Nanofiltration and Tight Ultrafiltration Membranes for the Recovery of Polyphenols from Agro-Food By-Products

Abstract

Pressure-driven membrane-based technologies represent a valid approach to reduce the environmental pollution of several agro-food by-products. Recently, in relation to the major interest for natural compounds with biological activities, their use has been also addressed to the recovery, separation and fractionation of phenolic compounds from such by-products. In particular, tight ultrafiltration (UF) and nanolfiltration (NF) membranes have been recognized for their capability to recover phenolic compounds from several types of agro-food by-products. The separation capability of these membranes, as well as their productivity, depends on multiple factors such as membrane material, molecular weight cut-off (MWCO) and operating conditions (e.g., pressure, temperature, feed flow rate, volume reduction factor, etc.). This paper aims at providing a critical overview of the influence of these parameters on the recovery of phenolic compounds from agro-food by-products by using tight UF and NF membranes. The literature data are analyzed and discussed in relation to separation processes, molecule properties, membrane characteristics and other phenomena occurring in the process. Current extraction methodologies of phenolic compounds from raw materials are also introduced in order to drive the implementation of integrated systems for the production of actractive phenolic formulations of potential interest as food antioxidants.

Organic-Inorganic Hybrid Membranes for Agricultural Wastewater Treatment

“…As mentioned in previous section, MF and UF technologies are adopted to remove suspended particulates and organic matters in wastewater stream. Given that the pore size of semipermeable membranes in MF and UF are in the range of 0.1-10 and 0.01-0.1 μm, respectively [19,26]. MF membranes are commonly made from polymer materials, such as polysulfone (PS), polyether sulfone (PES), polyvinylidene fluoride (PVDF), polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), cellulose acetate (CA), ceramic metal or metal oxides [27].…”

“…Nanofiltration (NF) processes are an advanced separation technology applied to remove pesticides, ammonium ions from wastewater stream [32]. The pore size of NF membranes is in the range of 1-10 nm [19,26]. NF membranes are commonly made from polymer materials, such as polysulfone (PS), polyether sulfone (PES), polyaniline (PAN), polyether ether ketone (PEEK), polyimide (PI), and polyamide (PA) via phase inversion technique [33,34].…”

Metabolites recovery from fermentation broths via pressure‐driven membrane processes

“…Typically, MF has been used to remove organic matter and recover carbohydrates and proteins; UF has been applied to obtain specific compounds such as inulin and several high‐added value compounds (see Table ), whereas the NF has allowed to extract organic compounds with low molecular weight polyphenols (e.g., polyphenols), which are of interest in cosmetic and food industries. Table reports some of the compounds extracted from vegetables sources in the last decade, in which can be seen that UF process has been most used for this purpose.…”

“…The advantages of the MF, UF, and NF processes allow you to join each other (integrated membrane processes) to improve the extraction and purification of compounds. Therefore, the most suitable configuration involves the use of membranes from higher to lower MWCO aiming three different purposes: (a) the recovery of different compounds according to the molecular size of the membranes, (b) increase the purity of the recovered compounds, and (c) reduce the fouling phenomena in membranes …”

“…At this point, it is likely that the physical characteristics of the compounds are being crucial for their separation . When the MWCO of membranes is very close to the molecules' molecular weight, they both can easily interact causing greater fouling in the membrane, which is certainly provoking the increase of retention . In a different approach, Wang et al used two membranes with similar MWCO (300 Da) but different configuration (i.e., thin film and spiral), reporting that the best results using the thin‐film configuration due to better control of membrane fouling …”