Evaluating the Potential of Superhydrophobic Nanoporous Alumina Membranes for Direct Contact Membrane Distillation

N. Subramanian, A. Qamar, A. Alsaadi, A. Gallo Jr., M. Ghifari, J.-G. Lee, S. Pillai, S. Arunachalam, D. Anjum, F. Sharipov, N. Ghaffour, H. Mishra
Journal of Colloid and Interface Science, Vol. 533, pp. 723-732, (2019)

Evaluating the Potential of Superhydrophobic Nanoporous Alumina Membranes for Direct Contact Membrane Distillation

Keywords

Superhydrophobicity, Ceramic membranes, Thermal conductivity, Hydrodynamics, Membrane distillation, Temperature polarization

Abstract

​Hypothesis

Direct contact membrane distillation (DCMD) processes exploit water-repellant membranes to desalt warm seawaters by allowing only water vapor to transport across. While perfluorinated membranes/coatings are routinely used for DCMD, their vulnerability to abrasion, heat, and harsh chemicals necessitates alternatives, such as ceramics. Herein, we systematically assess the potential of ceramic membranes consisting of anodized aluminum oxide (AAO) for DCMD.


Experiments

We rendered AAO membranes superhydrophobic to accomplish the separation of hot salty water (343 K, 0.7 M NaCl) and cold deionized water (292 K) and quantified vapor transport. We also developed a multiscale model based on computational fluid dynamics, conjugate heat transfer, and the kinetic theory of gases to gain insights into our experiments.

Findings

The average vapor fluxes, J, across three sets of AAO membranes with average nanochannel diameters (and porosities) centered at 80 nm (32%), 100 nm (37%), and 160 nm (57%) varied by < 25%, while we had expected them to scale with the porosities. Our multiscale simulations unveiled how the high thermal conductivity of the AAO membranes reduced the effective temperature drive for the mass transfer. Our results highlight the limitations of AAO membranes for DCMD and might advance the rational development of desalination membranes.

Code

DOI: 10.1016/j.jcis.2018.08.054

Sources

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