Membrane-based Operations Research Articles

A membrane-assisted green strategy for purifying bioactive compounds from extracted white wine lees

This work was aimed at investigating the recovery of wine-derived bioactive compounds from white wine lees through a combination of hydroalcoholic extraction and membrane-based operations, as a potential alternative for winery wastewater treatment and valorisation.Hydroalcoholic extracts obtained in selected conditions of solid–liquid ratio, extraction time and working temperature (1:10, 25 % and 32 ± 2 °C, respectively) were previously clarified by ultrafiltration (UF) in order to produce a clarified solution free of suspended solids and colloidal substances. The concentration of bioactive compounds from the clarified extract was investigated by using three different spiral-wound NF membranes with molecular weight cut-off (MWCO) in the range of 200–1000 Da (TS40, XN45 and NP010, all from Microdyn-Nadir); their performance was analysed in terms of productivity, fouling index and retention towards target compounds (polyphenols, flavonoids, sugars) and antioxidant activity.Low molecular weight polyphenols (i.e. gallic acid, catechin, vanillic acid, epicatechin and caffeic acid) were highly rejected by the selected membranes despite their difference in MWCO; on the other hand, the rejection index for total phenolic content (TPC), flavonoids and glucose was in agreement with the MWCO. The TS40 membrane, with a lowest cut-off (200–300 Da), showed the highest rejection for flavonoids (100 %) and rejections for total phenolic compounds of 85 % resulting in concentrated fractions containing 1.7 g of gallic acid equivalents per liter (GAE/L); most of the components analysed in the retentate samples showed a concentration factor of approximately 3.5 in agreement with the weight reduction factor of the NF process. The analysis of fouling mechanisms according to the Hermia’s model revealed that the cake filtration mechanism was the predominant one for all selected NF membranes.

A highly durable and hydrophilic PVDF- MoS2/WO3-PVA membrane with visible light driven self-cleaning performance for pollutant-burdened natural rubber wastewater treatment

Recently, the unification of photocatalytic degradation and hydrophilic properties has received a remarkable attention in membrane-based operation. In this study, the PVDF membrane was tailored by the incorporation of MoS2/WO3 recognized as MSW photocatalyst material with a cross-linked PVA. The filtration process was conducted with and without visible-light irradiation, and the properties of the clean and fouled membrane were identified using a scanning electron microscope (SEM), infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analysis. The characterization results confirmed the successful blending of the composite material in the PVDF membrane. The PVDF-MSW-PVA membrane exhibited convincing performances with a high-photodegradation efficiency and excellent self-cleaning ability. The PVDF-MSW-PVA membrane achieved an initial flux of 100.66 L.m−2.h−1 and exhibited 98.77 % of chemical oxygen demand (COD), 94.30 % of total dissolved solid (TDS), and 96.66 % of ammonia nitrogen (NH3-N) rejection under visible-light illumination. The excellent antifouling and self-cleaning ability of the membrane was confirmed by the unnoticeable decrease of permeate flux after 5 cycle photo-filtration process, the highest flux recovery ratio of 96.93 %, and a decrease of total fouling retention of the membrane with the higher Rr than that of Rir. The modified membrane also demonstrated good reusability for long term-used upon 10 h of usage for the filtration process under visible-light irradiation. These results suggest the synergetic use of photocatalytic and hydrophilic material for the treatment of pollutant-burdened natural rubber wastewater via a combined degradation and filtration process.

NMR-Based Characterization of Citrus Tacle Juice and Low-Level NMR and UV-Vis Data Fusion for Monitoring Its Fractions from Membrane-Based Operations.

