The solvent extraction of metal chelates has been used for a long time for separation and determination of metal ions. The first quantitative description of the extraction process was, however, not made until 1941 when Kolthoff and Sandell compared experimental data with theoretical predictions for the extraction of metal dithizonates. They found that the theory they proposed was valid under wide experimental conditions. However, the systems used by Kolthoff and Sandell were simple ones and hence relatively simple theory was used to successfully explain their behaviour. In practice solvent extraction systems are complicated by other factors, e.g. hydrolysis, polymerisation and complex formation in the aqueous phase. It has subsequently become apparent that such factors have an important influence on the solvent extraction of chelates. Several authors have published reports since 1941 on the theory of solvent extraction of metal chelates which take these factors into account. In particular two publications by Irving, Rossotti and Williams and Stary (chapter 3) should be noted for their comprehensive treatment of the subject. The influence of these factors will be discussed in the following sections.

An investigation into the chemistry of solutions of titanium dioxide in fused alkali metal borates has been made, with the emphasis on the ability of the alkali borate melts to dissolve TiO2 and subsequently crystallize TiO2 and/or complex alkali metal titanates. The preparation and properties of potassium titanates with K2O/TiO2 mol ratio ≤1 has been studied. In addition the thermal decomposition of potassium hexafluorotitanate monohydrate (reported to yield potassium tetratitanate) has been investigated. The decomposition product has been identified as an oxyfluorotitanate. The compounds crystallized on slow cooling of alkali borate + TiO2 melts have been identified. The titanium containing product(s) have been correlated with the concentration of borate groups containing non-bridging oxygens, which depends on the alkali metal cation. Phase diagrams for the M2O.B2O3 + TiO2 (M = Na, K) systems have been obtained. Mass transport in M2O.2B2O3 + TiO2 (M = Li, Na, K) systems has been studied, via measurements of electrical conductivity, as a function of temperature and TiO2 concentration. Additional information on the alkali borate melts has been obtained from measurements of the optical basicity of M2O + B2O3 (M = Li, Na, K, Rb, Cs) glasses, using Pb(II) as probe ion. The results of these measurements have confirmed that the nature of the alkali metal cation significantly affects the basicity of fused alkali borate solvents. Extraction of TiO2 from ilmenite and titaniferous slag, using selected low-basicity alkali borate solvents has been attempted. The results indicate that TiO2 may be separated from ilmenite in essentially a one-step process.

The solvent extraction of metal chelates has been used for a long time for separation and determination of metal ions. The first quantitative description of the extraction process was, however, not made until 1941 when Kolthoff and Sandell compared experimental data with theoretical predictions for the extraction of metal dithizonates. They found that the theory they proposed was valid under wide experimental conditions. However, the systems used by Kolthoff and Sandell were simple ones and hence relatively simple theory was used to successfully explain their behaviour. In practice solvent extraction systems are complicated by other factors, e.g. hydrolysis, polymerisation and complex formation in the aqueous phase. It has subsequently become apparent that such factors have an important influence on the solvent extraction of chelates. Several authors have published reports since 1941 on the theory of solvent extraction of metal chelates which take these factors into account. In particular two publications by Irving, Rossotti and Williams and Stary (chapter 3) should be noted for their comprehensive treatment of the subject. The influence of these factors will be discussed in the following sections.

An investigation into the chemistry of solutions of titanium dioxide in fused alkali metal borates has been made, with the emphasis on the ability of the alkali borate melts to dissolve TiO2 and subsequently crystallize TiO2 and/or complex alkali metal titanates. The preparation and properties of potassium titanates with K2O/TiO2 mol ratio ≤1 has been studied. In addition the thermal decomposition of potassium hexafluorotitanate monohydrate (reported to yield potassium tetratitanate) has been investigated. The decomposition product has been identified as an oxyfluorotitanate. The compounds crystallized on slow cooling of alkali borate + TiO2 melts have been identified. The titanium containing product(s) have been correlated with the concentration of borate groups containing non-bridging oxygens, which depends on the alkali metal cation. Phase diagrams for the M2O.B2O3 + TiO2 (M = Na, K) systems have been obtained. Mass transport in M2O.2B2O3 + TiO2 (M = Li, Na, K) systems has been studied, via measurements of electrical conductivity, as a function of temperature and TiO2 concentration. Additional information on the alkali borate melts has been obtained from measurements of the optical basicity of M2O + B2O3 (M = Li, Na, K, Rb, Cs) glasses, using Pb(II) as probe ion. The results of these measurements have confirmed that the nature of the alkali metal cation significantly affects the basicity of fused alkali borate solvents. Extraction of TiO2 from ilmenite and titaniferous slag, using selected low-basicity alkali borate solvents has been attempted. The results indicate that TiO2 may be separated from ilmenite in essentially a one-step process.

Universiẗat, Diss., 2005--Marburg.

Univ., Magisterarbeit, 2007--Frankfurt (Main)

Techn. Universiẗat, Diss., 2006--Darmstadt.

Univ., Wirtschafts- und Sozialwiss. Fak., Diss.--Rostock, 2006.

Univ., Diss./97--Tübingen, 1996. / Literaturverz. S. [331] - 341 und Index.

Univ., Diss.--Freiburg (Breisgau), 1996.