Direct osmosis

Liberman, B. (2004) Methods of direct osmosis membrane cleaning online for... 

McCutcheon, J.R., McGinnis, R.L. and Elimelech, M. (2005) A novel ammonia-carbon dioxide forward (direct) osmosis desalination process. Desalination, 174, 1-11. 

Cath, T.Y., Adams, D. and Childress, A.E. (2005) Membrane contactor processes for wastewater reclamation in space II. Combined direct osmosis, osmotic distillation, and membrane distillation for treatment of metabolic wastewater. Journal of Membrane Science, 257 (1—2), 111-119. 

Direct osmosis 50 Good 1-5 Yes High High Low Under development... 

Bequdy, E.G. and Lampi, K.A. Membrane technology for direct osmosis concentration of fruit juices. Food Technol., 44, 121, 1990. 

Donnan dialysis and diffusion dialysis techniques are used [30] to deacidify and concentrate actinide bearing acidic solutions. Near complete deacidification could be achieved from 8 M nitric acid solutions with a high decontamination factor for the actinides. With cation-exchange membranes, the deacidification is accomphshed by the build up of neutralized salt in the feed. With an anion-exchange membrane, the feed acidic solution is deacidrfied free of salt buildup. By superimposing direct osmosis with free deacidiflcation, it was simultaneously possible to concentrate the deacidified actinide solution [30]. 

Some of the stated advantages of direct osmosis in comparison with other drying processes include minimized heat damage to color and flavor, less discoloration of fruit by enzymatic oxidative browning, better retention of flavor compounds, and less energy consumption since water can be removed without change of phase. However, products cannot be dried to completion solely by this method and some means of stabilizing them is required to extend their shelf lives. 

Direct osmosis of different fruits at 70°Bx sugar at atmospheric and low pressure (about 70 mmHg) revealed higher drying rates with the latter. The addition of a small amount of NaCl to different osmotic solutions increased the driving force of the drying process. 

R.A. Khaydarov, R.R. Khaydarov, Solar powered direct osmosis desahnation. Desalination 2007, 217, 225-232. 

Forward osmosis (FO) is a membrane-separation process that uses osmotic pressure difference between a concentrated draw solution and a feed stream to drive water across a semipermeable membrane [63]. The basis of FO is osmosis, a natural and spontaneously occurring process. It is strictly direct osmosis across an RO membrane. A draw solute of high osmotic pressure, e.g., ammonium carbonate passes across one side of the FO membrane, and a high salinity solution, e.g., seawater flows across the other side of the membrane, as shown in Figure 1.17. Water transfers from the seawater to the draw solute side due to osmotic flow. It is then necessary to regenerate the draw solute and recover the water transferred by the FO process, e.g., in a distillation unit. The primary challenge is... 

York RJ, Thiel RS, Beaudry EG (1999) Full-scale experience of direct osmosis concentration applied to leachate management. In The seventh international waste management and landfill symposium (Sardinia 99). S. Maigheaita di Pula, Cagliari... 

It is important to stress again that MD is not purely a mass transfer operation in the way that, for example, direct osmosis is, because heat transfer is also a very important element of the process due to the water evaporation at the feed side and water condensation at the extract side. In this case, a simultaneous heat and mass transfer takes place through the membrane. Simultaneously here means that the heat transfer and mass transfer are intimately connected the heat transfer rate depends on mass flux and vice versa. 

McCutcheon, J. R.., R. L. McGinnis, and M. Ehmelech, A Novel Ammonia-Carbon Dioxide Forward (Direct) Osmosis Desahnation Process, Desalination, 174,2005 (pages 1-11). 

Figure 11.5 illustrates the principle of reverse osmosis. An appropriate membrane is used to separate a concentrated saline solution (A) from a more diluted solution (B). The difference in chemical potential tends to make the water pass from the low potential compartment to one with the higher the potential (direct osmosis) the latter... 

Fig. 11.5. Principle of reverse osmosis (Guimberteau et ah, 1989) (a) direct osmosis (b) osmotic equilibrium (OP = osmotic pressure) (c) reverse osmosis (P = pressure greater than osmotic pressure)...

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