Synder Nanofiltration Membranes
Background
In the concentration of whey protein, the byproduct generated is a salty lactose solution. This lactose can be concentrated with a nanofiltration membrane for use in the food, pharmaceutical, and brewing industries. Synder offers two different NF membranes, the NFX (150-300Da) and the NFW(300-600Da), which were both tested for effectiveness in concentrating and desalting a simulated lactose feed stream.
Test 1: NFX
Feed Solution, Membrane, and Operating Conditions
| Feed Solution | |
| Material | Simulated Sweet Whey UF Permeate |
| Lactose Concentration | 4% |
| Salt Concentration (NaCl) | 0.5% |
| pH | 6-7 |
| Synder Membrane | |
| Element | NFX-2B-2540HM |
| Spacer Size (mil) | 31 |
| Surface Area (ft2) | 27 |
| Operating Parameters | |
| Inlet Pressure (PSI) | 220 |
| Pressure Drop (PSI) | 10 |
| Temperature (°C) | 22-28 |
| Cross Flow Rate (GPM) | 10 ± 0.3 |
| Feed Volume (Gal) | 25 |
Results
Conductivity and TOC were measured to evaluate the NFX’s performance in both concentrating lactose and rejecting salt. The performance is summarized below.
| Filtration Results | |
| Trial Time (min) | 50 |
| Lactose Concentration Factor | 3.5 |
| Lactose Concentration in Resulting Feed | 14% |
| Salt Concentration Factor | 1.06 |
| Initial Permeate Flux (GFD) | 35 |
| Average Permeate Flux (GFD) | 21 |
| Overall Lactose Rejection (%) | >98.5 |
Test 2: NFW
Synder’s NFW membrane was also tested in a constant volume diafiltration mode where DI water was added to the feed stream with an equal amount of permeate water extracted from the demineralization process. The operating conditions and membrane specification are listed below. The feed solution is a simulated UF permeate from sweet whey protein separation process, which contains 8% lactose and 0.44% sodium chloride.
Feed Solution, Membrane, and Operating Conditions
| Feed Solution | |
| Material | Simulated Sweet Whey UF Permeate |
| Lactose Concentration | 8% |
| Salt Concentration (NaCL, ppm) | 4400 |
| pH | 7-8 |
| Synder Membrane | |
| Element | NFW-2B-2540HF |
| Spacer Size (mil) | 31 |
| Surface Area ( ft2) | 28 |
| Operating Parameters | |
| Inlet Pressure (PSI) | 140 |
| Pressure Drop (PSI) | 10 |
| Temperature (°C) | 22-28 |
| Crossflow Rate (GPM) | 9.5 ± 0.3 |
| Feed Volume (Gal) | 10 |
Results
| Filtration Results | |
| Total Volume of DI Water Used (Gal) | 18 |
| Trial Time (min) | 93 |
| Salt Dilution Factor | 5.7 |
| Salt Concentration in Final Feed (ppm) | 770 |
| Initial Permeate Flux (GFD) | 17.4 |
| Average Permeate Flux (GFD) | 11.6 |
| Overall Lactose Rejection (%) | 94.5 |
- The permeate flux is displayed as a function of time during the demineralization process with the NFW membrane. The time intervals where the flux recovered correspond to the addition of DI water to the feed.
Conclusion
Both the NFX and NFW membranes were effective in concentrating lactose from simulated UF permeate. The NFX performs better with respect to overall lactose yield, while the NFW offers a better balance of lactose yield and salt passage through the membrane. The NFW achieves excellent fractionation of lactose and salt while operating at lower pressures than typical NF membranes. These results suggest that Synder’s NF membranes are well suited for multiple types of lactose concentration.
