Effect of Osmotic Pressure on Whey Protein Concentration in Forward Osmosis

Forward osmosis (FO) is an emerging process to dewater whey streams energy efficiently. The driving force for the process is the concentration gradient between the feed (FS) and the concentrated draw (DS) solution. Here we investigate not only the effect of the DS concentration on the performance, but also that of the FS is varied to maintain equal driving force at different absolute concentrations. Experiments with clean water as feed reveal a flux increase at higher osmotic pressure. When high product purities and thus low reverse salt fluxes are required, operation at lower DS concentrations is preferred. Whey as FS induces severe initial flux decline due to instantaneous protein fouling of the membrane. This is mostly due to reversible fouling, and to a smaller extent to irreversible fouling. Concentration factors in the range of 1.2–1.3 are obtained. When 0.5 M NaCl is added to whey as FS, clearly lower fluxes are obtained due to more severe concentration polarization. Multiple runs over longer times show though that irreversible fouling is fully suppressed due to salting in/out effects and flux decline is the result of reversible fouling only

Development of Polydopamine Forward Osmosis Membranes with Low Reverse Salt Flux

Application of forward osmosis (FO) is limited due to membrane fouling and, most importantly, high reverse salt fluxes that deteriorate the concentrated product. Polydopamine (PDA) is a widely used, easily applicable, hydrophilic, adhesive antifouling coating. Among the coating parameters, surprisingly, the effect of PDA coating temperature on the membrane properties has not been well studied. Polyethersulfone (PES) 30 kDa ultrafiltration membranes were PDA-coated with varying dopamine concentrations (0.5-3 g/L) and coating temperatures (4-55 °C). The quality of the applied coating has been determined by surface properties, water permeability and reverse salt flux using a 1.2 M MgSO4 draw solution. The coating thickness increased both with the dopamine concentration and coating temperature, the latter having a remarkably stronger effect resulting in a higher PDA deposition speed and smaller PDA aggregates. In dead‑end stirred cell, the membranes coated at 55 °C with 2.0 g/L dopamine showed NaCl and MgSO4 retentions of 41% and 93%, respectively. In crossflow FO, a low reverse MgSO4 flux (0.34 g/m2·h) was found making a very low specific reverse salt flux (Js/Jw) of 0.08 g/L, which outperformed the commercial CTA FO membranes, showing the strong benefit of high temperature PDA-coated PES membranes to assure high quality products

Apple Juice, Manure and Whey Concentration with Forward Osmosis Using Electrospun Supported Thin-Film Composite Membranes

Forward osmosis (FO), using the osmotic pressure difference over a membrane to remove water, can treat highly foul streams and can reach high concentration factors. In this work, electrospun TFC membranes with a very porous open support (porosity: 82.3%; mean flow pore size: 2.9 µm), a dense PA-separating layer (thickness: 0.63 µm) covalently attached to the support and, at 0.29 g/L, having a very low specific reverse salt flux (4 to 12 times lower than commercial membranes) are developed, and their FO performance for the concentration of apple juice, manure and whey is evaluated. Apple juice is a low-fouling feed. Manure concentration fouls the membrane, but this results in only a small decrease in overall water flux. Whey concentration results in instantaneous, very severe fouling and flux decline (especially at high DS concentrations) due to protein salting-out effects in the boundary layer of the membrane, causing a high drag force resulting in lower water flux. For all streams, concentration factors of approximately two can be obtained, which is realistic for industrial applications

Effect of osmotic pressure on whey protein concentration in forward osmosis

Forward osmosis (FO) is an emerging process to dewater whey streams energy efficiently. The driving force for the process is the concentration gradient between the feed (FS) and the concentrated draw (DS) solution. Here we investigate not only the effect of the DS concentration on the performance, but also that of the FS is varied to maintain equal driving force at different absolute concentrations. Experiments with clean water as feed reveal a flux increase at higher osmotic pressure. When high product purities and thus low reverse salt fluxes are required, operation at lower DS concentrations is preferred. Whey as FS induces severe initial flux decline due to instantaneous protein fouling of the membrane. This is mostly due to reversible fouling, and to a smaller extent to irreversible fouling. Concentration factors in the range of 1.2–1.3 are obtained. When 0.5 M NaCl is added to whey as FS, clearly lower fluxes are obtained due to more severe concentration polarization. Multiple runs over longer times show though that irreversible fouling is fully suppressed due to salting in/out effects and flux decline is the result of reversible fouling only