Enhancing the dewatering of oil sands mature fine tailings by coagulation-flocculation and pressure filtration with tannic acid-mediated polymeric complex network

This study presents a new method to improve the dewatering efficiency of oil sands mature fine tailings (MFT) by pressure filtration using a tannic acid-mediated polymeric complex network as a flocculant. It was found that the prior addition of tannic acid ahead of poly(ethylene oxide) and ferric chloride significantly increased the vacuum filtration rate by improving the permeability of the filter cake and reducing its specific resistance to filtration. The beneficial role of tannic acid was investigated by slurry shear stress, sedimentation, floc morphology and size distribution measurements, and UV-Vis and FTIR spectroscopic characterization. Results indicated that tannic acid acted as a crosslinker to complex with both poly(ethylene oxide) and ferric chloride to develop a tricomponent polymeric network. Within the network, numerous hydrogen bonds and coordination bonds enabled a sufficient crosslinking density, resulting in higher floc strength and compression resistance. Flocs generated by the tannic acid-mediated polymeric network were more rigid with an expanded structure, allowing drainage channels to remain open in the filter cake for better permeability. Scale-up experiments on a Millipore pressure filtration unit verified the beneficial role of tannic acid in filtering the mature fine tailings, achieving a much higher net water release rate and cake solid content.