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Membranes used for membrane distillation (MD) inhibit passage of liquid water while allowing permeability for free water molecules and thus, for water vapour. [1] These membranes are made of hydrophobic synthetic material (e.g. PTFE, PVDF or PP) and offer pores with a standard diameter between 0.1 and 0.5 μm (3.9 × 10 −6 and 1.97 × 10 −5 ...
Membrane distillation is a water purification process that utilises a hydrophobic membrane with pores to separate water vapour from contaminants, for example, oil and unwanted chemicals. [10] The filtration efficiency and stability of the membrane can be diminished by wetting.
The liquid entry pressure (LEP) of a hydrophobic membrane is the pressure that must be applied to a dry membrane so that the liquid penetrates inside the membrane. LEP with the application in membrane distillation or pervaporation can be calculated as a first parameter to indicate how wettable a membrane is toward different liquid solutions.
The term pervaporation is a portmanteau of the two steps of the process: (a) permeation through the membrane by the permeate, then (b) its evaporation into the vapor phase. . This process is used by a number of industries for several different processes, including purification and analysis, due to its simplicity and in-line natu
Membrane distillation (MD) utilizes pressure difference from two sides of a microporous hydrophobic membrane. [21] [23] Fresh water can be extracted through four MD methods: Direct Contact (DCMD), Air Gap (AGMD), Sweeping Gas (SGMD) and Vacuum (VMD). [21] [23] An estimated water cost of $15/m 3 and $18/m 3 support medium-scale solar-MD plants.
Rare earth oxides, which are found to exhibit intrinsically hydrophobic surfaces, offer an alternative to surface coatings, allowing the development of thermally stable hydrophobic surfaces for heat exchangers operating at high temperature [65] Ultrahydrophobic desalination membranes for membrane distillation have also been fabricated for ...
This difference is due to the different methods used to measure hydrophobicity. The method used to obtain the Janin and Rose et al. scales was to examine proteins with known 3-D structures and define the hydrophobic character as the tendency for a residue to be found inside of a protein rather than on its surface.
For example, if the feed is a saturated liquid, q = 1 and the slope of the q-line is infinite (drawn as a vertical line). As another example, if the feed is saturated vapor, q = 0 and the slope of the q-line is 0 (a horizontal line). [2] The typical McCabe–Thiele diagram in Figure 1 uses a q-line representing a partially vaporized feed.