Visualization of the UF polarized layer by holographic interferometry

Experimental study of concentration polarization in a crossflow reverse osmosis system using Digital Holographic Interferometry

“…This image is the interferogram finally studied. Methodology to obtain the concentration profile from the interferograms was described in previous papers [19,24].…”

“…As the relationship between refractive index and concentration of the solutions is known, interference fringes can be converted into a concentration profile. Methodology for this conversion has been described in previous papers [19,24]. It can be observed that, the higher the CF velocity, the flatter the concentration profile and the lesser the concentration at the membrane surface.…”

“…In previous papers [17,[19][20][21][22][23][24], the optical holographic interferometry technique was used to visualize the evolution of the concentration polarization layer during UF of BSA and PEG solutions, as well as RO of salts. This technique, which has also been used to study diffusion processes [25][26], allows interferometric fringe patterns to be obtained, that are indicative of changes in the optical path followed by the light and are related to changes in the refractive index.…”

Properties of Filter Cake in Cake Filtration and Membrane Filtration

“…Gowman and Ethier [38] used an automated, laser-based refractometric experimental technique for the measurement of concentration and concentration gradient in the concentration polarization layer during deadend ultrafiltration of the biopolymer hyaluronan. Fernández-Torres et al [39] obtained the evolution of concentration profiles during BSA ultrafiltration in an unstirred cell using the technique of holographic interferometry. Their results demonstrated that a filter cake was actually formed during BSA ultrafiltration.…”

Pore size analysis from retention of neutral solutes through nanofiltration membranes. The contribution of concentration–polarization

“…Knowing that the flow is "a priori" trivially measured, and retention values could be calculated from concentration at both sides. However, due to the concentration polarization effect, to measure real concentrations on the membrane surfaces, although possible, would require complex experimental techniques [5][6][7][8][9]. Some of these techniques are, for example: interferometric measurements of the concentration polarization profile in an unstirred batch cell [10,11], light deflection techniques (shadowgraphy, refractometry), magnetic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 -3-resonance imaging, radio isotope labeling, electron diode array microscope or direct pressure measurements as is reviewed in [12].…”