Thermomorphic Hydrophilicity Base-Induced Precipitation for Effective Descaling of Hypersaline Brines

Abstract

This study presents a novel technology, termed thermomorphic hydrophilicity base-induced precipitation (THBIP), for the effective removal of hardness ions from hypersaline brines with high-scaling propensity. THBIP utilizes thermoresponsive amine bases for the controlled precipitation of scaling constituents in alkaline conditions and subsequently uses low-temperature heat to trigger the phase separation of amine from aqueous solution, thus enabling reuse of the base. Three amines exhibiting distinct water solubility and basicity, specifically, diisopropylamine (DIPA), N-ethylcyclohexylamine (ECHA), and N,N-dimethylisopropylamine (DMIPA), were examined to identify the key parameters affecting THBIP performance. The amine bases were added to solutions containing hardness ions, Mg2+ or Ca2+, to induce the precipitation of hydroxide minerals (i.e., Mg­(OH)2(s) and Ca­(OH)2(s)). All three amines are effective in increasing solution pH, leading to high Mg2+ removals of over 90%. But because Ca­(OH)2(s) is relatively more soluble, only DIPA, which is both highly miscible in water and also the strongest base, obtained significant removal of Ca2+ ions (>33%). The observed precipitation and hardness removal are quantitatively consistent with the principles of aqueous chemistry. Using a simulated hypersaline feedwater (240 g/L total dissolved solids) of high-scaling propensity, THBIP with DIPA achieved ∼80% hardness removal. Subsequent elevation of the temperature from 15 to 70 °C triggered demixing of the thermoresponsive base from the aqueous solution, to enable liquid–liquid separation for amine reuse. The study demonstrates the proof-of-concept of using thermomorphic hydrophilicity bases as an alternative strategy to effectively reduce the scaling potential of hypersaline brines.

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

“…Solvent-driven fractional crystallization (SDFC) enables the efficient isolation and recovery of high-value metals and critical materials from brines and wastes. [1][2][3][4] In SDFC, a partially miscible organic solvent (MOS) induces fractional crystallization of dissolved inorganic ions at solid-liquid equilibrium. 5 However, unravelling the driving mechanism of solute-induced separations, is particularly challenging given the divergence of solution theory for electrolyte and non-electrolyte species.…”

Simultaneous Removal of Anionic and Cationic Species by Ionic Hydrogels via Positively Charged Complex: Adsorption Mechanism of Arsenic(V) and Chromium(III) in Highly Acidic System

“…Various methods have been proposed to address this, including chemical precipitation, ion exchange, oxidation–reduction, and adsorption. − For example, Boo et al proposed a new method, namely, thermomorphic hydrophilicity base-induced precipitation (THBIP), for the effective removal of hardness ions (Mg 2+ , Ca 2+ ) from hypersaline, which uses thermoresponsive amine bases to trigger the phase separation of amine . Geng et al recovered Mg 2+ from saline wastewater collected from a coal-fired power plant through thermomorphic hydrophilicity amines .…”

Thermodynamics of solvent-driven water extraction from hypersaline brines using dimethyl ether

“…Solvent-driven water extraction (SDWE) has the potential to efficiently desalinate highlysaline feed streams up to saturation using a partially water-miscible solvent [21][22][23][24][25][26][27][28][29][30][31][32]. In SDWE, the saline feed stream is contacted with an extraction solvent, typically an organic compound, in a liquid-liquid separator (LLS) forming two distinct liquid phases.…”