COMPLEXATION KINETICS IN HUMIC COLLOIDAL SYSTEMS

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complexation kinetics
in humic colloidal systems
martina klucáková pavla žbánková miloslav pekar
Brno University of Technology Faculty of
Chemistry Institute of Physical and Applied
Chemistry
Humic Science Technology VIIIMarch 16-18,
2005Northeastern University Boston, MA, USA
2
why...?

• interaction of metal ions with humic acids
• toxicity of natural systems
• carry on previous study (Cu2)
• etc.

Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
3
location...?
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
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material...?

• lignitic humic acid
• raw material South-Moravian lignite
• isolation alkalic extraction (NaOH)

C at. H at. N at. S at. O at. COOH mmol/g total acidity mmol/g
40.3 41.0 1.5 0.4 16.8 3.27 4.04
normalized on dry ash-free HA
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
5
experimental...?
humic sols
0.1-1.0 g/L
humic gels
17 HA
Co2
Ni2
0.01 - 0.20 M
physical chemical interactions
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
6
humic sols
previous results 0.2 M (Cu2) 1 g/dm3 (HA) I
0.1 M (sol)
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
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humic sols
0.2 M (Co2)
0.2 M (Ni2)
1 g/dm3 (HA) I 0.1 M (sol)
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
8
differences...
Co2 Ni2
Cu2
conductivity and pH increases stop in
the same moment
conductivity increases while
pH-value is constant
DH 110-6 mol/L 810-7 mol/L
DH 310-5 mol/L
pH increasing is slower than in the case of
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
9
humic sols
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
10
humic sols
Ni2 (0.01M)
sol (1 g/L)
sol (0.1 g/L)
0.01M Me2 conductivity decreases (sol 0.1 1
g/L) I 0.1 M
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
11
humic sols
sol (1 g/L)
Ni2 (0.01 M)
Ni2 (0.20 M)
I 0.5 M (sol 0.1 1 g/L) ? no minimum on
pH-curve
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
12
humic gels
gel
Co2 (0.01 M)
Co2 (0.20 M)
gel ? no minimum on pH-curve conductivity only
increases (Me2 0.01 0.20 M)
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
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humic sols gels
summary reaction
H2R Me2 MeR 2H

t 0 a b
0 h t gt 0 a x
b x x h 2x t ?8
0 b a a
h 2a
2nd order kinetic rate equation
dx / dt k (a-x) (b-x)
kt 1 / (b-a) ln a(b-x) / (b(a-x))
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
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humic sols gels
apparent rate constants sols (0.1 g/L I 0.1 M)
c0 mol/L Ni2 Co2 Cu2
0.08 1.46 ? 10-5 7.89 ? 10-5 2.02 ? 10-5
0.10 4.39 ? 10-6 6.38 ? 10-5 1.05 ? 10-5
0.15 1.13 ? 10-6 2.25 ? 10-6 2.66 ? 10-6
0.20 2.98 ? 10-7 8.88 ? 10-7 5.21 ? 10-7
b gtgt a
m3/mol.s
apparent rate constants gels
c0 mol/L Ni2 Co2 Cu2
0.08 1.12 ? 10-4 1.78 ? 10-4 1.67 ? 10-4
0.10 7.41 ? 10-5 1.64 ? 10-4 1.56 ? 10-4
0.15 5.23 ? 10-5 9.29 ? 10-5 9.13 ? 10-5
0.20 3.69 ? 10-5 7.92 ? 10-5 4.48 ? 10-5
m3/mol.s
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
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humic gels
diffusion from constant source

• one-dimensional diffusion
• T, p const. D ? D (c)

example Ni2
t 0 x ??0 L? c1 0
t ? 0 x 0 c1 c1,s const.
t ? 0 x L / 2 ?c1 / ?x 0
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
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humic gels
diffusion from constant source (24 h)
Def m2/s Dtab m2/s
Ni2 8.18 ? 10-10 1.32 ? 10-9
Co2 7.98 ? 10-10 1.46 ? 10-9
Cu2 1.07 ? 10-9 1.43 ? 10-9
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
17
humic gels
diffusion from time-variable source
example Co2
24 h
0.20 M
Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
18
conclusions...

• complex interaction mechanism HA - metal ions
• non-ideal kinetics
• diffusion-affected interaction with humic gel
• .

Humic Science Technology VIII, March 16-18,
2005, Northeastern University, Boston, MA, USA
19
thanks