(466f) DFT Calculations for Solvent Extraction Desalination: Electrostatic Potential, Hydrogen Bonding, and Solvation Free Energy

There is a need for improved desalination technologies in order to treat naturally-occurring and industrial brines [1]. Current options generally include membrane-based processes, such as reverse osmosis (RO) [2], as well as thermal- or evaporation-based processes like multi-stage flash (MSF) and multi-effect distillation (MED) [3]. However, these relatively mature technologies are challenging to deploy in developing regions, due to a variety of limitations: the evaporative processes involve high energy consumption, both processes require advanced support infrastructure and large centralized installations [4], and the operation and maintenance of membrane systems can be prohibitively expensive [5].

Solvent extraction desalination (SED) is an alternative membrane-free desalination technology, which only requires low grade, low temperature heat, and it is ideally suited to processing high-concentration brines. However, new solvents are still needed that can improve the molecular-level water selectivity, while minimizing solvent contamination in the aqueous phase. Improvements in solvent design for SED require a fundamental understanding of the molecular interactions governing solvation behavior. Herein, quantum chemical calculations are used to delineate different fundamental interactions in water-solvent systems involving 38 different solvents, with a particular focus on the role of the electrostatic potential characteristics. These interactions are rigorously analyzed using the independent gradient model based on Hirshfeld partition (IGMH), Symmetry-Adapted Perturbation Theory (SAPT), as well as the energy decomposition analysis based on force field (EDA-FF) to compare against a standard force field model. The solvation free energies and partition coefficients are also calculated to estimate water extraction performance in a bulk solvent system.

References:

[1] D.L. Shaffer, L.H. Arias Chavez, M. Ben-Sasson, S. Romero-Vargas Castrillón, N.Y. Yip, M. Elimelech, Desalination and Reuse of High-Salinity Shale Gas Produced Water: Drivers, Technologies, and Future Directions, Environ. Sci. Technol. 47 (2013) 9569-9583.

[2] L. Malaeb, G.M. Ayoub, Reverse Osmosis Technology for Water Treatment: State of the Art Review, Desalination 267 (2011) 1-8.

[3] A.D. Khawaji, I.K. Kutubkhanah, J.-M. Wie, Advances in Seawater Desalination Technologies, Desalination 221 (2008) 47-69.

[4] G. Ni, S.H. Zandavi, S.M. Javid, S.V. Boriskina, T.A. Cooper, G. Chen, A Salt-Rejecting Floating Solar Still for Low-Cost Desalination, Energy Environ. Sci. 11 (2018) 1510-1519.

[5] S. Alotaibi, O.M. Ibrahim, S. Luo, T. Luo, Modeling of a Continuous Water Desalination Process Using Directional Solvent Extraction, Desalination 420 (2017) 114-124.