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Electrodialysis with Bipolar Membranes (EDBM) is a promising process to produce acidic and basic solutions that are important in circular treatment chains. However, there is a lack of knowledge regarding the long-run performance of EDBM units fed multi-ionic solutions. This study aims to fill this gap by performing a long-run test, via an innovative feed and bleed configuration, with real brines coming from Trapani (Italy) saltworks and pre-treated to remove Mg and Ca. A laboratory EDBM unit with 5 triplets with an active membrane area of 100 cm2 was used. The results show that a steady-state concentration of 0.44 mol/L on average of OH- and H+ (in the form of NaOH and HCl) was reached in both acid and base outlet solutions, respectively, with a maximum deviation of 2 %. Stable performances were observed with a current efficiency of 69 % and 56 % and specific energy consumption of 1.78 kWh/kg and 2.19 kWh/kg on average for base and acid, respectively. These results demonstrate the potential of EDBM processes to maintain competitive and efficient performance. [ABSTRACT FROM AUTHOR]

Electrodialysis with bipolar membranes (EDBM) has been recently proposed as a promising strategy for the valorization of desalination waste brine. This process enables the production of chemicals (i.e., acids and bases) starting from a salty stream via the application of an electric field. Several process configurations have been reported in the literature, operating both in continuous and discontinuous mode. The continuous feed & bleed configuration has resulted the best option for the process scale-up. In this work, a performance evaluation of a large scale EDBM unit (19 m2 of total membrane area) operated in feed & bleed mode is presented. Time profile of acid and base concentrations as well as of voltage applied to the stack are reported, thus proving the stability of the process in galvanostatic condition. Four tests have been conducted at four different current density (200- 500 A m-2) and the results have been analysed utilizing appropriate performance parameters (i.e., Current Efficiency, Specific Energy Consumption and Specific production). Results suggest that increasing the current density, the acid concentration rises at fixed base concentration of 1 mol l-1. Furthermore, increasing the current density, the current efficiency of base remains fairly constant (60-63 %), while for acid a growth is observed. Specific energy consumption and specific production show an increasing trend with the current density: at 500 A m-2, values of 3.6 and 2.7 kWh kg-1 and 0.94 and 1.3 ton y-1 m-2 were obtained, respectively. [ABSTRACT FROM AUTHOR]

Nowadays scientists and communities are particularly worried about climate change and the transition towards renewable energies is a matter of crucial importance. In this context, European Community is strongly promoting the production of green hydrogen, i.e. the electrolysis of water coupled with renewable electrical sources. In addition to the energy issue, United Nations have identified the lack of water as another big issue for modern society. Electrodialysis (ED) is an electro-membrane process able to desalinate a salty feed by the application of an external power supply. It takes advantage of the use of ionic exchange membranes which allow a controlled separation of ions from the salty feed to obtain freshwater and brine as outputs. The present work tries to address the above issues by proposing the simultaneous production of fresh water and hydrogen with an integrated hydrogen-electrodialysis (HED) unit. The aim of the present work is that of assessing the economic feasibility of the process. To this purpose, a techno-economic model has been developed to predict the behaviour of the HED unit. The model is able to predict experimental data and should be regarded as a simple yet reliable tool to assess the process economic feasibility. Preliminary analyses suggest that the simultaneous production of hydrogen and fresh water may be profitable. [ABSTRACT FROM AUTHOR]

Water, energy, and minerals are fundamental pillars for the future of humankind. Sustainable and renewable productive processes and resources are the only possibility to face the continuously growing global population and high living standards requirements. The present work introduces a proof of concept for the pilot scale production of magnesium hydroxide, Mg(OH)2, from waste saltworks bitterns located in the district of Trapani, Italy. Mg(OH)2 was produced by adopting a proprietary "Magnesium Crystals Granulometry Controlled Reactor", Mg-CGCR. The influence of several parameters was investigated on Mg(OH)2 suspensions and powders characteristics: (i) the bittern flow rate, (ii) alkaline sodium hydroxide, NaOH, concentrations solutions (adopted as the precipitant agent) and (iii) the final suspension pH value (stoichiometric or OH- excess amounts). A Mg2+ recovery >99 % can be achieved thanks to the adoption of a product recycling strategy in the reactor. Furthermore, highly pure Mg(OH)2 powders, addressed by cationic purity, were synthesized. Results demonstrate the possibility of producing highly pure Mg(OH)2 products from waste-concentrated saline solutions, thus turning waste into valuable compounds. [ABSTRACT FROM AUTHOR]

Recently, the utilisation of renewable energy sources is a matter of increasing importance in Europe for Energy Transition and to achieve energy independence. To this aim, tailored Electric Energy Storage (EES) devices must be employed to tackle the issue of fluctuating production from renewables. The Acid/Base Flow Battery (AB-FB) is a cutting-edge technology that allows energy to be stored in the form of acidic and alkaline solutions (van Egmond et al., 2018). This method employs two membrane processes, one for the charge phase and one for the discharge phase, namely Electrodialysis with Bipolar Membrane (EDBM) and Reverse Electrodialysis with Bipolar Membrane (REDBM), respectively. The polymeric membranes and the two electrodes are the main components of this battery. The AB-FB is a novel technology, and a lot of effort is needed to properly assess its current and future potential and identify the geometrical and operating conditions maximising its performance. This study presents a techno-economic analysis (TEA) carried out by using technically optimal results from a previous bi-objective optimisation (Culcasi, et al., 2022b). By assessing the sensitivity on the input parameters, the Levelized Cost of Storage (LCOS) of a battery operating in closed-loop and using current commercial membranes spanned from 0.17 € kWh−1 to 0.45 € kWh−1, indicating that the AB-FB has significant potential in the commercial market. [ABSTRACT FROM AUTHOR]