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complexation kinetics. in humic colloidal systems. martina klučáková pavla žbánková miloslav pekař. Brno University of Technology Faculty of Chemistry Institute of Physical and Applied Chemistry. Humic Science & Technology VIII March 16-18, 2005 Northeastern University Boston, MA, USA.

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slide1

complexation kinetics

in humic colloidal systems

martina klučáková

pavla žbánková

miloslav pekař

Brno University of Technology

Faculty of Chemistry

Institute of Physical and Applied Chemistry

Humic Science & Technology VIIIMarch 16-18, 2005Northeastern University

Boston, MA, USA

slide2

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

slide3

lignite mine

location...?

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

slide4

material...?

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

normalized on dry ash-free HA

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

slide5

experimental...?

0.1-1.0 g/L

humic sols

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

slide6

Cu2+ + HR CuR+ + H+

2CuR+ CuR2 + Cu2+

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

slide7

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

slide8

differences...

Co2+&Ni2+

Cu2+

conductivity and pH increases stop in the same moment

conductivity increases while pH-value is constant

D[H+]

1×10-6 mol/L

8×10-7 mol/L

D[H+]

3×10-5 mol/L

pH increasing is slower than in the case of

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

slide9

MeCl2 Me2+ + 2Cl-

Me2+ + 4H2O Me(OH)2 + 2H3O+

HR + H2O H3O+ + R-

2H2O H3O+ + OH-

Me2+ + R- MeR+

Me2+ + HR + H2O MeR+ + H3O+

2MeR+ MeR2 + Me2+

MeR+ + HR + H2O MeR2 + H3O+

MeR+ + R- MeR2

humic sols

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

slide10

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

slide11

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

slide12

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

slide13

humic sols & gels

summary reaction:

H2R + Me2+ MeR + 2H+

t = 0a b 0 h

t>0 a – x b – x x h + 2x

t ∞ 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

slide14

humic sols & gels

apparent rate constants: sols (0.1 g/L; I = 0.1 M)

b>> a

[m3/mol.s]

apparent rate constants: gels

[m3/mol.s]

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

slide15

humic gels

diffusion from constant source

  • one-dimensional diffusion
  • T, p = const.; D D (c)

example: Ni2+

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

slide16

humic gels

diffusion from constant source (24 h)

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

slide17

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

slide18

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

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