0000000000610691
AUTHOR
Antonia Filingeri
Limiting current phenomena in electro-membrane processes: local occurrence or stack-dependent one?
Background Electro-membrane processes are gaining great interest in the field of desalination and brine valorisation. However, limiting current phenomena can be a bottleneck for their techno-economic performances. In the present work, the in-out distribution of current density is measured to elucidate the achievement of limiting conditions in real stacks. Materials and Methods A 10-cell pairs Electrodialysis stack (10×40 cm2 active area), equipped with four-segmented electrodes, was tested. NaCl solutions at an inlet concentration ranging from 0.5 to 60 g/l were fed at velocities of either 2 or 4 cm/s in parallel flow. Current density-voltage curves were built by applying equal increasing s…
A new process for resourse recovery from surface water RO brine from permeate remineralization
Low-Pressure Reverse Osmosis (LPRO) membranes could be valuable alternatives to conventional surface water potabilization processes [1] thanks to a combined ability to: remove micropollutants, soften, disinfect and remove organic substances. However, these processes produce an aggressive permeate and a concentrated brine with discharge constraints [2]. Assisted Reverse Electrodialysis (A-RED, [3]) was tested for LPRO permeate remineralization by recovery of target minerals from the corresponding LPRO brine while maintaining the product water’s integrity with respect to the organic compounds present in the concentrate. Bench-scale experiments were carried out with SUEZ-WTS membranes (CR67T-A…
Current distribution along electrodialysis stacks and its influence on the current-voltage curve: behaviour from near-zero current to limiting plateau
The current maldistribution along the flow path of electrodialysis (ED) units is a well-known phenomenon. However, it has been poorly quantified via experimental tests so far. This work aimed at measuring the current distribution in an ED stack with 40 cm path length, provided with four-segment electrodes. The current-voltage curve (CVC) of each segment was recorded under several operating conditions of inlet concentrations and feed velocity. In the CVC of the first segment, the current increased approaching a saturation, while in that of the remaining segments it passed through a maximum and then settled at near-zero values when high voltage values were applied. The current fraction on the…
Surface water RO permeate remineralization through minerals recovery from brines
Assisted-Reverse Electrodialysis (A-RED) technology was applied following reverse osmosis (RO) of a surface water resource in order to recover minerals from its brine and directly remineralize the RO unit's permeate. Four different sets of cation/anion exchange membranes were benchmarked using single- and mixed-salts synthetic solutions as well as real brine and permeate streams produced from three-stage reverse osmosis applied to Seine River water. The process, operating under equal permeate and brine channel flows (2 cm/s velocities) and applied voltage varying from 0 to 10 V, showed viable remineralization results. Optimal recovery at 10 V applied allowed increasing permeate mineral cont…
Electrodialysis with asymmetrically profiled membranes: Influence of profiles geometry on desalination performance and limiting current phenomena
Abstract Electrodialysis (ED) has recently gained much attention in the wide field of desalination and water treatment. However, energy consumption and capital costs may impair the process competitiveness. In this regard, limiting current density (LCD) and current efficiency (η) are key performance parameters for optimized ED systems. In this work, an experimental campaign was carried out characterizing the performance of ED stacks when adopting asymmetrically profiled membranes. Current–voltage curves were recorded under different operating conditions mimicking the operation of brackish water or seawater desalination units. Results showed that there was a preferable direction of the electr…
Valorization of surface-water RO brines via Assisted-Reverse Electrodialysis for minerals recovery: performance analysis and scale-up perspectives
Reverse Osmosis (RO) plays a key role in seawater and brackish water desalination to fulfill the growing demand for fresh water. In recent years, RO has also been more and more adopted for the treatment and potabilization of surface waters, leading to two main problems: (i) the depletion in minerals of the product water, making it aggressive and unsuitable for drinking purposes and (ii) the production of a concentrated brine requiring proper disposal. Permeate remineralization post-treatments include pH adjustment and addition of minerals, such as bicarbonates, calcium and magnesium, which are essential for human health and required to meet drinking water guidelines. However, such solutions…
Acid and alkaline production from multi-ionic brines via Electrodialysis with Bipolar Membranes
In recent years, a great attention has grown towards the brine valorization through chemicals production and mineral recovery as an alternative to conventional disposal. Electrodialysis with Bipolar Membranes (EDBM) is an emerging process that can be used for the production of alkaline and acidic solutions from salt solutions. Within the SEArcularMINE project framework, the exploitation of saltworks bitterns (highly concentrated solutions generated during the sea-salt production process) is proposed for minerals recovery and NaOH and HCl solutions production. In this work, an EDBM unit, equipped with commercial ion exchange membranes, was tested for the first time in closed-loop mode with: …
Production of acidic and alkaline solutions via Electrodialysis with bipolar membranes from synthetic and real brines from saltworks
1. Introduction In recent decades, there has been a great deal of interest at both the industrial and academic levels in identifying unconventional sources for chemical production and raw material recovery. In this context, brine disposal, which was previously addressed as a priority to reduce environmental problems, is now seen as an opportunity to apply new or existing technologies in circular processes that allow for the valorization of previously considered waste solutions [1]. In this regard, Electrodialysis with bipolar membranes (EDBM) can be used to produce acidic and alkaline solutions from salty solutions. EDBM is an electro-membrane process distinguished by the alternated positio…