Magnesium recovery from desalination reject brine as pretreatment for membraneless electrolysis

Mahmud, Nafis; Alvarez, Daniela V. Fraga; Ibrahim, Mohamed H.; El‐Naas, Muftah H.; Esposito, Daniel V.

doi:10.1016/j.desal.2021.115489

Cited by 27 publications

(5 citation statements)

References 37 publications

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“…When brine from RO plants was tested as a source of industrial water in the copper mining industry, the removal of and reduction in the calcium and magnesium ion concentration were also required to improve the copper recovery in the flotation process [19]. Magnesium and calcium removal in sequence was also studied in the pretreatment of desalination brine before subjecting it to electrolysis [20,21]. In the concentration of SWRO brines by electrodialysis, a calcium removal of 94-96% as carbonate with simultaneous magnesium removal higher than 60% at 60 • C was obtained by Casas et al [22].…”

Section: Introductionmentioning

confidence: 99%

Selective Calcium Removal at Near-Ambient Temperature in a Multimineral Recovery Process from Seawater Reverse Osmosis Synthetic Brine and Ex Ante Life Cycle Assessment

Molinari,

Avci,

Curcio

et al. 2024

Water

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Potable water production from seawater generates brines that can produce stress in ecosystems, but they are also a potential source of metal and minerals. In our multi-mineral modular seawater brine mining process under development, calcium removal with minimal magnesium removal was the first stage. Even though calcium removal from reverse osmosis brine has been widely studied, there is no relevant research on its precipitation by carbonates at a near-ambient temperature (a range of 15–35 °C) and its selectivity over other minerals, as well as studies on operating conditions for selective precipitation considering the presence of antiscalants. We studied its reaction kinetics and equilibrium and conducted an ex ante life cycle assessment (LCA). The control of pH levels together with the Ostwald ripening process were very important factors to obtain a selective CaCO3 precipitation. The first-order average kinetic constant of the precipitation at 35 °C was 0.582 ± 0.141 h−1. The presence of minor ions and an antiscalant did not influence the precipitation, obtaining 85–90% on average for the %Ca2+ precipitation while the Mg2+ co-precipitation was lower than 5–7%. A lab-scale plant, tested in continuous (5 L/h synthetic brine) and in batch (15 L) modes, showed that the latter performs better and could be of interest at a larger scale. The ex ante LCA for the batch (100 L) showed that the main environmentally impactful factors were the thermostatic heating and the addition of a precipitant (Na2CO3), but these could be mitigated at the industrial level.

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Section: Introductionmentioning

confidence: 99%

Selective Calcium Removal at Near-Ambient Temperature in a Multimineral Recovery Process from Seawater Reverse Osmosis Synthetic Brine and Ex Ante Life Cycle Assessment

Molinari,

Avci,

Curcio

et al. 2024

Water

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“…During electrolysis of brine, the base (OH – ) is generated at the porous flow-through cathode by the reduction of H 2 O through the hydrogen evolution reaction (HER, eq ), while the oxygen evolution reaction (OER, eq ) and/or chlorine evolution reaction (CER, eq ) occurs at the counter electrode. Since the current study is focused on porous cathodes for the HER, brine solutions comprised of Na 2 SO 4 with similar ionic conductivity as reject brine were used to avoid complications associated with undesirable CER at the counter electrode. , normalc athode ( HER ) : 0.25em 4 normalH 2 O + 4 e − → 2 H 2 + 4 OH − goodbreak0em1em⁣ E ° = 0.00 V 0.25em vs 0.25em RHE normala node ( OER ) : 2 normalH 2 O → 4 H + + O 2 + 4 e − goodbreak0em1em⁣ E ° = 1.23 0.25em normalV 0.25em vs 0.25em RHE or: normala node ( CER ) : 0.25em 2 Cl − → Cl 2 + 2 e − goodbreak0em1em⁣ ...…”

Section: Introductionmentioning

confidence: 99%

“…Desalination offers an approach to address freshwater shortages, with some countries in arid regions of the world relying on desalinated water to meet water demands for more than half of their water needs. , However, conventional desalination technologies present major environmental concerns due to the cogeneration of concentrated reject brine streams that contain various organic compounds, metals, and other contaminants. − Electrochemical treatment of brine through electrolysis or electrodialysis creates an opportunity to generate hydrogen (H 2 ) fuel, sodium hydroxide (NaOH), and hydrochloric acid (HCl) − and convert environmentally unfriendly reject brine into value-added products while simultaneously reducing the salinity of the brine.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alkalinity Enhancement during Reject Brine Electrolysis: Role of Electrocatalyst Placement on the Outer Surfaces of Porous Flow-Through Electrodes

Fraga Alvarez,

Livitz,

Pang

et al. 2023

ACS Sustainable Chem. Eng.

