Hydrogen production from industrial wastewaters: An integrated reverse electrodialysis - Water electrolysis energy system

This work presents a novel approach combining reverse electrodialysis (RED) and alkaline polymer electrolyte water electrolysis (APWEL) for renewable hydrogen production. APWEL is fuelled by salinity gradient power (SGP) extracted from sulfate (SO42-)-rich industrial wastewater. The performance of a pilot-scale RED unit (200 cells, active area: 31.5 x 63.5 cm(2)), using salt solutions mimicking sulfate -rich waste streams (0.01-0.3 M Na2SO4), was evaluated. An open circuit voltage (OCV) of 12.3 V, a maximum power density of 0.22 W/m(2)MP (MP: membrane pair) and internal area resistance of 43.2 Omega cm(2)/cell were recorded by using 0.01 M/0.3 M Na2SO4 solutions at 35 degrees C. The APWEL stack (6 cells, active area: 5 x 5 cm(2)), equipped with Ni foam electrodes and heterogeneous anion-selective membranes, was tested with varying concentrations of liquid electrolyte (0.85-2.5 M KOH) and varying temperatures (28-48 degrees C). The APWEL stack attained a maximum current density of 110 mA/m(2) at 1.85 V/cell (i.e. 11 V per stack), 2.5 M KOH and 48 C. Under these conditions, the integrated system exhibited a maximum hydrogen production rate of 50 cm(3)/h-cm(2). This study opens up a new perspective on renewable hydrogen production fuelled by non -intermittent SGP from SO42--rich industrial effluents. (C) 2018 Elsevier Ltd. All rights reserved.