Direct electrosynthesis of sodium hydroxide and hydrochloric acid from brine streams

Kumar, Amit; Phillips, Katherine R.; Thiel, Gregory P.; Schröder, Uwe; Lienhard, John H.

doi:10.1038/s41929-018-0218-y

Cited by 92 publications

(78 citation statements)

References 86 publications

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“…In most cases, saline water electrolyser technologies will need to have competitive capital and operational costs (CAPEX and OPEX) compared to electrolyser technologies coupled to desalination and purification units. Extra revenue may be obtainable if a careful management of the waste stream is utilized 97 . We believe that islands can be ideal places to test new technologies given the abundance of renewable energy and the desire for storage and self-sufficiency 98 , combined with the inherent current costs of importing fossil fuels not available in these territories.…”

Section: Discussionmentioning

confidence: 99%

Electrolysis of low-grade and saline surface water

et al. 2020

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Powered by renewable energy sources such as solar, marine, geothermal and wind, generation of storable hydrogen fuel through water electrolysis provides a promising path towards energy sustainability. However, state-of-the-art electrolysis requires support from associated processes such as desalination of water sources, further purification of desalinated water, and transportation of water, which often contribute financial and energy costs. One strategy to avoid these operations is to develop electrolysers that are capable of operating with impure water feeds directly. Here we review recent developments in electrode materials/catalysts for water electrolysis using low-grade and saline water, a significantly more abundant resource worldwide compared to potable water. We address the associated challenges in design of electrolysers, and discuss future potential approaches that may yield highly active and selective materials for water electrolysis in the presence of common impurities such as metal ions, chloride and bio-organisms. Freshwater is likely to become a scarce resource for many communities, with more than 80% of the world's population exposed to high risk levels of water security 1. This has been recognized within the Sustainable Development Goal 6 (SDG 6) on Clean Water and Sanitation 2. At the same time, low-grade and saline water is a largely abundant resource which, used properly, can address SDG 7 on Affordable and Clean Energy as well as SDG 13 on Climate Action. Hydrogen, a storable fuel, can be generated through water electrolysis and it may provide headway towards combating climate change and reaching zero emissions 3 , since the cycle of generation, consumption and regeneration of hydrogen can achieve carbon neutrality. In addition to providing a suitable energy store, hydrogen can be easily distributed and used in industry, households and transport. Hydrogen, and the related fuel cell industry, has the potential to bring positive economic and social impacts to local communities in terms of energy efficiency and job markets; globally the hydrogen market is expected to grow 33% to US$155 billion in 2022 4. However, there are remaining challenges related to the minimization of the cost and integration of hydrogen into daily life, as well as meeting the ultimate hydrogen cost targets of

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Section: Discussionmentioning

confidence: 99%

Electrolysis of low-grade and saline surface water

et al. 2020

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“…Processes not requiring as much brine concentration as electrolysis could yield very significant energy savings. 38,58 SENSITIVITY STUDIES…”

Section: Energy Consumption and Second Law Efficiency Of Componentsmentioning

confidence: 99%

Sodium Hydroxide Production from Seawater Desalination Brine: Process Design and Energy Efficiency

Warsinger

Urmi

et al. 2018

Environ. Sci. Technol.

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107

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The ability to increase pH is a crucial need for desalination pretreatment (especially in reverse osmosis) and for other industries, but processes used to raise pH often incur significant emissions and nonrenewable resource use. Alternatively, waste brine from desalination can be used to create sodium hydroxide, via appropriate concentration and purification pretreatment steps, for input into the chlor-alkali process. In this work, an efficient process train (with variations) is developed and modeled for sodium hydroxide production from seawater desalination brine using membrane chlor-alkali electrolysis. The integrated system includes nanofiltration, concentration via evaporation or mechanical vapor compression, chemical softening, further ion-exchange softening, dechlorination, and membrane electrolysis. System productivity, component performance, and energy consumption of the NaOH production process are highlighted, and their dependencies on electrolyzer outlet conditions and brine recirculation are investigated. The analysis of the process also includes assessment of the energy efficiency of major components, estimation of system operating expense and comparison with similar processes. The brine-to-caustic process is shown to be technically feasible while offering several advantages, that is, the reduced environmental impact of desalination through lessened brine discharge, and the increase in the overall water recovery ratio of the reverse osmosis facility. Additionally, best-use conditions are given for producing caustic not only for use within the plant, but also in excess amounts for potential revenue.

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“…5 ). The CER is also important for generating active chlorine (AC) as a disinfectant for wastewater and ship ballast water treatments on account of its effectiveness in removing harmful organisms or invasive aquatic species with a long residual time [9][10][11][12] . AC generation is typically conducted in neutral pH, where the oxygen evolution reaction (OER), the side reaction of CER, shows much lower overpotential than that in acidic pH 13,14 , leading to low CER selectivity.…”

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confidence: 99%

Atomically dispersed Pt–N4 sites as efficient and selective electrocatalysts for the chlorine evolution reaction

et al. 2020

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Chlorine evolution reaction (CER) is a critical anode reaction in chlor-alkali electrolysis. Although precious metal-based mixed metal oxides (MMOs) have been widely used as CER catalysts, they suffer from the concomitant generation of oxygen during the CER. Herein, we demonstrate that atomically dispersed Pt−N 4 sites doped on a carbon nanotube (Pt 1 /CNT) can catalyse the CER with excellent activity and selectivity. The Pt 1 /CNT catalyst shows superior CER activity to a Pt nanoparticle-based catalyst and a commercial Ru/Ir-based MMO catalyst. Notably, Pt 1 /CNT exhibits near 100% CER selectivity even in acidic media, with low Cl − concentrations (0.1 M), as well as in neutral media, whereas the MMO catalyst shows substantially lower CER selectivity. In situ electrochemical X-ray absorption spectroscopy reveals the direct adsorption of Cl − on Pt−N 4 sites during the CER. Density functional theory calculations suggest the PtN 4 C 12 site as the most plausible active site structure for the CER.

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Direct electrosynthesis of sodium hydroxide and hydrochloric acid from brine streams

Cited by 92 publications

References 86 publications

Electrolysis of low-grade and saline surface water

Electrolysis of low-grade and saline surface water

Sodium Hydroxide Production from Seawater Desalination Brine: Process Design and Energy Efficiency

Atomically dispersed Pt–N4 sites as efficient and selective electrocatalysts for the chlorine evolution reaction

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