RESUMEN
The wine industry is a sector of great importance in the Spanish economy, contributing substantial annual revenues. However, one challenge facing the industry is the amount of waste generated, reaching millions of tons annually. These residues consist of organic matter of industrial interest, such as polyphenols. These substances are characterised by their excellent antioxidant properties, making them ideal for use in the food, cosmetic, and pharmaceutical industries. Modern techniques, such as membrane technology, are explored for their extraction based on separating compounds according to size. This work studies a sequential filtration process using ultrafiltration (UF) and nanofiltration (NF) membranes at different operating conditions (2 bar and 9.5 bar for UF and NF, respectively, at 20 °C) to extract polyphenols from wine lees. The results show a total polyphenols rejection rate for each process of 54% for UF and 90% for NF. Pore blocking models have been studied for the UF process and an intermediate pore blocking of the membrane upon wine lees filtration has been identified. A mathematical model that justifies the behavior of a polymeric NF membrane with the filtration of pre-treated vinasse residues has been validated. This study shows a viable process for extracting polyphenols from wine lees with sequential membrane technology.
RESUMEN
In the present study, nine fabrics have been tested for brackish water treatment with the aim of industrial application under the concept of zero liquid discharge (ZLD). Moisture content was determined, where it was observed that the lignocellulosic fabrics had a moisture content ranging from 2.5 to 8.5%. The wetting contact angle showed that the flax with polylactic acid (LPLA) was the most hydrophobic. The determination of the liquid absorption capacity showed that, of the synthetic fabrics, the one with the highest absorption, both in distilled water and in brackish water, was the polyester (PES) fabric with an absorption of 816% compared to its initial weight. In the natural fabrics, the highest absorption capacity was shown by the wet-laid without treatment (WL-WT) fabric for both distilled water and brackish water, although it required several cycles of operation to maintain this stable absorption. Exposure to brackish water improved the absorption capacity of all samples. Mechanical and thermal characterization showed that the synthetic fabrics were more resistant than the natural fabrics, although they may compete in terms of applicability. The capillarity study showed that the most hydrophilic fabrics completed the test the fastest. Finally, the composting degradation test showed that those fabrics with polylactic acid (PLA) content degraded faster in the first 14 days and thereafter the degradation of the lignocellulosic content showed a slower degradation until 112 days. The Bam fabric did not degrade during the course of the experiment.
RESUMEN
The winemaking process in Spain generates a significant amount of wastes such as wine lees. Currently, the nanofiltration process is a viable technique for the revalorization of compounds from wastes. In this aspect, this technique can be used for the recovery of compounds, such as polyphenols, as well as active principles widely used in industries, such as pharmaceuticals or cosmetics. Polyphenols are found in acceptable amounts in wine lees wastes and it is interesting to study the nanofiltration process viability to recover them. In order to study this possibility, it is necessary to determine the choice of the best membrane to use and the effect of operational parameters such as pressure, temperature, cross-flow rates, and concentration. In addition, it is important to be able to develop a mathematical model that can help in the future design of lees treatment plants. The treatment of red wine lees to concentrate polyphenols has been studied in a laboratory plant using different membranes (RO and NF) at different pressures (4.5, 9.5, and 14.5 bar), different temperatures (293, 303, and 308 K), and two concentrations (2100 and 1100 mg tyrosol eq·L-1). The results have been encouraging to consider nanofiltration as a viable technique for the treatment and revalorization of this waste. The most suitable membrane has been the NF270, in which 96% rejection rates have been obtained, with a flux of 30 L·h-1·m-2. Moreover, in this study, the Spiegler-Kedem model (SKM) was used to calculate mass transfer constants and permeabilities. Suitable adjustments of these parameters were obtained to validate this mathematical model. For this reason, the SKM might be used in future studies to continue in the research work of the treatment of wine lees wastes.
