Correlation between the adsorption of sodium dodecyl sulphate on calcium fluoride (fluorite) and its floatability — An infra-red internal reflection spectrophotometric study

The adsorption of sodium dodecyl sulphate (DSNa) on the surface of calcium fluoride and fluorite was investigated by means of internal reflection spectroscopy in the infra-red range of the spectrum. Samples of calcium fluoride in the form of thin layers evaporated onto the surface of germanium reflection elements, and samples of calcium fluoride and fluorite in the form of finely ground powders were used. As was stated, dodecyl sulphate anions are chemisorbed onto the surfaces of fluoride and of calcium fluoride. Halimondtube flotation experiments showed that a good floatability of calcium fluoride is obtained in the range of concentrations (up to about 1 × 10^?3 mol.dm^?3) where the surface is covered by the chemisorbed product. For concentrations higher than about 1.24 × 10^?3 mol.dm^?3 precipitation of calcium dodecyl sulphate has been observed, accompanied by an abrupt decrease in floatability. The adsorption is greatly affected by the presence of calcium ions and impurities in the solution.