In this osmotic distillation program we will develop high water flux hydrophobic and organophobic non-porous coating for microporous hydrophobic membranes that should have sufficient water vapor transport and should eliminate significant concern for membrane wetting out. Enhanced system design will minimize concentration polarization.
Concentration of fruit juices is a valuable unit operation. The current preferred method of juice concentration is triple effect evaporation. This technique cannot concentrate to high (75%) solids content without (1) developing a burnt taste to the sugar content and (2) driving off the low molecular weight hydrocarbons that provide most of the flavor and aroma difference between fresh and frozen concentrated juice. The need for a gentler process continues to be a major need associated with juice concentration. While membrane processes (reverse osmosis, ultrafiltration) offer excellent opportunity for avoiding exposure to high temperature they have complications associated with irreversible interactions between membrane and juice components. Osmotic distillation (popular term for isothermal membrane distillation) is a process for removing water by water vapor transport across a non-wetted microporous membrane using concentrated salt solution to dewater the juice. While this process works well initially, surfactants and oils in juices tend to wet out the membrane, plus high viscosity concentrate builds up at surface, and performance is lost.
High water flux non-porous hydrophobic/organophobic membranes should eliminate wetting out for osmotic distillation. The successful development of non-wetting osmotic distillation membranes should provide a valuable uni operation for developing high concentrations of various fruit juices with mininal loss in quality. Therefore almost all juices (orange, apple, grape-wine, tomato, etc.) can be prepared cost-effectively as concentrate with no significant loss in performance.