PRINT; -status false
PHASES
 Ferrihydrite;  Fe(OH)3 + 3H+ = Fe+3 + 3H2O; log_k 4.891
RATES
 CaEdta
# E is short for Edta...
# Reactions:  FeOH-E + Ca = Ca-E + FeOH  &  Zn-E + Ca = Ca-E + Zn
#
# d(Ca-E)/dt = k_f1 * [FeOH-E] * [Ca+2] - k_b1 * [Ca-E} * [FeOH+2]
#  +  k_f2 * [Zn-E] * [Ca+2] - k_b2 * [Ca-E} * [Zn+2]
#
# k_f1 = 10 /s.   k_b1 = K_FeOH-E/K_Ca-E * k_f1 
# k_f2 = 1200 /s. k_b2 = K_Zn-E/K_Ca-E * k_f2
#
# parms: 1= k_f1. 2= K_FeOH-E. 3= K_Ca-E. 4= k_f2. 5= K_Zn-E.
 -start
 10 k_b1 = parm(1) * parm(2) / parm(3)
 12 FeE = kin("FeEdta")
 20 rate = parm(1)*FeE*act("Ca+2") - k_b1 * m * act("FeOH+2")
 30 k_b2 = parm(4) * parm(5) / parm(3)
 32 ZnE = kin("ZnEdta")
 40 rate = rate + parm(4)*ZnE*act("Ca+2") - k_b2 * m * act("Zn+2")
 50 moles = rate * time
 60 save -moles
 70 put(moles, 1)
 -end

 ZnEdta
# Reactions:  FeOH-E + Zn = Zn-E + FeOH  &  Ca-E + Zn = Zn-E + Ca
# d(Zn-E)/dt = ... as for CaEdta
#
# parms: 1= k_f1. 2= K_FeOH-E. 3= K_Zn-E. 4= k_f2. 5= K_Ca-E.
 -start
 10 k_b1 = parm(1) * parm(2) / parm(3)
 12 FeE = kin("FeEdta")
 20 rate = parm(1)*FeE*act("Zn+2") - k_b1 * m * act("FeOH+2")
 30 k_b2 = parm(4) * parm(5) / parm(3)
 32 CaE = kin("CaEdta")
 40 rate = rate + parm(4)*CaE*act("Zn+2") - k_b2 * m * act("Ca+2")
 50 moles = rate * time
 60 save -moles
 70 put(get(1) + moles, 1)
 -end

 FeEdta
# Initially from waste stream, otherwise by mass balance...
 -start
 10 save get(1)
 -end

SOLUTION 1 Simplified Glatt river water
 pH 7.9; pe 12 O2(g) -0.68;
 Fe 0.2e-3 Ferrihydrite -1.69
# Run file with Ca or Zn crossed out, adapt step...
 Ca 1.83
# Zn 91.8e-6

KINETICS 1
 -step 432 in 50                                # for Ca, 0.12 hr
# -step 21.6e6 in 50                            # for Zn, 6000 hr
# -step 3.6e6 in 50                      # for Zn and Ca, 1000 hr

 CaEdta; -formula Ca 1; m0 0; -parms 10 3.09e21 2.51e12 1200 1.1e17
 ZnEdta; -formula Zn 1; m0 0; -parms 10 3.09e21 1.1e17 1200 2.51e12
 FeEdta; -formula Fe 1; m0 6e-8
 -tol 1e-12
 -cvode true
INCREMENTAL_REACTIONS true

EQUILIBRIUM_PHASES 1; Ferrihydrite -1.69
USER_GRAPH
 -head hours FeEdta CaEdta ZnEdta
 -axis_titles Hours mol/L
 -init false
 -start
 10 graph_x total_time / 3600
 20 graph_y kin("FeEdta"), kin("CaEdta"), kin("ZnEdta")
 -end
END