The Effects of Acidic, Alkaline, and Neutral Anolytes on Electrochemical Seawater Deoxygenation

Abstract

Electrochemical deoxygenation of seawater has advantages over available chemical and physical methods. For seawater deoxygenation, acidic, neutral, or alkaline anolytes can be used. The effects of acidic, alkaline, and neutral buffered and non-buffered anolytes were studied in two compartment deoxygenation cells. The pH, conductivity, H2O2 production, and current were measured throughout the experiments. The optimum applied potentials for oxygen reduction were between 1.9 V–2.2 V, giving water as product; reducing the applied potential also resulted in the formation of H2O2. Analysis after the experiments using a scanning electron microscope with electron-dispersive X-ray spectroscopy showed that both the silver mesh and the cation exchange membrane remained stable during the experiments. The use of alkaline anolytes resulted in the maximum oxygen removal with minimal side reactions in the cell.

Electrochemical Desalination of a 50% w/w Sodium Hydroxide Solution, a Pharmaceutical Sterilization Agent

“…6) must be higher than 357. Nickell et al [26] suggested the following equation to determine the activity of water in a concentrated NaOH solution: (7) where m is the molal concentration of NaOH, and T is the temperature in Kelvin. Based on this calculation, the water activity in a 50% w/w NaOH solution at 50 o C (i.e., a H2O(l) in Eq.…”

“…As NaOH solutions are typically produced from sodium chloride (NaCl) solutions through a chloro-alkali process [4], the development of a process to selectively remove Cl¯ from the NaOH solutions is critical. Thus far, adsorption [5], precipitation [6], and electrodialysis [7] processes have been employed for this purpose. Commercially available 50% w/w NaOH solutions contain approximately 100 ppm Cl¯ (i.e., 100 mg Cl¯/kg NaOH).…”

The growth mechanism of ordered nanoporous alumina

“…Growing, the oxide islands interface between each other through a thin barrier layer, forcing the current to become localized in the gap of the joined protrusions. The rise of the electrolyte chemical activity nearby the anode [10] leads to the local dissolution of the oxide layer. Cavities, filled with the electrolyte, and transforming according to the oxide film growth into pores, are formed in the film.…”

Integrated Valorization of Desalination Brine through NaOH Recovery: Opportunities and Challenges

“…[43] By separating the divalent anions and cations,t he formation of molecules that often cause scaling in BMED systems (e.g.,C aCO 3 and calcium sulfate (CaSO 4 )) can be prevented. [48] Furthermore,b ench-and pilot-scale [44,45] Fori nstance,c oating the surface of am embrane with polyethyleneimine improved the selectivity for monovalent cations over divalent cations while simultaneously increasing the overall water recovery after RO treatment.…”