Basic principles of osmosis and osmotic pressure

This book brings together a number of engineering process technologies, which all have the principle of osmotic pressure, or rather differences in osmotic pressure between two solutions, at the heart of their operation. For instance, reverse osmosis requires the application of hydraulic pressure at a magnitude greater than the difference between the feedwater and the permeate water to allow membrane flux to occur against the osmotic pressure gradient. Conversely, in forward osmosis osmotic pressure gradients are harnessed to allow permeate flow from the feedwater to a draw solution of greater osmotic potential. In this chapter, we outline the general principles of osmosis and osmotic pressure, which underpin the technologies discussed in more detail later in this book.