Sanjuán, Ignacio, Benavente, David, García García, Vicente, Expósito Rodríguez, Eduardo, Montiel, Vicente
Electrochemical softening of concentrates from an electrodialysis brackish water desalination plant: Efficiency enhancement using a three-dimensional cathode
Separation and Purification Technology. 2019, 208: 217-226. doi:10.1016/j.seppur.2018.01.066
URI: http://hdl.handle.net/10045/81887
DOI: 10.1016/j.seppur.2018.01.066
ISSN: 1383-5866 (Print)
Abstract: 
The electrochemical softening method to remove hardness from water has not been applied in desalination practice due to a high cathodic area requirement. In this work, the use of a 3D stainless steel wool cathode is proposed to overcome this technical limitation. An extensive comparison between the 3D cathode and a 2D Ti mesh has been presented, showing higher hardness removal for the 3D one. Experiments have been conducted with waters similar to concentrates derived from a brackish water treatment by electrodialysis. In addition, the method has been proved to be efficient for different water compositions in terms of hardness, alkalinity or the presence of an anti-scalant. The main influencing parameters (flow rate and current density) have been studied and it can be concluded that lower flow rates (below 1.2 L h−1) give rise to a better efficiencies and 100 A m−2 is the optimum current density. Moreover, the precipitate was characterised by SEM, EDX and XRD showing that Ca2+ is removed as calcite and aragonite (CaCO3), whereas Mg2+ is precipitated as brucite (Mg(OH)2). Finally, long-term experiments revealed that the 3D stainless steel cathode has a better performance than the 2D Ti mesh, but only at short times.
Keywords:Electrochemical softening, Hardness removal, Three-dimensional electrodes, Electroprecipitation, Concentrate, Wastewater treatment
Elsevier
info:eu-repo/semantics/article