1. CE 510 Hazardous Waste Engineering
Department of Civil Engineering
Southern Illinois University Carbondale
Instructor: Jemil Yesuf
Dr. L.R. Chevalier
Lecture Series 5:
Partitioning

2. Course Goals
Review the history and impact of environmental laws in the United States
Understand the terminology, nomenclature, and significance of properties of hazardous wastes and hazardous materials
Develop strategies to find information of nomenclature, transport and behavior, and toxicity for hazardous compounds
Elucidate procedures for describing, assessing, and sampling hazardous wastes at industrial facilities and contaminated sites
Predict the behavior of hazardous chemicals in surface impoundments, soils, groundwater and treatment systems
Assess the toxicity and risk associated with exposure to hazardous chemicals
Apply scientific principles and process designs of hazardous wastes management, remediation and treatment

3. Partitioning
General phenomenon that describes tendency of contaminants to exist at equilibrium between phases
AIR
WATER
WATER
SOLID
WATER
BIOTIC

4. Partitioning WATER SOLID
sorption
WATER
SOLID
Accumulation of contaminants on or in the solid
adsorption
absorption

5. Partitioning WATER SOLID Sorbents include: Soils Sludges
sorption
WATER
SOLID
Sorbents include:
Soils
Sludges
Hazardous waste containment material (clay liner)
Granular activated carbon
In hazardous waste, the solvent is generally water

6. Factors of Sorption
Properties of the sorbent, the sorbate and the liquid media
Sorbent
Hydrophobic
Specific surface area
Sorbate
Low water solubility
Octanol-water partition coefficient, Kow
Solvent
Mostly water
Air in emissions and unsaturated zone

7. Sorption Mechanisms
Exchange adsorption (ion exchange)– electrostatic due to charged sites on the surface. Adsorption goes up as ionic charge goes up and as hydrated radius goes down.
Physical adsorption: Van der Waals attraction between adsorbate and adsorbent. The attraction is not fixed to a specific site and the adsorbate is relatively free to move on the surface. This is relatively weak, reversible, adsorption capable of multilayer adsorption.    
Chemical adsorption: Some degree of chemical bonding between adsorbate and adsorbent characterized by strong attractiveness. Adsorbed molecules are not free to move on the surface. There is a high degree of specificity and typically a monolayer is formed. The process is seldom reversible.
Generally some combination of physical and chemical adsorption is responsible for activated carbon adsorption.

8. Aqueous PhaseTransport in Soil
dispersion
advection
sorption
reaction
Bd = bulk density of the aquifer
Θ = volumetric moisture content (porosity for saturated soils)
C* = amount of solute sorbed per unit weight of solid
rxn = subscript indicating a biological or chemical reaction of the solute, or radioactive decay (other than sorption)

9. Aqueous Phase Transport in Soil

10. Properties of Soil
Pre-regulatory hazardous waste disposal occurred in soils
Need to review fundamental properties of soil
Compared to aqueous and air systems, soils are heterogeneous composed of solid, liquid and gaseous phases

11. Properties of Soil

12. Properties of Soil Gravel Sand Silt Clay 2.0-15 mm 0.075-2.0 mm
USDA Soil Particle Size Separates

13. Relationship between soil class and particle size distribution
Soil Triangle
Calculator

14. Class Example Determine the classification of the following:
22 % Sand , 42 % Silt , 36 % Clay
40 % Sand , 30 % Silt , 30 % Clay
60 % Sand , 30 % Silt , 10 % Clay
64 % Sand , 26 % Silt , 10 % Clay
46 % Sand , 30 % Silt , 24 % Clay

15. Class Example Solution
Soil Triangle
Calculator
Determine the classification of the following:
Clay Loam
22 % Sand , 42 % Silt , 36 % Clay
Clay Loam
40 % Sand , 30 % Silt , 30 % Clay
60 % Sand , 30 % Silt , 10 % Clay
Sandy Loam
64 % Sand , 26 % Silt , 10 % Clay
Sandy Loam
46 % Sand , 30 % Silt , 24 % Clay
Loam

