Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines

Craig Turchi, Li Tang, Arpita Iddya, Xiaobo Zhu, Alexander Dudchenko, Wenyan Duan, Johann Vanneste, Tzahi Cath, David Jassby

Research output: Contribution to journalArticlepeer-review

86 Scopus Citations

Abstract

The desalination of inland brackish groundwater offers the opportunity to provide potable drinking water to residents and industrial cooling water to industries located in arid regions. Geothermal brines are used to generate electricity, but often contain high concentrations of dissolved salt. Here, we demonstrate how the residual heat left in spent geothermal brines can be used to drive a membrane distillation (MD) process and recover desalinated water. Porous polypropylene membranes were coated with a carbon nanotube (CNT)/poly(vinyl alcohol) layer, resulting in composite membranes having a binary structure that combines the hydrophobic properties critical for MD with the hydrophilic and conductive properties of the CNTs. We demonstrate that the addition of the CNT layer increases membrane flux due to enhanced heat transport from the bulk feed to the membrane surface, a result of CNT's high thermal transport properties. Furthermore, we show how hydroxide ion generation, driven by water electrolysis on the electrically conducting membrane surface, can be used to efficiently dissolve silicate scaling that developed during the process of desalinating the geothermal brine, negating the need for chemical cleaning.

Original languageAmerican English
Pages (from-to)38594-38605
Number of pages12
JournalACS Applied Materials and Interfaces
Volume9
Issue number44
DOIs
StatePublished - 8 Nov 2017

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

NREL Publication Number

  • NREL/JA-5500-68957

Keywords

  • carbon nanotubes
  • electrochemical cleaning
  • membrane distillation
  • silicate scaling

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