Properties and Fates of Environmental Contaminants

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Chapter 2

• Properties and Fates of Environmental Contaminants

2
Introduction

• Essentially all processes produce some kind of
  wastes
• Disposal of a toxic material may not always mean
  long term liability or costs
• Wastes may be quickly and easily bio-degradable,
  or immobilized, thus minimizing risks
• This chapter looks into impacts and fates of some
  common wastes/pollutants

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Division of Organic Chemicals
4
Nomenclature of Organic Compounds

• IUPAC International Union of Applied Chemists
• Common Names
• Most of the time, IUPAC names will be used in
  this course

5
Aliphatic CompoundsALKANES

• single carbon bonds
• general formula CnH2n2
• all alkane names end in -ane
• isomers compounds having same number of carbon
  atoms but with different structures and
  properties
• straight chain alkanes normal compounds (symbol
  n- is usually put in front of the compound name)

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Aliphatic CompoundsALKANES

• Naming branched alkanes
• find longest continuous chain of carbon atoms
• start numbering so that branched carbons get the
  lowest possible numbers
• when more than one group is present, start
  numbering in alphabetical order

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Aliphatic CompoundsALKANES
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Alkane Series
Name of Compound Number of Carbons Methane 1
Ethane 2 Propane 3 Butane 4 Pentane
5 Hexane 6 Heptane 7 Octane 8 Nonane
9 Decane 10 Undecane
11 Dodecane 12
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Aliphatic CompoundsALKENES

• carbon-carbon double bonds
• general formula CnH2n
• names end in -ene
• in the past, names ended in -ylene
• unsaturated

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Aliphatic CompoundsALKENES

• Naming branched alkenes
• find longest continuous chain of carbon atoms
• start numbering so that double carbon bond gets
  the lowest number
• when more than one group is present, start in
  alphabetical order

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Alkene Example
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Aliphatic CompoundsALKYNES

• carbon-carbon triple bond
• general formula CnH2n-2
• names end in -yne
• naming is done as it is done for alkenes.

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Organic Acids

• have a carboxylic acid group -COOH
• general formula R-COOH
• name ends in -anoic acid
• common names used more often
• unsaturated organic acids also found
• same naming convention is followed

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Common Normal Saturated Organic Acids
Common name IUPAC name Formula Formic
acid Methanoic acid HCOOH Acetic acid Ethanoic
acid CH3COOH Propionic acid Propanoic
acid C2H5COOH Butyric acid Butanoic
acid C3H7COOH Valeric acid Pentanoic
acid C4H9COOH Caproic acid Hexanoic
acid C5H11COOH Enanthic acid Heptanoic
acid C6H13COOH Caprylic acid Octanoic
acid C7H15COOH Perlagoric acid Nonanoic
acid C8H17COOH Capric acid Decanoic
acid C9H19COOH Palmitic acid Hexadecanoic
acid C15H31COOH Stearic acid Octadecanoic
acid C17H35COOH
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Common Unsaturated Organic Acids
Name Formula Oleic acid CH3(CH2)7CHCH(CH2)7C
OOH Linoleic acid CH3(CH2)4CHCHCH2CHCH(CH2)7CO
OH Linolenic acid CH3(CH2CHCH)3CH2(CH2)6COOH
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Esters

• general formula R-COO-R
• alcohol acid ester
• naming based on alkyl nomenclature
• one exception - acetate, not ethanate
• alkyl group name placed first, then name of the
  salt of acid ending in -ate

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Ethers

• general formula R-O-R
• alcohol 1 alcohol 2 ether
• widely used as solvents
• highly flammable
• named by combining the names of two alcohols

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Aldehydes

• oxidation products of primary alcohols
• have a double bonded oxygen hydrogen at the
  terminal carbon
• named by adding -al to the basic alkane name

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Common Aldehydes and Ketones
Common name IUPAC name Formula Aldehydes
Formaldehyde Methanal HCHO
Acetaldehyde Ethanal CH3CHO
Propionaldehyde Propanal C2H5CHO
Butyraldehyde Butanal C3H7CHO
Acrolein 2-Propenal CH2CHCHO Ketones
Acetone Propanone CH3COCH3 Methyl ethyl
ketone Butanone CH3COC2H5 Methyl isopropyl
ketone 3-Methyl-2-butanone CH3COC3H7 Methyl
isobutyl ketone 4-Methyl-2-pentanone
CH3COCH2CH(CH3)2
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Ketones

• oxidation products of secondary alcohols
  (R-(C(OH)H-R)
• have two alkyl groups attached to the carbonyl
  group (-CO-)
• named by adding -one to the basic alkane name

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Cyclic Aliphatic Compounds

• usually five or six ring saturated aliphatic
  compounds
• cyclic alkenes are also known

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Aromatic Compounds

• ring compounds bonds alternate between single
  double ones (bonds actually resonate)
• most common is benzene
• when one hydrogen is replaced name by placing
  the name of the substituent first, followed by
  -benzene
• when two hydrogens replaced ortho (o-), meta
  (m-) or para (p-) used
• when more hydrogens replaced use numbering
  system for positions on the ring

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Polycyclic Aromatic Hydrocarbons (PAHs)

• two or more benzene rings fused together, sharing
  pairs of carbon atoms
• PNAs polynuclear aromatic compounds
• PCBs Polychlorinated biphenyls
• PCDDs Polychlorinated dibenzodioxins
• PCDFs Polychlorinated dibenzofurans

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Distribution of Elements
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Arsenic

