Presenter
Abstract
Switchable-polarity-solvent forward osmosis (SPS-FO) is a very attractive technology for the treatment of high-salinity water because of its ability to recover a large fraction of the water from the feed solution. It involves novel sets of draw solutions called switchable-polarity solvents (SPSs), which are tertiary amines that dissolve in an aqueous phase by forming bicarbonate salts after reacting with carbon dioxide; upon the application of heat, carbon dioxide is liberated and SPSs become insoluble. The speaker will describe research with 1-cyclohexylpiperidine (CHP), an SPS with smooth switchable behavior, good chemical compatibility, and high osmotic potential. Different methods of introducing CO2 to a heterogeneous mixture of water and CHP were explored to generate a single-phase aqueous 1-cyclohexylpiperidinium bicarbonate draw solution. Membrane gas contacting was found to be an effective method for adding CO2. The solution temperature, gas pressure, solution pressure, solution flow rate, and membrane area were varied to determine and minimize mass transport and phenomena that limit the chemical reaction. Both mass transport limitations and chemical kinetic limitations were found for industrially relevant process conditions. Follow-up included designing and optimizing the gas contactor, degasser, liquid-liquid mechanical separator, forward osmosis, double staged “nanofiltration” and reverse osmosis, and a stationary polishing unit. It was concluded that the technology could significantly reduce the cost of managing the wastewater in oil and gas industries and that it has potential in other industrial water management scenarios. The research team also looked into high-temperature nanofiltration and other desalination techniques to complement the technology.