Abstract
Electro-membrane technologies are versatile processes that could contribute towards more sustainable seawater reverse osmosis (SWRO) desalination in both freshwater production and brine management, facilitating the recovery of materials and energy and driving the introduction of the circular economy paradigm in the desalination industry. Besides the potential possibilities, the implementation of electro-membrane technologies remains a challenge. The aim of this work is to present and evaluate different alternatives for harvesting renewable energy and the recovery of chemicals on an SWRO facility by means of electro-membrane technology. Acid and base self-supply by means of electrodialysis with bipolar membranes is considered, together with salinity gradient energy harvesting by means of reverse electrodialysis and pH gradient energy by means of reverse electrodialysis with bipolar membranes. The potential benefits of the proposed alternatives rely on environmental impact reduction is three-fold: (a) water bodies protection, as direct brine discharge is avoided, (b) improvements in the climate change indicator, as the recovery of renewable energy reduces the indirect emissions related to energy production, and (c) reduction of raw material consumption, as the main chemicals used in the facility are produced in-situ. Moreover, further development towards an increase in their technology readiness level (TRL) and cost reduction are the main challenges to face.
Highlights
Electricallydriven processes, which are those that operate under an electrical gradient and use ionexchange membranes (IEMs) allowing the selective flow of ions of two confronted solutions with different concentrations, present a lower implementation in real processes requiring a higher degree of research and technical development to overcome the current challenges minding their potential integration in a number of industrial applications
The alternatives presented in the previous section have certain advantages mainly related to the environmental impact reduction of seawater reverse osmosis (SWRO); there are disadvantages that must be taken into account before selecting which alternative is the most favorable for a specific desalination plant
Electro-membrane processes are advanced separation technologies that can contribute to implementing the Circular Economy philosophy in different industrial activities
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. One of the most widespread options is the use of batteries that allow the accumulation of energy surplus to be used when energy input is insufficient In this sense, electrochemical batteries such as lead-acid, li-ion, and vanadium-redox are currently employed at an industrial scale; these batteries present environmental issues regarding chemical disposal [16,17]. The aim of the present work is to present the current status and challenges of electro-membrane processes: ED, RED, EDBM, and R-EDBM and evaluate different approaches for their integration in SWRO brines valorization processes aiming at (i) harvesting RE and (ii), generating self-supply commodities like acids and bases to be used in desalination pre, post-treatment and cleaning stages
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