In this study, a three-in-one nanoflocculent that consists of nanoparticles of titanomagnetite (NTM) grafted with multiple segments of hydrophobically modified chains of polyacrylamide (PAM) with sodium laurel sulfate (SLS) was developed for enhanced settling and dewatering of oil sands mature fine tailings (MFT). The existence of NTM allowed more than one segment to graft/functionalize (i.e., hydrophobic and hydrophilic) on the same surface. This three-in-one nanoflocculent not only provides better exposure for the functionalized species, but it also increases the nanoflocculant specific gravity and dispersibility for better interactions. The NTM was initially synthesized by the coprecipitation method and subsequently grafted with PAM and SLS at room conditions. The flocculation and dewatering performance of the as-synthesized nanoflocculants was evaluated using the initial settling rate (ISR), supernatant turbidity, sludge volume index, capillary suction time (CST), and specific resistance to filtration (SRF). Flocculation of the MFT suspension using the novel optimized nanoflocculants at 3000 ppm had 15 times faster ISR, and the supernatant turbidity, CST, and SRF had stronger outcomes than the traditionally used 20,000 ppm commercial anionic PAM. This study demonstrates the potential of designing nanoflocculants to effectively enhance settling and dewatering of oil sands tailings, while reducing the required amount of coagulants. 

Enhanced Settling and Dewatering of Oil Sands Mature Fine Tailings with Titanomagnetite Nanoparticles Grafted with Polyacrylamide and Lauryl Sulfate

Recovery of residual bitumen, dewatering, and consolidation of oil sands tailings with poly(acrylamide-co-lauric acid)

The extraction of bitumen from sand by utilizing hot water processes results in the production of a slurry waste which is stored in so called “tailings ponds”. Within these ponds, while fast settling sand particles segregate from the slurry in relatively short time, the fines fraction accumulates in the center of the pond and then settles, becoming mature fine tailings (MFT). Most of the water content of the pond is recycled back, however around 86% of the volume of MFT consist of water and it cannot be recycled. It takes a few years after placement for MFT to settle to around 35% solids. By 2008 there were about 750 million cubic meters of MFT within the tailing ponds. Assuming the tailing management remains the same, the amount of fluid tailings is expected to reach two billion cubic meters by 2034. In 2009 it was estimated that there were around 130 square kilometers of tailings ponds in the oil sand region at Canada. Thus, one of the most important environmental challenges regarding oil sands mining is developing a process to separate water from the fine tailings within a reasonable time frame, in order to allow for the reclamation of the site. Bearing in mind these problems we initiated a preliminary applied research program in order to prove the concept of speeding up sedimentation of MFT by means of nanoparticles, and more specifically by using paramagnetic nanofluids manufactured with these nanoparticles. This preliminary series of tests proved that the concept of enhancing settling of MFT by means of paramagnetic nanofluids is feasible. Clarification of samples treated with magnetic nanoparticles achieved a 50% value as compared to only a 10% clarification in the same lapse for untreated samples, while dosage of conventional flocculants resulted in erratic behavior.

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Enhanced settling of mature fine tailings (MFT) by paramagnetic nanofluids based on nanoiron

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María Florencia Goddio

Papers

Enhanced settling of mature fine tailings (MFT) by paramagnetic nanofluids based on nanoiron

A continuous method for arsenic removal from groundwater using hybrid biopolymer‐iron‐nanoaggregates: improvement through factorial designs