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ACS Omega Article Figure 1. Principle of a rocking chair desalination battery. In the charging step, the cations in the negative compartment solution are captured by a chemical reaction with the negative electrode, whereas cations intercalated into the positive electrode are released into the positive compartment solution. Anions in the negative compartment solution pass through the anion-exchange membrane by diffusion. After exchange of the treated water with the source water, the solutions are diluted and concentrated by the reverse movement of ions during the discharging step. has an efficient energy consumption for seawater desalination (0.29 Wh/L for the 25% salt-removal efficiency),24 its economic impact is limited due to the high price of silver. The HCDI system uses a battery electrode, an anion-exchange membrane, and an activated carbon electrode. The ion removal performance of the HCDI system shows a high ion removal capacity and a rapid ion removal rate compared to those of a typical CDI, but the ion removal capacity of HCDI is still limited by the carbon material. Symmetric NID is a simulated system that operates in a similar manner to electrodialysis using a porous sodium manganese oxide (Na0.44MnO2) electrode with an anion-selective membrane. In this system, Na ions are captured in the battery material, whereas Cl ions are removed by diffusion through the anion-selective membrane. From the modeling data, NID has a remarkable energy efficiency (0.74 kWh/m3 for seawater-level NaCl) with the possibility of a high water recovery rate (maximum: 95% water recovery).27 However, the symmetric system is difficult to use due to the uncertain charging/discharging step but also because Na0.44MnO2 has a low specific charge capacity (35 mAh/g); there are also competing intercalation reactions with alkaline cations (K+, Mg2+, and Ca2+). Here, we investigated a novel, simple, and high-efficiency desalination system using Prussian blue electrodes. Figure 1 represents the principle of the rocking chair desalination battery; this system consists of sodium nickel hexacyanoferrate (NaNiHCF) and sodium iron HCF (NaFeHCF) electrodes for capturing cations, and there are two solution compartments, which are formed by an anion-exchange membrane in the cell. The system operates similar to rocking chair batteries, as shown by the movement of ions during the charging and discharging steps; however, the anion-exchange membrane blocks cation 1654 movement into another solution, whereas anions pass through the anion-exchange membrane by diffusion, inducing a charge imbalance of the solutions. From the ion movement in the cell, the solutions are concentrated and diluted during both the charging and discharging steps, and it does not require a regeneration step that creates brine in a desalination battery. Prussian blue analogues AxM[Fe(CN)6] (A: alkali cations, M: transition metal ions) have an open framework structure with the large cages surrounded by an FeCNFe bridge, and it allows to react with various cations, including K+, Mg2+, and Ca2+, which are the main alkaline ions in seawater.28,29 They are suitable materials for aqueous batteries because of their reversible reaction, long life cycle, and high specific capacity.30,31 Furthermore, they have the characteristics of being environmentally benign and of low cost,32 meaning that they can be applied for the capacitive-based desalination technology. In this work, a rocking chair desalination battery that consists of two Prussian blue materials was used for the electrochemical desalination process, and the salt removal performance and electrochemical properties were evaluated using actual seawater. 2. EXPERIMENTAL SECTION 2.1. Synthesis of Prussian Blue Materials. The Prussian blue materials used in this study were synthesized by a controlled crystallization reaction with citrate ions to obtain an ordered nanocube structure. NaNiHCF particles were prepared by mixing 100 mL of a 0.05 M NiCl2 + 0.35 M Na-citrate solution and 100 mL of a 0.05 M Na4Fe(CN)6 solution under vigorous stirring. The reaction was carried out for 24 h at room temperature, and the obtained solution was aged for 20 h at room temperature. The precipitated products were filtered and DOI: 10.1021/acsomega.6b00526 ACS Omega 2017, 2, 1653−1659PDF Image | Rocking Chair Desalination Battery Prussian Blue Electrodes
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Product and Development Focus for Salgenx
Redox Flow Battery Technology: With the advent of the new USA tax credits for producing and selling batteries ($35/kW) we are focussing on a simple flow battery using shipping containers as the modular electrolyte storage units with tax credits up to $140,000 per system. Our main focus is on the salt battery. This battery can be used for both thermal and electrical storage applications. We call it the Cogeneration Battery or Cogen Battery. One project is converting salt (brine) based water conditioners to simultaneously produce power. In addition, there are many opportunities to extract Lithium from brine (salt lakes, groundwater, and producer water).Salt water or brine are huge sources for lithium. Most of the worlds lithium is acquired from a brine source. It's even in seawater in a low concentration. Brine is also a byproduct of huge powerplants, which can now use that as an electrolyte and a huge flow battery (which allows storage at the source).We welcome any business and equipment inquiries, as well as licensing our flow battery manufacturing.CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)