The reaction between kaolinite and neutral and acid sodium fluoride solutions was investigated at different temperatures and over the acid pH range.The stoicheiometric replacement of hydroxyls in the kaolinite crystal lattice by fluoride ions, as reported by earlier workers, was not coiifirmed. The release of hydroxyl ions into solution was due predominantly to the disruption of the kaolinite crystal lattice. In the presence of sodium ions and at pH < 7, sodium fluorosilicate and cryolite were found as solid phases. At pH > 7, only cryolite was found as a solid phase. Small, spherical, particles were observed in all cases. These particles were believed to be amorphous silica, formed as an intermediate phase in the disruption process.
The reaction between kaolinite and neutral and acid sodium fluoride solutions was investigated at different temperatures and over the acid pH range.
The stoicheiometric replacement of hydroxyls in the kaolinite crystal lattice by fluoride ions, as reported by earlier workers, was not confirmed. The release of hydroxyl ions into solution was due predominantly to the disruption of the kaolinite crystal lattice. In the presence of sodium ions and at pH < 7, sodium fluoro‐silicate and cryolite were found as solid phases. At pH > 7, only cryolite was found as a solid phase. Small, spherical, particles were observed in all cases. These particles were believed to be amorphous silica, formed as an intermediate phase in the disruption process.
The dissolution of kaolinite in aqueous solutions of hydrofluoric acid was investigated at different temperatures and fluoride concentrations. The percentage dissolution of kaolinite was greater than was to be expected from a theoretical consideration of the reaction. The percentage dissolution was less for Na‐kaolinite than for a H‐kaolinite under the same experimental conditions. Two reaction rates were observed. The relative intensities of the 001 and 002 basal reflections decreased with reaction time, temperature and hydrofluoric acid concentration. The decrease was probably due to an amorphous phase. Although kaolinite samples after treatment at the lower temperature showed very little change in their infra‐red absorption spectra, a marked change in the spectra was observed at the higher temperature. The disruption of the kaolinite crystal lattice is believed to be due to the preferential extraction of aluminium from the lattice leaving an intermediate silica phase, which dissolves to form fluorosilicic acid.
A study has been made into the effects of a low frequency semi‐corona discharge on carbon disulphide, ethyl mercaptan, amyl mercaptan and thiophene present as 1–2% sulphur/hydrocarbon mixtures. Semi‐corona discharge, which was carried out at atmospheric pressure, has resulted in the partial desulphurisation of the sulphur‐containing hydrocarbon mixtures. The efficiency of the desulphurisation was influenced by the techniques employed and by the nature of the central electrode. In almost all instances the reactions were accompanied by the formation of solid material.
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