United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97330
EPA-600'3-80-049
May 1980
Research and Development
REDEQL-EPAK
Aqueous Chemical
Equilibrium Computer
Program
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-80-049
May 1980
REDEQL.EPAK
Aqueous Chemical Equilibrium Computer Program
by
Sara E. Ingle
James A. Keniston
Donald W. Schults
Marine Division
Con/all is Environmental Research Laboratory
Corvallis, Oregon 97330
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
-U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
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DISCLAIMER
This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
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FOREWORD
Effective regulatory and enforcement actions by the Environmental Protec-
tion Agency would be virtually impossible without sound scientific data on
pollutants and their impact on environmental stability and human health.
Responsibility for building this data base has been assigned to EPA's Office
of Research and Development and its fifteen major field installations, one of
which is the Corvallis Environmental Research Laboratory.
The primary mission of the Corvallis laboratory is research on the
effects of environmental pollutants on terrestrial, freshwater, and marine
ecosystems; the behavior, effects, and control of pollutants in lake systems;
and the development of predictive models on the movement of pollutants in the
biosphere.
This report describes an expanded version of a computer program
(REDEQL.EPA) for determining aqueous chemical equilibria among metals and
ligands under various conditions of pH, oxidation, and temperature. This book
is designed to be used in conjunction with the previously published A User's
Guide for REDEQL.EPA (EPA-600/3-78-024; NTIS PB 280 149/6BE).
Thomas A. Murphy, Director
Corvallis Environmental Research Laboratory
m
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ABSTRACT
This user's guide is a companion to the previously published report A
User's Guide for REDEQL.EPA (EPA-600/3-78-024) which explains the use of a
computerized chemical equilibrium program for determining the equilibrium and
speciation of metals and ligands in aqueous systems. Changes in this guide
include temperature correction for equilibrium constants and activity coef-
ficients, calculations of degree of saturation for selected solids, attainment
of an electrically neutral solution, and the use of an adsorption routine.
Application of the program including these modifications is illustrated with a
sample case of river water. The program is equally appropriate for the marine
environment. Also included in the guide are sample input data sheets and
illustrations of redox reactions under various pH and redox conditions.
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CONTENTS
Page
Foreword iii
Abstract iv
List of Tables vi
List of Figures vi
I. Introduction 1
II. Data input 3
III. Running REDEQL.EPAK 5
IV. Temperature corrections 7
V. TOTH and pH calculations; electroneutrality 8
VI. Redox reactions 11
VII. Saturation ratios 13
VIII. Adsorption 14
IX. Internal changes in the REDEQL program 17
i
References 20
Table 23
Figures 28
Appendix A 45
Appendix B Foldoiit
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LIST OF TABLES
Number
Table 1. Changes to Tables in Previous User's Guide 23
LIST OF FIGURES
Figure 1. Flow diagram for REDEQL.EPAK 28
Figure 2a. Input data 29
Figure 2b. Thermodynamic data at 20°C, 0.1 ionic strength 31
Figure 2c. Thermodynamic data at 25°C shown for comparison 32
Figure 2d. Input data printout 33
Figure 2e. Case progress for first case 34
Figure 2f. Speciation of metals for first case 35
Figure 2g. Concentration of complexes for first case 36
Figure 2h. Distribution of metals and ligands for first case 37
Figure 2i. Saturation of selected solids as log (ion product/solubility
product) 37
Figure 2j. Case progress for second case 38
Figure 2k. Distribution of metals and ligands for second case 39
Figure 21. Distribution of metals and ligands for second case at 25°C, for
comparison 39
Figure 3. pE-pH plots of Fe, Mn and Hg species 40
Figure 4. pE-pH plots of Pb, Co, C03~ and S species 41
Figure 5. pE-pH plots of NH3, H202, Sn and Fe species 42
Figure 6. pE-pH plots of Mn, Cr and S species 43
Figure 7. pE-pH plots of S and Cu species 44
vi
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ACKNOWLEDGEMENT
The authors wish to thank Steven Wolf for his work in preparing plots and
data supporting this manuscript. The authors also thank Drs. Thomas Theis
(University of Notre Dame) and Robert Volk (University of Florida) and Daniel
Krawczyk (Corvallis Environmental Research Laboratory) for their constructive
comments in preparing the manuscript.
vn
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I. INTRODUCTION
There are many computer programs1-6 available which allow the user to
calculate chemical speciation at equilibrium in aquatic systems. Generally,
these programs apply physical chemical principles to analytical data to calcu-
late the distribution of species among oxidation states, associated forms and
solids. REDEQL7, a computer program developed at California Institute of
Technology, has been used to determine Cu complexing capacity of natural
waters8, calculate Cd speciation in soil/water systems9, account for the fate
of trace metals in ocean discharges10, assess the sorption and leaching of
heavy metals in groundwater11, and relate species of Cu to toxicity12. A few
potential applications of REDEQL include the calculation of acid precipitation
effects on water bodies, the determination of sorption of heavy metals onto
particulate material, determination of the influence of pH or redox on the
solubility of chemical components and definition of the association between
heavy metals and organics such as EDTA or NTA. Obviously, results from REDEQL
and similar chemical equilibrium programs are only as reliable as the analyt-
ical data and thermodynamic constants used with the program. The REDEQL
program does not include kinetic considerations or mixed ligand complexes.
Frequently, necessary thermodynamic data may be unavailable or inadequate;
this is especially true for sorption data. In spite of these limitations,
chemical computer programs can provide the user with aquatic chemistry infor-
mation which may help interpret experimental results or predict chemical
behavior.
EPA has modified the original REDEQL program and the use of this modified
model was presented in an EPA publication entitled "A User's Guide for
REDEQL.EPA"13. This report is a modification and updating of REDEQL.EPA (now
called REDEQL.EPAK) and should be used as a companion to the original User's
Guide. The modifications have been made so that input to the program remains
basically unchanged from that described in the previous User's Guide; there
are several optional additions and one deletion. The major computational
changes in the program include temperature corrections for equilibrium
constants and activity coefficients, calculation of degree of saturation for
selected solids, and theoretical attainment of an electrically neutral solu-
tion for a more realistic system. These features are illustrated with a
sample case of river water. A description of the "Swiss" (surface complexa-
tion) adsorption model is included.
For easi-er use and understanding of the program, this guide includes a
flow diagram of the computational process. Outputs are more clearly labeled.
Sample data sheets for input data formats are given. A discussion of TOTH
(total hydrogen less total hydroxide) is included and there is an expanded
section on redox reactions with illustration of the pH and redox conditions
under which various reactions might be considered. Methods for calculating pE
(the negative log of the electron activity, by convention) are reviewed.
Data in the thermodynamic data file have been slightly improved with
updated constants appearing in the recent compilation of Smith and Martell14.
Mercury (I) and chrdmate have been added to the lists of metals and ligands.
* Superscripts denote references listed at end of report.
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For the computer programmer, the current version of the program is now
documented with comment cards and accompanied by a flow diagram for the sub-
routines (see Foldout). Many computational changes which allow the program to
execute more efficiently have been made. The basic flow of the program is
shown in Figure 1. This diagram illustrates the order in which various facets
of the complex equilibrium problem are considered. The basic algorithm used
was described by Morel and Morgan15.
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II. DATA INPUT AND OUTPUT
The format of the input data deck described in the previous User's Guide
remains unchanged except for addition of four fields to the program header
card, one optional card for checking saturation of solids, and elimination of
the TOTH card. The new formats for these cards are given in Table 1 under 4p
Program Input Cards (the p refers to tables in the previous User's Guide).
Table 1 also shows the addition of mercury (I) and chromate to Table Ip. They
are included as metal 35 and ligand 59, respectively.
Use of the program, including improvements, is illustrated with input
data for river water. The program can be also applied to the seawater envi-
ronment. Two cases are shown: the first with insignificant quantities of
EDTA (ethylenediaminetetraacetic acid) and the second with large enough
amounts of EDTA to cause complexing. The sample input and output are given in
Figure 2. The input data are shown in three forms in Figure 2a. The first is
the analytical data to be used, Figure 2a(i). Two alternative forms of the
cards are shown in Figure 2a(ii) and 2a(iii). They are equally correct.
Figure 2a(ii) is easier to read; Figure 2a(iii) is easier to keypunch and
would result from use of the data sheets shown in Appendix A. The 2 in column
54 of the program header card (1) signifies that saturation of two solids will
be checked (see Section VII). The temperature, with one decimal place, is
shown in columns 56-59 (see Section IV). Because columns 60-65 are blank and
pH is fixed, ligand concentrations will be adjusted to achieve electroneu-
trality. In cards (3) and (4), remember the first concentration given is the
guess of final free concentration, the second is the total concentration for
the first case. The total concentration for the second case need not be shown
if it is the same as the first case (see Section V). The two solids whose
degree of saturation will be checked are identified by their metal, ligand,
and solid numbers in card (10a). which follows card (10) in the user data
deck.
