% by a two stage combustion process.

 

                  (i)  The fuel (coal/gas/oil) is fired at a relatively high temp .whit a sub-stoichiometric amount of air, say 90- 90 % of the stoichiometric requirement. This yield of NO is limited in the absence of excess of O₂.

                   (ii)   Fuel burnout is completed at a relatively low temperature in excess air, under this condition NO is not favored. A  possible  approach to NOx  removed from stack gas is the chemical sorption process using H₂SO₄ solutions or alkaline scrubbing solution containing Ca(OH)₂ & Mg(OH)₂.Simultaneously SO₂ is also removed. NO is converted into N₂O₃ which is easily absorbed.

Then NO₂ + NO          N₂O₃

Ø NO₂   is recycled. Four steps are involved in scrubbing process. Flue gas and NO₂ and introduced into an oxidizer.

NO₂ +SO₂ +H₂O            H₂SO₄ +NO

Ø NO & +NO₂ react to form N₂O₃ which is scrubbed by H₂SO₄ in a scrubber.

The cleaned flue gas is released into the atmosphere.

NO₂ + NO                  N₂O₃

N₂O₃ + 2H₂SO₄           2NOHSO₄ + H₂O

Ø The reaction product is decomposed & the resulting H₂SO₄ recycled to the scrubber.

2NOHSO₄ + ½ O₂ +H₂O           2H₂SO₄ + 2NO₂

Ø NO₂   produces HNO₃ in HNO₃ reactor.

3NO₂ + H₂O          2HNO₃ +NO

         Excess NO₂ & NO are recirculated through the oxidizer in first step.

 

 

Sulphur dioxide so₂

It is colorless gas with a pungent odour. It is produced from the combination of sulphur-bearing material.

                                            

Natural process e.g. volcanoes. Provide 67%  SOx pollution distributed all over the globe. Men sources 33%. Fuel combustion, transportation, coal fired power station.

   

                 

This gives rise to the phenomenon of acid rain.

Control

4 possible ways to the removal & control of SO_X emissions.

·        Removal of Sox from flue gases.

·        Removal of S from fuel before burning.

·        Uses of low sulphur fuels

·        Substitution of other energy sources of fuel combustion.

Sox from flue gases can be conveniently eliminated by using chemical scrubbers. The flue stack are passed through a slurry of limestone, CaCO₃, which absorbs SO₂ quite efficiently.

CaCO₃ + SO₂ + O₂    CaSO₄ + CO₂

An alternate process is based on a reaction between HSO₃⁻ ions (from SO₂) and citrate ions. The flue gas is cooled to 50⁰C or lower and freed from particulates and traces of H₂SO₄. Then pass to a Absorption tower into a solution containing citrate ions (H₂Cit⁻)

                                

Acid rain

Much of the NOx and SOx entering into the atmosphere are converted into HNO₃ & H₂SO₄ respectively. The detailed photochemical reactions in the atmosphere are summarized:

HNO₃ in removed as precipited or as particular nitrates after reaction with bases (NH₃, particulate lime)

 

HNO₃ & H₂SO₄ Combine with HCl emission (both by natural and anthropogenic sources) to generate acidic precipitation which is widely known as acid rain. Acid rain now a major pollution problem in some areas.

           Acid rains causes extensive damage to buildings & sculptural materials of marble, limestone, slate, mortar etc. These materials become pitted and weakened mechanically as the soluble sulphates are leached out by rainwater.

Particulates : Small, solid particles and liquid droplets are collectively termed particulates. These are presents in the atmosphere in fairly large numbers and sometimes pose a serious air pollution problem.

Sources:  Numerous natural processes injecting particulate matter in the atmosphere (800-2000 million tons each year) volcanic eruption, blowing dust & soil by the wind, spraying salt & other solid particles by the seas & oceans.

Man-made:

·        Fly ash from power plants                                                                                     

·        smelters from mining operation                                                                                      

·        smoke from incomplete combustion process

Effects of particulates on materials:

Air borne particles including soot, fumes and mist are potentially harmful for a variety of materials. The extent & type of damage depend upon chemical composition & physical state of the pollutant. Extensive damage occurs when the particulates themselves are corrosive or when they carry toxic substances along with them.

Control: There are 4 types of equipment used for the control of particulates.

·        Gravity setting chamber                                                                                                     

·        cyclone collector                                                                                                                     

·        wet scrubbers                                                                                                                          

·        Electro static precipitators.

