Understanding the behaviour of dodecylamine as a model cationic collector in oil sands tailings dewatering applications using a novel FTIR based method

Tailings treatment technology is currently being developed at Syncrude Canada Ltd. (SCL) that involves adding a cationic surfactant (collector) to fluid fine tailings (FFT) in order to alter clay surfaces from hydrophilic to hydrophobic and promote faster dewatering. To understand the behaviour and effects of cationic collectors, a robust analytical method for measuring concentrations of aliphatic amine collectors in aqueous samples was developed. Dodecylamine (DDA) was used as the model collector molecule for this study. The method involves a liquid-liquid extraction with dichloromethane (DCM) at basic pH followed by Fourier transform infrared (FTIR) detection of the primary amine N─H stretch of DDA at ~3382 cm^?1. This method was successfully used to measure DDA in the matrices of recycled oil sands process affected water (RCW) and FFT. The optimized method was then used to understand the behaviour of DDA in a number of geochemical environments that could occur during tailings treatment. Analysis of the solubility of DDA in RCW found that the solubility of DDA increases with decreasing pH, while increasing temperature increased the solubility of DDA to a lesser degree. The solubility of DDA in RCW at its natural pH of 9.16 was found to be 4.22 mg · kg^?1. Lastly, preliminary tests verified that FFT solids have a high relative DDA adsorption capacity and that the current standard DDA dosage used at SCL of 650 g/t, is effective as all the DDA was found tightly bound to clay surfaces with no excess DDA left in the water, even under acidic conditions.