Dewatering Oil Sands Tailings with Degradable Polymer Flocculants

Abstract

We synthesized hydrolytically degradable cationic polymers by micellar radical polymerization of a short-chain polyester macromonomer, polycaprolactone choline iodide ester methacrylate (PCLChMA) with two polyester units, and used them to flocculate oil sands mature fine tailings (MFT). We evaluated the flocculation performance of the homopolymer and copolymers with 30 mol % acrylamide (AM) by measuring initial settling rate (ISR), supernatant turbidity, and capillary suction time (CST) of the sediments. Flocculants made with trimethylaminoethyl methacrylate chloride (TMAEMC), the monomer corresponding to PCLChMA with n = 0, have improved performance over poly(PCLChMA) at equivalent loadings due to their higher charge density per gram of polymer. However, MFT sediments flocculated using the PCLChMA-based polymers are easier to dewater (up to an 85% reduction in CST) after accelerated hydrolytic degradation of the polyester side chains. This study demonstrates the potential of designing cationic polymers that effectively flocculate oil sands tailings ponds, and also further dewater the resulting solids through polymer degradation.

Multifunctional CO2‐switchable polymers for the flocculation of oil sands tailings

“…The Dean−Stark extraction method was used to determine the amount of solids, water, and bitumen in the MFT sample (Table ). The details of this method are described elsewhere . In brief, the method is based on extractive distillation in which water in the tailings sample is vaporized by the boiling solvent, then condensed and collected in a calibrated trap.…”

“…The novel approaches of using thermoresponsive polymers, hydrophobically modified polymers, grafted or degradable polymers, can add multifunctionality to the flocculant and improve its flocculation performance in tailings . Although thermoresponsive polymers that reversibly change from hydrophilic (for efficient flocculation of the MFT) to hydrophobic (for efficient release of the water captured in the sediments) are promising, their implementation in the field remains a challenge because the energy costs associated with switching thermoresponsive polymers from hydrophilic to hydrophobic limit their large‐scale implementation .…”

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

“…Gumfekar et al. synthesized a similar flocculant with an average of two polycaprolactone units in the methacrylic ester side chain, poly(PCL 2 ChMA), to facilitate degradation at lower temperatures and shorter times . To validate the phenomenon of hydrolytic degradation of polyester side chains in poly(PCL 2 ChMA), they compared the flocculation performance with a structurally similar, yet hydrolytically non‐degradable poly(trimethylaminoethyl methacrylate chloride) [poly(TMAEMC)].…”

“…Comparison of capillary suction time obtained using degradable poly(PCL 2 ChMA) and non‐degradable poly(TMAEMC), before and after the degradation. Reproduced with permission . Copyright 2017, American Chemical Society.…”

Using Polymer Reaction Engineering Principles to Help the Environment: The Case of the Canadian Oil Sands Tailings

“…26 Following up the initial promising results with the kaolin-based model tailings, 26 we investigated the influence of copolymer structure on MFT flocculation behavior. 27 In order to make a homopolymer with both appreciable cationic density and hydrophobic content, while still maintaining its hydrolytic degradation characteristics, we adjusted the average number of degradable units in the polyester side chain to 2 (PCL 2 ChMA). We also investigated the influence of copolymerizing PCL 2 ChMA with PAM.…”