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The distribution of the species at pH are shown in Tables 6 and 7. According to the modelling calculations, the Ca ions going into solution remained constant at all pH values for the three chelating ligands, while the Pb and Zn species concentrations changed according to the pH (Table 6).

Table 6

PHREEQC speciation outputs based on the total Ca and labile Pb. Alkalinity was expressed as hydrogen carbonate in the PHREEQC input files

SpeciesHumic acid
Catechol
Tannic acid
Log (Molality)
 
 
pH = 4pH = 8pH = 4pH = 8pH = 4pH = 8
 −7.08 −4.78 −7.08 −4.90 −7.08 −4.976 
 −13.429 −7.131 −13.429 −7.249 −13.429 −7.326 
 −9.286 −7.547 −9.286 −7.136 −9.286 −7.017 
 −9.907 −7.607 −9.907 −7.723 −9.907 −7.801 
CaCO3 −14.174 −7.871 −14.174 −7.991 −14.174 −8.068 
PbCO3 −11.331 −5.591 −11.331 −5.180 −11.331 −5.061 
Ca2+ −3.858 −3.858 −3.858 −3.858 −3.858 −3.858 
Pb2+ −5.068 −5.633 −5.068 −5.102 −5.068 −4.905 
CaOH+ −12.605 −8.663 −12.605 −8.664 −12.605 −8.664 
PbOH+ −8.806 −5.368 −8.806 −4.838 −8.806 −4.642 
CO2 −4.78 −6.407 −4.78 −6.626 −4.78 −6.603 
SpeciesHumic acid
Catechol
Tannic acid
Log (Molality)
 
 
pH = 4pH = 8pH = 4pH = 8pH = 4pH = 8
 −7.08 −4.78 −7.08 −4.90 −7.08 −4.976 
 −13.429 −7.131 −13.429 −7.249 −13.429 −7.326 
 −9.286 −7.547 −9.286 −7.136 −9.286 −7.017 
 −9.907 −7.607 −9.907 −7.723 −9.907 −7.801 
CaCO3 −14.174 −7.871 −14.174 −7.991 −14.174 −8.068 
PbCO3 −11.331 −5.591 −11.331 −5.180 −11.331 −5.061 
Ca2+ −3.858 −3.858 −3.858 −3.858 −3.858 −3.858 
Pb2+ −5.068 −5.633 −5.068 −5.102 −5.068 −4.905 
CaOH+ −12.605 −8.663 −12.605 −8.664 −12.605 −8.664 
PbOH+ −8.806 −5.368 −8.806 −4.838 −8.806 −4.642 
CO2 −4.78 −6.407 −4.78 −6.626 −4.78 −6.603 
Table 7

PHREEQC speciation outputs based on total Ca and labile Zn. Alkalinity was expressed as hydrogen carbonate in the PHREEQC input files

SpeciesLog (Molality)
Humic acid
Catechol
Tannic acid
pH 4pH 8pH 4pH8pH 4pH 8
CO2 −4.708 −6.358 −4.708 −6.36 −4.078 −6.384 
 −13.419 −7.703 −13.442 −7.075 −13.422 −7.093 
 −7.078 −4.729 −7.079 −4.731 −7.079 −4.754 
 −9.256 −7.265 −9.651 −7.165 −9.796 −6.701 
 −9.742 −7.388 −9.74 −7.391 −9.738 −7.419 
ZnCO3 −12.443 −6.451 −12.837 −6.352 −12.983 −5.889 
CaCO3 −14.012 −7.658 −14.009 −7.661 −14.009 −7.69 
 −21.532 −9.193 −21.929 −9.096 −22.075 −8.652 
Ca+2 −3.86 −3.68 −3.686 −3.686 −3.686 −3.686 
CaOH+ −12.501 −8.508 −12.499 −8.498 −12.498 −8.502 
Zn+2 −4.231 −4.593 −4.628 −4.491 −4.774 −3.999 
ZnOH+ −9.394 −5.753 −9.788 −5.651 −9.934 −5.163 
Zn(OH)2 −13.178 −5.536 −13.572 −5.434 −13.718 −4.947 
 −20.666 −9.025 −21.061 −8.934 −21.207 −8.435 
 −29.431 −13.793 −29.828 −13.691 −29.974 −13.198 
SpeciesLog (Molality)
Humic acid
Catechol
Tannic acid
pH 4pH 8pH 4pH8pH 4pH 8
CO2 −4.708 −6.358 −4.708 −6.36 −4.078 −6.384 
 −13.419 −7.703 −13.442 −7.075 −13.422 −7.093 
 −7.078 −4.729 −7.079 −4.731 −7.079 −4.754 
 −9.256 −7.265 −9.651 −7.165 −9.796 −6.701 
 −9.742 −7.388 −9.74 −7.391 −9.738 −7.419 
ZnCO3 −12.443 −6.451 −12.837 −6.352 −12.983 −5.889 
CaCO3 −14.012 −7.658 −14.009 −7.661 −14.009 −7.69 
 −21.532 −9.193 −21.929 −9.096 −22.075 −8.652 
Ca+2 −3.86 −3.68 −3.686 −3.686 −3.686 −3.686 
CaOH+ −12.501 −8.508 −12.499 −8.498 −12.498 −8.502 
Zn+2 −4.231 −4.593 −4.628 −4.491 −4.774 −3.999 
ZnOH+ −9.394 −5.753 −9.788 −5.651 −9.934 −5.163 
Zn(OH)2 −13.178 −5.536 −13.572 −5.434 −13.718 −4.947 
 −20.666 −9.025 −21.061 −8.934 −21.207 −8.435 
 −29.431 −13.793 −29.828 −13.691 −29.974 −13.198 

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