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Projeto de investigação
Circular Processing of Seawater Brines from Saltworks for Recovery of Valuable Raw Materials
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How should flow electrode capacitive deionization (FCDI) be operated to achieve efficient desalination and scalability?
Publication . Saif, H. M.; Crespo, J. G.; Pawlowski, S.; DQ - Departamento de Química; LAQV@REQUIMTE; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Elsevier
Flow electrode capacitive deionization (FCDI) is an emerging desalination technology that utilises flowable electrodes and can be operated in diverse configuration modes. This study provides a systematic assessment of the three main configuration arrangements under a voltage range between 0.8 and 2.0 V: isolated closed-cycle (ICC), short-circuited closed-cycle (SCC), and single-cycle with separate concentrate chamber (SCSC). The ICC mode shows the highest specific energy consumption (up to 72.02 Wh/mol of NaCl at 2.0 V) and low operational stability manifested by extreme alteration of pH in the electrode compartments (anode compartment pH down to 2.17; cathode compartment pH up to 12.08), which leads to the need for frequent electrode regeneration or replacement. In comparison to the ICC mode, the SCC mode exhibited superior performance, with a 44.3 % increase in salt removal and up to 3.95 % higher current efficiency at 2.0 V, due to the regeneration of electrodes through short-circuiting, as it reduces the electrical resistance and minimises the side reactions. The SCSC mode emerged as the most stable and reliable among the three, with uniform current and conductivity profiles, as well as minimal pH fluctuations, which is critical to produce treated water within desired quality standards. These findings highlight the promising potential of SCSC mode as an optimal configuration for scalable, continuous and energy-efficient FCDI systems, providing a balanced solution for long-term desalination with reduced operational complexity and costs.
The influence of flow electrode channel design on flow capacitive deionization performance
Publication . Saif, H. M.; Gebregeorgis, T. H.; Crespo, J. G.; Pawlowski, S.; DQ - Departamento de Química; LAQV@REQUIMTE; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Elsevier
Flow capacitive deionization (FCDI) is an emerging desalination technology at which flow electrodes (shear-thinning flowable carbon slurries) are used to remove ions from saline water. The geometry of flow electrode channels, which provide the path and ensure the distribution and mixing of the flow electrodes, is one of the most important aspects to be optimized. This work presents experimental and computational fluid dynamics (CFD) modelling analysis of the influence of the geometry of flow electrode channels on FCDI performance. Flow electrode gaskets (with open, serpentine (short) horizontal and serpentine (long) vertical channels) were 3D printed using a polyethylene terephthalate glycol (PET-G) filament. The FCDI cell with a vertical serpentine flow electrode channel exhibited the poorest performance due to channel blockage by carbon particles, while the best results were achieved with a horizontal serpentine flow electrode channel. CFD simulations aided in understanding this behaviour by showing that the channel geometry strongly affects the local shear rate, and thus the local viscosity of flow electrodes. Thus, it is recommended to design channels that induce flow disturbance aiming for increasing the shear rate and hence reducing flow electrode viscosity, therefore promoting their flowability and reducing clogging chances.
Development of highly selective composite polymeric membranes for Li+/Mg2+ separation
Publication . Saif, Hafiz Muhammad; Huertas, Rosa Maria; Pawlowski, Sylwin; Crespo, João Goulão; Velizarov, Svetlozar; DQ - Departamento de Química; LAQV@REQUIMTE; Elsevier
To meet the exponentially rising demand for lithium, it becomes vital to develop environmentally friendly processes for its recovery from brines, salt lakes and/or seawater. In this work, novel composite lithium transport selective polymeric membranes were developed to separate lithium and magnesium ions. Hydrogen manganese oxide (HMO) (at weight percentage from 0 to 25%), polystyrene sulfonate sodium salt (PSS–Na) and lithium triflate (LiCF3SO3) were added into the sulfonated polyethersulfone (SPES) matrix to prepare composite membranes. The developed membranes showed high mechanical stability and a homogeneous distribution of HMO. The most promising membrane, containing 20% (w/w) of HMO, showed an almost 13 times higher Li+ ionic conductivity (8.28 mS/cm) compared to the control composite membrane (without HMO) and an average ideal selectivity of 11.75 for the Li+/Mg2+ pair. The composite-20% membrane had the lowest intermolecular distance between the polymer chains (according to X-ray diffraction (XRD) analysis), the most flexible structure (lowest Tg) and showed the homogeneous dispersion of HMO (SEM images), which explains its highest Li+/Mg2+ selectivity among the tested membranes. The lithium ion transport performance and separation efficiency were investigated through diffusion dialysis experiments, under different operating conditions. A binary separation factor of 9.10 for Li+/Mg2+ and Li+ molar flux of 0.026 mol/(m2.h) was achieved without applying any external potential difference. When an external potential difference of 0.2 V was applied, the binary separation factor of Li+/Mg2+ pair was 5, while the Li+ molar flux increased almost 5 times. The obtained results provide the basis to design and develop composite lithium transport selective polymeric membranes, thus representing a promising step for future implementation of such membranes to recover lithium from saline streams.
Lithium recovery from brines by lithium membrane flow capacitive deionization (Li-MFCDI)
Publication . Saif, H. M.; Crespo, J. G.; Pawlowski, S.; DQ - Departamento de Química; LAQV@REQUIMTE; Elsevier
The demand of lithium for electric vehicles and energy storage devices is increasing rapidly, thus new sources of lithium (such as seawater and natural or industrial brines), as well as sustainable methods for its recovery, will need to be explored/developed soon. This work presents a novel electromembrane process, called Lithium Membrane Flow Capacitive Deionization (Li-MFCDI), which was tested to recover lithium from a synthetic geothermal brine containing a much higher mass concentration of sodium than lithium (more than 650 times). Specifically, a ceramic lithium-selective membrane was integrated into a flow capacitive deionization (FCDI) cell, which was specifically designed, and 3D printed, to allow simultaneous charging and regeneration of the employed flow electrodes. Despite the extremely high Na+/Li+ mass ratio in the feed stream, 99.98% of the sodium was rejected and the process selectivity for lithium over other monovalent cations was 141 ± 5.85 for Li+/Na+ and 46 ± 1.46 for Li+/K+. The Li-MFCDI process exhibited a stable behaviour over a 7-day test period, and the estimated energy consumption was 16.70 ± 1.63 kWh/kg of Li+ recovered in the draw solution. These results demonstrate promising potential of the Li-MFCDI for the sustainable lithium recovery from saline streams.
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Entidade financiadora
European Commission
Programa de financiamento
H2020
Número da atribuição
869467