Lecture.Packet.3.Equil.Partitioning

Lecture.Packet.3.Equil.Partitioning - CEE 440 © 2011...

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Unformatted text preview: CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 1 CHAPTER 3. CONTAMINANT PROPERTIES AFFECTING POLLUTANT FATE AND REMEDIATION My teaching goals for Chapter 3 are for you to: 1. Use thermodynamic relationships to determine whether a system is at equilibrium. 2. Calculate the distribution of chemicals between different phases. 3. Use Fick's laws to calculate diffusion rates for chemicals in air and water. 4. Use boundary layer theory to calculate the rate that chemicals move from one phase to another. 5. Appreciate how chemical equilibrium and mass transfer characteristics affect contaminant transport and fate in the environment. CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 2 3.1 Introduction Equilibrium Properties – Control contaminant distribution between phases Mass Transfer Properties – Control the rate that equilibrium is attained Equilibrium Properties Affecting the Distribution and Fate of Chemicals in the Environment Organic and inorganic chemicals can exist in several phases in soil, sediment, and groundwater. Right is a conceptual picture of these phases. CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 3 Understanding the distribution and fate of organic and inorganic chemicals between and within phases is paramount to predicting pollutant transport, fate, and remediation effectiveness. Chemical properties/parameters that determine the distribution and fate of chemicals in the environment that you will learn about are: -Henry’s Constant (H cc ) -Octonal-water partition coefficient (K ow ) -Water-Solid or Air-Solid Equilibrium Distribution Coefficients (K d ) -Water/Organic Interfacial tension ( γ ), Water/Organic Contact Angle ( θ ), Density ( ρ ) CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 4 3.2 Thermodynamics of Equilibrium At equilibrium the amount of mass in each phase is constant. Thermodynamics can be used to derive the phase equilibrium relationships. The primary variable that governs equilibrium: G = Gibbs free energy change in G defines favorability of a system For a change from one phase to another or from reactant A to product B we talk about the change in the Gibbs free energy, Δ G - Δ G + Δ G air water favorable unfavorable CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 5 The change in the Gibbs free energy can be defined in terms of: Δ G = Δ H - T Δ S (3.0) T = temperature Δ H = enthalpy change if negative heat produced during process (exothermic) if positive heat consumed during process (endothermic) Δ S = entropy change if negative system becomes more ordered if positive system becomes less ordered (more disordered) CEE 440 © 2011 Charles J. Werth, University of Illinois at Urbana-Champaign. All rights reserved. 6 when we have the transfer of mass from one phase to another we talk about...
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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.3.Equil.Partitioning - CEE 440 © 2011...

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