Contact

Siriwan Dulnee
Molecular Structures

PhD thesis


Sorption and interfacial redox of Sn(II) under anoxic conditions


PhD student:
Siriwan Dulnee
Supervisor:
Dr. Andreas Scheinost (HZDR)
Division:
Molecular Structure
Period:
05/2010–04/2013


Motivation of work:

The presence of a long half-life Sn-126 (250,000 yr) from nuclear fission is a potential concern in nuclear waste management, so sorption and migration behavior needs to be well understood to predict its risk in a long term. But the redox state (di- or tetravalent) under the expected anoxic conditions is still a matter of debate., and thermodynamic speciation of Sn is still lacking of agreement in the exiting literatures especially under neutral pH and low Cl. We therefore investigated the stability of Sn(II) in the presence of a highly redox-reactive mineral, magnetite (FeIIFeIII2O4), as functions of pH and time. The experiments were performed at < 2 ppm O2, and redox state and local structure was monitored over time by X-ray absorption spectroscopy (XAS).

Objectives:

  1. To study sorption behavior of Sn(II) on nano-magnetite as a function of pH and time.
  2. To study interfacial redox of Sn(II) by using active-redox magnetite.
  3. To model Sn surface complexation by Monte Carlo and nonlinear optimization program of PEST with PHREEQC.

Contact

Siriwan Dulnee
Molecular Structures