To simplify the program, data sheets were designed with the various card
fields blocked out on a grid and the decimal point appearing where approp-
riate. Integers should always be right justified. Use of a decimal point in
any real field will override the implied decimal points shown on the data
sheets. Blanks are equivalent to zero, but zero is often keypunched for ease
in counting spaces or reading cards. These data sheets are shown in Appendix
A. They may be reproduced for continued use.
The output from REDEQL.EPAK run with the test data from Figure 2a is
shown in Figures 2b-l. Labeling of output is more complete than that of
previous REDEQL versions. The temperature of the computation is shown at the
top of the thermodynamic constant output (Figures 2b, 2c). The changes of
total ligand concentrations are observed by comparing total concentrations
shown in case progress (Figures 2e, 2j) with the total concentrations in the
input data (Figure 2d). Also, the extent of changes in the ligand concen-
trations are reflected in the adjustment factor(s) (1.007 in this case, Figure
2e). If concentrations are repeatedly adjusted, as is usually the case, the
total amount of adjustment is the product of all the adjustment factors.
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The computed TOTH as well as TOTH in solution (soluble H) are given in
Figure 2e. The difference between them should be the hydrogen in solids:
TOTH = soluble H + [solid] X H+/mole solid
or, in this case,
9.5979 X 10-4 = 9.59872 X 10-4 - 3 X 1.988 X 10-8 - 2 X 9.943 X 10-9
The most interesting outputs for many users will be the free concentra-
tions of metals and ligands (Figures 2e and 2j) and the distribution of metals
and ligands (Figures 2h and 2k). The impact of the EDTA is readily seen in
the Cu2+, Zn2+, and Cr3+ speciation.
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III. RUNNING REDEQL.EPAK
There are various ways in which the program can be run depending on the
computer system available. Users should check with their computer staff for
aid in getting the program on line. The user input data is read from logical
unit 5, the thermodynamic data file from logical unit 10, and the output is on
logical unit 6. An IBM computer requires a region of 160K to run from a load
module. More is required for compilation. Since IBM does not routinely use
double-precision, users may find compiling with double precision to be helpful
in minimizing underflows and overflows.
The new program is called .REDEQL.EPAK. The new data deck is called
.THERMM. Standard IBM cards for creating a load module from the source deck
and running from that load module are shown below. These cards may need
modification (certainly of user number) on other IBM systems, but will be of
help to systems personnel. The control cards for creating a load module are:
//(Job card),TIME=2,
// REGION=175K,MSGLEVEL=(1,1)
//STEPA EXEC FORTGCL,PARM,LKED='NOSOURCE,NOXREF,NOMAP'
//FORT.SYSIN DD DSN=CN.EPABAJ.CPR1.REDEQL.EPAK,
// DISP=SHR,UNIT=3330-1
//LKED.SYSLMOD DD DSN=CN.EPABDJ.CPR1.ZUNS(ZARRUN),DISP=(NEW,CATLG),
// UNIT=3330-1,VOL=SER=WORK51
/*
After the load module has been saved as shown above, the program may be
used with the cards shown below. The cards call the load module and the
thermodynamic data deck. The user input is read from cards.
//(Job card ),TIME=2,
// REGION=160K,MSGLEVEL=(0,0)
// EXEC PGM=ZARRUN
//STEPLIB DD DSN=CN.EPABDJ.CPR1.ZUNS,DISP=SHR,UNIT=3330-1
//FT05F001 DD DDNAME=SYSIN
//FT06F00T DD SYSOUT=A
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//FT10F001 DD DSN=CN.EPABDJ.CPRV.THERMM,
// DISP=SHR,UNIT=3330-1
//GO.SYSIN DD *
(Insert input cards here.)
/*
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; IV. TEMPERATURE CORRECTIONS
Two types of temperature corrections are added to the program: both
activity coefficients and formation constants change with temperature. These
corrections occur automatically when a temperature other than 25°C (0 reads as
25°C) is entered in field 19 of the program header card.
Allowance for linear change of formation constants with temperature has
been introduced with the Van't Hoff relation:
log KT = log K25 - fHj| (j -
where T represents the new Kelvin temperature and AH is the enthalpy change
for the reaction at 25°C. Enthalpy data for solids and complexes are stored
as ten times AH for each solid and complex in a data line following the forma-
tion constant data line for that metal-ligand combination. If any enthalpy
data are available for a metal-ligand pair, a 1 (one) in column 79 of the
solid and complex card (5) indicates that an enthalpy card (5a) follows.
These modifications are described in Table 1 under Table 6p. The enthalpy
data for the formation constant of water and carbon dioxide have been added to
the solid and complex header card (4).
For activity coefficients, the temperature corrections are incorporated
in the Debye-Hiickel coefficient A in the Davies equation:
3/2
where A = 1.82483 x 10-6 (e T) , Z is the charge on the ion, and I is the
ionic strength. T is in degrees Kelvin, and e is the dielectric constant of
water4 approximated by
e = 87.74 - 0.4008 TC + 9.398 x 10-4TC2 - 1.410 x 10-6TC3
with T- the Celsius temperature.
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V. TOTH AND pH CALCULATIONS, ELECTRONEUTRALITY
REDEQL was designed to solve mass balance equations for every metal and
ligand component and a mass balance equation for TOTH, total hydrogen as
described in the User's Guide. In a system prepared from electrically neutral
substances (compounds), the TOTH mass balance requirement is the same re-
quirement as the electroneutrality condition:
all metals all ligands
J [LJ]tot + Mtot - COH]tot = °
1-1 j = 1
where Z. represents the charge on species i and the concentrations are total
concentrations (free plus complexed plus solid) of metals [M], ligands [L]
hydrogen, and hydroxide. This equation is not valid when redox complexes or
solids are present because it does not include concentrations of e- and pH
should not be calculated when redox is considered with the program
REDEQL. EPAK. The last two terms of equation (1) are TOTH so
all metals all ligands
-TOTH = ^ *i C^tot + 2 Zj CLj]tot <2>
i = 1 j = 1
This can be calculated from the input data for metals and ligands in the
REDEQL program. It is redundant to allow input of TOTH when pH is to be
calculated. The old program will solve the equilibrium problem for any given
value of TOTH, but only one value can satisfy the electroneutrality require-
ment (2). The REDEQL. EPAK program no longer requires a TOTH card when pH is to
be calculated.
The pH can only be calculated by REDEQL. EPAK when the total metal and
ligand concentrations are known accurately. Field concentration data will
rarely be sufficiently good to calculate pH, therefore, it is recommended that
a carefully measured field pH be used with REDEQL. EPAK. On the other hand,
there are two cases when pH can be calculated successfully. In a controlled
laboratory situation where the system being studied is composed only of known
compounds the program will work, e.g., for NaHC03, NaOH, and NaCl at known
concentrations:
[Na]tot = [NaHC03] + [NaOH] + [NaCl]
[C03]tot = [NaHC03]
8
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and the concentration pf TOTH will be calculated according to
- TOTH = [Na]tot - 2[C08]tot - [Cl]^ (3)
= [NaHC03] + [NaOH] + [NaCl] - 2[NaHC03J - [NaCl]
= [NaOH] - [NaHC03] (4)
A
Equation 3 is that which the computer uses to find TOTH (Charge balance),.
Equation 4 is the way a user would calculate TOTH (total H less total OH
present). A second and more important instance in which pH can be calculated
is in predictive modeling, particularly in cases where two aqueous solutions
are to be combined. If each solution has been modeled using REDEQL.EPAK, each
will be well-balanced with respect to charge (see below) and therefore any
combined solution will be neutral. Therefore TOTH will be calculated
correctly and the correct pH of the system can then be calculated. Reliable
pH prediction has not been available in the previous model. However pH should
never be predicted using this program with redox at a fixed potential because
it is unlikely that pH is not known when pE is, and also because TOTH, and
consequently pH, will not be calculated properly if any redox complexes or
solids exist as initial components. A program which allows prediction of both
pH and pE is under development.
If TOTH is no longer necessary when pH is to be calculated, then is pH
necessary to the fixed pH situation? In practice, the answer to this question
is, of course, yes, because pH is often known better than total metal and
ligand concentrations. However, specifying total concentrations, pH, and
electroneutrality leads to an over-specified system even though the user may
"know" all these parameters. In the past, electroneutrality has been neglec-
ted. This often led to solutions having charges up to 50% of their ionic
strength. The program discussed here can adjust one or all ligand concentra-
tions to achieve electroneutrality within one percent of ionic strength. The
check on charge relative to ionic strength is made in an external loop after
all other constraints of the system have been satisfied. If the charge on the
final equilibrated solution is greater than one percent of the ionic strength
three options can be taken. The first, used if no other option is selected as
described below, adjusts the concentration of all ligands according to:
[L]
all metals
i = 1
Zi ^tot + CH]tot
ktot,new kld all ligands
2
j = 1
[LJJtot
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Since many ligands have hydrogen associated with them in normal pH ranges, the
"positive" charge of the solution in the numerator of equation (5) increases
also and several iterations are needed to achieve balance.
The second option is to adjust only one ligand concentration. This must
be a ligand already present in the system. It is specified by reference
number in field 20 of the program header card. Its normal charge must be
specified in field 21 of the header card which means that if that ligand is
normally protonated at the pH specified, -the charge of the protonated form
should be given, including the negative sign. The ligand must be present in
sufficient amounts so that its total concentration does not become negative.
