Seawater injection into reservoirs is a common method to enhance oil recovery. In order to avoid corrosion in pipes, the oxygen has to be removed from the seawater. This study focuses on the use of silver cathodes in electrochemical cells for oxygen removal, and the physical parameters that affect the efficiency of this process. Three electrochemical cells have been constructed and tested with packed bed cathodes made up of pure silver particles and silver plated brass spheres. Experimental results showed that silver was a suitable cathode material for oxygen removal. The most important parameter for optimizing cell performance was the depth of the cathode chamber. In addition, the thickness of the silver plating is also an important parameter to adjust since a too-thin layer results in erosion giving rise to galvanic corrosion between brass and silver, which reduces the efficiency of the cell.

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.

In this study, electrochemical removal of oxygen from seawater in industrial scale is demonstrated. A test rig with an industrial scale electrochemical cell has been constructed and tested with filtrated oxygen rich seawater. The electrochemical cell was comprised of a silver mesh cathode and an iridium oxide anode with a cation exchange membrane. The effects of flow rate, pressure, and applied voltage on oxygen removal efficiency and resulting current were studied. Also, the differential pressure between the anode and cathode chambers affected the performance of the cell, and an overpressure of 0.20−0.30 bar in the anode chamber was optimal in order to obtain maximum oxygen removal. It was possible to achieve an oxygen concentration lower than 5 ppb in seawater at a flow rate of 5 L min −1 . No scaling or biofilm problems were observed during a 200 h test period.