Environmental Engineering Reference
In-Depth Information
Separation techniques can be classified broadly into five categories as shown in
Figure 1.4 (Seader and Henley, 1998). In every one of these processes, the rate of
separation is dependent on selectively increasing the rate of diffusion of the contami-
nant species relative to the transfer of all other species by advection (bulk movement)
within the contaminated feed. Equilibrium limits the ultimate compositions of the
effluent streams (pollutant-rich and pollutant-free). The rate of separation within the
reactor is determined by the mass transfer limitations (“driving force”), whereas the
extent of separation is determined by equilibrium thermodynamic factors. Both ther-
modynamic and kinetic (transport) properties are thus instrumental in environmental
separations.
The above discussions of applications in environmental engineering show that
for both natural and engineered systems, two types of issues are paramount—an
equilibrium study to describe the final distribution of pollutants within different com-
partments and a kinetic study to describe the rate of transformations of chemicals
within each compartment and the rate of movement of chemicals between compart-
ments. A list of processes common to both natural and engineered systems is given
in Table 1.3. It summarizes the associated thermodynamic and kinetic properties that
are necessary for understanding each process.
In summary, we can look at chemical thermodynamics in environmental engineer-
ing as the essential element by which we connect observations on simplified systems
to the segment of the environment (natural or engineered) that we are interested
in. To put it in context, Figure 1.5 appropriately places the role of thermodynam-
ics in our endeavor to understand and design processes in natural and engineered
systems.
hermodynamic models
(chemical properties)
Mathematical models
(dynamics, mass balances)
Model
parameters
Design
Optimize
Predict
Control
Reproduction
Evaluation
Regression
Feedback
Adjust
System
(chemical plant,
environmental
compartment)
Observations
(experimental
data on
simplified systems)
FIGURE 1.5 Role of chemical thermodynamics in understanding natural and engineered
systems. (Modified from http://www.codata.org/codata02/04physci/rarey.pdf.)
 
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