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Membraneless electrolyzers offer a promising approach to convert environmentally harmful reject brine waste streams generated from desalination into valuable products, such as mineral carbonates, by using electrochemical reactions to split the brine into acidic and alkaline streams. However, membraneless electrolyzers suffer from a trade-off between current density and current utilization that stems from undesired back-reactions that arise from the crossover of redox species between the anode and cathode. This study employed a combination of in situ high-speed video, colorimetric pH imaging, modeling, and electroanalytical methods to evaluate how the performance of a porous flow-through cathode is affected by the operating current density, electrolyte flow rate, and choice of catalyst placement on a porous support. It is found that the placement of the active catalyst on the outer surface of the electrodefacing away from the anodeincreases the cathode current utilization by 51%, on average, relative to when the catalyst is deposited on the inner surface of the electrode. This finding is explained by the ability of the porous electrode support to serve as a barrier to suppress crossover for the outward-facing catalyst configuration. In addition, the outward-facing catalyst configuration leads to a more stable operation while incurring minor increases (90–170 mV) in overpotentials. For both catalyst configurations, this study also shows that the Damköhler number (Da) is a practical descriptor for predicting operating conditions that maximize the concentration of OH– in the cathode effluent stream.

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“…Benefited by the advantages of the high purity of separated gas, ion exchange membrane electrolysis [ 11 , 12 ] is now the most common used technology in the brine electrolysis process, even though its electrolytic efficiency depends largely on the performance of the ion membrane. Since there are all kinds of ions with various concentrations in saline wastewater, the pores of the ion membrane might be blocked, resulting in higher tank voltage and lower electrolysis efficiency [ 13 , 14 ]. Therefore, it is necessary to explore the suitable concentrations of impurity ions during saline wastewater electrolysis to ensure a stable and economic electrolytic performance with minimal damage to the ion membrane.…”

Section: Introductionmentioning

confidence: 99%

In-Depth Study on the Effects of Impurity Ions in Saline Wastewater Electrolysis

Pan,

Zhao,

Gao

et al. 2023

Molecules

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Concentration followed by electrolysis is one of the most promising ways for saline wastewater treatment, since it could produce H2, Cl2, and an alkaline solution with deacidification potential. However, due to the diversity and difference of wastewater, knowledge on the suitable salt concentration for wastewater electrolysis and the effects of mixed ions are still lacking. In this work, electrolysis experiments of mixed saline water were conducted. The salt concentration for stable dechlorination was explored, with in-depth discussions on the effects of typical ions such as K+, Ca2+, Mg2+, and SO42−. Results showed that K+ had a positive effect on the H2/Cl2 production of saline wastewater through accelerating the mass transfer efficiency in the electrolyte. However, the existence of Ca2+ and Mg2+ had negative effects on the electrolysis performance by forming precipitates, which would adhere to the membrane, reduce the membrane permeability, occupy the active sites on the cathode surface, and also increase the transport resistance of the electrons in the electrolyte. Compared to Mg2+, the damaging effect of Ca2+ on the membrane was even worse. Additionally, the existence of SO42− reduced the current density of the salt solution by affecting the anodic reaction while having less of an effect on the membrane. Overall, Ca2+ ≤ 0.01 mol/L, Mg2+ ≤ 0.1 mol/L and SO42− ≤ 0.01 mol/L were allowable to ensure the continuous and stable dechlorination electrolysis of saline wastewater.

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Magnesium recovery from desalination reject brine as pretreatment for membraneless electrolysis

Cited by 27 publications

References 37 publications

Selective Calcium Removal at Near-Ambient Temperature in a Multimineral Recovery Process from Seawater Reverse Osmosis Synthetic Brine and Ex Ante Life Cycle Assessment

Selective Calcium Removal at Near-Ambient Temperature in a Multimineral Recovery Process from Seawater Reverse Osmosis Synthetic Brine and Ex Ante Life Cycle Assessment

Alkalinity Enhancement during Reject Brine Electrolysis: Role of Electrocatalyst Placement on the Outer Surfaces of Porous Flow-Through Electrodes

In-Depth Study on the Effects of Impurity Ions in Saline Wastewater Electrolysis

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