16. How to Measure Sorption
Batch experiments are conducted to determine the amount of solute removed
varying the concentration of solute in solution
varying the amount of soil
The capacity of a solid to remove a solute is a function of the concentration of the solute

17. How to Measure Sorption
If the adsorbent and adsorbate are contacted long enough, an equilibrium will be established between the amount of adsorbate adsorbed and the amount of adsorbate in solution.
The results of the experiment are plotted on a graph, called an isotherm
Equilibrium sorption isotherm
can be used when the sorption process is rapid compared to the flow velocity
Kinetic sorption isotherm
needed when the sorptive process is slow compared with the rate of fluid flow

18. Equilibrium Sorption Isotherms
Linear Sorption Isotherm
Freundlich Sorption Isotherm
Langmuir sorption Isotherm

19. Equilibrium Sorption Isotherms

20. Linear Sorption Isotherm
C* = mass of solute sorbed per dry unit weight of solid (mg/kg)
C = concentration of solute in solution at equilibrium with the solid (mg/L)
Kd = distribution coefficient Kd 1

21. Linear Sorption Isotherm
Retardation Factor
The average velocity of the solute front where the concentration is 1/2 of Co is designated as vc.
If the average linear velocity of groundwater is vx, vc can be estimated as:

22. Freundlich Sorption Isotherm
If the sorption characteristics can be described by the Freundlich sorption isotherm, then C*=f(C) will be curvilinear, and
log C* = log K + N log C
will be linear. We can easily determine the coefficients K and N through linear regression.

23. Freundlich Sorption Isotherm
log C* = log K + N log C
N>1
log C*
N=1 N
N<1 1
log K
log C

24. Freundlich Sorption Isotherm
Show that the retardation factor, R for Freundlich Sorption Isotherm is given as:

25. Langmuir Sorption Isotherm
Developed with the concept that a solid surface possesses a finite number of sorption sites.
Once filled, the surface will no longer sorb solute from solution
β = adsorption constant related to the binding energy (L/mg)
α = maximum amount of solute that can be sorbed by the solid (mg/kg)

26. Problem
If the sorption characteristics can be described by the Langmuir sorption isotherm, then C/C*=f(C) is linear. In addition, we can estimate a and b from this linear plot. Prove this.

27. Solution

28. Solution C
C/C*
......end of example

29. Langmuir Sorption Isotherm
Linear transformation

30. Langmuir Sorption Isotherm

31. Text example Spreadsheet
Five beakers are filled with one liter of 400 mg/L 2,4-D. 2 g of soil are added to the first beaker, 3 g to the second, 4 g to the third, and 5 g to the last beaker.. The fifth beaker is used as control and no addition of soil. After letting the beakers reach equilibrium, the following aqueous concentrations are observed:
Beaker
C of 2,4-D (mg/L) 1
289 2
234 3
179 4
124
Fit these data to the Langmuir and Freundlich isotherms and determine the empirical constants for the best fit isotherm.
Spreadsheet

32. Text Problem 5.9
A soil evaluated for malathion sorption has been found to follow the Langmuir isotherm with a=0.01 and b=4.5. A remediation team has proposed adding 200 kg (441 lb) of the soil to a 500,000 L (132,100 gal) pond as an emergency response measure against a spill with malathion concentration of 6 mg/L. If the aqueous concentration needs to be less than 0.01 mg/L, will the process work?

33. Solution Langmuir isotherm: a = 0.01, b = 4.5
Mass of contaminant sorbed from mass balance is:
x = (Co – C) (V) = (6-C)(mg/L)(500000)(L)(g/1000mg)
= ( C) g malathion
The mass of the soil (m) = 200 kg = 200,000 g

34. Solution From the Langmuir isotherm: Not effective!
......end of example
What is the minimum mass of soil (kg) that would make the response effective?

