Process Economic Evaluation of Resource Valorization of Seawater Concentrate by Membrane Technology

In this study, a process design consisting of chemical precipitation, electrodialysis with monovalent-selective membranes, and bipolar membrane electrodialysis (BMED) is proposed to valorize seawater concentrate discharged from an RO (reverse osmosis) plant for the production of acid/base and coarse salt with high purity. After pre-precipitation and electrodialysis with monovalent-selective membranes, a high purity of coarse salt (∼92%) was obtained. Furthermore, the effect of current density and feed concentration of the BMED process on the production of acid/base with high purity was investigated. It is acceptable to attain acid/base with a purity of ∼95%/∼85% when operating at a current density of 10 mA/cm2 and a feed conductivity of 100 mS/cm by applying the screened BMED stack. Finally, the total process cost for the acid/base production was estimated at $0.50/kg at the current density of 10 mA/cm2, which is appropriate and competitive for industrial application.