Application of metal-air fuel cell electrocoagulation for the harvesting of Nannochloropsis salina marine microalgae

Abstract

The main goal of this study was to evaluate the applicability of Fe-, Al-, and Mg-air fuel cell fuel cell electrocoagulation (EC) for harvesting Nannochloropsis salina (marine microalgae). During the operation of metal-air fuel cell EC, the charge neutralization and sweep flocculation of the microalgae floc with metal hydroxides occurred as the zeta potential of the microalgae floc increased with time; subsequently, the microalgae recovery was effectively possible. A system using an Fe anode had a harvesting efficiency of <85% with an EC operation time of 3 h and a settling time of 4 h. However, in systems using Al and Mg anodes, 100% microalgae recovery was achieved within EC operation times of 2 and 1 h, respectively. The maximum lipid recovery efficiencies of N. salina using Fe, Al, and Mg anodes were approximately 15.8, 23.8, and 28.9%, respectively. The maximum power densities using Fe, Al, and Mg anodes ranged from 0.35 to 1.09, 0.16-1.83, and 4.6-15 Wm(-2), respectively, within the NaCl concentration range of 0-100 mM. The maximum electric energy production (EEP) from the microalgae using Fe, Al, and Mg anodes ranged from 1.96 to 32, 0.08-37.6, and 38.7-683 Wh kg(-1), respectively, within the NaCl concentration range of 0-100 mM.