Membrane-less and Non-Evaporative Desalination of Hypersaline Brines by Temperature Swing Solvent Extraction

Abstract

Hypersaline brines are of growing environmental importance but are technologically under-served by today's desalination methods. Temperature swing solvent extraction (TSSE) is a radically different desalination technology that is membrane-less and not based on evaporative phase change. TSSE utilizes lowtemperature heat and a low-polarity solvent with temperature-dependent water solubility for the selective extraction of water over salt from saline feeds. This study demonstrates TSSE desalination of high-salinity brines simulated by NaCl solutions with three amine solvents: diisopropylamine (DIPA), N-ethylcyclohexylamine (ECHA), and N,N-dimethylcyclohexylamine (DMCHA). We show that TSSE can desalinate brines with salinities as high as ≈234000 ppm total dissolved solids (i.e., 4.0 M NaCl) and achieve salt removals up to 98.4%. Among the solvents, DIPA exhibited the highest water extraction efficiency whereas ECHA and DMCHA produced water with the lowest salt content and solvent residue content, respectively. Lastly, a high water recovery of >50% was demonstrated for TSSE desalination of 1.5 M NaCl brine using DIPA in semibatch experiments with multiple extraction cycles. This study underscores the unique capabilities of TSSE for the desalination of hypersaline brines.

Solute displacement in the aqueous phase of water–NaCl–organic ternary mixtures relevant to solvent-driven water treatment

“…The existence of an LL boundary provides an added potential for water selective solvent extraction. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] To account for the phenomenon of liquid phase separation in the conceptual models, solubility limits were imposed for the aqueous phase in eqn (1) to describe a partially-miscible organic solvent, thereby superimposing a liquid-liquid phase equilibria Fig. 5 Ternary phase diagrams examining the aqueous-rich phase of water-NaCl-MOS for: (A) DMF when plotted monomolecularly and as a dimer; and (B) alcohols, acetone and MOS that exhibited a LL boundary in addition to a LS boundary.…”

“…The organic phase will selectively extract water from a brine inducing further precipitation of a salt. This water-selective extraction [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] is a mechanism distinct from FP. Several conceptual and mathematical models have been developed to describe FP, but those models ignore these distinct mechanisms, thereby oversimplifying the process.…”

Climate Change Mitigation Strategy through Membranes Replacement and Determination Methodology of Carbon Footprint in Reverse Osmosis RO Desalination Plants for Islands and Isolated Territories

“…For example, the high-pressure pump may be at about 2.64 kWh/m 3 and the booster pump at 0.11 kWh/m 3 [3][4][5]9].…”

“…A reduction in energy consumption will have a direct impact on environmental improvement and we study this through the carbon footprint produced by these desalination plants and their ecological footprint, the latter as a future line of action [1][2][3][4][5]. To produce a quantity of water from a reverse osmosis plant, a quantity of electrical energy must be consumed, and to generate this energy, in a conventional electrical network, a quantity of emissions in the form of greenhouse gases is emitted [6][7][8][9][10][11][12]. The magnitude of these emissions depends on the set of technologies that make up the energy generation system of the electrical network to which the water production plant is connected.…”

“…Therefore, sometimes it requires a second pass of the permeate water, so practically double the number of plant membranes, if the second pass is required, in total. The permeate water has to feed a new reverse osmosis system, which is very expensive, or the system has to work with high rejection membranes in a single pass with higher pressures, i.e., consuming more energy and increasing this cost which is also one of the most significant of the variable costs of the installation [9][10][11][12].…”