• Energy Research

Membrane bioreactor (MBR) technology has attracted great attention over the last 3 decades and achieved rapid growth in an increasing number of practical small- and large-scale applications worldwide. However, its application in Sub-Saharan Africa as well as in aquaculture was so far limited. The installation and operation of a pilot membrane bioreactor (MBR) in Kisumu, Kenya, adopts an integrated approach by providing an integral, sustainable, cost-effective, and robust solution for water sanitation, which also meets the demand for clean water in the fish processing industry, aquaculture, and irrigation. The innovative system comprises a pilot MBR coupled with a recirculating aquaculture system (RAS) which is linked to a 14.3 kW photovoltaic (PV) system, including a 30 kWh Li battery storage to supply sustainable energy. The RAS is able to recirculate 90-95% of its water volume; only the water loss through evaporation and drum filter back flushing has to be replaced. To compensate for this water deficit, the MBR treats domestic wastewater for further reuse. Additionally, excess MBR treated water was used for irrigating a variety of local vegetables and could be also used in fish processing plants. The pilot-scale MBR plant with around 6 m2 submerged commercial UF polyethersulfone (PES) membranes provides treated water in basic agreement with Food and Agriculture Organization (FAO) standards for irrigation and aquaculture, showing no adverse effects on tilapia fingerlings production. A novel membrane module with a low-fouling coating technology is operating stably but has not yet shown improved performance compared to the commercial one.

The sustainable production of H2 and its use as a new and alternative energy carrier are receiving growing attention as a valid alternative to fossil fuel exploitation, contributing to the development of the so-called H2 economy [1]. Traditionally, H2 is produced at industrial scale by steam reforming of natural gas; recently, membrane engineering is receiving considerable interest in this field as testified by a large literature about the membrane reactors (MRs), which represent alternative devices allowing the simultaneous generation of H2 and its purification in a unique stage process. The exploitation of biogas as a renewable source instead of natural gas to generate H2 in reforming processes could contribute to deplete the greenhouse gases pollution pursuing the net-zero carbon emission. This work focuses on the reforming of a CH4:CO2 = 60:40 mixture simulating biogas to produce a COx-free H2 stream in a tubular Pd-Ag MR, packed with a novel, non-commercial bimetallic catalyst, 0.5wt%Ru-7wt%Ni/La0,3Y0,3Zr0,4Ox, prepared by the solution combustion method. Preliminary XRD and TPR characterizations reveal the presence of weak and strong interactions between the support and the active phases (Ni and Ru). Mainly, the TPR analysis shows a complex reduction profile, characterized by multiple reduction peaks, located in the temperature range between 100 and 700°C, and ascribed to different ruthenium (ca. 130°C) and nickel species (ca. 200-700°C), Figure 1(a). As best result of the experimental reaction campaign, a CH4 conversion equal to 99% was reached in the MR (@ H2O/CH4 feed molar ratio = 2 and feed pressure of 250 kPa), with a COx-free H2 recovery of 37%. Globally, the MR behaved better than the traditional reactor (TR), reaching CH4 conversion more than 2.5 times greater than the former .

This chapter gives an overview of the different technologies available for energy recovery and power generation from membrane-based desalination processes. In addition to introducing current desalination technologies, the basic principle of salinity gradient energy and technologies such as pressure-retarded osmosis and reverse electrodialysis are presented. This chapter also summarizes state-of-the-art devices for energy recovery used in reverse osmosis desalination as well as promising, novel alternative techniques for power production with membranes.

Membrane processes are employed in a wide variety of industrial applications such as separation of complex mixtures, hydrogen isolation, CO2 removal, wastewater treatment, etc. Their use allows energy savings on the production cost compared to other traditional separation technologies. Nevertheless, the preparation of membranes not always fulfills sustainability obligations, especially when considering the commonly employed solvents, i.e., N-methyl- 2-pyrrolidone and N,N-dimethylformamide, to mention just a few. Dialkyl carbonates (DACs) are well-known green solvents and reagents that have been extensively investigated as safe alternatives to chlorine-based compounds and media such as alkyl halides, phosgene, and chlorinated solvents. Following our recent study on a scale-up procedure to non-commercially available or expensive DACs, herein we report for the first time the application of organic carbonates as green media for membrane preparation. Theoretical thermodynamic studies were first carried out to predict the solubilities in DACs of different polymers commonly employed for membranes preparation. As a result, the use of selected organic carbonates as media for polyvinylidene difluoride membrane preparation was investigated by nonsolvent-induced phase separation (NIPS) and a combination of vapor-induced phase separation (VIPS)-NIPS techniques. Membranes obtained with custom-made DACs displayed greater structural resistances and smaller pore sizes compared to the ones achieved using commercially available cyclic organic carbonates. Data collected showed that it was possible to achieve a wide variety of dense and porous membranes by using a single family of compounds, highlighting once again the great versatility of DACs as green solvents.

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight, a miniaturized electrolysis cell with a 36 cm2 active area of PEM over a total surface area of 76 cm2 of the device was used. H2 and O2 production rates, electrical power, energy efficiency, Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H2 production was about 0.02 g min−1 with a current density of 1.1 A cm−2 and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance, and this results in lower ohmic and activation resistances.

This work deals with the utilization of the poly(lactic acid) (PLA) to fabricate biopolymer membranes by phase inversion technique for the treatment of gaseous streams rich in CO2 and CH4. PLA is an excellent biopolymer constituting a viable option to most of the traditional fossil-based polymers, possessing zero environmental impact once exhausted and interesting gas separation properties as membranes. Several parameters of the phase inversion process were studied in order to identify the optimal PLA membrane preparation, as a function of the best performance in terms of ideal CO2/CH4 selectivity, CO2 permeability and membrane degradability. The PLA membranes were fully characterized in terms of morphology, thickness, differential scanning calorimetry, Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy analyses. Afterwards, single gas permeation tests were performed in order to prove the relevance of PLA membranes in CO2/CH4 separation, and membrane degradation tests under water as well. The results of the wide experimental campaign on PLA membranes preparation evidenced how specific membrane samples (thickness > 25 ?m) possess quite high CO2/ CH4 ideal selectivity (between 220 and 230) and CO2 permeability ~ 11 Barrer at ambient temperature, which allowed to collocate this biopolymer based membrane material above the correspondent Robeson's upper bound.

Poly(vinyl pyrrolidone) (PVP) was used as an additive to modify the structure and the physical–chemical properties of poly(lactic acid) (PLA) membranes. The membranes with different PVP contents up to 21.33 wt% were employed for pervaporation separation of ethanol/cyclohexane (EtOH/CHx) azeotropic mixture. Several characterization tests were carried out on the membranes including contact angle measurements, mechanical properties before and after immersion in solvent mixtures of different compositions, swelling properties, SEM and FTIR-ATR. The membranes were able to selectively separate EtOH from the feed. The fluxes were continuously increased at higher PVP contents from 0.02 to 0.05 kg/(m2 h) due to the higher affinity to EtOH, together with the more porous structure obtained. However, this will cause the separation factor trend to level off at around 120. This behavior was expected since the addition of PVP made the membranes more hydrophilic, decreasing the water contact angle from 74æ in pure PLA to 54æ with the maximum studied PVP content (21.33 wt%). Furthermore, swelling experiments confirmed the same affinity to EtOH at higher PVP contents. The values of Young’s modulus decreased, contrary to the membrane elongation, at higher EtOH concentrations in comparison with the untreated membranes. The same trends exist for the blend membranes with higher amount of PVP.