• commonly used in industry as a process chemical
• extremely toxic lt0.1gm lethal
• known carcinogen
• semi-metal or metalloid
• average drinking water concentration 2.5ug/L
• maximum allowable 0.05mg/L

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Cadmium

• widely used in metal plating industry
• Ni-Cd battery TV screens
• stabilizer in PVC plastics
• mostly found in 2 valence state
• highly toxic only 1g is lethal
• drinking water standard 5ug/L
• not eliminated from human system and easily
  bio-accumulates

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Chromium

• transition metal valence states -2 to 6
• used primarily in metal plating because of its
  resistance to acid attack
• used in leather tanning, catalyst, pigments, in
  electronic instruments
• salts irritating to exposed tissues
• salts are known carcinogens
• drinking water limit 0.1 mg/L

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Lead

• heavy metal generally in 2 state
• widely used in industry
• low melting point, high density, high
  malleability, high acid resistance
• primary use in automobile batteries
• pure form innocuous to health, but in ionic form
  is toxic

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Lead (cont.)

• at high levels, metabolic poison
• lower concentrations, interferes with the
  production of hemoglobin leading to anemia
• causes kidney dysfunction, high blood pressure
  and permanent brain damage
• lead poisoning in young children

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Mercury

• metal, liquid at room temperature
• exists in both inorganic and organic forms
• highly volatile
• mercury vapors are very toxic
• causes nervous disorders, depression and insanity
• maximum allowable is 2ug/L in drinking water

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Cyanides

• not an element
• an inorganic non-metallic anion, CN-
• under neutral or acidic conditions, highly toxic
  HCN gas is formed
• binds with metal-containing enzymes (cytochromes)
  that participate in respiration
• maximum allowable in drinking water 0.2mg/L

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Fate Analysis

• Transport moves materials from one point to
  another
• associated with partitioning processes
• dependent on solubility, density, polarity, ionic
  state and vapor pressure
• Transformation alters the contaminants to new
  compounds of lower, equal, or more toxicity

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Concentration

• expressed in many ways
• by weight
• by volume
• ppm, ppb, ppt etc

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Transport Process
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Fate of Industrial Contaminants in the Environment
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Plume Migration
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Acid-Base Ionization

• Acid hydrogen ion donor electron acceptor
• Base hydrogen ion receptor electron donor
• Ionization degree of dissociation
• Monoprotic one H ion donor
• Strength depends on dissociation constant of the
  acid or base
• pH -logH

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Ionization Constants for Organic Acids and Bases
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Typical Distribution Diagram for Pentachlorophenol
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Solubility

• defined as the max. conc. of a substance that
  will dissolve in water at a given temp., pressure
  etc.
• NAPLs Nonaqueous Phase Liquids undissolved
  fractions of solute
• solubility depends on large number of factors.

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Factors Affecting Solubility of Organic Comounds
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Water Solubility
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Migration and Fate of LNAPLs and DNAPLS
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Different Sorptions
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Sorption Equilibrium Concentration Models

• Isotherms a line representing conc. of sorbed
  compound to the aqueous conc.
• Langmuir isotherm assumes a homogeneous surface
  and that the adsorbed layer is only one molecule
  thick
• Freundlich isotherm assumes a heterogeneous
  surface with different types of adsorption sites

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Volatilization

• defined as the transfer of matter from the
  dissolved phase to the gaseous phase
• major cause of fugitive emissions
• volatility depends on vapor pressure
• vapor pressure pressure exerted by the vapor on
  the liquid at equilibrium
• increases with temperature

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Henrys Law

• valid only for dilute solutions
• relates the concentration of a dissolved chemical
  to the concentration of the chemical in the
  gaseous phase at equilibrium
• P KHCW
• KH Henrys Law Constant
• Cw equilibrium contaminant conc.
• P contaminant partial pressure

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Transformation Processes

• involve breaking of chemical bonds
• creation of new compounds
• includes hydrolysis, elimination, redox,
  photolysis biodegradation

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Transformation processes (cont.)

• Hydrolysis addition of water molecule
• involves the attack of an electron-rich water
  molecule on an electron-poor organic bond in the
  compound
• water molecule is added and the constituent
  originally in the bond leaves with either H or
  OH- from the water molecule
• results in alteration of the original compound
  product not necessarily less toxic
• strongly pH dependent

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Transformation processes (cont.)

• Elimination Reaction involves the removal of
  adjacent element from an organic molecule chain,
  leaving a double bond between affected carbon
  atoms
• dehydrodehalogenation adjacent halogen and
  hydrogen atoms are removed, leaving an alkene

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Transformation processes (cont.)

• Redox Reactions Oxidation-reduction reactions
• involves transfer of electrons
• Oxidation loss of electron addition of oxygen
• Reduction gain of electron loss of oxygen
• abiotic systems e- comes from highly reducing
  chemicals
• biotic systems e- comes from microbial oxidation
  of a wide variety of materials, both organic and
  inorganic.

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Transformation processes (cont.)

• Photochemical Reactions conversion of CO2, in
  the presence of sunlight, to organic matter
• smog photochemical reaction produced in the
  lower atmosphere by reaction between
  hydrocarbons, and NOX in the presence of sunlight

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Transformation processes (cont.)

• Biological carried out by microorganisms, which
  are ubiquitous in nature
• biodegradation carried out in small steps
• bacteria are capable of oxidizing almost every
  natural organic matter, resulting in recovery of
  energy
• many capable of degrading synthetic organics

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Biodegradation

• cometabolism degradation of two or more
  compounds for mutual benefit
• Mineralization conversion of organic matter to
  CO2 and water