Effect of alkyl sulfate chain length on flocculation and flotation of barite suspensions

Abstract

The degree of flocculation of fine barite suspensions in aqueous alkyl sulfate solutions at 25 ± 2°C depended on sulfate concentration, on alkyl chain length and on whether the Krafft point for the particular sulfate was higher or lower than 25°C. For C 14-C 8 sulfates, whose Krafft point was higher than this temperature, not only was the maximum flocculation achieved at much lower surfactant concentrations than for the C 10 and C 12 sulfates, but also the average size of the aggregations was substantially greater. For the longer chain lengths, formation of hemimicelles within the double layer appears not possible since the temperature of the experiment was less than the Krafft temperature. Thus, from this and from a correlation between alkyl sulfate concentrations of maximum flocculation and rough solubilities of divalent metal alkyl sulfates, the abstraction of alkyl sulfate by barite appears to be through formation of an insoluble barium sulfate surface. Hemimicelle formation may contribute to alkyl sulfate adsorption for the C 10 and C 12 analogs. However, even here there is evidence, particularly for the C 12 sulfate, that maximum flocculation occurs near the solubility limit of the barium alkyl sulfate. An interesting correlation appears between the sulfate concentration of maximum aggregation of suspensions and maximum flotation of barite using alkyl sufates as collectors.