The third option is to leave the solution electrically unbalanced. This
will be indicated in a warning message. This option is called by placing 100
in field 20 of the program header card.
10
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VI. REDOX REACTIONS
A
When redox reactions are considered, the redox potential used, given as
pE, is critical to the solution chemistry but this is a difficult parameter to
determine. There is no resolution of this problem because solutions generally
are not at redox equilibrium. One can determine whether a solution is oxidiz-
ing or reducing with respect to a given half reaction, but when one calculates
pE from several different half reactions, the results usually disagree. The
introduction of biological systems further complicates redox state because
oxidation-reduction reactions in biologically active systems are often in
dynamic flux. Three half reactions commonly used to determine redox potential
at 25°C are iron (III)/iron (II), sulfate-sulfide, and dissolved oxygen:
Fe3+ + e- -» Fe2+ pE = 13.0 + log({Fe3V{Fe2+})
S042" + 8H+ + 8e- -> S2" + 4H20 pE = 2.5 + (1/8) log({S042~}/{S2'}) - pH
%02(g) + 2H+ + 2e- -> H20 pE = 20.8 + log p~ /4 - pH
U2
The symbol { } represents activity which equals molar concentration at infi-
nite dilution.
The metal Hg22 and ligand Cr042 were added to the list of available
species so that they could complex with other ligands and metals. Formerly
they were treated as redox complexation products. These changes transformed
reaction 4 from type 3 to -10, eliminated reactions 16 and 17 because HCr04
and Cr2072 are complexes of chromate and hydrogen, and changed reaction 18 to
type -11 (Table 2p). This is a new reaction type recognized by the program
for metal-to-ligand redox. The ligand for reaction 18 becomes 59 (Cr042 )
rather than 99 (OH-). The stoichiometry of the first species in the metal-
metal, metal-ligand, or ligand-ligand reaction must be given, e.g. two mercury
(II) atoms produce one mercury (I) ion, Hg22 . This means that field 8,
columns 36-40, of the redox reaction cards is always the stoichiometric coef-
ficient of the ion given in field 2 (Table 6p).
To help the user evaluate which redox equations to use under given cir-
cumstances, pE-pH plots of relative activities of primary species for most of
the redox equations available are shown in Figures 3 to 7. The purpose of
these plots is to illustrate in what pE-pH regions redox reactiops should be
considered. In the areas outside the curves, redox is probably not necessary
and may lead to computational problems in program execution.
11
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For a redox equation involving two soluble species, the curves shown are
for fixed values of the log of the product concentration over the reactant
concentration. For instance Figure 3, reaction 1, shows curves for log
({Fe2 }/{Fe3 }) equal to 10, 5, and 0 (equal amounts of each). In the region
where pE is less than 3, the prevalence of Fe2 is so dominant that all iron
could be considered Fe2 and redox reaction 1 and Fe3 could be ignored. When
reactions involve one mole of product and one mole of reactant, the curves do
not depend on total concentrations. However, when unequal amounts of product
and reactant are involved, then curves also depend on total concentration. An
example of this is shown by reaction 4. The total concentrations shown are
the sums of the activities of free mercury (I) and free mercury (II). They do
not necessarily represent total dissolved mercury. In this figure, the curve
labeled 15b represents the pE and pH conditions at which log ({Hg22 }/{Hg2 })
= 15 and {Hg2+} + 2{Hg22+} = 10-5M.
The representations for solids differ slightly. As solubility decreases,
the concentrations of reacting species become necessarily smaller. The curves
show under what pE and pH conditions a particular activity (usually 10-5,
10-10, 10-15M) of the reacting species would be in equilibrium with solid.
When the maximum free concentration of the reacting species is very small,
much of that species is considered to be in the solid form. For example, in
reaction 2 at pH 8 and pE 12 most Mn2 would be oxidized to Mn02(s).
In uSring these diagrams it is well to remember that one is dealing with
multiple simultaneous reactions. Precipitation of solids and formation of
complexes may lead to a large total concentration of a species in a given
oxidation state even though the free concentration of that state may be
smaller than the free concentration of a different oxidation state.
Comptitations using redox reactions lead to many errors in running the
REDEQL program. Those reactions in which the curves are close together on the
pE - pH diagrams (e.g. reactions 8 and 9) are the most difficult to use be-
cause numbers which are too small or too large for the computer to handle can
easily be generated during computation. This causes the program to fail.
12
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VII. SATURATION RATIOS
A chemist or geologist is often interested in whether a solution is
supersatured or undersaturated with respect to a particular solid phase.
REDEQL.EPAK will determine this for any solids specified, even if imposed or
disallowed. The number of solids to be checked (up to 13) is given in field
18 of the program header card (see Table 1). The solids to be checked, ident-
ified by metal and ligand reference numbers and 1, 2, or 3 for their position
in the thermodynamic data base, are given on card .type lOa which precedes the
card listing redox reactions in the input data deck (see Table 1). Only one
solid of a given metal and ligand may be checked. The logs of the ratio of
ion products to the solubility products are given by an output routine called
immediately after the case progress output routine.
13
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VIII. ADSORPTION
The adsorption routine available with REDEQL.EPAK is a surface complexa-
tion adsorption model. The prototype of this model was described in a draft
of the California Institute of Technology Technical Report EQ-76-01 by McDuff
and Morgan17. Their work was patterned after that of Schindler et aj. 18, Hohl
and Stumm19, and Vuceta20. Only "ligand" surfaces are considered. There are
no thermodynamic data on file; data must be provided by the user. The
constants given here are for the sake of example only. Experimentally deter-
mined adsorption constants depend heavily upon the hydrolysis constants of the
adsqrbing metals. The user should ensure that hydrolysis constants in the
thef(i]pdynamic data base are consistent with those that were used to determine
adsorption constants. Numerous adsorption models are currently in use by
various researchers. Their abundancy is a reflection on their general inade-
quacy, and the model used here is no exception.
The model allows one to consider five surfaces at one time. Any number
of petals and hydrolyzed metals may adsorb on any or all of the surfaces.
This^ model does not include adsorption of ligands or metal-ligand complexes.
For each surface one must know the pH at which it carries no charge
(pH¥Q_) and the constants for association with, or loss of, hydrogen ions.
fr1"
Surface concentrations of hydrogen exchange sites or surface complexes are
giyeri in moles of the species on surfaces in one liter of solution and will be
denoted { }, while molar concentrations are denoted [ ]. Every surface HS can
op lose H :
"
app
so
,s
Ka2,app
and
J-1 {HS}
The constants are apparent constants because they depend on the local electric
field at the surface which, in this work is considered to be a function only
of pH due to a Nernstian surface potential. Validity of this type of poten-
14
-------
tial generally is limited to a narrow pH range about pHZpc- The apparent
constants may be related to intrinsic constants by
Ks - Ks ina(pH7PC " pH)
K- 10 ZPC
a^app
The constant a is a scaling parameter (0-1) for the influence of the surface
potential. The intrtffsic constants are required by the program.
For metal adsorption or exchange of the types
M+z + HS - H+ •* MS2"1 V
and
the amounts of surface complexes formed are
{MS2"1} = *K* {HS} [MZ+][H+]-1
and
The apparent constants are related to the intrinsic constants by
{MS2Z~2} = % {HS}2[MZ+][H+]-2
*KS = *KS . + io(z'1)a(PH " pHZPC}
i.app !,intr
*s _ *s ,0(z-2)«(pH -
This theory assumes that surface potential is not affected by. adsorption of
metal ions, which is a good assumption only when a small fraction of the
surface sites are used in adsorption.
Because of the form of these equations the complexes between surfaces and
adsorbing metals can be treated just as other complexes in the program. The
intrinsic constant is corrected to an apparent constant every time pH is
modified during program execution. The constants (intrinsic and apparent) are
15
-------
very dependent on the ionic strength and also ionic medium and must be meas-
ured for each medium. These constants are not corrected within the program
for changes in ionic strength.
As a brief example of typical data, Schindler et ah18 found that for
adsorption of Cu (II) on crquartz (pHzpc = 2.0), log Kf & -8.3 and log *01 =
-17.6 in 1M NaC104. These were apparent constants but appeared to be inde-
pendent of pH so Kf = K?,intr and a = 0.0. Schindler and Kamber21 found
that log K| = -6.8. This constant however will definitely vary with pH
and to use the constant a = 0, the user would probably want to calculate
Kfl for each pH considered from the expression given above or from
empirical expressions given by authors, e.g. from Schindler et aj. 18, when
(SiOH) =1.45 total moles/kg
log (SID") = -5.349
where (SiO ) is the surface concentration in moles per kg.
The formats for adsorption input data are shown in Table 1 (Table 4p).
The number of ligand surfaces is indicated in field 6 (column 18) of the
program header card (1). The data cards are required for each ligand surface.
