Advanced Polymer Flocculants for Solid-Liquid Separation in Oil Sands Tailings

Exploring Alternatives to Polyacrylamide: A Comparative Study of Novel Polymers in the Flocculation and Dewatering of Iron Ore Tailings

Despite being widely used in tailings treatment, polyacrylamide continues to face performance challenges. In this study, two commercial polyacrylamides with different molecular weights were used to flocculate iron ore tailings and their performance was compared with two polymers designed to treat oil sand tailings: poly(vinylbenzyl)trimethylammonium chloride and partially hydrolyzed poly(methyl acrylate) grafted onto ethylene-propylene-diene copolymer backbones. The polyacrylamide with the highest molecular weight performed better than the one with the lowest molecular weight, but its efficiency was still considerably lower than what would be desired for good solid-liquid separation. The new polymer flocculants performed better than the commercially available polyacrylamides but retained high amounts of water in the sediments. This comparison shows that polymers other than polyacrylamide may be used to treat iron ore tailings.

A review of the roles of constituent minerals and residual bitumen in the solid-liquid separation of oil sands tailings

The efficient dewatering of fluid fine tailings (FFT) generated from warm-water extraction of Canadian oil sands is a major challenge that has limited the timely reclamation of the tailings. It is generally recognized that both chemical amendments and physical/mechanical solid-liquid separation treatments are required to speed up FFT dewatering. Significant efforts have been made to enhance the rate of solid-liquid separation of FFT in the past several decades. The fact that these efforts have met with limited successes calls for a better fundamental understanding of the solid-liquid separation process. In this work, we reviewed and critically analyzed the factors that contribute to the difficult dewatering of FFT, including the role of constituent minerals and residual bitumen. In particular, the effects of mineralogical composition, mineral particle size, and the role of residual bitumen on settling rate, hydraulic conductivity, and filtration rate are reviewed and discussed. This review also points out directions to accelerate the dewatering of FFT, such as reducing the effective volume fraction of swelling clays and releasing bitumen coating from clay surfaces, that may significantly increase the filtration rate of oil sands tailings.

Albumin-loaded thermo/pH dual-responsive nanogels based on sodium alginate and poly (N-vinyl caprolactam)

During the past decades, many researchers have tried to encapsulate medicines in biopolymer nanogels as injectable medicines. In the present study, dual-responsive bovine serum albumin (BSA)-loaded nanogels prepared from sodium alginate grafted poly (N-vinyl caprolactam) (PNVCL) have been reported. First, PNVCL-g-sodium alginate (PNVCL-g-Alg) was synthesized through free radical polymerization, and then nanogels were obtained from ionic crosslinking of sodium alginate in the presence of BSA. FTIR spectra showed that PNVCL-g-Alg nanogels were successfully prepared. Turbidimetry and rheometry analyses demonstrated the cloud point temperature near the human body. Particle size was evaluated using FE-SEM and dynamic light scattering and it was found that the size of particles in dry and swollen state are about 30 and 280 nm, respectively. The effect of temperature and pH on BSA release was evaluated. By comparing the drug release behavior, we found that the release of the protein at the temperature above the cloud point is faster than that at the temperature below the cloud point. The pH sensitivity of BSA-loaded PNVCL-g-Alg was evaluated at pH 5.5 and 7.4 and showed that the drug release was faster at acidic pH than at neutral pH.

Thermoresponsive Starch for the Flocculation of Oil Sands Mature Fine Tailings

The reclamation of land and recovery of water from tailing ponds created during bitumen extraction from oil sands is a major technical and environmental challenge. In the current study, thermoresponsive hydroxybutylated (HB) corn starch (HB-CS) and potato starch (HB-PS), with lower critical solution temperatures (LCSTs) ranging from 36 to 45 °C, were examined as flocculants for oil sands mature fine tailings (MFT). The ability of different doses of the HB-CS and HB-PS to flocculate 2 and 10 wt % MFT, prepared by diluting 35 wt % MFT in tap water, in terms of the initial settling rate (ISR), supernatant turbidity (ST), sediment solids content (SSC), and water recovery (WR), was examined at temperatures below and above their LCSTs. The thermoresponsive HB-CS and HB-PS were good flocculants of MFT, and their thermoresponsive behavior was essential for optimal results in that they were considerably more effective in several aspects at temperatures above their LCSTs than below. In terms of ISRs, the HB-PS was a considerably better flocculant than the HB-CS, and this was especially so with the 10 wt % MFT. With the HB-PS, the ISR was lower when using diluted MFT prepared with tap water as opposed to simulated oil sands process water.

Evaluation of a Novel Polymeric Flocculant for Enhanced Water Recovery of Mature Fine Tailings

The novel cationic flocculant, poly(lactic acid) choline iodide ester methacrylate (poly(PLA4ChMA)), has been shown to provide improved flocculation of 5.0 wt.% mature fine tailings (MFT) diluted in deionized water compared to commercial anionic polymers, with continued dewatering of the sediment occurring as the polymer undergoes partial hydrolytic degradation. However, the elevated dosages (10,000 ppm) required would make the polymer costly to implement on an industrial scale. With this motivation, the impact of MFT loading and the use of process water is explored while comparing the settling performance of poly(PLA4ChMA) to available commercial alternatives such as anionic FLOPAM A3338. Improved consolidation of 5.0 wt.% MFT diluted with process water could be achieved at reduced dosages (500 ppm) with poly(PLA4ChMA). However, the final compaction levels after polymer degradation were similar to those achieved with the nondegradable commercial flocculants. Flocculation-filtration experiments with undiluted MFT are also conducted to compare the performance of the polymers. Significantly faster rates of water release were observed with the cationic flocculants compared to FLOPAM A3338, but no improvement in the overall tailings compaction was found either before or after poly(PLA4ChMA) degradation. Thus, the improved dewatering observed with poly(PLA4ChMA) in dilute MFT suspensions does not extend to conditions that would be encountered in the field.