The 2SPNE SC/CE model (Bradbury and Baeyens)

//———————————————————————————————————————
// ORCHESTRA implementation of the 2SPNE SC/CE surface complexation model by Bradbury and Baeyens,

// as described in:
//
// Sorption of Eu(III)/Cm(III) on Ca-montmorillonite and Na-illite. Part 2:Surface complexation modelling
// M. H. BRADBURY,1, B. BAEYENS, H. GECKEIS, and TH. RABUNG
// Geochimica et Cosmochimica Acta, Vol. 69, No. 23, pp. 5403–5412, 2005
//
// doi:10.1016/j.gca.2005.06.031
//
// Hans Meeussen, January 2018
//———————————————————————————————————————-

The complete database file can be found: here

A complete self-contained ORCHESTRA example folder can be downloaded: here

 

//——–  The aqueous Eu species used: ——–
@species(Eu+3, 3)

@species(EuOH+2, 2)
@logKreaction(EuOH+2,    -7.2,  1.0, Eu+3, -1.0, H+,  1.0, H2O)

@species(Eu[OH]2+, 1)
@logKreaction(Eu[OH]2+, -15.1,  1.0, Eu+3, -2.0, H+,  2.0, H2O)

@species(Eu[OH]3, 0)
@logKreaction(Eu[OH]3,  -26.2,  1.0, Eu+3, -3.0, H+,  3.0, H2O)
//————————————————————–

//——–  The adsorption model ——–
//
// First we define the the “BB_surface” class, which basically is just a phase.
// There are no electrostatic or other model equations involved in this model
// The definition below should be uncommented and placed in the input (chemistry) file
//
//   @Class: BB_surface(name, parent_phase ,concentration){
//      @phase(<name>, <parent_phase>, <concentration>)
//   }
//————————————————————–

//——–  Define a default “particle” phase, which can be changed in the GUI ——–
@phase(part)
//————————————————————–

// define the components of the BB_montm model
//        modelname, parent particle, kg/kg, modeltype
@adsmodel(BB_montm,  part ,           1,      BB_surface)
//————————————————————–

//——–  Three surface sites with individual site densities (mol/kg) ——–
@surfsite(BB_montm, sOH,  2e-3, 1)
@surfsite(BB_montm, w1OH, 4e-2, 1)
@surfsite(BB_montm, w2OH, 4e-2, 1)
//————————————————————–

//——–  The site protonation reactions ——–
@surfspecies(BB_montm, sOH, sOH2+, 1)
@logKsurfreaction(BB_montm_sOH2+,    4.5,  1.0, BB_montm_sOH,  1.0, H+)

@surfspecies(BB_montm, sOH, sO-, 1)
@logKsurfreaction(BB_montm_sO-,     -7.9,  1.0, BB_montm_sOH, -1.0, H+)

@surfspecies(BB_montm, w1OH, w1OH2+, 1)
@logKsurfreaction(BB_montm_w1OH2+,  4.5,  1.0, BB_montm_w1OH,  1.0, H+)

@surfspecies(BB_montm, w1OH, w1O-, 1)
@logKsurfreaction(BB_montm_w1O-,   -7.9,  1.0, BB_montm_w1OH, -1.0, H+)

@surfspecies(BB_montm, w2OH, w2OH2+, 1)
@logKsurfreaction(BB_montm_w2OH2+,  6.0,  1.0, BB_montm_w2OH,  1.0, H+)

@surfspecies(BB_montm, w2OH, w2O-, 1)
@logKsurfreaction(BB_montm_w2O-,  -10.5,  1.0, BB_montm_w2OH, -1.0, H+)
//————————————————————–

//——– The adsorbed EU species ——–
@surfspecies(BB_montm, sOH, sO-EU, 1)
@logKsurfreaction(BB_montm_sO-EU, 0.6,  1.0, BB_montm_sOH,  1.0, Eu+3, -1.0, H+)

@surfspecies(BB_montm, sOH, sO-EUOH, 1)
@logKsurfreaction(BB_montm_sO-EUOH,    -6.2,   1.0, BB_montm_sOH,  1.0, Eu+3, -2.0, H+)

@surfspecies(BB_montm, sOH, sO-EU[OH]2, 1)
@logKsurfreaction(BB_montm_sO-EU[OH]2, -14.2,  1.0, BB_montm_sOH,  1.0, Eu+3, -3.0, H+)

@surfspecies(BB_montm, w1OH, w1O-EU, 1)
@logKsurfreaction(BB_montm_w1O-EU,      -1.4,  1.0, BB_montm_w1OH,  1.0, Eu+3, -1.0, H+)
//————————————————————–

//The CEC part according to the Gaines and Thomas convention:

//  @Class: GT_surface(name, parent_phase ,concentration){
//      @phase(<name>, <parent_phase>, <concentration>)
//   }

//********* Adsorption Model BB_CEC *******************
@adsmodel(BB_CEC, clay ,1, GT_surface)
@surfsite(BB_CEC, X, 0.87, 0)
@surfspecies(BB_CEC, X, X2-Ca, 0.5)
@logKsurfreaction(BB_CEC_X2-Ca,  0.0 ,  2.0, BB_CEC_X,  1.0, Ca+2)
@surfspecies(BB_CEC, X, X3-Eu, 0.333333)
@logKsurfreaction(BB_CEC_X3-Eu,  1.114,  3.0, BB_CEC_X,  1.0, Eu+3)
//********* End of Adsorption Model BB_CEC *************