Oleate Flotation of a Nigerian Baryte: The Relation between Flotation Recovery and Adsorption Density at Varying Oleate Concentrations, pH, and Temperatures

Abstract

Crude Nigerian baryte was floated with sodium oleate as collector at varying oleate concentrations, pulp pH, and temperatures. Using “pure” baryte selected from the crude baryte, oleate adsorption densities at the baryte–water interface were determined also at varying oleate concentrations, pulp pH, and temperatures, using electrical conductivity measurements. The specific surface area of the pure baryte powder was determined using the method of adsorption of paranitrophenol in aqueous solution. The variation of oleate adsorption density and flotation recovery of baryte with oleate concentration, pulp pH, and temperature was studied. At ambient temperature (29°C) and pulp pH (8.2) flotation recovery of baryte increased with increasing oleate adsorption density, to a maximum recovery at the critical micelle concentration of sodium oleate. Flotation recovery increased with increasing adsorption density to about 100% recovery at maximum oleate adsorption density at pH 9.0 to 10.0 in the region of the zero point of charge (zpc) of the Nigerian baryte and to about 100% recovery and maximum oleate adsorption density at the temperature range 30 to 40°C, also at the zpc of the baryte. It is considered that oleate chemisorbs onto the Nigerian baryte predominantly at ambient temperature and up to 40°C; above 40°C the chemisorbed species probably dissociate from the mineral surface while the primary mode of adsorption becomes physical processes.