Boztepe, Inci (2018) Examination of Hydrophobic/Hydrophilic Dual Layer Membranes for Membrane Distillation. Research Master thesis, Victoria University.

Abstract

Membrane Distillation (MD) is a separation technology that uses a temperature difference across a membrane to purify water. Membrane distillation has been known since the early 1960s and there are still breakthroughs to be made. Improvements in the module design or new membranes materials, such as composite membranes, are being investigated, and much research has focused on these aspects. This study focused on membrane distillation performance for direct contact membrane distillation with 5 different membranes, which included 3 hydrophobic and 2 hydrophobic/hydrophilic dual layer membranes. Their performance was modelled using mathematical modelling program MATLAB. The purpose of the study was to predict the flux and energy efficiency for membranes, and verify with the experimental work. This work extended membrane distillation 1-D modelling to dual layer membranes, which has not previously been performed. The approach of the study required membrane characterization tests to provide input parameters to the model, and also serve as parameters for explaining the flux performance of the membranes. The membrane characteristics measured were porosity, thickness, tortuosity and pore size. Membrane distillation experiments were performed at different feed and cold inlet temperatures and flowrates, and permeate fluxes for various membranes and different operating conditions were measured and analysed. The experimental results were compared with predictions from the mathematical modelling for both the single layer and dual layer membranes, and very good agreements have been found. Error was within 10% for flux and energy efficiencies between the experiments and the model. Single layer membranes’ performances were found better than dual layer membranes. The thickness of the hydrophobic layer was the highest among the other membranes, hence it affected heat and mass transfer across the membrane adversely compared to single layer membranes. Therefore, the permeate flux and energy efficiency was lower for dual layer membrane compared to single layer membranes. Better performance for single layer membranes can be attributed to their characteristics.

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