title: Microbial electrolysis cell accelerates phosphate remobilisation from iron phosphate contained in sewage sludge.
abstract: Phosphate was remobilised from iron phosphate contained in digested sewage sludge using a bio-electric cell. A significant acceleration above former results was caused by strongly basic catholytes. For these experiments a dual chambered microbial electrolysis cell with a small cathode (40 mL) and an 80 times larger anode (2.5 L) was equipped with a platinum sputtered reticulated vitreous carbon cathode. Various applied voltages (0.2-6.0 V) generated moderate to strongly basic catholytes using artificial waste water with pH close to neutral. Phosphate from iron phosphate contained in digested sewage sludge was remobilised most effectively at pH ∼13 with up to 95% yield. Beside minor electrochemical reduction, hydroxyl substitution was the dominating remobilisation mechanism. Particle-fluid kinetics using the "shrinking core" model allowed us to determine the reaction controlling step. Reaction rates changed with temperature (15-40 °C) and an activation energy of Ea = 55 kJ mol(-1) was found. These analyses indicated chemical and physical reaction control, which is of interest for future scale-up work. Phosphate remobilisation rates increased significantly, yields doubled and recovered PO4(3-) concentrations increased four times using a task specific bio-electric system. The result is a sustainable process for decentralized phosphate mining and a green chemical base generator useful also for many other sustainable processing needs.
authors.affiliation: Institute of Life Technologies, University of Applied Sciences and Arts Western Switzerland, HES-SO Valais-Wallis, Route du Rawyl 64, CH-1950 Sion 2, Switzerland. fabian.fischer@hevs.ch.
authors.forename: Fabian
authors.initials: F
authors.lastname: Fischer
authors.forename: Géraldine
authors.initials: G
authors.lastname: Zufferey
authors.forename: Marc
authors.initials: M
authors.lastname: Sugnaux
authors.forename: Manuel
authors.initials: M
authors.lastname: Happe
mesh_terms: D001673:Biodegradation, Environmental; D004572:Electrolysis; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000032:analysis / Q000378:metabolism*; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
chemical_list: D010710:Phosphates; D012722:Sewage; D062065:Wastewater; D014874:Water Pollutants, Chemical