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

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 in this paper, 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.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [3] ; ORCiD logo [1]
  1. Univ. of California, Riverside, CA (United States). Dept. of Chemical and Environmental Engineering
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. Colorado School of Mines, Golden, CO (United States). Dept. of Civil and Environmental Engineering
Publication Date:
Report Number(s):
NREL/JA-5500-68957
Journal ID: ISSN 1944-8244
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 9; Journal Issue: 44; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G)
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; membrane distillation; silicate scaling; carbon nanotubes; electrochemical cleaning
OSTI Identifier:
1408810

Tang, Li, Iddya, Arpita, Zhu, Xiaobo, Dudchenko, Alexander V., Duan, Wenyan, Turchi, Craig, Vanneste, Johann, Cath, Tzahi Y., and Jassby, David. Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines. United States: N. p., Web. doi:10.1021/acsami.7b12615.
Tang, Li, Iddya, Arpita, Zhu, Xiaobo, Dudchenko, Alexander V., Duan, Wenyan, Turchi, Craig, Vanneste, Johann, Cath, Tzahi Y., & Jassby, David. Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines. United States. doi:10.1021/acsami.7b12615.
Tang, Li, Iddya, Arpita, Zhu, Xiaobo, Dudchenko, Alexander V., Duan, Wenyan, Turchi, Craig, Vanneste, Johann, Cath, Tzahi Y., and Jassby, David. 2017. "Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines". United States. doi:10.1021/acsami.7b12615. https://www.osti.gov/servlets/purl/1408810.
@article{osti_1408810,
title = {Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines},
author = {Tang, Li and Iddya, Arpita and Zhu, Xiaobo and Dudchenko, Alexander V. and Duan, Wenyan and Turchi, Craig and Vanneste, Johann and Cath, Tzahi Y. and Jassby, David},
abstractNote = {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 in this paper, 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.},
doi = {10.1021/acsami.7b12615},
journal = {ACS Applied Materials and Interfaces},
number = 44,
volume = 9,
place = {United States},
year = {2017},
month = {10}
}