The first surface card (type 4a) follows the ligand input and contains the
surface concentration of the surface as moles of adsorbing sites per liter of
solution (calculated from surface sites/kg and kg/1) for each case as well as
an initial guess as to free surface sites and a reference number (90-95) for
the ligand. The other adsorption cards are placed at the end of the deck.
There is one card of type (13) for each surface. It contains pHzpc, the
intrinsic constant for loss of H , the intrinsic constant for gain of H if
given, a, and the number of metals which can complex with the ligand. Each
metal requires a card of type (14) following the ligand surface card (13).
The metal cards give the reference number of the metal, the number of
complexes formed, and the intrinsic constant and stiochiometry (metal, ligand,
and H ) for each complex.
16
-------
IX. INTERNAL CHANGES IN THE REDEQL PROGRAM
In addition to the functional changes mentioned in this report, the
FORTRAN version of the program has been rewritten. As a first step, the
variables used in many subroutines were regrouped into new blocks of common in
an attempt to clarify which variables were used in each subroutine and to
decrease the number of lines of common at the beginning of each subroutine.
4
Code was changed so that metals and ligands are treated more similarly,
often by using subroutines called first for metals then for ligands. Repeti-
tive activity coefficient computations were eliminated. A new internal system
of indexing complexes and solids was designed so that many large arrays,
(20,30,6) and (20,30,3), were replaced by smaller arrays, (750) and (100).
The FORTRAN version of the program which now contains many comment cards
is available upon request or can be listed from COMNET by logging on to WCC
and using the following command
PRINT CN.EPABDJ. CPR1.REDEQL.EPAK,ROUTE=REMOTENN
where NN is the user's terminal number.
For those wishing to modify the program, expand it, or to understand it,
this guide includes a flow diagram of the program subroutines. Appendix B
shows all of the subroutines in REDEQL.EPAK. Every subroutine is called
unless a diamond-shaped decision box is shown. Areas enclosed in dashed-line
boxes involve operations of a single subroutine. Routines SUB!, SUB2, and
SUBS control the calling of almost all other subroutines and their calls and
decisions are shown in a column and are not enclosed in dashed-lines for
simplicity. Utility subroutines called at different points in the flow are
shown each time they are called. An explanation of the purpose of the sub-
routine is shown to the side of the flow diagram the first time the subroutine
is called. Subroutines called repeatedly at one point in the program flow are
shown only once. Subroutines which involve input or output are shown as
parallelograms.
The program was written for an IBM compiler and much of the program is
language dependent. If the user wishes to adapt the program to another com-
puter system the following problems may be encountered. Suggested solutions
and time estimates are given below.
1) Problem: The program uses four types of variables:
INTEGER*2 2 Bytes (1 Byte = 8 bits)
INTEGER 4 Bytes
REAL 4 Bytes
REAL*8 8 Bytes
17
-------
The INTEGER*2 declaration is used for arrays of integer values
to save memory. Arrays of 8-character names (i.e. NAMEM and
NAMER) are declared REAL *8.
Solution: Change all INTEGER*2 and REAL*8 declarations to integer.
(Trivial)
2) Problem: The main program has no program statement.
Solution: Add the program statement.
TAPES = User Data Deck
TAPE10 = Thermodynamic Data File
TAPE6 = Printout
(Trivial)
3) Problem: Values in common arrays must be initialized in BLOCK DATA
modules. The module in REDEQL.EPAK that zeroes out the common
blocks assumes that certain arrays are INTEGER*2.
Solution: A) If BLOCK DATA is allowed, rewrite the first BLOCK DATA
module using recomputed common block lengths. (2 hr).
B) If block data is disallowed, move the text of the BLOCK DATA
modules to the main program. (Trivial)
C) If the system automatically initializes common blocks to
zero, delete the first module. (Trivial)
4) Problem: Common statements in different subroutines may imply different
lengths for the same common block.
Solution: Use the complete common statement each time a block is
declared. (1 Day).
5) Problem: Subscript expressions are not limited to the standard forms.
Solution: Rewrite statements that use unacceptable subscript expressions.
(3 Days)
6) Problem: To save source code, many arithmetic expressions mix real and
integer (or INTEGER*2) variables without the benefit of FLOAT
and IFIX functions.
Solution: A) Leave mixed-mode expressions for the compiler to handle.
(Trivial)
B) Add calls to FLOAT and IFIX where they are appropriate. (5
days)
C) Change variable type from INTEGER(*2) to REAL where it is
appropriate. (8 days)
7) Problem: Subroutine IONCR uses a statement function, GAM.
18
-------
Solution: Rewrite GAM as a function subroutine. (Trivial)
8) Problem: Several subroutines use multiple returns to replace IF state-
ments in the calling routines.
Solution: Set flags in the called routines and check them in the calling
routines. (1 Day)
9) Problem: Some format statements use the P scale factor.
*
Solution: Input -- Omit scale factors and perform the implied scaling
after the appropriate read statements. (4 Hr.)
Output — Omit scale factors. (2 hr.)
10) Problem: Subroutine ERRSET, called by the main program, is an IBM system
routine.
Solution: Delete the call to errset. (Trivial)
11) Problem: Certain parameters in the subroutine statements are enclosed in
slashes (i.e. /T/ in DEFALT, /MI/ in INCONC, and /CSTOIC/ in
OUT141).
Solution: Delete the slashes. (Trivial)
19
-------
REFERENCES
1. Kjaraka, Y. K. and I. Barnes. SOLMNEQ: Solution-Mineral Equilibrium
Computations, NTIS Tech. Rept. PB214-899, Springfield, VA. 82 p.
(1973).
2. Mattigod, S. V. and G. Sposito. Chemical Modeling of Trace Metal Equil-
ibria in Contaminated Soil Solutions Using the Computer Program
GEOCHEM, Jenne, E. A., ed., iji Chemical Modeling in Aqeous Systems.
Speciation, Sorption, Solubility, and Kinetics. Amer. Chem. Soc.,
Symposium Series 93. Wash. D.C. 914 p. (1979).
3. Plummer, L. N., B. F. Jones, and A. H. Truesdell. WATEQF—a FORTRAN IV
Version of WATEQ, a Computer Program for Calculating Chemical Equil-
ibrium of Natural Waters, U.S. Geol. Survey Water Resour. Invest.
76-13. 61 p. (1976).
4. Truesdell, A. H. and B. F. Jones. WATEQ, a Computer Program for Calcu-
lating Chemical Equilibria of Natural Waters, J. Res. U.S. Geol.
Survey 2, 233-274 (1974).
5. Westall, J. C., J. L. Zachary, and F. M. M. Morel. MINEQL, a Computer
Program for the Calculation of Chemical Equilibrium Composition of
Aqueous Systems, Tech. Note 18, Dept. Civil Eng. Mass. Inst. Tech.,
Cambridge, MA. 91 p. (1976).
6. Wigley, T. M. L. WATSPEC: a Computer Program for Determining the Equil-
ibrium Speciation of Aqueous Solutions, Brit. Geomorph. Res. Group
Tech. Bull. 20. 48 p. (1977).
7. McDuff, R. E. and F. M. Morel. Description and Use of the Chemical
Equilibrium Program REDEQL2, Keck Lab. Tech. Rept. EQ-73-02, Calif.
Inst. Tech., Pasadena, CA. 75 p. (1973).
8. McCrady, J. K., and G. A. Chapman. Determinations of Copper Complexing
Capacity of Natural River Water, Well Water and Artificially Recon-
stituted Water. Water Research 13:143-150 (1979).
9. Volk, B. G. , and B. Lighthart. Computed Equilibrium Speciation of
Cadmium in Soil Solutions of Varying Organic Content, pH, and C02
Concentration. International Soc. of Soil Science, llth Congress,
Abstract for Commission Papers. Vol 1. p. 292, Edmonton, Canada.
(1978).
10. Morel, F. M.- M. , J. C. Westall, C. R. O'Melia and J. J. Morgan. Fate of
Trace Metals in Los Angeles County Wastewater Discharge. Environ.
Sci. Tech., 9:756-761 (1975).
11. Theis, T. L. and R. 0. Richter. Chemical Speciation of Heavy Metals in
Power Plant Ash Pond Leachate. Environ. Sci. Tech., 13:219-224
(1979).
20
-------
12. Magnuson, V. R., D. K. Harriss, M. S. Sun, D. K. Taylor and G. E. Glass.
Relationship of Activities of Metal-Ligand Species to Aquatic
Toxicity, Jenne, E. A., ed. , i_n Chemical Modeling in Aqueous
Systems. Speciation, Sorption, Solubility and Kinetics. Amer.
Chem. Soc. Symposium Series 93, Wash. D.C. 914 p. (1979).
13. Ingle, S. E., M. D. Schuldt, and D. W. Schults. A User's Guide to
REDEQL.EPA, A Computer Program for Chemical Equilibria in Aqueous
Systems, USEPA Corvallis Environmental Research Laboratory,
EPA-600/3-78-024, NTIS PB 280 149/6BE, Corvallis, OR (1978).
14. Smith, R., and A. Martell. Critical Stability Constants, Vol 1 (1974),
Vol. 2 (1975), Vol. 3 (1977), Vol. 4 (1976), Plenum Press, New York.
