Description
In the dairy industry around 22 million metric tons of cheese is produced on a yearly base, with cheese whey being the biggest by-product. Approximately 80-90 kg of liquid whey is produced for every 100 kg of processed milk [1]. From this stream, many valuable components can be recovered. Lactose is one of these high-value components, which is used in multiple industries. Currently, lactose is mainly produced by crystallizing concentrate streams of whey effluent. A problem that arises in this stage is that dissolved minerals in this stream cause scaling on equipment, which in return reduce process efficiency and deteriorate product quality. Thus, demineralization is crucial for preventing scaling and achieving high product purity, particularly in the presence of significant calcium levels.In this research, we propose polyelectrolyte multilayer membranes (PEMMs) for separation of lactose from the dissolved minerals in whey effluent. To better understand the separation mechanism, we investigate how molecular interactions in whey effluent influence the demineralization. PEMMs are known for their low molecular weight cut-off and salt rejections, while maintaining a high permeability [2]. To achieve the selective separation of lactose and calcium, polyelectrolyte solutions with different ionic strengths, low for polycation and high for polyanion, were used to fabricate PEMMs by layer-by-layer dip-coating [3]. This approach aims to create multilayers with an excess of negative fixed charges, enhancing the calcium permeation. Initial experiments with PEMMs on whey effluent samples have not achieved these low salt rejections, hinting at complex molecular interactions in the stream, possibly induced by the presence of high quantities of citric acid, which can act as a chelation agent [4]. Therefore, the effect of whey effluent pH on chelation and PEMM separation properties was investigated.
This research provides valuable insights into the development of modified membranes for the selective separation of lactose and calcium. The results indicate that across pH values of 2, 6, and 8, the rejection of lactose from whey effluent consistently exceeded 90%. However, at pH levels of 6 and 8, the rejection of calcium was approximately 80%. Upon further investigation at a low pH of 2, it was observed that calcium permeation increased, resulting in a rejection rate of approximately 25%. This suggests that at lower pH levels, the degree of chelation was reduced, thereby allowing for higher calcium permeation.
This study indicates that chelation is most pronounced at higher pH levels due to increased molecule complexation in the feed, while being minimal at lower pH values. It also shows how feed conditions in dairy streams can profoundly alter membrane separation performance through molecular interactions. Finally, by taking into account adjusted process conditions with fabricated PEMMs, scaling can be minimized, while achieving high lactose purities.
| Period | 11 Sept 2024 |
|---|---|
| Event title | Euromembrane 2024 |
| Event type | Conference |
| Location | Prague, Czech RepublicShow on map |
| Degree of Recognition | International |