Simultaneous hydrogen production and struvite recovery within a microbial reverse-electrodialysis electrolysis cell

In this research, a novel Microbial reverse-electrodialysis electrolysis struvite-precipitation cell (MRESC) was developed for energy recovery through struvite (MgNH4PO4 center dot 6H(2)O) crystallization and hydrogen production concurrently in a single process without any electrical-grid energy consumption. This hybrid system can effectively transfer the salinity gradient energy to electrical energy as a driving force to produce hydrogen gas coupled with struvite recovery and organic wastewater degradation. A MRESC containing 10 pairs of RED cells, supplied solutions typical of high concentration (600 mM NaCl) and low concentration (12 mM NaCl) at 1.0 mL/min, was operated in the fed-batch mode. The rates of hydrogen production and struvite crystallization were determined to be 0.71 m(3)-H-2 /m(3) -V-an/d and 7.62 g/m(2)/h, respectively. The gas produced was >92% H-2. The Coulombic efficiency was close to or above 100% with a COD removal of 84 +/- 6%, and an overall energy efficiency of 28%. The morphology and structure of the main component of accumulated crystal at the cathode were verified by a scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction. These results showed that the MRESC system could be used as an effective bioelectrochemical method for energy recovery in the form of pure hydrogen gas and struvite simultaneously. (C) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

A novel Microbial Reverse-Electrodialysis Electrolysis Struvite-Precipitation Cell (MRESC) has been developed for energy recovery through simultaneous struvite crystallization and hydrogen production. The system demonstrated high Coulombic efficiency and COD removal with an overall energy efficiency of 28%, proving to be an effective bioelectrochemical method for energy recovery.