Effect of Sodium Citrate on the Aggregation of Bitumen Droplets

The bitumen droplet size is a key factor affecting recovery in mined oil sand extraction. In this study, we investigate the impact of sodium citrate (Na(3)Cit), a secondary processing aid, on the bitumen droplet size after the oil sand liberation process. By developing a model mixing system, we found that Na(3)Cit facilitates the aggregation of midsized droplets of similar to 50-100 mu m to form larger droplet flocs of similar to 500-600 mu m. To unveil the underlying mechanism, we further studied the size evolution of emulsified bitumen droplets under different water chemistries using focused beam reflectance measurement and smart online particle analysis technology. The results further confirmed that Na(3)Cit can facilitate droplet aggregation; typically, an optimum dosage could be identified, above which the beneficial effect on aggregation started to decrease and eventually became detrimental. The impact of Na(3)Cit on the bitumen droplet size may be attributed to the interplay of three major factors: slime coating, surface properties, and surface forces under different water chemistries. This research indicates that larger bitumen flocs can be formed at an optimum Na(3)Cit concentration, which in turn results in a higher bitumen flotation and increased bitumen recovery.