15. Morel, F., and J. J. Morgan. A Numerical Method for Computing Equilib-
rium in Aqueous Chemical Systems. Environ. Sci. Tech., 6:58-67
(1972).
16. Malmberg, C. G., and A. A. Maryott. Dielectric Constant of Water from 0°
to 100°C. J. Res. Nat. Bur. Stds., 56, 1-8 (1956).
17. McDuff, R. E. , and J. J. Morgan. Adsorption of Metal Ions as Surface
Complex Formation (How REDEQL Absorps the "Swiss" Adsorption). Keck
Laboratories, Calif. Inst. Tech., Pasadena, CA (1976).
18. Schindler, P. W., B. Fiirst, R. Dick, and P. U. Wolf. Ligand Properties
of Surface Silanol Groups. J. Colloid Interface Sci., 55, 469-475
(1976).
19. Hohl, H., and W. Stumm. Interaction of Pb2 with Hydrous y - A1203. J.
Colloid Interface Sci., 55, 231 (1976).
20. Vuceta, J. Adsorption of Pb (II) and Cu (II) on a-Quartz from Aqueous
Solution: Influence of pH, Ionic Strength and Complexing Ligands.
Ph.D. Thesis, Calif. Inst. Tech., Pasadena, CA (1976).
21. Schindler, P., and H. R. Kamber. The Acidity of Silanol groups.
Helvetica Chimica Acta, 51, 1781-1786 (1968).
21
-------
Table 1. Changes to Tables in Previous User's Guide**
A
Table Ip. Reference Numbers for Metals and Ligands
Metal 35 = Hg22+
Ligand 59 = Cr042"
Table 2p. Redox Reactions
Reference Reaction
Number Type Reaction Log K
2e- -> Hg22+ (aq) 30.7
4
16
17
18
-10
DELETE
DELETE
-11
2Hg2+ +
Cr3+ + 4
4H20 -> Cr042" + 8H+ + 3e- -74.9
Table 4p. Program Input Cards
Card Card
Type Field Columns Description
(1) Program Header Card: 1 card, Format (1813,IX,F4.1,213). All blanks are
read as zeros.
1-5 As described previously
6 17-18 Number of adsorbing ligand surfaces
7-17 As described previously
18 53-54 Selects degree of saturation output routine.
0 means none will be checked.
N, where 0
-------
Table 1. (Continued)
20 60-62 Reference number of ligand to be adjusted
for charge balance if pH is fixed.
0 if all adjusted
100 if none adjusted
21 64-65 Normal charge of ligand in field 20 including
sign.
(4a) Adsorbing surface concentration cards, # cards = # given in field 6,
column 18 of the program header card, Format (I2,2X,11(1X,F5.2)).
1 1-2 Reference number assigned to the surface.
(90-95)
2 6-10 Guess for moles of unreacted surface sites on
surfaces in one liter of solution.
3 12-16 Total moles of exchange sites on surface in
one liter of solution for first case.
4 18-22 Total moles of exchange sites per liter of
solution for second case.
5 24-28 Etc.
6-12
(6) OMIT TOTH CARD NEVER NEEDED
(lOa) (Follows 10, before 11)
Saturation card: 1 card used only if the degree of saturation of one or
more solids is to be checked (field 18 of the program header card > 0).
Format 3912.
1 1-2 Reference number of metal in Solid A.
2 3-4 Reference number of ligand in Solid A.
3 5-6 1, 2, or 3 depending on whether A is the
first, second or third solid listed in the
thermodynamic data file.
4 7-8 Reference number of metal in Solid B.
Etc. As in card 10.
24
-------
Table 1. (Continued)
(13) Adsorbing surface cards, # cards = # given in field 6, column 18 of the
program header card, Format (3F5.2,2I5,F5.2).
1 1-5
2 6-10
3 11-15
4 20
5 24-25
6 28-30
(14) Metal adsorption cards:
card (13), Format (215,
1 4-5
2 10
3 11-15
4 19-20
5 24-25
6 29-30
7 31-35
8 9-40
9-14
phLpp for adsorbing surface
-loa *KS
a a2, intrinsic
-log *KS . . . .
M alf intrinsic
1, if a value given in field 3.
0, if no value given in field 3.
Number of metals which will complex with the
surface.
Alpha, (1.0 - 0.0).
# cards = # given in field 5 of preceding surface
3(F5. 0,315)).
Reference number of the metal .
Number of complexes to follow (< 3).
100 x log of intrinsic formation constant for
the first complex.
Stoichiometric coefficient of metal in the
first complex.
Stoichiometric coefficient of the ligand
surface in the first complex.
Stoichiometric coefficient of hydrogen
(hydroxide if negative) in the first complex.
100 x log of intrinsic formation constant for
the second complex.
Stoichiometric coefficient of metal in the
second complex.
Etc.
25
-------
Table 1. (Continued)
Table 6p. Thermodynamic Data Deck
Card Card
Type Field Columns Description
(4) Solid and complex header card: 1 card, Format (I5.F5.2,F5.1,F6.2,F5.2).
1~3 As described previously
4 16-21 AH for the dissociation of water in Kcal/mole.
5 22-27 10 X AH for the reaction 2H+ + C032" -* C02(g)
+ H20 in Kcal/mole.
(5) Solid and complex cards: # cards = # given on header card (4), Format
212,9(14,211,12),2X,II.
1-38 As described previously
39 79 0 if no enthalpy card (5a) follows.
1 if enthalpy card (5a) follows.
(5a) (One card follows each card of type (5) which contains 1 in column 79.)
Solid and complex enthalpy data cards: Format (2I3,9(4X,F4.0)).
1 1-2 Reference number of metal
2 3-4 Reference number of ligand
3 9-12 10 x enthalpy of formation of the first solid
listed on the proceeding type (5) card.
4 17-20 10 x enthalpy of formation of the second
solid.
5 25-28 10 x enthalpy of formation of the third solid.
6 33-36 10 x enthal'py of formation of the first
complex.
Etc. Enthalpies for remaining five complexes.
(7) Redox reaction cards: # cards = # given on header card (6), Format
(9I5,A8,F4.0)
2 9-10 Reference # of reacting metal (if type -11).
26
-------
* Table 1. (Continued)
3 14-15 Reference # of ligand produced (if type -11).
4 18-20 Reaction type -11 metal to ligand redox, as
well as those reaction types given previously.
8 39-40 Stoichiometric coefficient of ion given in
field 2.
11 54-57 10 x enthalpy of formation
(9) Mixed solids cards: # cards = # given on header card (8), Format (1114,16,
2I3,A8,2F7.2)
1-16 As described previously.
17 72-78 10 x enthalpy of reaction
27
-------
y
t
Correct
ionic strength
no
Figure 1
Flow diagram for REDEQL.EPAK
28
-------
Figure 2. An example with two cases.
2a. Input data.
2a(i). The raw data.
Data
10 metals (shown below + H }
10 ligands (shown below +OH )
2 cases
No solids initially present
No adsorption
Fixed pH
8.0 (both cases)
No redox, no mixed solids
Ionic strength to be calculated
Guess 0.1
Normal outputs
Check saturation of 2 solids
CaC03, MgC03
Temperature, 20.0°C
Adjust ligands for charge balance
Card 3
Where, Field
Card
Card
Card
Card
Card
Card
Card
Card
Card
Card
Card
Card
Card
Card
Card
1,
1,
1,
1,
1,
1,
5
1,
1,
2
1,
1,
lOa
1,
1,
field
field
field
field
field
field
fields
field
fields
field
field
field
1
2
3
4
5+6
7
8,
10
11-
lS
19
20
9
17
Field 1
Metals Ref.
M
Ca2T
Mg2
K \
Na++
Fe»*
Fe2+
Cu2t
Zn«*
Cr*+
1
2
4
5
6
7
9
12
19
7.
4.
2.
5.
2.
4.
1.
2.
2.
4
6
3
2
0
3
2
5
2
X
X
X
X
X
X
X
X
X
io-5
io-5
IO-5
IO-4
IO-8
IO-7
IO-7
IO-7
10-7
4.
4.
4.
3.
7.
6.
6.
6.
6.
15
34
64
28
70
37
93
61
66
Card 4
Metal s
co32I
S0d2
Cl
NH3
P043
Si032_
EDTA4
N03"
Cr04
Field
Ref.
1
2
3
7
9
12
28
57
59
1
3.7
3.6
4.0
9.8
3.2
2.5
1.0
(2.7
2.5
1.0
M
X
X
X
X
X
X
X
X
X
X
10-4
10-5
10-4
10-5
10-7
10-4
10_20
10-7
io-5
10-9
Field 3
-log M
3.43
4.44
3.40
4.01
6.49
3.61
20.00
(6.57)
4.60
9.00
Card 7
Partial Pressure C02 =0.0
29
-------
Figure 2. (continued)
2a(ii). One form of the input data.
Mj'3
li
fiart ft
m i c
(21 2 El . C
(3) 3 1
4 [
5 ;
7
9
1 2
}
3 2 ;
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s 7
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8 2 8
957
a 5 9^
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34
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a
27 J
28
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1
2a(iii). The input data employing input data sheets.
