Transport of salts and monoethylene glycol (MEG) during electrodialysis desalination of industrial hypersaline MEG wastewater

Abstract

The rapid development of deep water gas fields exploitation has generated large amounts of hazardous waste in the form of monoethylene glycol (MEG) wastewater, raising major environmental and public health concerns. Desalination process is a key step in waste MEG reclamation system. In this study, electrodialysis (ED) was evaluated as an alternative technology for removing salts from the stream. The transfer behaviors of salts and MEG in the ED process were examined, which would aid in facilitating desalination depending on the applications. The results indicated that MEG transport was mainly attributed to salt flux-induced cotransport and it was clearly relative in operating parameters as well as MEG percentage. In a single-batch ED process, the relationship between MEG and mixed salt fluxes decreased nonlinearly. Also, the MEG flux was positively related to the initial MEG percentage in feed solution. In a continuous ED system, the MEG flux increased exponentially with incrementally increased salt flux, which was attributed to a hydrogen-bonding effect between hydrated ions and MEG molecules. The MEG transport percentage only ranged from 0.29 to 1.60% when salt removal ratio was from 56.3 to 89.0%. This investigation provided prospects and guidance for recovering valuable nonelectrolytes from various salt-containing waste streams.