Lecture.Packet.7.advection.dispersion.sorption

Lecture.Packet.7.adv - Chap 4 Site properties affecting remediation Sorption My teaching goals for this section of Chapter 4 are for you to 1

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CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 1 My teaching goals for this section of Chapter 4 are for you to: 1) Understand physical and chemical forces that control sorption 2) Determine how soil and sediment properties affect sorption 3) Quantify the effects of linear sorption on contaminant migration in groundwater 4) Appreciate how nonlinear sorption and mass transfer limitations during sorption affect contaminant migration in groundwater Chap. 4. Site properties affecting remediation - Sorption
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CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 2 The fugacity relationship was previously used to examine some general models for sorption (i.e. linear isotherm, Freundlich isotherm). However, site factors affecting sorption were not considered. We now examine the different site factors affecting sorption and we examine how sorption affects the transport of chemicals in the subsurface. Understanding these factors is necessary in order to predict contaminant transport and in order to choose the best remediation technology. First we need a working knowledge of the physics behind sorption. 4.4. Sorption
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CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 3 Three types of bonds or forces control sorption: 1) physical forces or van der Waals forces 4.4.1. Types of forces control sorption 2) covalent forces or chemical forces 3) electrostatic forces - weak forces extending short distances which arise from dipole/induced dipole moments within molecules - heat of adsorption: 5~10 KJ/mol - strong forces extending only short distances which are due to a chemical bond between two atoms - heat of adsorption: 100~400 KJ/mol - moderate forces extending long distances which arise from attraction between oppositely charged molecules (i.e. ions) - heat of adsorption: ~200 KJ/mol
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CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 4 4.4.2. Types of sorption processes These three forces result in four different types of sorption processes: adsorption, chemisorption, absorption, and ion exchange. 1) Adsorption : 2) Chemisorption : 3) Absorption: 4) Ion Exchange : adsorbed in solution solid organic matter absorbed in solution solid solid ion exchange Me 2+ Oxygen: Me Si or Al: Metal: H Hydrogen: H Me 1+ H chemisorption -- the process by which solutes cling to solid surfaces -- Van der Waals forces -- a process where a solute is incorporated onto a sediment, soil, or rock surface via a chemical reaction -- covalent bonding forces -- occurs when the the solute is taken into a porous matrix -- Van der Waals and electrostatic forces -- occurs when ionic chemicals are attracted to an oppositely charged mineral, soil, or sediment surface and held there by electrostatic forces
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CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 5 4.4.3. Characteristics of soils and sediments -- porous aggregates containing a variety of minerals, natural organic matter types, and black carbon.
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This note was uploaded on 09/30/2011 for the course CEE 440 taught by Professor Werth,c during the Spring '08 term at University of Illinois, Urbana Champaign.

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Lecture.Packet.7.adv - Chap 4 Site properties affecting remediation Sorption My teaching goals for this section of Chapter 4 are for you to 1

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