Tacle is a citrus variety which recently gained further interest due to its antioxidant and biological properties. This study suggests using Nuclear Magnetic Resonance (NMR) imaging to characterize Tacle juice's metabolic composition as it is intimately linked to its quality. First, polar and apolar solvent systems were used to identify a significant fraction of the Tacle metabolome. Furthermore, the antioxidant capacity and the total content of flavonoids, polyphenols and β-carotene in the juice were investigated with UV-Visible spectroscopy. Tacle juice was clarified and fractionated by ultrafiltration (UF) and nanofiltration (NF) membranes in order to recover and purify its bioactive principles. Finally, the second part of this work sheds light on the spectrophotometric assays and 1H-NMR spectra of fractions coming from membrane operations coupled with a multivariate data analysis technique, PCA, to explore the impact of UF and NF processes on the metabolic profile of the juice.

Membrane-based Operations for the Fractionation of Polyphenols and Polysaccharides From Winery Sludges

The present work investigated the impact of ultrafiltration (UF) and nanofiltration (NF) membranes on the recovery and fractionation of polyphenolic compounds and polysaccharides from Sangiovese and Cabernet Sauvignon wine lees. A laboratory-made flat-sheet membrane in cellulose acetate (CA400-38) was used in the UF treatment of Sangiovese wine lees; three laboratory-made flat-sheet membranes in cellulose acetate (CA316, CA316-70, CA400-22) and a polyamide commercial membrane (NF90) were used in the NF treatment of Cabernet Sauvignon wine lees. All membranes were characterized in terms of hydraulic permeability and rejection toward references solutes; the performances of the membranes were measured in terms of productivity, fouling index, cleaning efficiency and retention toward target compounds.Experimental results indicated that all UF and NF membranes were effective in separating target compounds rejecting more than 92% of polysaccharides with polyphenols preferentially permeating through the membrane. The UF membrane rejected more than 40% of total polyphenols; rejections toward non-flavonoids and flavonoids were less than 25% and 12.5%, respectively.The laboratory-made NF membranes exhibited higher permeate flux values (of the order of 11–12 L/m2h) in comparison with the commercial NF membrane, despite the observed differences in the retention of specific solutes. Among the prepared membranes the CA316 showed a total rejection toward most part of non-flavonoids and flavonoids.The experimental results support the use of UF and NF processes in a sequential design to fractionate and refine phenolic compounds from winery sludge for the production of concentrated fractions with high antioxidant activities.

Perspective of Membrane Technology in Pomegranate Juice Processing: A Review.

Pomegranate (Punica granatum L.) juice is well recognized for its high content of phytochemicals with proven health-promoting effects. Conventional processing techniques including clarification with fining agents, pasteurization and thermal concentration have significant influences on bioactive compounds and antioxidant activity of the juice. The growing consumers demand for high-quality pomegranate juice as well as the industrial interest for the production of functional foods, nutraceuticals, and cosmetics from its bioactive compounds have promoted the interest for minimal processing technologies. In this context, membrane-based operations represent an innovative approach to improve the overall quality of pomegranate juice production. This review focuses on the recent advances and developments related to the application of membrane technology in pomegranate juice processing. Conventional pressure-driven membrane operations and innovative membrane operations, such as osmotic distillation and pervaporation, are discussed in relation to their potential in juice clarification, fractionation, concentration and aroma recovery. Their implementation in integrated systems offer new opportunities to improve the healthiness and quality of the juice as well as to recover, purify and concentrate bioactive compounds for the formulation of functional ingredients.

Biologically Active Compounds from Goji (Lycium Barbarum L.) Leaves Aqueous Extracts: Purification and Concentration by Membrane Processes.

Goji (Lycium barbarum L.) leaves and fruits have been described as a valuable source of bioactive compounds with a great potential for the development of health-promoting formulations. The present study aimed to evaluate the potential of a sustainable process for the recovery of phenolic compounds from Goji leaves through a combination of aqueous extraction and membrane-based operations. Water was used as a safe, cheap, and non-hazardous extraction solvent, and parameters of extraction of dried Goji leaves were optimized in order to maximize the yield of polyphenols, total soluble solids (TSS), and total antioxidants simultaneously. The aqueous extract was clarified by ultrafiltration and then processed with three flat-sheet polyethersulphone (PES) membranes with molecular weight cut-off (MWCO) values in the range of 0.3–4.0 kDa, in order to remove sugar compounds from polyphenols and improve the antioxidant activity of the produced fractions. Among the selected membranes, a 1 kDa membrane exhibited the best performance in terms of purification of polyphenols from the clarified aqueous extract. The rejection by this membrane of TSS and total carbohydrates was in the range of 15.8–25.3%, and was decreased by increasing the volume reduction factor (VRF). On the other hand, the retention values for total polyphenols and total antioxidant activity (TAA) were in the range of 73–80%, and were increased by increasing the VRF.

