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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: POSTER: Colloids and Nanoparticles

CPP 9.17: Poster

Montag, 26. März 2007, 16:00–18:00, Poster B

Molecular dynamics simulation of the formation of NaCl-nanoparticles in supercritical water — •Norbert Lümmen and Bjørn Kvamme — University in Bergen, Institute for Physics and Technology, Allégaten 55, N-5007 Bergen, Norway

The formation of salt particles in supercritical water happens in both natural hydrothermal environments and industrial processes. Wherever the ocean is deeper than 2800m and heat sources like intrusive basalts are present, water can attain the supercritical state and salt particle formation takes place. The plugging of reactor pipes due to salt formation is a known technological problem in the Supercritical Water Oxidation (SCWO), a proposed method to purify water contaminated with organic waste.

NaCl-nanoparticle formation in supercritical water was investigated by molecular dynamics simulations as a test case for further studies on metal salt formation. The rigid SPC/E water model was employed while the ionic interactions were treated by the model of Smith and Dang. Constant temperature was achieved by a Nosé-Hoover thermostat and the density was chosen to match a system pressure around 25 MPa at different system temperatures and sizes at constant water to ion ratio. Particle formation takes place within a few hundred picoseconds after the jump from ambient to supercritical conditions. After nucleation clusters first grow by adding monomers and later via cluster-cluster-collisions. We present results on the time development of distributions of cluster sizes, compositions, and temperatures, radial distribution functions and an estimate of nucleation rates.