Inorganic particulate matter: Metal oxide comprise a major class of inorganic particles in the atmosphere. They are produced whenever fuels containing metals are burnt. Thus particulate Fe3O4 in formed during the combustion of pyrite containing coal.

3FeS2 + 8O2 Fe3O4 + 6SO2 & V converted to V2O5, CaCO3         CaO + CO2

Pb(C2H5)4 + O2 + C2H4Cl2 + C2H4Br2 CO2 + H2O + PbCl2 + PbBrCl + PbBr2

                   dichloroethane   dibromoethane

then Pb-halides which are volatile & emerge through exhaust system which condenses to form particles. This is basic of Pb pollutions in the atmosphere. Due to presence of H2SO4 (SO2 + O2 + 2H20       H2SO4) & basis air pollutant, such as NH3 OR CaO, Salts are formed

                                     H2SO4 +NH3  (NH4)2SO4

                                     H2SO4 + CaO  CaSO4 + H2O

Organic particulate matter :

These are benzene extracted substances poly cyclic aromatic hydrocarbon (PAH) are important components of organic particulate matter because of their carcinogenic nature. Some typical PAH compounds are Banzo pyrene, chrysene etc.

Most of PAH compounds are absorbed into soot particles.

 

Monitoring

Analysis of CO :  

(i)Infrared spectrophotometry. It is based on the principle that CO strongly absorbs infra-red radiation at certain wavelengths. When IR radiation is passed through a long cell containing a trace of CO, part of the energy is absorbed by the gas. At higher CO level more of the IR energy is absorbed.

 

(ii)Gas chromatography: 10 ppm or lower levels of CO can be conveniently measured by gas chromatography.

 

Hydrocarbon and photochemical smog

Natural source :

Natural sources, particularly trees, emit large quantities of hydrocarbons in the atmosphere. Methane is the major naturally occurring hydrocarbon emitted into the atmosphere. It is produced in considerable quantities by bacteria in the anaerobic decomposition of organic matter in water, sediments and soil.

                

2{CH₂0}    ^bacteria           CO₂ + CH₄

Man-made source:

Automobiles are the major sources of hydrocarbon emitted to the atmosphere.

Control

          Hydrocarbons are removed from the atmosphere by several chemical & photochemical reactions. The end product are CO₂, solid organic particulate matter that settles from the atmosphere or water- soluble products e.g. acids & aldehydes which are washed by rain .The majority of the harmful effects of hydrocarbon pollution are not due to the hydrocarbon themselves, but the products of photochemical reactions. An important characteristics of atmosphere which are loaded with large quantities of automobiles exhausts, trapped by an inversion layer (stagnant air masses) and at the same time exposed to intense sunlight, is the formation of photochemical oxidants in the atmosphere. This gives rise to the phenomenon of photochemical smog. Photochemical smog is characterized by brown, hazy fumes which irritate in eyes & lungs, lead to the cracking of rubber and extensive damage of plant life.

The probable mechanism of smog forming reactions as follows.

1. Reactive hydrocarbon ( those with C=C group ) from auto exhaust interact with O₃ to from a hydrocarbon free radical RCH₂•
2. RCH₂• rapidly reacts with O₂ to from another free radical RCH₂O₂•
3. RCH₂O₂• reacts with NO to produce NO₂ & the free radical RCH₂O•
4. This new free radical  next interacts with O₂ to yield a stable aldehyde, RCHO, and hydroperoxyl radical, HO₂•
5. HO₂• then reactive with another molecule of NO to give NO₂ & HO•
6. HO• is extremely reactive & rapidly reacts with a stable hydrocarbon RCH₃ to yield H₂O & regenerate the hydrocarbon free radical RCH₂• , thereby completing cycle.

 

Reactive hydrocarbon

                      

Route of PAN formation

                                             

The aldehyde RCHO may initiate another route by interaction with the HO• Radical, leading to the formation of an acyl radical RC=O, peroxyacyl radical RCOO₂ (by reaction with O₂) & finally peroxyacyl nitrate PAN( by reaction with NO₂). PAN is one of the most potent eye irritants found smog.

Control of hydrocarbon & photochemical pollutants.

O₃ & PAN secondary pollutants, so their control ultimately depends on the control of their primary precursors, hydrocarbons & nitrogen oxides. The control of NOx has been described earlier & that of HC in connection with the control of auto exhaust emissions.