Navaladian Subramanian1, Adnan Qamar1, Ahmad Alsaadi1, Adair Gallo1, Muhammed Ghifari Ridwan1, Jung-Gil Lee1, Sreekiran Pillai1, Sankara Arunachalam1, Dalaver Anjum2, Felix Sharipov3, Noreddine Ghaffour1, Himanshu Mishra4. 1. King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science & Engineering Division (BESE), Thuwal 23955-6900, Saudi Arabia. 2. King Abdullah University of Science and Technology (KAUST), Core Laboratory, Thuwal 23955-6900, Saudi Arabia. 3. Departamento de Fisica, Universidade Federal do Parana, Caixa Postal 19044, Curitiba 81531-990, Brazil. 4. King Abdullah University of Science and Technology (KAUST), Water Desalination and Reuse Center (WDRC), Biological and Environmental Science & Engineering Division (BESE), Thuwal 23955-6900, Saudi Arabia. Electronic address: Himanshu.Mishra@kaust.edu.sa.
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.
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.
Authors: G A Mahadik; J F Hernandez-Sanchez; S Arunachalam; A Gallo; L Cheng; A S Farinha; S T Thoroddsen; H Mishra; Carlos M Duarte Journal: Sci Rep Date: 2020-05-08 Impact factor: 4.379