Experimental and computational analysis of R152a hydrate-based desalination: A promising solution for hypersaline brine treatment

Abstract

This study addressed the treatment of hypersaline brine, specifically solutions containing 5.0 wt% and 10.0 wt% NaCl, by exploring the use of 1,1-difluoroethane (C2H4F2, R152a) hydrate-based desalination (HBD). The thermodynamic stability of R152a hydrates under hypersaline conditions was experimentally measured and predicted utilizing the Hu-Lee-Sum correlation. Powder X-ray diffraction analysis confirmed that the crystal structure of R152a hydrates (structure I) remained unchanged under hypersaline brine conditions. Hydrate growth kinetics and desalination efficiency were investigated under various temperature driving forces (ΔT = 2 K, 3 K, and 5 K) to elucidate the impact of temperature variations on hydrate growth rates and salt removal capabilities. Elevated temperatures resulted in slower growth rates but yielded higher desalination efficiency. Furthermore, molecular dynamics simulations provided microscopic insights into the mechanisms underlying these observations. Molecular dynamics analyses of hydrate growth and ion diffusion demonstrated that at lower temperatures, ion movement slowed down, leading to more ions being trapped within the hydrates. Additionally, free energy calculations corroborated that Na+ ions were more easily removed than Cl- ions due to their lower free energy barriers. This study highlights the potential of R152a HBD as a sustainable solution for hypersaline brine treatment, emphasizing the necessity for further optimization and development to fully realize its practical applications.