280290 Membrane Distillation with Carbon-Based Membranes
Membrane distillation (MD) is an emerging technology for water desalination, industrial wastewater and radioactive waste treatment, removal of volatile organic compounds, concentration of agro-based and organic solutions, and other separation applications. In spite of having high potentials, MD is still an emerging separation technology mainly due to the short comings of available membrane materials and limitations of existing MD systems. Available membranes are relatively expensive and cannot be used at high temperatures. Carbon-based membranes (CBMs) can be alternative types of membrane materials for the MD process. Surface chemistry of CBMs can be tailored for different MD separation or simultaneous MD separation/catalytic applications even at high temperatures under harsh chemical conditions.
Different types of carbon membranes are developed by using different support materials including porous graphite sheet, carbon nanofiber mat, porous alumina disc, and quartz fiber tissue, and coated with chemical vapor deposition of pyrolytic carbon and/or deposition of amorphous carbon by pyrolysis of sucrose. CBM were heat treated in hydrogen or grafted with methyl groups by sonication in acetone to enhance their hydrophobicity. These membranes (e.g., Figure 1) had different porosities ranging from 100 nm to 1000 nm, demonstrated high degree of hydrophobicity, and maintained their properties at temperatures up to 400 °C under harsh conditions. Membranes were characterized by water contact angle measurement, nitrogen permeability, SEM, and XPS.
The CBMs were tested in a sweeping gas MD system for water desalination at a temperature range of 50-150 °C. Developed CBMs can be potentially used for water desalination and other separation applications at elevated temperatures where the existing polymer-based membranes cannot be properly used due to structural changes and thermal decomposition effects.
Figure 1: An example of developed CBM: Pyrolytic carbon-coated tissue quartz membrane.
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