Membrane-Based Operations in the Fruit Juice Processing Industry: A Review

The fruit juice industry is one of the food sectors that has invested the most in the implementation of new technologies, such as non-thermal technologies. Among them, membrane processes are considered today well-established separation techniques to support the production and marketing of innovative fruit juices designed to exploit the sensory characteristics and nutritional peculiarities of fresh fruits. Pressure-driven membrane operations, membrane distillation, osmotic distillation and pervaporation have been widely investigated in the last few decades to replace conventional technologies used in fruit juice processing industry (i.e., clarification, stabilization, concentration and recovery of aroma compounds). This paper will review the significant progresses on the use of membrane-based operations in fruit juice processing industry in the light of the growing interest towards products with improved safety, quality and nutritional value and sustainable processes characterized by low energy consumption and low environmental impact.

Membrane Distillation: Principles, Applications and Perspectives

Membrane Distillation (MD) is a membrane-based operation able to give 100% theoretical ions rejection and to efficiently work with high concentrated brines. Both features make MD of interest for the purification of wastewater, the production of ultra-pure water and the concentration of brines produced in desalination. MD, also integrated with other membrane operations, can be a valuable way to improve the performance of separation processes.

A process synthesis-intensification framework for the development of sustainable membrane-based operations

In this paper a multi-level, multi-scale framework for process synthesis-intensification that aims to make the process more sustainable than a base-case, which may represent a new process or an existing process, is presented. At the first level (operation-scale) a conceptual base case design is synthesized through the sequencing of unit operations and subsequently analyzed for identifying process hot-spots using economic, life cycle and sustainability metrics. These hot-spots are limitations/bottlenecks associated with tasks that may be targeted for overall process improvement. At the second level (task-scale) a task-based synthesis method is applied where one or more tasks representing unit operations are identified and analyzed in terms of means-ends for generating intensified flowsheet alternatives. At the third level (phenomena-scale) a phenomena-based synthesis method is applied, where the involved phenomena in various tasks are identified, manipulated and recombined to generate new and/or existing unit operations configured into flowsheet alternatives that target the tasks associated with hot-spots. Every lower-scale or higher-level, generates more alternatives than their corresponding larger-scale. Those alternatives that are able to address the identified hot-spots therefore give innovative and more sustainable process designs that otherwise could not be found from the larger-scales. In this paper, membrane-based operations identified through this framework are highlighted in terms of extension of the combined intensification-synthesis method and its application to generate membrane-based operations. Also, application of the framework is illustrated through a case study involving the production of methyl acetate where membrane-based intensified operations play a major role in determining more sustainable process design alternatives.

An annular dual-membrane continuous cation exchanger packed with ion exchange resin

Design, construction details and performance characteristics are described for an annular perfluorosulfonate (Nafion) dual tubular membrane assembly where inside of the inner membrane tube and outside of the outer membrane tube are packed with ion exchange resin beads. During operation, the solution to be ion exchanged flows in the annular space between the two membrane tubes and a regenerant solution flows countercurrent to the principal flow, through the inner tube and outside the outer tube. With a principal channel hold up volume of ∼ 125 μl and capability of operation at head pressures up to 200 psi, the device can continuously exchange 200-250 μeq of Na + per minute for H +. While this particular device was intended for use as a “suppressor” in anion chromatography, the design concept should be of utility in other membrane-based operations.