Harvesting Renewable Energy from Saltworks Waste Brines via Reverse Electrodialysis

The present work presents an experimental campaign devoted to producing electric power from waste brines with a laboratory-scale reverse electrodialysis (RED) unit. In particular, two saltworks waste brines (i.e., Margi and Nubia basins in Trapani, Italy) were used as feeds. Two different homogeneous ion exchange membranes (IEMs), developed by (I) Fujifilm Manufacturing Europe BV (The Netherlands) and (II) Suez (France), were investigated under several experimental conditions. Membrane ion sorption, fixed charge concentration, and permselectivity were investigated. Both real/pretreated brine and artificial solutions (5 M NaCl comparable to sodium chloride concentration in real brine) were investigated as feed solutions at 30 °C. Fujifilm IEMs resulted in higher stack permselectivity and yet exhibited higher resistance compared to Suez membranes. Monovalent ion sorption and counterion concentration of Fujifilm IEMs were higher than those of Suez membranes, while the co-ion concentrations in both IEMs were comparable. The RED application with hypersaline Margi-A and Nubia-A brine (TDS; 364.60 and 359.28 g/L) showed power densities of 3.57 and 4.32 W/m² for Fujifilm IEMs, respectively. Conversely, Suez IEMs provided significantly lower power densities of 0.77 and 0.69 W/m², respectively.