Obrada voda naprednom osmozom

Forward osmosis is osmotically driven membrane process that uses the osmotic pressure gradient to encourage the flux of water through a semi-permeable membrane from feed solution (low osmotic pressure) to draw solution (high osmotic pressure). Transportation of water molecules allows a balance between the two systems. This paper explains the challenges related to forward osmosis such as: external and internal concentration polarization, reverse solute diffusion and membrane fouling. The most effective ways, so far, to reduce these problems are also described. Requirements that the draw solution should fulfill are numerous: high osmotic pressure, minimal reverse diffusion, low molecular weight and low viscosity, easy recovery, easy manipulation, compatibility with the membrane and zero toxicity. In addition, there are requirements for an ideal membrane: they must provide a high flux of water, high rejection of substances from the feed solution and the draw solution, low concentration polarization, high chemical resistance, high mechanical robustness and low fouling. Therefore, different osmotic agents and membranes that more or less meet these requirements, have been developed. Forward osmosis as new technology has different applications, some of which can be highlighted: desalination, wastewater treatment, food and pharmaceutical industry and power generation.