Canl f
(11 1
(2) a
(?) '
»
1
1
]
14
IS
11
17
II
«
•
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9
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30
-------
I'."111 DM* FOX VERIFICATION
Irlt -4MUUTN*mC CONSTANTS CUMMtCTtl) \it IONIC
Mt 1
n
H
M
H
H
H
H
H
H
H
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
«G
Mil
Mb
MO
*<>
Mf,
Mb
6
0
b
A
NA
NA
NA
NA
NA
NA
NA
NA
NA
Ft 3
FEJ
Ft 3
FF3
Ft 3
Ft3
FE3
Ft )
ftJ
FE3
FL3
FF?
Ff ?
Ft«>
Fl*?
Ffe?
l-'tZ
F£/
Ft?
Ft 2
cu
cu
cu
cu
cu
cu
cu
CU
cu
cu
/N
la
IN
in
In
/N
in
IN
It
CK
C«
CH
Ch
r.»
C«
c«
CO
CH
CH
L III
1.1)4-
i04
Cl
NMJ
KO*
M'l J
EUI«
NOJ
CHU.
OH
C01-
Slli
CL
NHJ
P04
M'H
H>IA
NOJ
I.HU*
CH
COJ-
b04
cu
Nri i
PQ4
blUJ
bUf A
HUJ
CK04
OH
COJ-
SU"»
CL
NHJ
H0«t
SIUJ
IDIA
NOJ
CHU.
OH
CUJ-
b04
CL
NHJ
^04
SI<)J
fOU
M>4
C&U4
(JH
COJ-
bUS
CL
NHJ
HOl
SIOJ
EDIA
NUJ
CWJ4
t)H
C03-
b()<,
£^_
NHJ
KU*
SI'IJ
EOIA
NO 3
CB04
()H
CO 3-
501.
fL
NH3
C0«
MOJ
tDIi
NO.)
CH04
OH
COJ-
S<»
CL
NHJ
P04
fOU
no 3
CHO«,
UH
C04-
S04
CL
NHJ
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ooo
000
Figure 2c. Thermodynamic: data at 25°C shown for comparison
32
-------
IN^UT DATA
THESE COMPUTATIONS INVOLVE 10 METALS. 10 LIGANDS. 12<"> COMPLEXES AND 39 POSSIBLE SOLIDS.
IONIC STRENGTH = 0.9999996E-01
IONIC STRENGTH CORRECTIONS WILL 8E PERFORMED.
2 DIFFERENT CASES ARE TREATED.
THE CONDITIONS FOR THE DIFFERENT CASES ARE:
METAL CONCENTRATIONS
NAME REF. 0 FREE TOTAL 1
CONCENTRATIONS IN -LOG(MOLES/L)
TOTAL 2
CA
Mti
K
NA
FEJ
FE2
CU
2N
CR
1
2
4
b
6
7
9
12
19
4.1 JO
4.340
4.640
3.2HU
21.000
6.370
28.000
6.610
14.000
4.130
4,340
4.640
3.280
7.700
6.370
6.930
6.610
6.660
4.130
4.340
4.640
3.280
7.700
6.370
6.930
6.610
6.660
LIGANO CONCENTRATIONS
NAME REF. «
CONCENTRATIONS
C03-
S04
CL
NHJ
HU4
SI03
EOTA
NO i
CR04
1
2
3
7
9
12
28
57
59
FREE TOTAL 1
IN -LOG (MOLES/L)
3.430
4.440
3.400
4.010
12.000
10.000
20.000
4.600
9.000
3.430
4.440
3.400
4.010
6.490
3.610
20.000
4.600
9.000
CASE 1
TOTAL 2
3.430
4.440
3.400
4.010
6.490
3.610
6.570
4.600
9.000
CASE 2
FIXFO PH
H.OOO
0.0
Figure 2d. Input data printout
33
-------
NUMflEH 1
CASE PRObHESS
NOMBEH OF ITCHAT IONS =
SOLIO FE3 OH 1 0-3
NUMBER OF I TEHAT IONS =
SOLIO ZN SIOJ 110
NUMBER OF ITERATIONS =
SOLID CO C03- 2 1-2
NUMREH OF ITERATIONS =
NUMBER OF ITERATIONS =
NUMBER OF ITERATIONS =
PRECIPITATES.
9
PRECIPITATES.
14
PRECIPITATES.
\t>
?5
27
CMAHGfc ON SOLUTION (MOLES/L)
POSITIVE 0.174E-02
NeGATIVE-0.173E-U2
TOTAL 0.123E-0*
LIGANI) TOTAL CONCENTRATIONS ADJUSTED BY A FACTOR OF 1.007
NUMBER OF ITERATIONS = 29
CriARSt ON SOLUTION (HOLES/L)
POSITIVF 0.175E-02
NEGAriVE-0.174E-02
TOTAL O.OH1E-05
IONIC STRENGTH - 1 .0340665F.-03
FIXED PH - 8.000 COMPUTED TOTH = 0.9603139E-03
SOLUBLE H = 0.9603936F.-U3
CA
HG
K
NA
FE3
FE2
CU
ZN
CH
C03-
so*
CL
NH3
PU4
SI03
EOT A
N03
CR04
FREE CONC
MOLES/L
7.3592309E-05
4.54269J2E-Ob
2.2903099t-05
5.2472367E-04
2.0774336E-P1
4.1151907E-07
1..191&169E-08
1.44549H3E-08
1.5630841E-1S
7.6H07873E-07
*.(}()93Rf9E-04
4.079493DE-06
9.5839P57E-12
2.919781 1E-11
7.385366SE-34
2.b298024E-05
9.7983421E-10
-LOG FRFF CONC
4.13117
4.34269
4.64011
3.28007
20.68248
6.38661
7.85652
7.83998
14.80602
6.11459
4.44471
3.39692
5.38939
11.01845
10.53466
33.13162
4.59691
9.00885
TOT CONC
MOLES/L
7.4131327E-05
4.57090Q6.E-05
2.2908745E-05
5.2480842E-04
1.9952950E-08
4.2658104E-07
1.1749034E-07
2.3332711E-07
2.1877867E-07
3.7418446E-04
3.6566722E-05
4.0094578F-04
9.8420729E-05
J.2590378E-07
2.4722144E-04
1.0071444E-20
2.5298024E-05
1.0071430E-09
-LOG TOT CONC
4.13000
4.34000
4.64000
3.28000
7.69999
6.37000
6.93000
6.63204
6.66000
3.42691
4.43691
3.39691
4.00691
6.48691
3.60691
19.99690
4.59691
d.99691
REMAINDER
MOLES/L
3.6237680E-13
-5.9010574E-12
-4.6433968E-12
-7.7307050E-12
0.0
3.9425846E-14
0.0
-1.1766645E-08
0.0
8.6338048E-11
-4.3827858E-12
-3.6979489E-U
4.3655746E-11
1.7709220E-12
0.0
1.2129605E-27
0.0
-3.1896190E-16
SOLID MOLES PEP LITER &F SOLUTION
Ft 3 OH 1 0-3 1.987B716E-08
CU COJ- 2 1-2
ZN SI03 1 1 0
9.9416226E-09
2.1395681E-07
Figure 2e. Case progress for first case
34
-------
SPECI«TION OF METALS AMU LICJANOS
SUM OF CONCENTRATIONS OF ALL bPF.CIES WF.POHTEO AS -L06IMI
FrtEF. MET C03- S04 CL
FKEE LII3 6.1 1 4.44 3.40
H H.OO 3.4J 10.57 •«•••
CA 4.1J 6.81 6.42 «»••«
MG 4.34 7.13 6.73 «•««•
w K 4.64 «•••• R.25 o«««o
cn
A1A ? 3£1 O O*» 7 In O4A44
NA J.28 8.2O 7.10 »»«»«
Ffc3 20.68 •«••• 21.31 22.74
FE2 6.39 •««•• fl.76 B.95
CO 7.86 7.29 10. OS P. 22
iN 7.84 8.75 10.03 10.21
CK 14.81 ••••• 16.74 17.50
NH3 P04 SI03 E.OTA N03 CR04 OH
5.39 11. 0<>
Figure 2f. Speciation of metals for first case
-------
CONCENTRATIONS OF COMPLFXES
CA)
METAL
H
H
H
ri
H
H
H
CA
CA
CA
CA
CA
CA
MG
Mb
MG
MG
MG
Mb
K
NA
NA
NA
FES
FE3
FE3
FE3
FE3
FE3
FE2
FE2
FE2
FE2
FE2
FE2
CU
CU
CU
CU
CU
CU
CU
ZN
ZN
ZN
ZN
ZN
ZN
ZN
CM
CM
CM
CU
CK
LIGANO
C03-
504
NH3
P04
SI03
EOTA
CK04
C03-
S04
NH3
H04
EOTA
OH
C03-
S04
NH3
P04
EOTA
OH
S04
C03-
S04
EOTA
S04
CL
P04
SI03
EDTA
OH
S04
CL
NH3
H04
EOTA
OH
C03-
S04
CL
NH3
P04
EDTA
OH
C03-
S04
CL
NHJ
P04
EDTA
OH
S04
CL
P04
EOTA
UH
CONC.
