Study and development of membrane operations and membrane integrated membrane systems in wastewater treatment, agro-food processing and other industrial sectors 

ABSTRACT

Among the main activities to be carried out there are those provided by the research projects supported by the European Community, the Ministry of Education, private Companies, etc. These activities concern further developments of the ongoing activities in order to improve the transport properties of the compounds of interest and, for the catalytic membranes, also the reactivity and selectivity properties towards the desired reaction products. These activities include: the preparation of new artificial membranes of polymeric nature or in mixed matrix (inorganic and metal) possibly with catalytic properties, for molecular separations, in addition to the study of their transport properties. Further areas of research concern the study and development of catalytic membrane reactors and membrane contactors (such as crystallizers, membrane distillation, strippers, scrubbers, etc.). An integral part of the issues appear to be the molecular dynamics techniques and quantum-mechanical simulation and modeling of the transport mechanisms and membrane operations. 

State of advancement activities

Performed activities

Within the Project Matreco (PON 01_02239) "Advanced materials for environmentally sustainable transport” funded by MIUR (Programma Operativo Nazionale "Ricerca e Competitività 2007-2013), the experimental activities allowed to elaborate and define the operating parameters for the treatment of spent solutions coming from the extraction of Spanish brooms (according to the Digestion-Compression-Decompression (DiCoDe) method) by using microfiltration (MF) and ultrafiltration (UF) operations also combined with each other.

A series of collaborations with Calabrian Companies, related to the use of membrane operations for the recovery of bioactive substances and high value-added substances from agro-food products and by-products have been also established. In particular, the recovery of aromatic compounds from the condensation water resulted from the evaporation of citrus juices has been studied by reverse osmosis. The performance of the used membranes was evaluated in terms of productivity and rejection towards a series of aromatic compounds by analysis carried out in collaboration with the Department of Chemistry of the University of Calabria. The fractionation of pomegranate juice by using membrane operations such as UF and NF has been also studied in order to obtain fractions enriched in bioactive substances of potential interest for nutraceutical or pharmaceutical applications.

Within the Project PON OLIO PIU’ (PON01_01545) an innovative process for the recovery of water and the encapsulation of phenolic compounds has been studied through the integration of conventional membrane processes, such as MF and NF, and innovative processes such as osmotic distillation (OD) and membrane emulsification (ME).

A study for the extraction of phenolic compounds from by-products of the citrus processing industry by using conventional solid/liquid extraction and ultrasound-assisted extraction has benn performed within a collaboration with the Institute of Food Engineering of the University of Valencia.

Experimental data related to the clarification of blood orange juice with polymeric membranes have been analyzed by using a mathematical model in cooperation with researchers of the Department of Chemical Engineering of the Indian Institute of Technology (Kharagpour, India). The proposed model developed from the first principle boundary layer analysis, describes the physical mass transport phenomena and can quantify the various extents of fouling by using different membrane materials and operating conditions.

The potential of NF membranes for the purification of oligosaccharides enzymatically produced has been investigated in cooperation with the School of Biochemical Engineering of the Catholic University of Valparaiso (Chile).

An approach based on the combination of the electrospun methodology and reactive sputtering processes has been studied in collaboration with the Department of Engineering of the University of Catania and the Institute for Microelectronics and Microsystems (IMM) of the CNR in order to realise a porous mesh of polyethersulfone fibers wrapped by TiO₂ layers, active under UV illumination.

Experimental activities related to the treatment of aqueous extracts obtained from both berries and Goji leaves provided by a Calabrian Company for the separation and recovery of bioactive compounds (essentially beta-carotene and phenolic substances) by means of membrane operations are in progress. The use of UF and NF membranes is also evaluated for the separation, purification and concentration of high added-value compounds from by-products of the licorice working process.

Achievements

A pilot plant for the alkaline extraction of cellulosic fibers in combination with the continuous microfiltration treatment of the spent solution has been realised within the Matreco Project "Advanced materials for environmentally sustainable transport" according to the Project specifications. The pretreatment system of the spent alkaline solution is constituted by a prefiltering section and a series of filters with filter mesh of 90, 60 and 5 m. The MF section is essentially constituted by a centrifugal feed pump, a recycle pump, a cylindrical tank for washing operations, an electrical control panel, a container for multitube ceramic membranes and a series of control systems of operating parameters.

Within the Project PON OLIO PIU’ (PON01_01545) a new process for the recovery of water and the encapsulation of phenolic compounds has been studied. The process is based on the combination of conventional membrane processes, such as MF and NF, and innovative membrane processes such as OD and ME. High productivities were measured in MF and NF operations in comparison with data reported in literature. In addition, high rejections of NF membranes towards phenolic compounds were measured. The concentration of the NF retentate by OD produced an enriched fraction of low molecular weight phenolic compounds. That fraction is formulated by means of ME for the production of an oil/water emulsion with a 90% encapsulation efficiency.

 

 

 

 

 

 

The extraction of flavonoids from citrus by-products has been studied within a cooperation with the Institute of Food Engineering of the University of Valencia by using the conventional solid/liquid extraction and the ultrasound-assisted extraction. The effect of operating variables such as ethanol/water ratio, extraction temperature and extraction time on the yield of phenolic compounds and antioxidant activity was evaluated according to the Response Surface Methodology (RSM) approach. Optimization of multiple responses permitted to establish operating conditions giving maximum yields of phenolic compounds and the predicted results were experimentally validated.

As part of the partnership developed with the Department of Chemical Engineering of the Indian Institute of Technology (Kharagpour, India) experimental data related to the clarification of blood orange juice with polymeric membranes were analyzed by using a mathematical model developed from the first principle of boundary layer analysis. The model describes the mass transport phenomena and can quantify the various extents of fouling with different membrane materials and operating conditions. The model results are useful in the understanding of the complex interaction between solute and membranes. The effect of the thickness of the gel layer on the productivity of the process can be also predicted. The model results were experimentally validated. High transmembrane pressures showed a key role in the formation of fouling layers in polysulfone membranes.

 

The potential of NF membranes in the purification of oligosaccharides enzymatically produced has been studied within a collaboration developed with the School of Biochemical Engineering of the Catholic University of Valparaiso (Chile). Experimental results showed that polyethersulfone membranes exhibited good performances in terms of low apparent rejections for monosaccharides and disaccharides at transmembrane pressure values lower than 25 bars when compared with other polymeric membranes.

 

The combination of the electrospun methodology and reactive sputtering processes has been studied in collaboration with the Department of Engineering of the University of Catania and the Institute for Microelectronics and Microsystems (IMM) of the CNR for the development of a porous mesh of polyethersulfone (PES) fibers wrapped by TiO₂ layers, active under UV illumination. The effectiveness of the TiO₂/PES system has been verified in experiments of methylene blue dissociation under UV light. The combination of these techniques is of great interest for developing purification techniques with high porosity and productivity, high yield and low cost.

Experimental data related to the above mentioned activities have been published on international journals and conference proceedings.