Nitrogen-containing polymers as potent ionogens for aqueous solutions of switchable ionic strength: application to separation of organic liquids and clay particles from water

Abstract

Polymeric tertiary amines react reversibly with CO₂ in the presence of water to form trialkylammonium-bicarbonate polyelectrolytes. These polyamines are useful as ionogens for “switchable water”, meaning an aqueous solution having switchable ionic strength. The performance of the polymeric ionogens in two different water purification applications was evaluated. Moderate results were obtained in the salting out of organic contaminants from aqueous solutions with up to 77% of CH₃CN forced out from a 1 : 1 (w/w) mixture of CH₃CN–H₂O. However, very promising results were obtained in the sedimentation of clay particles. A notable enhancement in both the settling time required and the supernatant turbidity was observed even with low loadings of the polymers (>10 ppm). The addition of CO₂ is required for the polymers to induce settling. Dimethylamino-functionalized polymethyl methacrylate proved to be the best polymer evaluated thus far in this process. In addition to enhancing the settling of both kaolinite and montmorillonite suspensions at different concentrations, it was also successfully shown to enhance the settling of oil sand tailings.