Lec 6 Flashcards
What are the concepts that equilibrium concentrations of contaminants are based on?
Partitioning, sorption and exhange
Partitioning
Tendency of a contaminant to exist at equilibrium between two phases
Sorption
A partitioning and exchange phenomenon that describes a contaminant to accumulate at the solid surface from the surrounding solution/air
Exchange
Displacement of the charged species by another species that has higher affinity for the same site on the solid surface
Fugacity
Molecule’s tendency or driving force to escape the system it is in
Sorption types
Electrostatic
Physical
Chemical
Sorbent characteristics for sorption of organic compounds
Hydrophobicity
Specific surface
Sorbate (contaminant) characteristics to influence sorption
Hydrophobicity
Ionic charge
Kow
Water solubility (?)
Which do sorb charged species
Clays, smaller particles
Measures of hydrophobicity of a compound
Low water solubility ~ sorption tendency
Kow (octanol water partition coefficient)
Partition coefficients
Kow: octanol water partition coefficient
Kd: soil distribution coefficient
Koc: soil adsorption coefficient
Is Kow related with water solubility of the compound?
NOOOOO
high logKow means?
-more hydrophobic
-partitioning more into octanol than water
-potential to bioconcentrate in living organisms
-logKow ?
Kow < 1
İt is partitioning more into water than octanol
Soil components (extremely variable, heterogeneous)
inorganic fraction (45-49.9%)
organic matter (0.1-5%)
water
air
Most important soil properties of HWM & most critical factors im sorption of chemicals
CEC (cation exchange capacity)
SOM (soil organic matter)
CEC
quantity of cations sorbed per mass of soil (meq/100g soil)
Higher CEC
Higher removal potential
Higher sorption of ionic compounds into soil
SOM
Determines how much a soil can adsorb org contaminants
Humic (org) + Non-humic (inorg)
MMMOST COMMON SORBENT IN SOILSSS
Higher SOM
Higher sorption of org compounds into soil
Humic fraction (org)
Humin
Humic acids
Fulvic acids
Isotherm
Langmuir: monolayer adsorption of sorbate
Freundlich: multilayer adsorptionof sorbate
Langmuir
Ce/qe (y) vs Ce (x)
slope: 1/a
y-intercept: 1/ab
Freundlich
lnqe (y) vs lnCe (x)
slope: 1/n
y-intercept: lnKf
Kd (mL/g)
Soil distribution coefficient
(mg/g) / (mg/mL)
Koc (mL/g)
Soil adsorption coefficient
(mg/g) / (mg/L)
Retardation factor (R)
If R > 1, contaminant is moving slower than groundwater: advantageous for waste management context
What is R directly related with
HYDROPHOBICITY OF CONTAMINANT
Non-polar sorbents
GAC
SOM (Soil organic matter)
