Water and solute transport across cellulose acetate membranes in the treatment of soybean whey by reverse osmosis

Abstract

AbstractIn processing full‐fat soy flour to produce an acid‐precipitated lipid protein concentrate, there results a by‐product whey fraction which, because of its high biological oxygen demand, represents a serious disposal problem. Processing of food waste streams by reverse osmosis has received considerable attention because of its low theoretical energy requirement, since no phase change is involved. A series of statistically designed and analyzed experiments were conducted on a pilot‐plant reverse osmosis unit to study the effect of the operating parameters on solute and solvent transport in cellulose acetate membranes. Sucrose and sodium chloride solutions were tested in addition to soybean whey to relate the mixed solute system in whey to that of single‐solute organic and inorganic feed solutions. Water flux was shown to have an Arrhenius dependency on temperature, and some membrane compaction was observed with the more porous membrane. Concentration polarization for sucrose and sodium chloride solutions increased linearly with water flux. Solute flux for soybean whey solutions decreased with molarity and was independent of pressure, whereas solute rejection increased with temperature and pressure and was independent of molarity. Good agreement was obtained using the derived parameters A, B, and τ for soy whey in the diffusion transport model when compared to the observed experimental values.