-LOGIM) M
3.43 0
10.57 0
4.03 0
6.66 U
b.49 0
29.95 0
10.56 0
7.17
6.42
9.62
8.26
24.92
8.87
7.68
6.73
9.62
U.27
2(3.63
7.78
8.25
8.26
7.10
33.74
21.32
22.74
19.28
15.87
25.39
14.95
8.76
8.95
10.48
9.62
23.07
7.92
7.30
10.05
10.92
9.25
11.09
20.04
7.60
8.78
10.03
10.90
11.03
11.87
22.22
8.88
16.74
17.50
12.60
21.51
10.93
L
1
1
1
C
H
0
0
0
1
0
-1
0
0
0
1
0
-1
0
0
0
0
0
0
1
1
0
-1
0
0
0
1
0
-1
0
0
0
0
1
0
-1
0
0
0
0
1
0
-1
0
0
1
0
J-l
CONC.
-LOG (M)
5.49
7.02
3.61
30.84
lfl.79
7.07
15.61
P. 84
29.67
7.27
14.92
32. 1«
25.34
24.42
25.53
31.71
10.49
15.06
11.31
27.72
14.41
10.31
12.54
11.14
13.78
?4.49
9.20
9.87
13.03
14.12
Z6.6W
12.26
21.76
27.14
7.72
M L H
0 1 2
0 2
0 2
0 2
0 2
1 1
1 2 0
1 1 0
1 1 1
1 1 1
1 2 0
1 1 1
4 0-4
1 2 0
1 2 0
1 1 1
1 0-2
1 2 0
1 1 2
1 1 1
1 0-3
1 2 0
1 ? 0
1 2 0
1 1 2
1 1 1
1 0-2
1 1 1
1 2 0
1 2 0
1 1 1
1 0-3
1 2 0
1 1 1
1 0-2
CONC.
-LOGIM)
13.18
35.79
19.50
2l.no
20.81
29.76
25.14
10.38
24.34
20.75
9.59
16.24
13.72
24.05
10.68
17.62
17.11
17.01
21.26
6.70
M L H
0 1 3
0 1 3
022
1 3 U
1 3 0
1 3 0
1 1-1
1 0-4
1 4 0
1 0-4
1 1 1
1 3 0
1 3 0
1 1-1
1 0-3
1 1 0
1 3 0
1 0-4
1 1-1
1 0-4
CONC.
-LOGIM) M L H
41.61 0 1 4
27.55 023
28.29 1 4 0
26.90 140
27.15 1 1-2
28.28 2 0-2
11.02 1 1-2
20.11 1 4 0
17.61 1 4 0
15.43 1 0-4
10.31 1 1-1
20.50 1 4 0
8.79 1 0-2
CONC.
CONC.
-LOGIM) M L H
8.32 1 1-1
10.06 2 0-2
21.29 1 4 0
16.66 2 0-1
Figure 2g. Concentration of complexes for first case
-------
UJSTWIHUTION OF MtI»LS AND LIOANDS
Si'tCIES OVEH O.S * SHOWN
CA
99.3 £ AS A FHEE METAL
o.s * COMPLEXED WITH so*.
* AS A
METAL
NA
100.0 % AS A FrtEE METAL
100.0 * AS A FWtE META.L
FE3
99.6 % IN SOLID FOkM WITH OH
FE2
CO
9b.S *
d.U %
11. B *
43.3 %
16.9 *
5.1 •*
AS A FHEE MtT«L
COMFLEXtD WITH OH
AS A FHtE MtliL
COMPLEXED WITH coj-
IN SULIO FORM WITH C03-
COMPLE'XED WITH CL
22.3 * COMPLEXED WITH OH
6.2 * AS A FrtEE METAL
O.B t ClHPLEXliD •'ITjH_ C03-
VI. I * IN SUL1U "FDRH~«i IT H "STDT"
1.3 % COMPLEXED WITH OH
100.0 * COMPLETED WITH OH
99.7 % COMPLEXfcD WITH H
JH.i; * AS A FH£E LIGAND
1.0 * COMPLEXEO WITH CA
U.5¥CUMPLtAtU WJTH HG
CL
LlbArtU
95.9 * COMPLEXEO WITH H
90.2 •*• COMPLEXED WITH H
2.1 % COMPLEXEO WITH CA
SI03
SATURATION OF SOLIDS
SOLID
OEliHEE OF
SATURATION
C» C03- _ 1 1 0
~
iLOG)
-1.973
-3.0B3
Figure 2i Saturation of selected
solids as log ( ion product/
solubility product )
EUTA
9-i.y % COMPLtxED WITH H
90.M % C'JMPLEXEO WITH CU
0.6 % CO"«?PLE"XEO WITH ZN
d.5 £ COMPLEXED WITH CH
100.0 % AS A FrttE LI^AND
CHO4
97.1 * AS A FREE LIbANO
-------
CASE
CASE
NUMBER OF ITERATIONS
SOLID CU C03- 2 1-8
NUM8EK OF ITERATIONS =
DISSOLVES.
9
CHANGE ON SOLUTION (MQLES/L)
POSITIVE 0.174E-02
NEGATIVF.-0.173E-02
TOTAL 0.118E-0*
LI6AND TOTAL CONCENTRATIONS ADJUSTED BY A FACTOR OF 1.007
NUMBER OF ITERATIONS = 12
CHARGE ON SOLUTION (HOLES/L)
POSITIVE 0.175E-02
NEGATIVE-0.174E-02
TOTAL 0.653E-05
IONIC STRENGTH = 1.0343057E-03
FIXED PH _ 8.000 COMPUTED TOTH = 0.9605822E-03
SOLUBLE H = 0.9606418E-03
CA
MG
K
NA
FE3
FE?
CU
ZN
CH
C03-
S04
CL
NH3
P04
SIOJ
EDTA
N03
CH04
FREE CUNC
MOLES/L
7.3592382E-05
4.5426990E-05
2.2903099E-05
5.2472367E-04
2.0774336E-21
4.0841911E-07
4.5911541E-10
1.4458692E-08
6.2921292E-16
7.6797397E-07
3.5905920E-05
4.0082610E-04
4.0783234E-06
9.5813713E-12
2.9190678E-11
2.7970497E-19
2.b29054SE-05
9.?954467E-10
-LOG FRFF CONC
4.13317
4.34269
4.64011
3.28007
20.682^8
6.38889
9.33B07
7.83987
15.20120
6.11465
4.44483
3.39704
5.38952
11.01857
10.53476
18.55330
4.59704
9.00897
TOT CONC
HOLES/L
7.4131312E-05
4.5709006E-05
2.2908745E-05
5.2480819E-04
1.9952950E-08
4.265«093E-07
1.1748978E-07
2.4392943E-07
2.1877588E-07
3.7407409E-04
3.6555924E-OS
4.0082750E-04
9.8391843E-05
3.2580425E-07
2.4714856E-04
2.7099162E-07
2.5290545E-05
1.0068457E-09
-LOG TOT CONC
4.13000
4.34000
4.64000
3.28000
7.69999
6.37000
6.93000
6.61274
6.66000
3.42704
4.43704
3.39704
4.00704
6.48704
3.6Q704
6.56704
4.59704
8.99703
-1
REMAINDER
MOLES/L
1.4025892E-11
1.2825296E-11
6.2811978E-12
3.1377567E-11
0.0
2402828E-13
-3.3852877E-12
-1.4815100E-09
-6.0822458E-12
1.8371793E-10
-1.7271323E-12
-1.1921420E-11
-5.8207661E-11
-1.4691703E-12
0.0
-8.7534051E-12
0.0
-1.3650815E-17
SOLID
FE3
/N
OH
SI03
1 0-3
1 1 U
MOLES PER LITER OF SOLUTION
1.9835291E-08
2.018496?E-07
Figure 2j. Case progress for second case
38
-------
PRIMARY DISTRIBUTION OF METALS AND LIGANDS
SPECIES OVER O.S * SHOWN
CA
99.3 % AS A FREE METAL
0.5 * COMPLEXED WITH S04
PRIMARY DISTRIBUTION OF METALS AND LIGANDS
SPECIES OVER O.b * SHOWN
MG
NA
FE3
Ft?
