Enhanced ethylene glycol (EG)-blocking property of cation exchange membrane by layered double hydroxides modification for electrodialysis-based reclamation of EG waste fluid

Recycling toxic ethylene glycol (EG) solutions, which act as an inhibitor in the process of deep water gas fields exploitation activities, is an indispensable procedure for saving economic costs and avoid potential environmental hazards. In the recovery process, electrodialysis (ED) is an alternative technology for removing salts from high-saline EG wastewater caused by seawater infiltration. To further reduce the leakage transport of EG during ED desalination, a cation exchange membrane (CEM) layer facing the dilute cell was fabricated by electrodepositing layered double hydroxides (LDHs). Introduction of a LDH-modified layer enabled CEMs to have better EG-blocking properties without affecting cation transport, which was due to dense and hydrophilic transport channels formed by the two-dimensional (2D) lamellar structure of LDHs. This further led to differences in migration rates between hydrated cations and EG molecules. The results of ED desalination tests showed that these modified CEMs reduced the EG leakage content by 81 and 46%, compared with commercial CEMs in high saline EG solution, with EG content of 20 and 60 wt%, respectively. Therefore, this study provided new insight for the application of CEMs based on LDHs surface modification in the special ED field of EG solution desalination.

Automated summary

Recycling toxic ethylene glycol (EG) solutions is crucial for saving costs and preventing environmental hazards. Electrodialysis (ED) with a modified cation exchange membrane (CEM) was used to remove salts from high-saline EG wastewater. The modified CEM significantly reduced the leakage of EG, providing new insights for the desalination of EG solutions.