Flotation of sodium carbonate and sodium bicarbonate salts from their saturated brines

Abstract

The flotation behavior of sodium carbonates and sodium bicarbonate has been studied with dodecyl amine hydrochloride (DAH) and sodium dodecyl sulfate (SDS) as part of a research program to evaluate the potential of flotation technology for use in the trona industry. Laboratory microflotation experiments generally show that flotation of sodium carbonate salts is possible at least to some extent with cationic (DAH) and anionic (SDS) collectors if the salt is thermodynamically stable under the prevailing experimental conditions. Anhydrous sodium carbonate does not float at any collector concentration because of its instability at the temperatures considered. Sodium carbonate monohydrate can be floated to completion with DAH and SDS at temperatures higher than 40 °C where it is thermodynamically stable but not at lower temperatures. Sodium carbonate decahydrate is difficult to float (30% yield) even at room temperature where it is thermodynamically stable. Even modest flotation of decahydrate is not possible for temperatures exceeding 32 °C under which conditions the decahydrate salt becomes unstable. In general, the sodium carbonate salts are difficult to float even when they are thermodynamically stable because of their strong water structure making influence.In contrast, strong and complete flotation of sodium bicarbonate can be achieved with both DAH and SDS at all temperatures. Such a flotation response was expected since sodium bicarbonate is stable at these temperatures and since the sodium bicarbonate salt does not promote the formation of water structure. Addition of sodium carbonate to the saturated bicarbonate solution, however, destroys the flotation of sodium bicarbonate completely. It is evident that the amount of sodium carbonate in the saturated solution is a most important parameter which controls the flotation response of sodium bicarbonate.Finally trona, sodium sesquicarbonate, the double salt of sodium carbonate and bicarbonate, was found not to float at room temperature with either the DAH or SDS collectors. These flotation results are discussed with regard to interfacial water structure as influenced by salt properties.