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Can Chemical Equilibrium
studying aquatic chemistry, there are
many applications for chemical equilibria. For
instance, it is possible to be looking into the mechanisms
that control the movement of solutes in groundwater or surface water;
or one could be interested in controlling the pH, alkalinity or
corrosivity of drinking water; or one may be interested in the
toxicological effects of dissolved metals on the biota. Actually,
are so many possible applications of chemical equilibria to aqueous
systems that it would be hard to list them all.
a person interested in aquatic systems (or soil systems, or marine
systems, for that matter) a few assumptions hold true: Dissolved ions
interact with each other (form complexes), interact with particulate
surfaces (adsorb) and possibly form solid phases (precipitate). In a
typical natural system, say a stream water, there may be 10 to 20 major
chemical components dissolved in solution. These components have the
potential to form hundreds of dissolved chemical complexes, solids
phases or adsorbed species. Some of these chemical species may be
biologically active or even toxic while others may be inert. All of
this depends on factors like the total concentration of each component,
the pH, pe, ionic strength and temperature.
This is where calculating chemical equilibrium is helpful. As the name
implies, chemical equilibrium assumes that all reactions have gone to
completion and are in equilibrium with one another. So time dependent
reactions -- those reactions that have kinetic restrictions -- are not
addressed in this approach. In essence, the chemical equilibrium
approach provides you with a thermodynamic snapshot of your system: the
pH, ionic strength, the distribution of dissolved chemical species, how
much solid phase formed, etc. This is the type of information that is
critical to understanding what happens chemically in water.
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Vista compatible, 32-bit, version 4.6 is released. |
May - 2002 Version 4.5: Thermodynamic
database is upgraded, documented and conforms to USEPA standards.
All reaction data is referenced.
- 1998 Version
4.0: Windows, 16-bit version released. Numerical stability
in for wide range of chemical conditions. New report writing
features. Titrations, sensitivity
analysis, processing of huge datasets now possible.
June - 1992
Version 3.0: DOS, 8-bit version is released. First spatial user
interface for MINEQL. Tableau view of input
data. Object oriented management of output data to fit any
application. MINTEQ data is included.
Prior to our
Late 1980's USEPA
combines MINEQL numerical code and the USGS's WATEQ thermodynamic
data to produce MINTEQ.
1987 At MIT, Dave
Dzombak collects Two Layer surface complexation data for a wide range
of aqueous ions on FeO
The USGS develops a chemical equilibrium program called WATEQ. Their
work continues throughout the decade to provide critical review of
MINEQL "+Stanford" (because of the work at Stanford University)
electrostatic surface complexation reactions within MINEQL.
MINEQL is developed at MIT, by John Westall and Francois Morel. The
FORTRAN program uses a generic tableau
approach to describe equilibria and mass balance in aqueoous systems.
REDEQL is developed by James Morgan and Francois Morel. First
chemical equilibrium program with a vast scope of application. Becomes
the prototype for MINEQL.
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