4. Recent development of forward osmosis:
As mentioned above, FO technology is faced by several challenges that limit its application in large scale processes. The development of FO process can be governed by two major factors; the development of high-performing draw solutions and highly efficient FO membrane.
4.1. Draw solutes development:
The draw solution has several factors that can affect FO performance. These factors mainly comprise of draw and feed solution osmotic pressures [61], draw solute solubility, temperature, concentration of draw solution, draw solute molecular weight and particle size. An ideal solution’s osmotic pressure was given by Van’t Hoff equation as follows [3]:
Where n is the number of mole of dissociated solutes species in the solution, c is the solute concentration in g/L, MW is the solute molecular weight, R is the gas constant and T is the solution absolute temperature in Kelvin.
One study concluded that the above equation is limited to extremely dilute solutions and it can be used for …show more content…
Based on its performance, the high ranking draw solutes are calcium chloride (CaCl2), potassium hydrogen carbonate (KHCO3), magnesium chloride (MgCl2), and sodium hydrogen carbonate (NaHCO3), while based on cost replenishment, they can be ranked as KHCO3, magnesium sulfate (MgSO4), sodium chloride (NaCl), NaHCO3, and sodium sulfate (Na2SO4) [66]. Although, NaHCO3, KHCO3, and MgSO4 were rated high and can be considered for FO process, there uses are limited due to the fact that they might pose scaling threats. NaCl was found to be the most widely draw solute in different applications [64]. This may be due to saline water is plentiful on earth, making seawater a natural and cheap source of draw solution. In addition, NaCl is can re-concentrate with RO process with minimum scaling problems, also it is high soluble in water and has high osmotic
As mentioned above, FO technology is faced by several challenges that limit its application in large scale processes. The development of FO process can be governed by two major factors; the development of high-performing draw solutions and highly efficient FO membrane.
4.1. Draw solutes development:
The draw solution has several factors that can affect FO performance. These factors mainly comprise of draw and feed solution osmotic pressures [61], draw solute solubility, temperature, concentration of draw solution, draw solute molecular weight and particle size. An ideal solution’s osmotic pressure was given by Van’t Hoff equation as follows [3]:
Where n is the number of mole of dissociated solutes species in the solution, c is the solute concentration in g/L, MW is the solute molecular weight, R is the gas constant and T is the solution absolute temperature in Kelvin.
One study concluded that the above equation is limited to extremely dilute solutions and it can be used for …show more content…
Based on its performance, the high ranking draw solutes are calcium chloride (CaCl2), potassium hydrogen carbonate (KHCO3), magnesium chloride (MgCl2), and sodium hydrogen carbonate (NaHCO3), while based on cost replenishment, they can be ranked as KHCO3, magnesium sulfate (MgSO4), sodium chloride (NaCl), NaHCO3, and sodium sulfate (Na2SO4) [66]. Although, NaHCO3, KHCO3, and MgSO4 were rated high and can be considered for FO process, there uses are limited due to the fact that they might pose scaling threats. NaCl was found to be the most widely draw solute in different applications [64]. This may be due to saline water is plentiful on earth, making seawater a natural and cheap source of draw solution. In addition, NaCl is can re-concentrate with RO process with minimum scaling problems, also it is high soluble in water and has high osmotic