Hydrogen Gas Production from Tannery Wastewater by Electrocoagulation of a Continuous Mode with Simultaneous Pollutants Removal

Abstract

The performance of a continuous electrocoagulation (EC) process was investigated for tannery wastewater treatment using aluminum and iron electrodes. The effects of the operating parameters, such as current density, pH of solution and inlet flow rate, on pollutants removal efficiency and recovery of hydrogen gas were investigated in order to optimize process performance. In the case of aluminum electrodes, The results showed that for tannery wastewater with an influent pH adjusted at about 6, the use of a current density of 14 mA/cm 2 , and an EC time of 125 min, gave access to pollutants (COD, Color, Cr, and NH3-N) removal efficiency 73, 94, 100 and 51%, respectively. The energy yield of harvested hydrogen was 16% of the electrical energy demand of the electrocoagulation process. However, in the case of iron electrodes, with effluent pH adjusted at about 7, , the use of a current density of 14 mA/cm 2 , and an EC time of 125 min, gave access to pollutants (COD, Color, Cr, and NH3-N) removal efficiency 67, 93, 100 and 46 %, respectively. And also, the energy yield of harvested hydrogen was 15 % of the electrical energy demand of the electrocoagulation process. Thus, the operating costs for two cases were found to be 0.675 $/m 3 wastewater. It could be seen that hydrogen gas production coupled with pollutants removal efficiency by EC continuous mode would be an effective approach for energy recovery and wastewater reutilization.