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

摘要

A series of multifunctional homopolymer and copolymer of 2-dimethylamino ethyl methacrylate (DMAEMA) and N-isopropyl acrylamide (NIPAM) were designed and used to flocculate oil sands mature fine tailings (MFTs). Carbon dioxide (CO2) protonated the tertiary amine groups of P(DMAEMA) and P(DMAEMA-NIPAM) making their chains positively charged. The pH sensitivity of these polymers favored the flocculation of the negatively charged clays in MFT due to charge neutralization. Three different polymers, P(DMAEMA), P(NIPAM(33)-DMAEMA(67)), and P(NIPAM(67)-DMAEMA(33)) were synthesized via aqueous free-radical polymerization and used to flocculate MFT in the presence of CO2. Experimentally, CO2 was introduced in the system in three different ways: (1) CO2 was first bubbled into polymer solution, then the polymer solution was added to MFT, (2) CO2 was first bubbled into MFT and then the CO2-free polymer solution was added to MFT, and (3) both polymers and MFT were bubbled with CO2 separately, then mixed together. We compared the effects of the method of CO2 addition, copolymer composition, and polymer molecular weight on MFT flocculation performance. Our results indicate that CO2-switchable polymers can be employed to enhance the dewatering of challenging wastewaters such as oil sands tailings. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47578.