35. Additional Comments: Kd
Simplest to use
Linear Isotherm
Linear portion of Freundlich
For soils with a high organic content, can be estimated from empirical equations based on
foc – fraction of organic carbon
Koc – soil adsorption coefficient
Kow – octanol-water coefficient
Let’s consider these in more detail

36. Octanol-Water Partition Coefficient, Kow
A key parameter for estimating toxicity, bioaccumulation, and sorption to soils and sediments
Used for estimating contaminant pore water concentrations in sediments, global transport of persistent organic pollutants
octanol
contaminant
water
Range between to over 100,000,000 (Table 5.7 p. 273)

37. Minimum Soil Organic Matter for Sorption, f*oc
Kow = octanol water coefficient
Sa = surface area
Sample Range of values for Sa
Sandy loam soil m2/g
Clay m2/g

38. Soil Adsorption Coefficient,Koc
Range of KOC values p. 277 Table 5.8
Empirical equations based on Kow Table 5.9, p. 278

39. Estimate of Kd
If foc > f*oc
Kd = Kocfoc

40. Class Example
Determine R for the herbicide atrazine given the following soil properties:
Bulk density: 1.4 g/cm3
Porosity: 0.3
Surface area: 8.2 m2/g
Soil organic carbon: 0.3%

41. Solution Step one, estimate Kow = 2.68 from Table 5.7
Calculate f*oc = 0.018%
f*oc < 0.3%
From Table 5.8 , Koc = 175

42. Text Problem 5.20 Spreadsheet
The following data have been collected for batch isotherm analysis of hexachlorocyclopentadiene in well cuttings from a contaminated ground water system.
Volume of aqueous solution used: 500 mL
Mass of well cuttings: 50 g
Organic carbon content of well cuttings: 0.2%
Co (mg/L)
C (mg/L)
0.4
0.02
1.8
0.04
3.7
0.05
5.1
0.1
7.6
1.2
9.2
3.8 11
4.9
12.4
5.3
Based on these data, estimate Kd, and Koc for the groundwater system.
Spreadsheet

43. Metals Rate of metals migration is also slower than water
Factors include pH
Cation exchange capacity
Iron oxide content
Redox potential

44. Metals Kd from Table 5.11 p. 283 Empirical estimate of velocity
Where = velocity at relative concentration evaluated
V = pore water velocity
Ai = regression coefficients
Xi = concentration of parameters
K = constant

45. Example
A landfill leachate contains 10 mg/L Cd and migrates with a pore water velocity of 4 cm/day. The leachate contains 0.08% total suspended solids (TSS) and 0.2% total organic carbon (TOC). The soil composition is:
2% free iron oxide
8% clay
22% sand
70% silt
Determine the time required for a concentration of 5 mg/L Cd to migrate 50 meters.

46. Solution Based on Table 5.13
Look down the center column for C/Co = 5/10 = 0.5
From here you get the values for the regression coefficients
spreadsheet

47. Solution V0.5 = (4/25)(7.54) = 1.21 cm/d
The time to migrate 50 meters is
T= (5000cm)/(1.21 cm/d) = 4132 days = 11.3 years

48. Summary of Important Points and Concepts
Sorption is the accumulation of chemicals onto surfaces from the surrounding solution
Two most common models for sorption onto soils and solids is the Langmuir and Freundlich isotherms
The octanol-water partition coefficient, Koc, is the most commonly used contaminant physiochemical property that correlates with potential for sorption. Sorptivity is also inversely related to water solubility

49. Summary of Important Points and Concepts
The soil distribution coefficient, Kd, is defined as the ratio of the mass of sorbed contaminant to the mass in the soil water.
In soil-water systems containing significant concentrations of organic carbon (i.e. > f*oc), the organic carbon is the primary sorbent. Koc may be used to describe the partitioning
Empirical equations are available to correlate Kow and Koc

50. Summary of Important Points and Concepts
Kd can be predicted from Koc and foc
Retardation is predicted from Kd
Bulk density
Porosity
Metal sorption can also be predicted through empirical equations