Modeling Henry's law and phase separations of water–NaCl–organic mixtures with solvation and ion-pairing

Wilson, Aaron D.; Foo, Zi Hao; Jayasinghe, Ashini S.; Stetson, Caleb; Lee, Hyeonseok; Rollins, Harry W.; Deshmukh, Akshay; Lienhard, John H.

doi:10.1039/d3cp02003g

Cited by 2 publications

(1 citation statement)

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“…Adding NaCl to a multiphase mixture of water and DME causes a rapid reduction in both the aqueous-phase DME content and the organic-phase water content. Small ions, such as sodium and chloride, preferentially interact with the more polar components of multisolvent mixtures. − Strong interactions between sodium and chloride ions and water “salt out” DME (Figure a inset) as the proportion of free water molecules available to solvate DME molecules decreases and molecular structure in the bulk water phase increases. − Furthermore, preferential interactions between the Na + and Cl – ions and water lead to its depletion from the organic phase. Consequently, the addition of NaCl leads to a simultaneous increase in the electrolyte-free water mole fraction in the aqueous phase false( x H 2 normalO ′ a q false) and a decrease in the electrolyte-free water mole fraction false( x H 2 normalO ′ o r g false) .…”

Section: Fluid Phase Equilibrium Calculationsmentioning

confidence: 99%

Electrically Powered High-Salinity Brine Separation Using Dimethyl Ether

Deshmukh,

Wilson,

Lienhard

2024

Ind. Eng. Chem. Res.

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Dewatering highly saline aqueous streams, from mining and geothermal leachates to industrial wastewater, is essential for effective resource recovery and safe disposal. Membraneless water extraction (MWE) uses a lowpolarity solvent to separate water from concentrated aqueous solutions. In this study, we design a new MWE that uses dimethyl ether (DME) to selectively extract water from high-salinity brines, leveraging the volatility of DME to achieve rapid solvent recovery. By separating water and dissolved salts at a liquid−liquid interface, MWE minimizes the deleterious effects of scaling on vulnerable membrane and heat exchanger surfaces, reducing the need for extensive pretreatment and expensive materials. We begin by developing a computational framework for a multistage counterflow liquid−liquid contactor, which extracts water into DME, coupled with a multistage solvent regenerator that uses vapor compression to efficiently separate the desalinated water from the DME extractant. Excess Gibbs free energy and equation of state frameworks are used to model fluid phase equilibria in water−DME−sodium chloride (NaCl) mixtures, with interaction parameters estimated from experimental data. Incorporating equilibrium calculations into a system-scale computational model, we examine the performance of MWE using DME for the first time. Our analysis demonstrates that MWE can concentrate seawater desalination brine (>1.0 mol NaCl kg −1 ) to zero-liquid discharge salinities, with an energy consumption of under 50 kW h per m 3 of water extracted with a solvent recovery ratio greater than 99.9%. We highlight the importance of staging the vapor compression process to simultaneously minimize energy consumption while enabling brine concentration and product water solvent contamination. The thermodynamic framework developed here allows for the robust evaluation of new MWE solvents and systems for critical brine concentration and fractional precipitation applications.

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