CU
ZN
CR
CO )-
so*
99.4 * AS A FREE M£TAL
100.Q % AS A FREE METAL
100.0 * AS A FREE METAL
99.4 * IN SOLID FORM WITH OH
CL
IMH3
PO4
95.7 $ AS A FREE METAL
0.8 % COMPLEXED WITH EDTA
2.8 * COMPLETED WITH OH
1.4 % COMPLEXED WITH C03-
97.3 % COMPLEXED WITH EOTA
0.7 S COMPLEXED WITH OH
5.9 * AS A FREE METAL
0.7 * COMPLFXEO WITH C03-
8?.7 * IN SOLID FORM WITH SI03
9.3 * COMPLEXED WITH EDTA
1.2 * COMPLEXED WITH OH
s<;.7 * COMPLEXEO WITH EDTA
40.3 * COMPLEXED WITH OH
99.7 * COMPLEXED WITH H
96.2 % AS A FREE LIGAND
1.0 * COMPLEXED WITH CA
U.S * COMPLEXED WITH MG
100.0 * AS A FPEE LIGAND
4.1 Sb AS A FREE LIGAND
9-3.9 % COMPLFXED WITH H
9h.2 « COMPLEXED WITH H
2.1 * COMPLEXED WITH CA
1.6 * COMPLEXED WITH MG
SIOJ
EOTA
N03
99.9 « COMPLEXED WITH H
1.2 « COMPLEXEO WITH FE2
42.2 * COMPLEXED WITH CU
8.4 % COMPLEXED WITH ZN
4H.2 * COMPLEXED WITH CR
100.0 % AS A FREE LIGAND
CR04
97.3 * AS A FREE LIGANO
2.7 * COMPLEXED WITH H
Figure 2k. Distribution of metals
and ligands for second case
CA
.Mb
FE3
FE2
CU
ZN
CK
98.9 * AS A FREE METAL
0.6 * COMPLEXEO WITH C03-
0.5 * COMPLEXEO WITH S04
99.1 * AS A FREE METAL
100.0 * AS A FREE METAL
100.0 * AS A FREE METAL
9V.9 * IN SOLID FORM WITH OH
95.7 * AS A FREE METAL
0.8 % COMPLEXED WITH EOTA
2.8 % COMPLEXED WITH OH
3.6 * COMPLEXEO WITH C03-
95.1 * COMPLEXED WITH EOTA
0.7 % COMPLtXED WITH OH
b.9 * AS A FREE METAL
2.0 % COMPLEXEO WITH COS-
SI.2 % IN SOLID FORM WITH SI03
9.6 % COMPLEXED WITH EDTA
1.2 % COMPLEXEO WITH OH
60.6 % COMPLEXEO WITH EOTA
39.4 % COMPLEXEO WITH OH
C03-
SO*
CL
NH3
P04
0.6 * AS A FHEE LIGAND
99.3 * COMPLEXED WITH H
98.2 * AS A FREE LIGAND
1.1 * COMPLEXED WITH CA
0.5 $ COMPLEXED WITH MG
100.0 % AS A FREE LIGAND
5.8 * AS A FREE LIGAND
94.2 * COMPLEXEO WITH H
94.8 % COMPLEXED WITH H
2.9 % COMPLEXEO WITH CA
2.2 •* COMPLEXED WITH MG
SI03
EDTA
NO 3
99.9 * COMPLEXED WITH M
1.2 * COMPLEXED WITH FE2
41.2 * COMPLEXED WITH CU
8.7 % COMPLEXEO WITH ZN
4ft. 9 * COMPLEXEO WITH CR
100.0 * AS A FREE
CR04
97.3 % AS A FREE LIGAND
2.7 * COMPLEXED WITH H
Figure 21. Distribution of metals and
ligands for second case at 25°C, for
compari son
39
-------
PH»
LOG (FE+2/FE+3)
PH»
0 2
PE
LOG (MN+2)
(to*2 * ZHjO — IM2(l) * 4H* « &'
lib 15i lOc lot) in 5c
H0 OH)
9
B
7
6
PHa
3
3
1
I
-v
I
J
-B -4 -2 1 2 « 66 10 12 ~B "4 -2 0 2 4 B B 10 12
LOG CHG+2) LOG (HG2+ + /HG++) • - tti. * me. -
10-1!.
Hg« + 2i- — * Hg(11q) «,« + ,.--* ^, «(.<,, b - til. H, me. - irt
z c- ttl. Hgeonc. • 10'%
Figure 3. pE-pH plots of Fe, Mn and Hg species
-------
PH»
-4 -2
PE
LOG tPB<-2)
* 2H20 • PW2(S) » 4H% 2t"
PH»
PE
LOG (CO+3/CO+2)
LOG (CH20/C03--)
-10
-s.
0
i •
PH»
LOG (S— /S04--)
10 12
CO,'2 • «H* * 4«"
CHjO (iq)
— • S'2 * *HjO
Figure 4. pE-pH plots of Pb, Co, C03 and S species
-------
-10 -I 0 I 10
PH»
124
LOG (N03
-/NH3)
e u 12
PH»
-M -II
-< -2 « 2 < «
LOG (H
202)
ro
PH:
-4-2 I 2 4 6 - B 10 12
LOG (SN-M/SN+2)
Sn** —-• Sn** + 2t"
'•A
-8-4-20 2 4 B
PE
LOG (FE+3)
Figure 5. pE-pH plots of NH3, H202, Sn and Fe species
-------
PH»
-10
LOG CMM+2)
•.«*«) —- * * «" *
PH»
-• -4
LOG (MN+2)
»*2«ttf —• H»»(O«) (s) »»*«§•
CO
PH»
LOG (CR04--7CR+3)
Cr* «
— — Clfl,"1 * •»*•!•"
PH»
-a i
LOG (S —)
ii a
Figure 6. pE-pH plots of Mn, Cr and S species
-------
Iflb IS. IQc 156 M. lie Mb
Me
3
7
B
PH»
4
3
2
1
0
^,-z
B -4 -2 0 2 4 6 8 10 12
PE
• - til. S cone. - IO"'N
. - b - ttl. S cone. • lO'^l
LOG (S4-2/S-2) c-ttl. Scone. -10-%
4S'2 — — S4'2 + t»~
•5 0 5 10
9
B
7
6
PH»
3
2
1
0
C"T
S -4 -2 « 2 4 6 ' 6 ' 10 ' 12
PE
LOG CCU+2/CU+)
Cu'2
10i I0b lit 10c 1S6 20i lie 206
i
B
7
6
PH»
4
3
2
0
V'
6-4-20 2 4 E B 10 12
PE
i - ttl. Scone. • 10''n
b - ttl . S cone. • 10'T4
LOG (S,"2/S~2) c - ttl. S cone.- 10""^
PH'
-4 -2
PE
LOG (CU+)
MS)
Figure 7. pE-pH plots of S and Cu species
-------
Appendix A. Input data sheets.
CJ1
Reference Guess
Number free cone
Case 1 Use 2
Case 3 Case 4
Case 5
Case 6 Case 7
Case 8 Case 9
Case 10
-------
on mi
1
2
3
4
5
6
7
8,9
10
1
T"
,
|
!
1
!!2|l3|M|lS
!
16
[l7J18J19lSii
1
1
pi 22
!
1
|
24125
( 1
1
1
i
t6b7l28i29!M
i
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100 X log K Stolcnlome'try stoUhjometryStolchiomet
for 3rd ot metal In of surface Inot H* In
complex 3rd coin) I ex Jrd complex 3rd complex
'> 100 X log K.StolcMometryilstolchlometrylStolclifametrv
Ninber of , for 1st °* "*tal "i bf surface tnlof H* in
complexes complex 1st complex fflst complex list complex
100 X loo K ktotchlometry StoichlouelrylStolchlometry
for 2nd »' metal "n ' ard!urf«ce if of H* In
complex ^nd complex IZno compTex 2nd complex
-------
100 X los K stolchloMtryilijoKhloTOlryStolcMoMt
for 2nd 18* "ewlin int surface Irlof H* In
corotex 2nd co»o\ex .Znd cpmolex Ijml torajltx
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for 3rd ~tot metal In Hof surface infof IT in
(j! Ads, surf, cds.13
O Metal adsorb^
tion cards
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-80-049
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
REDEQL-EPAK, Aqueous Chemical
Program
Equilibrium Computer
5. REPORT DATE
May 1980 issuinoidate
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Sara E. Ingle, Jim A. Keniston, D. W. Schults
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
200 S.W. 35th Street, Corvallis, Oregon
10. PROGRAM ELEMENT NO.
A31B1A
11. CONTRACT/GRANT NO.
97330
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory
Office of Research and Development
UoS. Environmental Protection Agency
200 S.W. 35th Street, Corvallis, Oregon
13. TYPE OF REPORT AND PERIOD COVERED
In-house July 1977 - Nov.1979
14. SPONSORING AGENCY CODE
97330
EPA/600/02
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This user's guide is a companion to the previously published report A User's
Guide for REDEQL.EPA which explains the use of a computerized chemical equilibrium
program for metals and ligands in aqueous systems. Changes in this guide include
temperature correction for equilibrium constants and activity coefficients, cal-
culations of degree of saturation for selected solids, attainment of an electrically
neutral solution, and the use of an adsorption routine. Use of the program in-
cluding these modification is illustrated with a sample case of river water.
Also included in the guide are sample input data sheets and illustrations of
redox reactions under various pH and redox conditions.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI f-'ield/Group
Chemical equilibrium
Chemical speices
Metals
Ligands
Computer program
Adsorption
Oxidation-reduction
Chemical Precipitation
Chemical complexation
Aquatic equilibra
07/B,C,D,
08/H
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
60
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
ft U. S. GOVERNMENT PRINTING OFPICE; 1980-699-121 / 193 REGION 10
51
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