Effects of polymeric surfactants on the crystallisation of inorganic materials

Doctoral thesis, 2003

This thesis concerns effects of polymeric surfactants on the crystal growth of inorganic structures. The crystal growth of calcium carbonate on steel surfaces was studied with a heat exchanger cell and with an electrochemical method. Two copolymeric surfactants, differing in hydrophobic / hydrophilic ratio, were synthesised and their effect on the crystallisation was investigated. It was found that the more hydrophobic of the polymers prevented CaCO3 crystallisation most efficiently. The same results were obtained with the electrochemical method. Lignin, a biopolymer occurring naturally in wood, was evaluated in the heat exchanger cell and its efficiency as an antiscalant was assessed. Lignin had a similar antiscaling efficiency as poly(acrylic acid), but it had only a minor effect on which polymorph that formed. In the second part of this thesis, synthesis of CaCO3, SrCO3, Ag and CdS with the use of liquid crystalline phases as templates, is described. Synthesis of CaCO3 was made in a hexagonal and reverse hexagonal phase. With both phases it was possible to obtain CaCO3 crystals of very small dimensions and corresponding high specific surface areas, 8 nm in diameter and 226 m2/g, respectively. A similar method was used to synthesise SrCO3. It was discovered that a high specific surface area of SrCO3 (232 m2/g) was only achievable with a reversed hexagonal phase as template. The normal hexagonal phase yielded surface areas of around 36 m2/g. Synthesis of metallic silver in a reverse hexagonal phase was studied, using a slightly different method to induce crystallisation. It was found that the surfactants acted as reducing agent, forming metallic silver from an aqueous silver nitrate solution.