The growing need to treat more difficult effluents such as brines, utilized low value heat, reduce discharge volumes, and recover valuable resources has driven a renewed interest in membrane distillation, pervaporation desalination and ion selective membranes. While hydrophobic or superhydrophobic membranes are typically used in membrane distillation, graphene oxide (GO) layers can offer further barriers to salt transport and wetting while enhancing water transport. Unlike graphene oxide membranes used in filtration membranes, the gradient of swelling in the graphene oxide layers during pervaporation as well as cross-linking due to ions with hydroxyl groups in the GO provides quite different pathways for water transport and ion rejection. Molecular dynamics (MD) provides insights into changes of sodium rejection in the presence of divalent ions, However, appropriate module design and operational design is also critical for scale up. Many laboratory studies do not address significant heat and mass transfer issues with industrial-size modules as well as scaling at the membrane interface. Furthermore, submerged vacuum membrane distillation (S-VMD) which offer some advantages in terms of solids handling and heat distribution on the feed side has not previously been analysed as an alternative to conventional crossflow configurations. The effects of intermittent operations and temperature cycling encountered during solar thermal operations can also contribute detrimental effects on scaling beyond those encountered in steady state operations. For resource recovery, additional separation of ionic species needs to achieved. While separation of monovalent from divalent ions can be achieved via a number of means such as nanofiltration and electrodialysis, separation between monovalent ions remains extremely challenging. An example is the recovery of lithium from sodium and potassium ions. Recently, there has been an increased focus on tailoring sub-nanometer channels in metal organic framework and graphene oxide increase selectivity. A new approach using nanoclay/vermiculite (VCT) membranes in an applied electric field shows promising increases in selectivity and fast ion transport. Molecular dynamic simulation was used to understand the mechanism by which Li+ions transport through VCT nanochannels

Membrane distillation, pevaporation, and ion selective membranes for desalination and resource recovery

2019 Fall National Meeting

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