Abstract
HypothesisCation exchange membranes (CEMs) are subject to fouling when utilized to desalinate wastewater from the oil and gas industry, hampering their performance. The kind and extent of the fouling are most likely dependent on the composition of the stream, which in practical applications can vary significantly. ExperimentsFouling experiments were performed on commercial cation exchange membranes, which were used in electrodialysis runs to desalinate solutions of varying composition. The variations included ionic strength, type of ions, amount of viscosifying polyelectrolyte (partially hydrolyzed polyacrylamide), presence of crude oil, and surfactants. Performance parameters, like electric potential and pH, were monitored during the runs, after which the membranes were recovered and analyzed. FindingsFouling was detected on most CEMs and occurred mainly in the presence of the viscosifying polyelectrolyte. Under normal pH conditions (pH ~ 8), the polyelectrolyte fouled the concentrate side of the CEMs, as expected due to electrophoresis. However, by applying a current in the opposite direction, the polyelectrolyte layer could be removed. Precipitation occurred mostly on the opposite side of the membrane, with different morphology depending on the feed composition.
Highlights
Polymer-flooding produced water (PFPW) is a by-product of industrial oil and gas production, especially when viscous polymeric solutions are pumped into the underground to increase the oil or gas recovery
Under the influence of the electric field, hydrolyzed polyacrylamide (HPAM) migration leads to formation of a gel layer on the concentrate side of the Cation exchange membrane (CEM)
The gel layer does not interfere significantly with the transport of charge through the membrane, which is translated in a minimal increase in the trans-membrane electric potential (TMEP)
Summary
Polymer-flooding produced water (PFPW) is a by-product of industrial oil and gas production, especially when viscous polymeric solutions are pumped into the underground to increase the oil or gas recovery. Among the two types (cationic and anionic) of ion exchange membranes (IEMs) used in an electrodialyzer, research has suggested that the anion exchange membrane (AEM) suffers most severe from fouling when desalinating PFPW [3,4] because many organic compounds in PFPW, including the partially hydrolyzed polyacrylamide (HPAM) used as a viscosifier, are negatively charged at neutral pH. These compounds move towards the anode under the electric field (electrophoresis) and deposit mainly on the positively charged AEM surface due to attractive electrical interactions [5]. The majority of studies have been dedicated to (prevent) fouling on this kind of membranes [6,7,8]
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